State of the
River Report
A report on the environmental health of the Rideau River
Prepared by the Research and Monitoring Committee of the
Rideau River Roundtable
December 2001
State of the
River Report
A report on the environmental health of the Rideau River
Prepared by the Research and Monitoring Committee of the
Rideau River Roundtable
December 2001
Acknowledgments
This report has been prepared by the Research and Monitoring Committee of the Rideau
River Roundtable, with funding provided by the Ontario Trillium Foundation.
The Rideau River
Roundtable is an association of
individuals and organizations working together to care for the health of the Rideau River from
Smiths Falls to Ottawa.
The Ontario Trillium
Foundation is an agency of
the Ministry of Citizenship, Culture and Recreation. The Foundation receives $100 million a year
from the Province’s charitable gaming initiative, and provides grants to eligible charitable and notfor-profit organizations in the arts, culture, sports, recreation, environment and social service
sectors.
Table of Contents
Executive Summary.....................................................................................................................................i
Introduction ....................................................................................................................................................iv
Acknowledgements ....................................................................................................................................vi
1
Overview: the Rideau River Landscape ............................................................................................1
2
Water Quality Indicators............................................................................................................................4
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
Introduction ............................................................................................................................................................4
Total phosphorus ...................................................................................................................................................5
Nitrate and nitrite ...................................................................................................................................................7
Dissolved oxygen...................................................................................................................................................8
Algal abundance ..................................................................................................................................................10
Metals...................................................................................................................................................................12
Bacteria (E. col)i...................................................................................................................................................14
Summary..............................................................................................................................................................16
3
Biological Indicators .................................................................................................................................18
3.0
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
Introduction ..........................................................................................................................................................18
Species diversity..................................................................................................................................................18
Species at risk......................................................................................................................................................20
Fish diversity and abundance .............................................................................................................................22
Restrictions on fish consumption ........................................................................................................................26
Aquatic plant diversity and abundance...............................................................................................................28
Aquatic plant harvesting ......................................................................................................................................31
Non-native species: zebra mussels ....................................................................................................................33
Summary..............................................................................................................................................................36
4
Stress Indicators .........................................................................................................................................37
Introduction ..........................................................................................................................................................37
Population growth ................................................................................................................................................37
Urban growth and density ...................................................................................................................................38
Permits to take water...........................................................................................................................................41
Boat traffic ............................................................................................................................................................42
Water level manipulation – effects on fish .........................................................................................................45
Population served by wastewater treatment ......................................................................................................47
Agricultural activities............................................................................................................................................49
Summary..............................................................................................................................................................51
4.0
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
Data Gaps .......................................................................................................................................................54
Recommendations .....................................................................................................................................55
Contacts and Data Sources ...................................................................................................................57
Bibliography ..................................................................................................................................................59
Appendices ....................................................................................................................................................62
i
List of Figures
Figure 1 Map of the Rideau River ...............................................................................................................................1
Figure 2 Average monthly discharge of the Rideau River at Ottawa, 1933-2000.....................................................2
Figure 3 Map of the Rideau River watershed .............................................................................................................3
Figure 4 Average annual total phosphorus, 1970-2000 .............................................................................................6
Figure 5 Average annual total phosphorus, 1993-2000 .............................................................................................6
Figure 6 Average annual nitrate + nitrite, 1993-2000.................................................................................................8
Figure 7 Average annual dissolved oxygen, 1998-2000 ............................................................................................9
Figure 8 Average annual chlorophyll a, 1993-2000..................................................................................................11
Figure 9 Average zinc concentrations, 1981-2000...................................................................................................13
Figure 10 Average E. coli concentrations, 1997-2000 ...............................................................................................15
Figure 11 Percent abundance of fish species in 6 reaches along the Rideau River, 1997-2000...........................25
Figure 12 Aquatic plant species richness, 1998-1999...............................................................................................29
Figure 13 Percent cover of dominant aquatic plants (1998-1999 .............................................................................30
Figure 14 Dominant aquatic plants harvested from the navigation channel, 1999-2000.........................................32
Figure 15 Annual aquatic plant harvest, 1996-2000 ..................................................................................................33
Figure 16 Zebra mussel distribution and density along the Rideau River, 1993-1999 ............................................34
Figure 17 Urban growth in the City of Ottawa, 1906-1999........................................................................................39
Figure 18 Urban area in the City of Ottawa, 1906-1991............................................................................................40
Figure 19 Urban density in the City of Ottawa, 1906-1991 .......................................................................................40
Figure 20 Growth in the number of permits to take surface water from the Rideau watershed, 1964-2001 ..........41
Figure 21 Total volume of water permitted to be taken daily from the Rideau River and tributaries or lakes
in the watershed, 1965-2001 .....................................................................................................................42
Figure 22 Total boat traffic through locks on the Rideau Canal, 1980-2001 ............................................................43
Figure 23 Total boat traffic through northern Rideau Canal locks, 1996-2000.........................................................44
Figure 24 Boat traffic through individual locks in the northern Rideau Canal, 1996-2000.......................................44
Figure 25 Land use on farms in municipalities bordering the Rideau River and its tributaries, 1996 .....................49
Figure 26 Area of farmland on which fertilizers, pesticides and irrigation were used in municipalities
bordering the Rideau River and its tributaries, 1996 .................................................................................50
Figure 27 Number of livestock in municipalities bordering the Rideau River and its tributaries, 1996....................51
ii
List of Tables
Table 1
State of the environment indicators used in this report ..............................................................................vii
Table 2
Metal concentrations in the Rideau River, 1997-2001................................................................................14
Table 3 Number of annual beach closures on the Rideau River, 1994-2001 ..........................................................16
Table 4 Species at risk along the Rideau River ........................................................................................................21
Table 5 Location of fisheries assessment reaches on the Rideau River .................................................................23
Table 6 Catch per unit effort (CUE) of fish species in the Rideau River, 1997-2000 ..............................................24
Table 7 Fish consumption recommendations for the Rideau River, 2000-2001 .....................................................27
Table 8
Fall draw down rate and related fish deaths in the Rideau River, 1995-1999 ...........................................46
Table 9 Population served by wastewater treatment facilities in the Rideau River watershed, 2000.....................47
Table 10 Wastewater treatment plant performance, 1995-2000................................................................................48
List of Appendices
Appendix 1 Canadian Water Quality Guidelines and Ontario Water Quality Objectives for the protection of
aquatic life in freshwater ........................................................................................................................62
Appendix 2 Location of Ministry of the Environment water quality monitoring sites on the Rideau River ............63
Appendix 3 Location of Canadian Museum of Nature Biodiversity Project water sampling sites on the Rideau
Appendix 4
River........................................................................................................................................................64
Location of Canadian Museum of Nature long-term aquatic plant monitoring plots on the Rideau
River........................................................................................................................................................64
Appendix 5 Rideau River Biodiversity Project species lists....................................................................................65
Appendix 6 COSEWIC terms and risk categories...................................................................................................72
Appendix 7 MNR status categories ..........................................................................................................................72
Appendix 8 Natural Heritage Information Centre (NHIC) provincial rank (SRANK) definitions .............................73
Appendix 9 Population of municipalities within the Rideau River watershed (1991 and 1996 ..............................74
Appendix 10 City of Ottawa sub-regional population, 1992-1999 ............................................................................75
Appendix 11 Agricultural land use in municipalities within the Rideau River watershed, 1996 ..............................76
Appendix 12 Agricultural practices in municipalities within the Rideau River watershed, 1996 .............................77
Appendix 13 Number of livestock in municipalities within the Rideau River watershed, 1996 ...............................78
Appendix 14 Percentage of land area farmed in municipalities bordering the Rideau River and its
tributaries,1996 .....................................................................................................................................79
Appendix 15 Livestock on farms in municipalities bordering the Rideau River and its tributaries, 1996 ...............80
iii
Executive Summary
The State of the Rideau River report has been produced by the Rideau River
Roundtable, an association of individuals and organizations working together to protect water
quality, biodiversity and habitat along the Rideau River. This report provides a picture of
current conditions along the river (and trends when possible), as it flows between Smiths Falls
and Ottawa. Information is provided on a set of indicators of water quality and biological
conditions, as well as some indicators of sources of stress on the river. While this set of
indicators is by no means complete, it represents an important first step in the process of
providing information and monitoring environmental conditions on the river. It is intended that
follow-up reports in future years will add information on management response indicators, as
well as reporting on any changes in environmental conditions on the Rideau. The main findings
of this report are summarized below:
Water Quality Indicators
•
Total phosphorus (TP)
TP levels have declined in the Rideau River overall, since the 1960s. However, TP in the lower Rideau River
(downstream of Kars) often continues to exceed the provincial water quality objective. We still do not know the
relative importance of the various sources of TP (ex. municipal wastewater, agricultural runoff, septic systems,
fertilizers etc.) to the river.
•
Nitrate + Nitrite
Average nitrate + nitrite concentrations are lower than those considered harmful to aquatic organisms and human
health. However, high nitrate + nitrite concentrations are still occasionally found in the lower Rideau River,
particularly downstream of the Jock River.
•
Dissolved Oxygen
Dissolved oxygen is generally high enough to support warm water aquatic life, but there are areas of low oxygen
levels in the deeper main channel of the river and in Mooney’s Bay. However, the overall impact on aquatic life is
not known.
•
Chlorophyll a (Chl a)
Phytoplankton concentrations are generally quite low in the Rideau, and the types of algae found suggest the
water is relatively clean. However, some “problem” algae have been found in the Rideau, which are not monitored
as part of current Chl a sampling programs (which focus on the main channel). These include floating algal mats
in shallow areas and occasional (and potentially toxic) cyanobacterial blooms.
•
Metals
iv
“Heavy” metal concentrations are generally very low in the Rideau. However, concentrations of several heavy
metals occasionally exceed provincial objectives, particularly in the lower Rideau (below the Jock River).
•
E. coli
E. coli levels usually meet provincial objectives for recreational uses such as swimming in most of the river.
Beaches are rarely closed due to high E. coli concentrations. However, E. coli concentrations are often high within
the downtown area of the City of Ottawa.
Biological Indicators
•
Species diversity
The Rideau River supports diverse communities of suspended algae, aquatic plants, amphibians and reptiles, fish,
aquatic birds, clams and other invertebrates. However, several invasive, introduced species have been found in
the Rideau, notably zebra mussels, Eurasian water milfoil and curly pondweed.
•
Species at risk
The Rideau River is home to a number of provincially rare species, and two vulnerable bird species, the black tern
and the least bittern. However, we know little about the size and health of the populations of these rare species.
•
Fish diversity & abundance
Fishing is great in the Rideau! There is a diverse community of fish in the Rideau, with a predominance of fish
species that are typical of fertile, productive freshwaters. However, the non-native common carp, which has been
found to cause the degradation of shoreline habitats (by uprooting aquatic plants), is now well established in the
Rideau River. Other non-native species are being introduced (for example when unwanted aquarium fish are
dumped into the river). This could have serious consequences for native aquatic communities in the Rideau.
•
Fish consumption
There are some restrictions on the consumption of fish caught in the Rideau River. However, the presence of
contaminants such as mercury in fish is a global problem, and the situation in the Rideau is comparable to (or even
better than) that in many other Canadian lakes and rivers.
•
Aquatic plant diversity & abundance
The Rideau River supports a diverse community of aquatic plants in its shallow areas, and even some uncommon
species, such as wild rice, in places.
•
Aquatic plant harvesting
The deeper main channel of the Rideau Canal system suffers from the heavy growth of invasive plant species
(such as Eurasian water milfoil and curly pondweed), which are harvested in some areas to make navigation
possible. These plants appear to be getting much thicker in recent years in the lower Rideau River (through
Ottawa).
•
Zebra mussels
Zebra mussels have invaded the Rideau, and continue to spread throughout the system. They have contributed to
serious declines in native clam populations in the lower Rideau River.
Stress Indicators
v
•
Population growth
Human population growth continues in the Rideau River watershed, with large increases in population projected for
the City of Ottawa over the next 20 years. The impact this growth has on the Rideau will depend largely on the
type and quality of development that occurs. Improvements in urban infrastructure and planning may mitigate
some of the environmental impacts associated with population growth.
•
Urban growth & density
The City of Ottawa continues to expand, particularly outside the Greenbelt. Urban density is declining, so it takes
more land to support a given population.
•
Permits to take water
The number of permits to take water from the Rideau continues to increase. However, the actual amount of water
taken, and the effect this has on the Rideau are unknown.
•
Boat traffic
The amount of boat traffic through the locks on the Rideau has declined somewhat in recent years. However,
much of the boat traffic on the Rideau comes from property and marinas along the river (and is therefore not
accounted for in these boat traffic figures). Trends in this local boat traffic, and its impacts are not currently known.
•
Draw down
The rapid draw down (or lowering) of Rideau River water levels in the fall has resulted in serious fish kills in the
past. The effects of refilling the river in the spring have not yet been studied. However, efforts are being made to
monitor and reduce the negative effects of draw down on fish communities.
•
Wastewater treatment
Most of the population within Rideau River watershed is served by some form of municipal wastewater treatment
system. However, 18% of the population relies on septic systems, and their impact on water quality in the Rideau
River is unknown. The performance of most of the municipal treatment plants that discharge into
the Rideau is
generally good to excellent.
•
Agricultural activities
About 40% of the land in municipalities bordering the Rideau River is farmland but the impacts of agricultural
activities have not yet been studied. Cattle continue to have access to the Rideau River in some areas, but the
extent of their impact is not known.
vi
Introduction
Objective and scope of the report
The State of the Rideau River report is an initiative of the Monitoring and Research sub-committee of the
Rideau River Roundtable. The Rideau River Roundtable is an association of individuals, community and
environmental groups, businesses, educational institutions, municipalities and government agencies, working
together to protect water quality and biodiversity and restore habitat in the Rideau River watershed, with a
particular focus on the area between Smiths Falls and Ottawa.
The goal of state-of-the-environment (SOE) reporting is to promote “environmental sustainability”, whereby
a balance is maintained between human impacts and the ability of the natural environment to accommodate these
impacts. Sustainable practices are those which conserve and protect natural systems and processes, as well as
maintaining resources for future generations. SOE reports allow us to monitor environmental change, assess
management efforts, provide information to the public, and provide a tool for policy formulation and decisionmaking.
The State of the Rideau River report has been designed to provide current, reliable and relevant
information about the Rideau River, for a broad audience. This information is drawn from several recent and
ongoing environmental monitoring programs and research initiatives focused on the Rideau River. It is based
largely on data collected within the past five years, but includes historical data where available. This report
represents a first attempt at developing a set of indicators that will help in monitoring and evaluating environmental
change over the long term. In addition, this report identifies gaps in knowledge about the condition of the river,
stressors on the river and our collective management responses to these challenges.
This report focuses on current physical and biological conditions of the Rideau River, providing information
on water quality, biodiversity, and aquatic habitat. It also provides information on various sources of stress on the
Rideau River. Current “baseline” conditions are reported for each indicator and trends over time are identified
whenever sufficient data are available. Unfortunately, few rivers in Ontario have been studied in sufficient detail to
provide a basis for comparison with the Rideau River. Follow-up reports in future years will report changes in
these indicators, and add information on management response indicators.
Framework of the report
Environment Canada has developed a framework for state-of-the-environment reporting (Environment
Canada, 1996). The Condition-Stress-Management Response model describes environmental change using three
types of indicators that illustrate what is happening in the environment, what is causing degradation or changes in
the environment, and what we are doing to minimize stresses and improve environmental quality.
vii
•
What is happening?
“Condition” indicators evaluate the condition or health of the environment. Measures of water quality and
assessments of biodiversity are examples of condition indicators.
•
What’s causing it?
“Stress” indicators are indicators of human activities that stress the environment. Trends in human population
growth, or the use of pesticides are examples of stress indicators.
•
What are we doing about it?
“Management response” indicators track policies, programs and initiatives designed to reduce, remove, or
mitigate environmental stress. Improvements in sewage treatment facilities, or the creation of protected areas
are examples of management responses.
Background information, a trend and/or a benchmark has been provided for each indicator in the State of
the Rideau River report. The background explains the importance of the indicator and its relationship to the issue
of concern. A figure, table or statement is used to describe the state or trend of the indicator along the course of
the river, and (if possible) over time. Regulatory standards, guidelines or objectives are provided where available,
to illustrate whether the current condition is good or needs improvement. Limitations of the indicator may be
discussed, if applicable. In the recommendation section of the report, information gaps are discussed, and other
potential indicators are identified, in order to guide future scientific and community-based monitoring efforts.
Method
The outline of this report was based on a review of the common elements of SOE reports produced at
municipal, provincial, national and international levels, as well as reports focused on particular issues such as
water quality or biodiversity. A preliminary list of indicators was drafted, based on the frequency of their use in
these reports. Indicators were selected, after assessing their usefulness according to criteria listed below. In
addition, the list of indicators was reviewed by a panel of experts drawn from the University of Ottawa, the
Canadian Museum of Nature, the Ontario Ministry of Natural Resources, Parks Canada, the Rideau Valley
Conservation Authority the City of Ottawa and private consultants.
What Makes a Good Indicator?
•
Is the indicator relevant and understandable? An indicator should say something meaningful about the
state of the environment, and be easily interpretable by the target audience.
•
Is it comparable? A good indicator can be compared to a reference point, such as a historical level, a policy
target, or a regulatory standard.
viii
•
Is the indicator at an appropriate scale? To be meaningful, the indicator should be at a scale that is
appropriate to the area of study. In the case of this report, it should reflect conditions at the watershed or river
scale.
•
Is it responsive to change? Condition indicators should be chosen which could be expected to respond to
changes in stresses or to management initiatives.
•
Are time-series data available? Indicators for which a historical trend is available are preferred.
•
Is long-term monitoring feasible? Indicators should be able to be monitored over time at a reasonable cost,
and long-term monitoring should be expected, to ensure that the indicator is useful in tracking trends in the
future.
Acknowledgements
The State of the Rideau River report has been prepared by J.G. Preece, under the guidance of the
Research and Monitoring sub-committee of the Rideau River Roundtable. This report builds on an undergraduate
thesis in Environmental Science on the State of the Rideau River, written by Vanessa Lyon under the direction of
Dr. Frances Pick at the University of Ottawa. I wish to gratefully acknowledge the generous assistance of Vanessa
Lyon for providing information used in the preparation of this report. I also wish to thank the many other individuals
who supplied assistance and advice, including those listed in the Contacts and Data Sources section at the end of
this report. Financial support for this report was provided by a Trillium grant from the province of Ontario.
ix
Table 1. State of the environment indicators used in this report
CATEGORY
INDICATOR
PARAMETER REPORTED
Water quality indicators
Total phosphorus (TP)
concentrations - trend
Nitrate + nitrite nitrogen
concentrations - trend
Dissolved oxygen
concentrations - trend
Suspended algae (chlorophyll a)
concentrations – trend
types of algae
Metals
# exceedances of PWQOs
E. coli
concentrations – trend
# beach closures
Species diversity
# species of various plant and
animal groups
Species at risk
# species at risk
Aquatic plants
# species, abundance (% cover)
Harvest of aquatic plants
annual harvest (tons)
Zebra mussels
abundance, trend
Fish
# species, abundance (CUE)
Contamination of fish tissue
fish consumption restrictions
Human population
watershed population, trend
Urban development
area of urban development,
density of urban development
Municipal wastewater treatment
% of population served,
treatment facility performance
Boat traffic
# boats through locks
Water-taking
# permits to take water,
volume of water permitted
Water level regulation
rate of fall draw down,
fish kills
Agricultural activities
# and area of farms
area of land with fertilizer,
pesticide, irrigation use
# livestock
Biological indicators
Stress indicators
x
xi
1
Overview: The Rideau River Landscape
The Rideau River is located in southeastern Ontario, and flows in a north-easterly direction from its
headwaters in Lower Rideau Lake for approximately 100 kilometres, joining the Ottawa River at Ottawa (Figure
1). The Rideau River drains an area of approximately 3,830 square kilometres. The Rideau River watershed
includes areas of both Precambrian bedrock (the Frontenac Axis, a southern extension of the Canadian Shield),
and more recent Palaeozoic sedimentary bedrock. This bedrock is overlain by sediments deposited while the
Champlain Sea covered the area following the last ice age, or since it receded about 10,000 years ago.
Figure 1 The Rideau River. Source: Canadian Museum of Nature
Between Smiths Falls and Merrickville, the Rideau River flows through the Smiths Falls Limestone Plain,
a mainly flat region of exposed limestone and shallow soils. Much of the shoreline in this region is undeveloped,
and composed of several extensive wetlands. Between Merrickville and Ottawa, the Rideau River flows through
the Ottawa Clay Plain, a flat fertile area, with a mixture of agricultural and intensive residential shoreline
development. The Rideau River is mainly lake-fed. The two main tributaries, Kemptville Creek and the Jock
River, contribute approximately 10% of the total discharge of the Rideau.
The Rideau River forms part of the Rideau Canal, a Canadian Heritage River and Historic Canal operated
by Parks Canada, extending between Kingston and Ottawa. The southern portion of the Rideau Canal flows
southwards from Upper Rideau Lake, the high point of the system, through the Cataraqui River to Kingston. The
Rideau River, which forms the northerly part of the Rideau Canal, drops approximately 83 metres, through 31
1
locks, between Smiths Falls and the Ottawa River. These locks, along with a series of dams, were built to bypass
rapids and waterfalls along the river. In some cases, several locks are joined together to create the necessary
change in water level. Water levels along the river are regulated by Parks Canada to ensure that a minimum
water depth of 1.5 m is maintained in the navigation channel.
The average annual discharge of the Rideau River at Ottawa is approximately 40 cubic metres per
second. Discharge varies through the year, with peak flows occurring between February and May, and relatively
low flow rates throughout the remainder of the year (Figure 2). During the summer when average discharge is
around 10 cubic metres per second, it takes approximately 15 days for water to travel through the main channel
from Lower Rideau Lake to Ottawa. However, as much as 70% of the area of the Rideau River is composed of
shallow areas (less than 2 metres in depth), with very low flow.
350
300
/sec)
3
250
200
150
Maximum
100
Average discharge (m
50
Average
0
Minimum
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Figure 2 Average monthly discharge of the Rideau River at Ottawa, 1933-2000.
Source: Water Survey of Canada, 1990
The Rideau River flows through a mixture of rural and urban communities, as well as wetlands, parks and
conservation areas. Eighteen municipalities are located (wholly or partially) within the Rideau watershed, and 5 of
these municipalities (Smiths Falls, Montague, Merrickville-Wolford, North Grenville and Ottawa) border the Rideau
River as it flows between Smiths Falls and the Ottawa River (Figure 3). There are no major industries located
along the Rideau River, and the river is primarily used for recreation and water supply.
1
Figure 3 The Rideau River Watershed
We apologize, but the map of the Rideau River Watershed is temporarily unavailable.
1
2.0 Water Quality- Introduction
Water quality is central to the health of the Rideau River. Water quality is important (and intimately linked)
to both human and natural communities along the river. Many human activities can have adverse affects on
water quality. Deterioration in water quality can arise from contamination by toxic substances and/or bacteria,
increases in suspended matter, and enrichment by nutrients. This pollution originates from easily identified point
sources, such as sewage treatment plants, as well as non-point (or diffuse) sources such as surface run-off, and
is hastened by human activities such as shoreline development, which result in the loss of riverbank vegetation
and accelerated erosion.
The definition of water quality differs, depending on how the water is to be used. Different water quality
criteria are set depending on whether the water is intended for drinking, recreation, industrial or agricultural use or
is considered as habitat for aquatic life. Water quality criteria have been established for a wide range of
parameters, at the national and provincial levels. These parameters include physical or chemical characteristics
(such as temperature and pH), major ions (ex. calcium and sodium), nutrients (ex. nitrogen and phosphorus),
organic compounds (such as pesticides), inorganics (metals) and microorganisms (ex. fecal coliform bacteria).
Water quality has been evaluated in the Rideau River by several different organizations. These include
the Ministry of the Environment (MOE), the City of Ottawa (formerly RMOC), the Canadian Museum of Nature
(CMN), the Rideau Valley Conservation Authority (RVCA) and a number of different health units. In addition,
several research projects conducted by researchers at the University of Ottawa have focused on water quality in
the Rideau River over the last decade.
The purpose of this section is to characterize the current surface water quality of the Rideau River
between Smiths Falls and Ottawa, and to discuss trends in various water quality parameters where long-term
monitoring results are available. Two water uses are considered in this report: water quality for aquatic habitat,
and water quality for recreational contact. Six water quality indicators are included in this report: total phosphorus,
nitrate/nitrite nitrogen, dissolved oxygen, algal abundance (chlorophyll a), metals, and bacteria (E. coli). Other
water quality indicators such as total suspended solids and pH were considered but it was decided that they are
not of particular concern in the Rideau River.
1
2.1 Water Quality Indicator: Total Phosphorus
Background
Phosphorus is an essential nutrient for all living organisms. Since phosphorus is usually available in very
small quantities in water, it is often a growth-limiting element.
However, human activities may result in high
phosphorus inputs to freshwaters, leading to the increased growth of algae and aquatic plants, the loss or
degradation of habitat and changes in biodiversity. In addition, the aesthetic and recreational value of lakes and
rivers may be impaired by algal blooms, which produce increased turbidity, discolouration, odours, and
occasionally, toxins.
Expansion of human populations and a variety of human activities have greatly increased the amount of
biologically available nutrients entering freshwaters.
The principal sources of phosphorus to Canadian
freshwaters include municipal and rural wastewater, manure and fertilizer in agricultural runoff, industrial
discharges, and aquaculture operations. The eutrophication (nutrient enrichment) of freshwaters due to inputs of
nutrients, particularly phosphorus, became a major environmental issue in the 1970s. Since then, controls on
phosphates in detergents and improvements to sewage systems have led to reductions in phosphorus inputs to
freshwaters.
Under the Ontario provincial water quality objectives (PWQOs) for the protection of aquatic life in
freshwater, the interim guideline for the maximum total phosphorus (TP) concentration to avoid excessive plant
growth in rivers is 0.030 mg/L.
Results
Since the 1960s, there has been a gradual but steady decrease in average TP concentrations in the
Rideau River (Figure 4). Until 1990, average TP levels were above the PWQO. Within the last decade, although
there has been an overall decline in TP concentrations, TP increases along the course of the Rideau River, and
continues to exceed the PWQO in the lower section of the river (Figure 5). Construction of a new tertiary
wastewater treatment facility in Smiths Falls in 1993 appears to have reduced TP levels immediately downstream
of Smiths Falls. The gradual increase in total phosphorus along the course of the river points to non-point
sources of nutrient pollution, but the relative importance of the different phosphorus loading sources along the
Rideau is not known.
Limitations
Total phosphorus concentration in the water may greatly underestimate the amount of phosphorus that is
actually available for plant growth in the river. Continued inputs of phosphorus to the river over the years can lead
to the accumulation of high levels of phosphorus in riverbed sediments. Therefore, decreases in TP
concentrations in the water of the Rideau may not lead to dramatic declines in the growth of rooted plants and
1
filamentous algae, which will continue to obtain the phosphorus they need from sediments, for many years to
come.
.P
St
atr
r
s
.
St
ck
ick
Ba
ve
Ri
on
ols
gs
rs
ck
Ho
Jo
Ka
ch
Ni
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lls
oc
Fa
0.10
arn
lm
Ki
s
ith
Sm
0.12
0.08
0.06
0.04
1966-70
1971-75
1976-80
1981-85
1986-90
1991-95
1996-2001
PWQO
Average TP (mg/L)
0.02
0.00
100
80
60
40
20
0
Distance above Rideau Falls, Ottawa (km)
Figure 4 Average annual total phosphorus, 1970-2000.
Source: Ministry of the Environment
St.
0.02
t.
y
Ba
L.
0.03
kS
's
er
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0.04
ith
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Lo
Sm
0.05
1993
1994
1995
1999
2000
PWQO
Average TP (mg/L)
0.01
0.00
120
100
80
60
40
20
0
Distance above Rideau Falls, Ottawa (km)
Figure 5 Average annual total phosphorus, 1993-2000.
Sources: Basu & Pick 1995, 1997 (1993-1995 data); Canadian Museum of Nature (1999-2000 data)
1
2.2 Water Quality Indicator: Nitrate and Nitrite
Background
Nitrogen is another essential nutrient for all living organisms. As with phosphorus, the biologically
available supply of nitrogen has greatly increased as a result of increasing human activities, principally from
municipal and rural wastewater, agriculture and industrial waste. While phosphorus compounds are the major
cause of eutrophication in freshwaters, there are also concerns about increasing concentrations of nitrogen
compounds.
Nitrogen plays a major role in eutrophication of saltwater ecosystems, and contributes to
acidification of freshwaters. In addition, excessive concentrations of nitrogen compounds such as ammonia and
nitrates can be toxic to aquatic organisms, and can be harmful in human drinking water supplies.
While nitrates are considered relatively non-toxic in water, concentrations between 1-10 mg/L have been
found to be lethal to some fish eggs and fry. Nitrate is also lethal to amphibians at concentrations ranging
between 13 and 40 mg/L, although concentrations as low as 2.5 mg/L can cause chronic effects. Nitrate is
thought to play a role in the decline in Canada’s amphibian populations. Nitrite is even more toxic, but high
concentrations of nitrite are uncommon, as it naturally undergoes rapid chemical reactions in the environment,
oxidizing to nitrate.
The Canadian water quality guidelines for the protection of aquatic life in freshwaters recommend a
maximum nitrite concentration of 0.06 mg/L, and state that nitrate concentrations that stimulate weed growth
should be avoided. There are no Ontario provincial water quality objectives (PWQOs) for the protection of aquatic life
for nitrate or nitrite. The guidelines for Canadian drinking water quality set the maximum acceptable nitrate
concentration at 10 mg/L and the maximum concentration of nitrite at 1 mg/L to protect human health.
Results
Unlike phosphorus, there has not been a dramatic decrease in average total nitrogen or nitrate
concentrations in the Rideau River since the 1970s. While phosphorus loading from municipal wastewater
treatment plants in Canada has declined greatly over the last 3 decades due to advanced treatment methods,
nitrogen loads from municipal wastewater have actually risen across the nation.
The average concentration of combined nitrate and nitrite, measured between 1993 and 2000, generally
remains low, under 0.05 mg/L, along the Rideau River, until downstream of Kars, where an increase is observed
in some years (Figure 6). This increase may be due to a reduction in the natural uptake of nitrogen, resulting from
channelization of the river and removal of shoreline habitat in areas of increasing residential development. Higher
nitrogen loading may also occur in the lower section of the river, due to inputs from agricultural land, or in
stormwater outfalls in the City of Ottawa. However, even in this lower region of the Rideau, average combined
nitrate and nitrite concentrations still remain far below the level considered a health risk to humans and aquatic
1
.
St
ick
atr
y
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Ba
St
's
ey
on
Mo
r
ve
Ri
ck
Jo
s
all
rs
Ka
lle
tvi
mp
Ke
sF
L
au
ide
rR
we
0.4
le
vil
ck
rri
Me
Lo
ith
Sm
0.5
.
1993
1994
1995
1998
1999
2000
0.3
0.2
0.1
Average nitrate + nitrite (mg/L)
0.0
120
100
80
60
40
20
0
Distance above Rideau Falls, Ottawa (km)
Figure 6 Average annual nitrate + nitrite, 1993-2000.
Sources: Basu & Pick 1995, 1997 (1993-1995 data); Canadian Museum of Nature (1998-2000 data)
life. In addition, total nitrite concentrations in the Rideau, measured by MOE between 1997 and 2001, have
ranged between 0.001 and 0.026 mg/L, well below the Canadian guideline for protection of aquatic life.
2.3 Water Quality Indicator – Dissolved Oxygen
Background
Dissolved oxygen (DO) is essential to aquatic life and plays an important role in biogeochemical
processes in freshwater environments. DO in water comes from two sources: atmospheric oxygen, and oxygen
generated by photosynthetic organisms (algae and aquatic plants) in the water. The amount of DO is dependent
on many factors, including temperature, turbulence (mixing), atmospheric pressure, nutrient levels, salinity, water
depth, the type of sediments, and biochemical oxygen demand (BOD).
While algae and aquatic plants produce oxygen during photosynthesis in daylight, they consume it at
night when only respiration occurs, thereby creating a diurnal pattern of alternating high and low oxygen
concentrations. Oxygen depletion at night may be sufficient to cause oxygen stress to fish and invertebrates in
some eutrophic (nutrient-rich) systems. High concentrations of algae and aquatic plants produce large amounts
1
of organic detritus, which can result in de-oxygenation of water during bacterial decomposition. High oxygen
consumption can greatly reduce the oxygen concentration at depths where photosynthesis is light-limited. Under
conditions of low or no oxygen (hypoxia or anoxia), phosphorus can be released from the bottom sediments,
during chemical reduction of iron-phosphate complexes, in a process known as “internal phosphorus loading”.
The Canadian guidelines and provincial water quality objectives for the protection of aquatic life
recommend minimum DO concentrations ranging between 4 and 9.5 mg/L, depending on water temperature, type
of biota (cold-water or warm-water species), and life stage (Appendix 1).
Results
In recent years, DO concentrations measured in the Rideau River (averaged for the whole water column)
between May and September have remained well above 4 mg/L, at least during the day (Figure 7). However,
average DO in Mooney’s Bay is consistently lower than in the rest of the river, because it contains some deep
regions, which become oxygen-depleted during the summer. Concentrations of DO lower than 5 mg/L (the
minimum concentration recommended for warm-water aquatic animals at summer water temperatures) are also
occasionally recorded in the deepest regions at other sites.
.
St
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Ba
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ick
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St
ve
le
lle
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Ri
on
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Mo
Jo
rs
Ka
mp
ck
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s
au
L.
8
Ke
Me
all
ide
sF
rR
10
ith
we
Lo
Sm
12
1998
1999
2000
6
4
2
Average Dissolved Oxygen (mg/
0
120
100
80
60
40
20
0
Distance above Rideau Falls, Ottawa (km)
Figure 7 Average dissolved oxygen concentration, 1998-2000.
Source: Canadian Museum of Nature
1
Limitations
Monitoring of DO in the Rideau is carried out in the main channel, and only during the day. A pattern of
alternating high oxygen concentrations (during daylight) and oxygen depletion (at night) is likely during the
summer when aquatic plants and algal mats are at their peak. In addition, dissolved oxygen may become
depleted when plants and algal mats decay. Therefore, although DO concentrations in the spring and summer
appear to be sufficient for the needs of fish and other aquatic animals, it is possible that this may not be the case
in shallow plant-rich areas (although this remains to be investigated in the Rideau).
2.4 Water Quality Indicator: Algal abundance
TT
Background
Microscopic algae (phytoplankton) in rivers are an essential food supply for microscopic animals, or
zooplankton, which in turn support larger animals including fish. Algal growth is dependent on a supply of
nutrients in the water, and is often limited by the amount of nutrients, particularly phosphorus, in freshwaters.
Thus, algal growth is mainly a function of the phosphorus concentration. High concentrations of nutrients may
produce excessive algal growth, or blooms, so that the water resembles pea soup. Algal blooms have many
deleterious effects in freshwaters, including reduced aesthetic appeal and recreational use, and taste and odour
problems in drinking water. Algal blooms can also have adverse ecological effects, including shading out of
aquatic plants, and depletion of oxygen as algae decay, which reduces the habitat available to fish. Some algae
can produce potent toxins, which can poison aquatic animals, and sometimes even livestock and humans.
Phytoplankton biomass can be estimated from the concentration of chlorophyll a
(Chl a ) in water
samples. Chl a is a photosynthetic pigment found in algae and other plants. There are no water quality objectives
or guidelines for Chl a concentrations in Ontario rivers or lakes. However, Chl a measurements can be used for
monitoring changes in algal biomass in rivers, or for comparing different rivers. Heavily polluted European rivers
may have Chl a concentrations as high as 250 or 300 micrograms per litre (_g/L). Canadian rivers, by contrast,
have much lower phytoplankton biomass.
A 1994 study of rivers in eastern Canada (Basu & Pick, 1996) found
Chl a ranging between 2and 28 _g/L (average 10 _g/L) in lowland rivers.
Results
Mid-channel Chl a concentrations along the Rideau River range between 2 and 28 _g/L throughout the
year. When compared with other lowland rivers in eastern Canada in 1994, Chl a in the Rideau was slightly lower
than average (8.8 _g/L). Chl a concentrations along the Rideau River, averaged for the months between May and
September or October, are shown in Figure 8. Chl a decreases somewhat as water flows out of Lower Rideau
Lake, builds gradually along the upper section of the Rideau River, and then decreases again in the lower part of
the river.
1
St.
Pa
kS
t.
ay
B
's
tric
ey
er
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s
le
lle
vil
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Mo
Jo
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all
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Ka
Ke
Me
Sm
we
Lo
0.015
L.
1993
1994
1995
1998
1999
2000
0.010
(mg/L)
a
0.005
Average Chl
0.000
120
100
80
60
40
20
0
Distance above Rideau Falls, Ottawa (km)
Figure 8 Average annual chlorophyll a concentration, 1993-2000.
Sources: Basu & Pick 1995, 1997 (1993-1995 data); Canadian Museum of Nature (1998-2000 data)
Overall, average Chl a levels along the Rideau have decreased somewhat since the 1993-1995 sampling
period, when they ranged between about 4 and 16 _g/L. During the 1998-2000 period, average Chl a dropped to
between 2 and 10 _g/L along the Rideau. The location at which Chl a begins to decline in the river has also
moved upstream, since the earlier sampling period. Decreased phytoplankton biomass in the lower part of the
Rideau River is due to colonization of the channel by zebra mussels, filter feeders that have been associated with
steep declines in phytoplankton density in other North American rivers and lakes.
The Rideau River supports a diverse community of algae. The dominant algae vary with site, season,
and year. Typically, cryptophytes are dominant in the community for most of the year, with blooms of diatoms
occurring for short periods in the spring, and blooms of chlorophytes and blue-green algae (cyanobacteria)
occurring in the summer. However, there is considerable variation between the algal communities found in
different years.
1
Limitations
While the Rideau River does not support excessive concentrations of phytoplankton, there are
nevertheless problems associated with algae in the river. Water monitoring takes place in the centre of the
navigation channel, and results do not reflect conditions in the shallower regions near the shores, which make up
as much as 70% of the area of the river. During spring and summer, these shallow near-shore areas with low or
no flow are dominated by dense colonies of filamentous green algae, which float to the surface in mid-summer as
they decay, forming thick algal mats. Algal mats are considered a problem, particularly in urban areas, where they
contribute to odours and clogging of the waterway.
Another concern is the possible development of toxic algal blooms in the Rideau River. Some species of
blue-green algae can produce toxins that are lethal to wildlife, and may cause contact irritation, gastroenteritis,
and even serious poisonings in humans. Microcystis aeruginosa, a species of blue-green algae which produces a
toxin called microcystin, has been found occasionally in the Rideau in past years. Microcystis colonies form a film
on the surface of water in shallow sheltered areas, and so are less likely to be detected during main-channel
water sampling.
2.5 Water Quality Indicator – Metals
Background
Some metals are trace elements, occurring naturally in low concentrations in rocks, water and the
atmosphere. Of these, some, including cobalt, copper, zinc, nickel and molybdenum, are essential to life in
minute quantities, although they can be harmful at higher concentrations. Other trace elements such as mercury
and lead are toxic to organisms even at extremely low concentrations.
Aquatic organisms ranging from phytoplankton to invertebrates and fish have been found to suffer from
the toxic effects of metals in surface waters. While metals may occur naturally in waters as a result of natural
weathering and erosion, they may also enter aquatic environments as a result of human activities. Processes
such as mining and smelting, manufacturing, combustion of gasoline and wood, waste incineration, and leaching
from landfill sites may all contribute to increased levels of metals in surface waters.
The concentration of zinc will be shown as an example of trends in metal concentrations in the Rideau
River. Zinc, along with 14 other metals (commonly referred to as “heavy” metals), is monitored monthly by the
Ontario Ministry of the Environment at 5 sites between Smiths Falls and Ottawa. Zinc has been found to produce
chronic toxic effects in invertebrates and fish at concentrations as low as 0.07 mg/L. The Ontario provincial water
quality objectives (PWQOs) for the protection of aquatic life in freshwaters recommend a maximum zinc
concentration of 0.02 mg/L (Appendix 1).
1
A common way of expressing water quality is to report the frequency with which water samples exceed
criteria such as the provincial water quality objectives. The frequency of these “exceedances” of PWQOs is
reported below, for the various metals measured in the Rideau River by MOE between 1997 and 2001.
Results
Since 1981, average zinc concentrations in the Rideau River have been lower than the PWQO for the
protection of aquatic life, generally ranging between about 0.002 and 0.010 mg/L (Figure 9). These values are
similar to average zinc concentrations reported in the Great Lakes, Ottawa River and St. Lawrence River between
1985 and 1990 (0.0073, 0.0111 and 0.0071 mg/L respectively). However, while average annual concentrations of
zinc remain below the objective of 0.02 mg/L, individual samples sometimes exceed it. Between 1981 and 2001,
59 samples (or 6.2%) exceeded the PWQO, ranging between 0.02 and 0.17 mg/L. (One sample, measuring 0.91
mg/L was taken at St. Patrick St. in 1987; this sample was excluded when preparing the graph below). Average
zinc levels appear to have risen somewhat in the last decade, at least within the City of Ottawa.
St.
t.
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Pa
Ba
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n's
rno
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Ho
Jo
ho
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Ka
Nic
ma
Kil
0.02
Zinc (mg/L)
1981-1985
1986-1990
1991-1995
1996-2001
PWQO
0.01
80
60
40
20
0
Distance above Rideau Falls, Ottawa (km)
Figure 9 Average zinc concentrations, 1981-2000.
Source: Ministry of the Environment
Between 1997 and 2001, the PWQO values for the protection of aquatic life were rarely exceeded for the
15 heavy metals monitored by MOE in the Rideau River (Table 2). Metal concentrations were usually very low,
(below or near the detection limits). Aluminum most frequently exceeded the PWQO, although this may have
been influenced by the presence of clay in samples. Aluminum is commonly associated with clay particles, and
samples taken from the Rideau are likely not clay-free (as specified in the PWQO). Levels of molybdenum and
1
nickel, considered highly toxic metals, never exceeded the objectives. Exceedances were also not recorded for
beryllium, copper, iron, or vanadium.
However, cadmium, another highly toxic metal, exceeded the PWQO in
4.4% of samples. The less toxic, zinc, lead and cobalt also occasionally exceeded the provincial objectives.
Table 2 Metal concentrations in the Rideau River, 1997-2001 (mean and maximum concentrations, and
percentage of samples exceeding provincial water quality objectives for the protection of aquatic life).
METAL
Aluminum
Barium
Beryllium
Cadmium
Chromium
Cobalt
Copper
Iron
Lead
Molybdenum
Nickel
Strontium
Titanium
Vanadium
Zinc
TOXICITY
RATING *
12
NA
NA
19
9
7
13
2
7
24
22
NA
NA
NA
10
PWQO (MG/L)
#SAMPLES
MEAN
MAX
75
none
1100
0.5
1(Cr VI),8.9(Cr III)
0.9
5
300
5
40
25
none
none
6
20
206
206
206
206
205
206
206
166
206
206
206
206
205
206
205
38.14
43.80
0.01
0.01
0.04
0.05
0.25
75.19
0.25
0.00
0.50
150.38
1.08
0.53
8.38
142
68.70
0.03
0.88
2.31
1.56
2.13
292
7.35
0.90
6.66
412
9.18
2.41
147
NUMBER OF
EXCEEDANCES
PERCENTAGE OF
EXCEEDANCES
16
7.8
0
9
?
7
0
0
9
0
0
0
4.4
?
3.4
0
0
4.4
0
0
0
14
0
6.8
* Toxicity ratings ≥14 = highly toxic; between 7 and 14 = medium toxicity; ≤ 7 = low toxicity; NA = not available
Source: Ministry of the Environment
Limitations
Changes in analytical methods, as well as high error values and reporting of negative values create
challenges for interpreting trends in metals data. Some metal concentrations cannot be compared to PWQO
values (ex. only total chromium is measured, but PWQOs are given for trivalent and hexavalent forms of
chromium). PWQO values are likely fairly conservative, and so it is not clear what the effect on aquatic life of
exceedances of these objectives may actually be.
2.6 Water Quality Indicator: Bacteria (E. coli)
Background
Both pathogenic and non-pathogenic microorganisms are found in freshwaters. Pathogenic bacteria,
viruses and protozoa may enter rivers through inadequately treated industrial and municipal sewage, storm water
overflows, agricultural runoff, leaking septic tanks, and even from large populations of waterfowl. Fecal coliform
bacteria, including Escherichia coli (E. coli) are members of the Enterobacteriaceae, which make up
1
approximately 10% of the intestinal microorganisms of humans and other animals. They are widely used as
indicator organisms, to provide an index of possible water contamination by human pathogens.
Contact with such fecal pathogens may occur during recreational activities such as swimming, canoeing
and sailing. Exposure can increase the risk of developing infections such as stomach disorders and minor
infections of the skin, eye, nose and throat. The Ontario Provincial Water Quality Objectives (PWQO) for safe
recreational use of freshwater recommend a maximum acceptable E. coli concentration of 200 cells per 100 mL.
However, local medical officers, who test the water at beaches weekly during the summer, use a more
conservative standard of 100 cells per 100 mL. When average (geometric mean of at least 5 samples) counts of
E. coli exceed 100 cells per 100 mL, beaches are closed for swimming.
Results
Average E. coli concentrations (monitored monthly by the Ministry of the Environment at 5 sites between
Smiths Falls and Ottawa) are well below the provincial objective along the Rideau River (Figure 10). However,
within the City of Ottawa, E. coli counts are consistently higher, and exceeded 100 cells per 100 mL on 18
occasions since 1997. Twelve of these samples were taken at the St. Patrick’s Street site, and four were taken
from Mooney’s Bay at Hog’s Back.
ick
.
St
k
ck
oc
s
all
Ba
atr
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St
Ho
arn
rs
lm
sF
ith
150
Ka
Ki
Sm
200
100
(cells / 100 mL)
E. coli
50
0
100
80
60
40
20
Distance above Rideau Falls (km)
Figure 10 Average E. coli concentrations, 1997-2001.
Source: Ministry of the Environment
1
0
1997
1998
1999
2000
2001
PWQO
Six public swimming beaches are located along the Rideau River (Table 3). Beach closures are rare at
most beaches; the Baxter Conservation Centre beach has never been closed due to high E. coli levels in more
than 15 years of operation. However, the Smiths Falls “junior” beach has been closed on at least one occasion
for each of the last six summers.
Table 3 Number of annual beach closures on the Rideau River, 1994-2001.
BEACH
NUMBER OF BEACH CLOSURES
1994
1995
1996
1997
1998
1999
2000
2001
Smiths Falls “Junior”
0
0
4
1
3
1
2
3
Smiths Falls “Senior”
0
0
0
0
1
0
1
2
Merrickville
0
0
3
1
0
0
2
1
Rideau River Provincial Park
0
0
0
0
0
0
0
1
Baxter Centre
0
0
0
0
0
0
0
0
Mooney’s Bay
N/A
0
0
0
0
0
3
0
Sources: Leeds, Grenville and Lanark Health Unit, MNR Public Health Inspector, RVCA (Baxter
Conservation Centre), City of Ottawa Public Health Department
2.7 Water Quality - Summary
Water quality in the Rideau River is generally very good. Although the Rideau is a moderately eutrophic,
or nutrient-rich river, it is characterized by abundant aquatic plant growth, rather than high concentrations of
suspended algae. Therefore, the Rideau River has relatively clear water, and its suspended algal community is
dominated by “clean” water species.
•
Total phosphorus (TP)
There has been a general decline in TP, an important indicator of nutrient enrichment, in the Rideau River since
the 1960s. Average annual TP concentrations in the water are currently below the PWQO for the prevention of
excessive plant growth in the upper Rideau River, between Smiths Falls and Merrickville. However, TP levels
increase downstream along the Rideau, often exceeding the PWQO in the lower reaches of the river. Monitoring
TP provides an indication of the level of phosphorus loading, and serves as a predictor of the amount of
suspended algae that can develop. However, much of the phosphorus used by rooted plants and filamentous
mat-forming algae may be supplied by sediments, rather than the water. Therefore, monitoring TP levels does not
necessarily provide information on phosphorus sources that encourage the growth of “problem” aquatic plants
and algal mats in the Rideau River. Even if water quality improves, there will still continue to be abundant plant
growth in the Rideau.
1
•
Nitrate + nitrite
Unlike phosphorus, there has not been a decline in nitrogen concentrations in the Rideau over the past few
decades.
Average annual nitrate + nitrite concentrations are relatively low in the upper Rideau River, but some
years they increase substantially in the urban section below the Jock River. This may be the result of inputs from
agricultural land along the Jock River or urban sources in the City of Ottawa, or decreases in the natural uptake of
nitrogen resulting from the loss of natural shoreline in developed areas. Substantial year-to-year variations may
be due to yearly differences in precipitation and river discharge. Nevertheless, nitrate + nitrite concentrations are
lower than those considered potentially harmful to aquatic life and hazardous to human health.
•
Dissolved oxygen (DO)
On average, DO concentrations are above the minimum concentrations recommended for the protection of warmwater aquatic life. However, during the summer, DO is sometimes very low at the river bottom in deep areas,
particularly in Mooney’s Bay. It is likely that aquatic organisms in these deep areas suffer from oxygen stress. In
addition, oxygen might become depleted in shallow weedy areas at nighttime or while plants and algal mats are
decaying, but these areas are currently not being monitored.
•
Algal abundance (Chl a)
On average, the Rideau River has somewhat lower Chl a than other lowland rivers in eastern Canada. Algal
biomass has declined slightly since 1993, particularly in the lower section of the Rideau (below Kars), probably as
a result of heavy colonization of the river by zebra mussels. While Chl a concentration is useful as a rough
estimate of the abundance of phytoplankton, it does not give any information regarding the composition of the
algal community. Continued monitoring of the taxonomic composition of this algal community is critical for
assessing water quality.
Currently, the main concerns with algae in the Rideau involve the widespread
development of filamentous algal mats, and the possibility of the growth of colonies of toxic blue-green algae.
These algae are mainly associated with the extensive shallow areas of the river, and monitoring efforts to date
have focused primarily on the deeper main navigation channel.
•
Metals
Metal concentrations generally meet the PWQOs for the protection of aquatic life. Most “heavy” metals are
usually found at trace levels, or at concentrations below detection limits.
The concentrations of some metals
(aluminum, cadmium, cobalt, lead and zinc) occasionally exceed PWQO levels, particularly in the lower Rideau
River as it passes through the City of Ottawa.
•
E. coli
Concentrations of E. coli are typically low in the Rideau River. Generally, beach closures are infrequent on the
Rideau. However, there are recurring problems with elevated levels of E. coli at some sites, notably in Ottawa,
(near St. Patrick St.) and at the “Junior” beach in Smiths Falls.
1
3.0 Biological Indicators - Introduction
The health of our environment is dependent on healthy communities of wildlife. The definition of wildlife
has recently been broadened by the Wildlife Ministers’ Council of Canada to include invertebrates, plants, algae,
fungi and bacteria, as well as mammals, birds, fish, reptiles and amphibians. These organisms play essential
ecological roles, and also provide a wide range of economic and social benefits to humans.
In order to protect the integrity of natural ecosystems and healthy waters, it is necessary to protect
biological diversity, or variety and variability in wildlife communities.
Human settlement puts many stresses on
wildlife communities, resulting in the loss of biological diversity. Pressures on wildlife result from the destruction
of habitat by agriculture, forestry, and urbanization, from pollution in the form of industrial, urban and agricultural
discharges and acid deposition, and through the introduction of non-native species.
Trends in wildlife diversity and abundance can be used as indicators of environmental health. In this
report, a number of biological indicators are used. These include species diversity (for a number of different
groups of organisms), species at risk, fish diversity and abundance, fish contaminant levels (indicated by
restrictions on fish consumption), aquatic plant diversity and abundance, abundance of introduced plant species
(indicated by plant harvesting), and exotic zebra mussel abundance and distribution.
3.1 Biological Indicator: Species Diversity
Background
Biological diversity or “biodiversity” refers to the variety of living organisms, which are found in a certain
area. Biodiversity is important because it provides stability and balance in natural systems. Healthy ecosystems
provide many benefits, including nutrient cycling, water purification, oxygen production, climate control, as well as
natural resources such as fish and wildlife. Biodiversity is threatened by numerous human activities, including the
destruction of habitat by agriculture, forestry and urban development, pollution, the introduction of non-native
species, over-harvesting of plants and animals, and global problems such as ozone depletion and climate
change.
Biodiversity may be measured at a variety of different levels, from genes to species, populations,
communities, ecosystems and, even, entire landscapes. Species diversity is a good indicator of the state of an
ecosystem. In river systems, species diversity typically declines in severe cases of cultural eutrophication
(nutrient enrichment caused by human activities). For example, in highly eutrophic freshwaters, plant biomass
may be extremely high, although few plant species are present. Higher species diversity would be expected in
aquatic systems that are relatively natural or undisturbed, as well as in those where there are a variety of different
1
habitat types (such as riffles, pools, and wetland areas). A distinction should be made between native and nonnative (introduced) species. Non-native species may lead to declines in biodiversity. The highly invasive zebra
mussel is one well-known example of an introduced species that has led to decreased biodiversity in North
American freshwaters.
Between 1998 and 2000, the Canadian Museum of Nature, along with the Rideau Valley Conservation
Authority and the University of Ottawa, carried out the Rideau River Biodiversity Project (RRBP), a 3-year
multidisciplinary community-based study of the environmental health of the Rideau.
One objective of this study
was to document biological diversity on the Rideau between Smiths Falls and Ottawa. The groups of organisms
investigated include phytoplankton, aquatic plants, molluscs, amphibians, reptiles, fish and aquatic birds.
Results
•
Phytoplankton – microscopic algae were the most diverse organisms studied in the RRBP. Three
hundred and fourteen species of phytoplankton were found in the Rideau River (Appendix 5a). This
number likely underestimates the true diversity of algae, as some could not be identified to the
species level.
The most diverse group of algae was the green algae (chlorophytes), with 172
species. However, the most common algae in the Rideau were cryptophytes, bi-flagellated algae that
are typically found in “clean” waters. However, in the lower section of the Rideau, species can be
found that are more typical of nutrient-enriched systems such as in degraded European rivers.
•
Aquatic plants - 59 species of submerged, floating and emergent plants were found in the Rideau
River (Appendix 5b). By comparison, 45 species of aquatic plants have been found in the Point Pelee
Marsh in southern Ontario. Four of the species found in the Rideau were non-native, invasive
species: Eurasian water milfoil, curly pondweed, European frog’s bit and flowering rush. However,
most shallow water sites have diverse communities of native plants. Beds of wild rice have even
been found in some areas of the river.
•
Fish – 31 species of fish from 11 families were found in the Rideau River during the study, and an
additional 3 species were found in tributaries of the Rideau (Appendix 5c). In addition, Oscars,
popular aquarium fish native to South America, were caught by anglers on two occasions in 1999.
Black crappie, rock bass, pumpkinseed and bluegill, all members of the sunfish family, were found at
most sites in the Rideau. Two species found during the study, the freshwater drum and the tadpole
madtom, had never before been recorded in the Rideau River. The freshwater drum may be a
recently introduced species. The common carp, another introduced species, was also found during
this study. Rainbow trout and brown trout, non-native species previously stocked in the Rideau, have
not been found for some years. The fish species diversity of the Rideau is similar to that of the Trent
River, in which 32 species were found during a study in 1999-2000.
•
Aquatic birds – 20 species of waterfowl and 3 other water bird species were found during the RRBP
(Appendix 5d). Heavy use of the Migratory Bird Sanctuary at Merrickville was observed. Waterfowl
traffic at this sanctuary was similar to that seen at other migratory bird sanctuaries in Prince Edward
County and in Lake Ontario around Wolfe Island.
1
•
Amphibians and reptiles – 28 species of amphibians and reptiles have been found along the
Rideau (Appendix 5e). These include 10 species of frogs, 6 species of turtles, 6 species of snakes
and 6 species of salamanders. Nineteen of these species were found during the Rideau River
Biodiversity Project. The most common were green frogs, bullfrogs, midland painted turtles and
snapping turtles. In contrast to some studies in southwestern Ontario, the RRBP did not find many
abnormalities, such as limb deformities in frogs.
•
Molluscs – 8 species of native freshwater clams and one introduced species (the zebra mussel)
were found in the Rideau River (Appendix 5f). Higher densities of live clams were found in the upper
reaches of the river, between Smiths Falls and Burritts Rapids, while larger numbers of dead clams
were found in the lower river, which is heavily colonized by zebra mussels.
•
Other invertebrates – there is a diverse community of other aquatic invertebrates in the Rideau
River (Appendix 5g). New species continue to be added as a result of ongoing research.
Limitations
Species lists may reflect the degree of interest in certain groups of organisms, and may change with
advances in knowledge.
Species richness alone does not convey information about the size or health of
populations.
3.2 Biological Indicator: Species at risk
Background
Wildlife conditions and trends can be used as an indicator of the overall health of the environment. The
occurrence of “species at risk” is one indicator of environmental problems. When a species is designated “at risk”
it indicates there are problems with its populations or habitat, and that the species requires protection or some
form of recovery action if it is to survive. In Canada, species at risk are identified at both national and provincial
levels.
At the national level, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC)
produces an annual listing of species considered to be endangered, threatened, or of special concern. The
numbers of species designated “at risk” nationally is likely greatly underestimated, however, as these numbers
represent only the handful of species that have so far been reviewed. The Committee on the Status of Species at
Risk in Ontario (COSSARO) evaluates species in Ontario, with the Ministry of Natural Resources (MNR)
producing a list of species considered endangered, threatened or vulnerable in this province. In addition, the
Natural Heritage Information Centre (NHIC) assigns provincial ranks to species, in order to set protection priorities
for rare species and natural communities.
1
Within Canada, almost half of the endangered and threatened species are found in the Great Lakes/St.
Lawrence Life Zone, one of seven landscape units that reflect the terrestrial ecozones of Canada. The Rideau
River is found within this Life Zone. Many of the endangered and threatened species in this zone are native to the
Carolinian deciduous forest ecosystem, and are at the northernmost limit of their range in southeastern Ontario
(hence their relative rarity). However, this zone has a long history of intensive agriculture, urbanization,
manufacturing and transportation, which have put great stress on the natural environment. Aquatic environments
in the Great Lakes and the St. Lawrence River have been particularly degraded, due to the introduction of nonnative species, heavy pollution, and the manipulation of watersheds for transportation purposes. While the
Rideau River has not been subject to the same intense industrialization as the Great Lakes and St. Lawrence, the
stresses associated with increasing urbanization and shoreline development may increase risks to species in this
area.
Results
Several species found along the Rideau River are considered uncommon to extremely rare in Ontario
(Table 4). Two bird species, the black tern and the least bittern are both considered rare and designated
“vulnerable” in Ontario, although the black tern is not considered at risk nationally. Nine other species, including
fish, birds, reptiles and molluscs, are considered rare to very rare in Ontario. No aquatic plant species, however,
are considered at risk in the Rideau. One plant found during the Rideau River Biodiversity Project, the eastern
mosquito-fern, is extremely rare in Ontario, but is thought to be an introduced (and not naturalized) species.
Table 4 Species at risk along the Rideau River.
CATEGORY
COMMON NAME
SCIENTIFIC NAME
Aquatic plants
Molluscs
Reptiles
Birds
Fish
Eastern mosquito-fern*
Black sand-shell
Ridged wedge-mussel
Blanding’s turtle
Black tern
Bufflehead
Greater scaup
Least bittern
Redhead
Eastern silvery minnow
Greater redhorse
Silver lamprey
Azolla caroliniana
Ligumia recta
Alasmidonta marginata
Emydoidea blandingii
Chlidonias niger
Bucephala albeola
Aythya marila
Ixobrychus exilis
Aythya americana
Hybognathus regius
Moxostoma valenciennesi
Ichthyomyzon unicuspis
COSEWIC
STATUS
MNR
NAR
VUL
SC
VUL
NAR
NHIC
S1
S3
S3
S3
S3B,SZN
S3B, SZN
S2B,SZN
S3B,SZN
S2B,SZN
S2
S3
S3
See Appendices 6 – 8 for explanation of status categories
* Considered introduced, not naturalized; NAR – not at risk; SC – special concern; VUL – vulnerable
S1 - Extremely rare in Ontario
S2B – Very rare in Ontario, breeding
S2 – Very rare in Ontario
S3B – Rare to uncommon in Ontario, breeding
S3 – Rare to uncommon in Ontario
SZN – Non-breeding migrants/vagrants
Sources: Canadian Museum of Nature, Friends of the Rideau Bird Sanctuary
1
The black rat snake, which occurs near the Rideau River and is considered rare in Ontario and
threatened both provincially and nationally, is a terrestrial species, and therefore not included in this listing of
species at risk in the Rideau River.
Limitations
Lists of species at risk reflect the degree of interest by researchers in certain groups of organisms. This
indicator does not convey information about the size or health of the populations. Increases in knowledge about
species and their habitats, or increased sampling effort could lead to increases in the number of species at risk
that are identified along the river.
3.3 Biological Indicator: Fish diversity and abundance
Background
Fish are important members of aquatic communities, and the health of fish communities is of great
concern on rivers such as the Rideau, where recreational fishing is a popular activity. Fish communities are
vulnerable to the effects of many human activities. The major stressors affecting freshwater fish populations are
changes to fish habitat through human activities, the presence of toxic substances, over-harvesting, and the
introduction of foreign species through deliberate or accidental means.
Aquatic habitat can be degraded or lost through channelization and the development of properties along
the shoreline. Construction activities and agricultural land management practices can lead to soil erosion, which
increases sediment transport into rivers, damages fish spawning areas, and reduces oxygen levels. Toxic
substances entering the environment can accumulate in fish tissues, causing acute effects such as death, or
other effects such as deformities, increased susceptibility to disease, and eventually the disappearance of the
species. Over-harvesting by commercial and recreational fisheries can also lead to the loss of fish species in
freshwater environments. The introduction of non-native species also threatens the diversity and abundance of
fish communities.
The diversity and abundance of fish are commonly monitored as a means of assessing the condition of
commercial and recreational fisheries, as well as the health of aquatic ecosystems. Standardized “index netting”
allows researchers to observe trends in fish populations over time. The Kemptville District Office of MNR conducts
Rideau River fisheries assessments, in partnership with the Surface Water Quality Branch of the City of Ottawa
(formerly RMOC). Six reaches are sampled between Smiths Falls and Ottawa (Table 5), with one or two reaches
sampled each year on a 4-year rotational basis. During these index netting surveys, fish are sampled using hoop
nets at a number of sites (ranging from 16 to 36) in each reach, and the “catch-per-unit-effort” (CUE) is calculated
for each fish species. Index netting on the Rideau River has been conducted with hoop nets since 1997; prior to
1
this, trap nets were used, so data cannot be compared between these two periods. However, the data collected
between 1997 and 2000 can be used as a baseline, against which to compare results in future years.
Table 5 Location of Fisheries Assessment Reaches on the
Rideau River.
SAMPLING REACH
LOCATION
Kilmarnock Reach
Smiths Falls to Merrickville
Andrewsville Reach
Merrickville to Burritts Rapids
Long Reach
Burritts Rapids to Long Island Locks
Eccolands Reach
Long Island Locks to Black Rapids
Mooney’s Bay Reach
Black Rapids to Hog’s Back Dam
Ottawa Reach
Hog’s Back Dam to Rideau Falls
(natural river channel)
Results
The Rideau River is home to a diverse fish community. Since 1883, 57 fish species have been reported
in the Rideau River and canal. By comparison, 64 species have been reported in the Ottawa River. However, not
all of the fish species reported in this historical record are still found in the Rideau, and some are rare. A fish
survey carried out in 1998 as part of the Rideau River Biodiversity Project identified 31 species of fish in the
Rideau River. This fish community is similar to that found in another similar canal system, the Trent Canal, where
32 species were found in 1999-2000. Twenty-four of these species were found in both the Trent and the Rideau
rivers.
Index netting results between 1997 and 2000 indicate that the highest total fish abundance was found in
the Kilmarnock reach (CUE = 48.0) (Table 6). The Andrewsville reach had the lowest abundance (9.2) and the
Long, Eccolands, Mooney’s Bay and Ottawa reaches had similar total fish abundance (19.8, 16.3, 16.3 and 18.6,
respectively). A total of 21 species of fish were netted during this program, with 13 or 14 species found within
each reach.
Overall, the three most abundant fish species in the Rideau River were bluegill, pumpkinseed and rock
bass. Bluegill were the most commonly sampled fish at the three upstream reaches (Kilmarnock, Andrewsville
and Long Reach), followed by pumpkinseed (Figure 11). In the lower three reaches (Eccolands, Mooney’s Bay
and Ottawa), pumpkinseed, rock bass and smallmouth bass were the most abundant.
1
Table 6 Catch per unit effort (CUE) (fish/net night) of fish species in the Rideau River, 1997-2000.
KILMARNOCK
1998
ANDREWSVILLE LONG REACH
1999
2000
ECCOLANDS
1998
MOONEY'S BAY
1997
OTTAWA
1999
0
0.04
0
0
0
0
TOTAL
CUE
0.04
2.72
0.75
1.03
1.25
0.38
0.05
6.18
18.5
5.33
7.94
2
0.62
0.7
35.09
Brown
Bullhead
Carp *
5.11
0.17
1.06
0.06
0.38
0.3
7.08
0.39
0.25
1.08
0.06
0.15
0.2
2.13
Channel
Catfish
Golden
Shiner
Greater
Redhorse
Largemouth
Bass
Muskellunge
0.06
0
0
0
0
0
0.06
0.06
0
0
0
0
0
0.06
0
0
0.11
1.5
0.23
0.05
1.89
3.17
0.46
1.25
0
0
0
4.88
0
0
0
0.19
0
0
0.19
1.72
0.33
0.22
0.31
0.31
0.05
2.94
10.17
1
5.11
5
1.92
4.7
27.90
1.39
0.17
0.50
2.44
5.54
9
19.04
0
0.38
0
0
0
0
0.38
0
0
0
0.31
0.15
0
0.46
0
0.08
0.33
1.63
3.62
3
8.66
0
0
0
0
0
0.05
0.05
0
0.04
0.08
0.13
0.23
0.05
0.53
1.06
0.04
0.03
0.31
0.46
0.1
2.00
0.67
0
0
0
0
0
0.67
3
0.17
1.08
1.13
2.31
0.3
7.99
48.02
9.21
19.83
16.32
16.3
18.55
128.23
FISH SPECIES
Alewife
Black
Crappie
Bluegill
Northern
pike
Pumpkinseed
Rock
Bass
Shorthead
Redhorse
Silver
Redhorse
Smallmouth
Bass
Tiger
Muskie **
Walleye
White
Sucker
Yellow
Bullhead
Yellow
Perch
TOTAL
CUE
* non-native species
** pike-muskellunge hybrid
Sources: MNR 2000; RMOC 2000
1
60
60
Eccolands Reach
Kilmarnock Reach
40
40
20
20
0
0
BC BG BB CC C GS LB M NP P
BC BG BB CC C GS LB M NP P
R RB SB W WS YP
60
R RB SB W WS YP
60
Andrewsville Reach
Mooney's Bay Reach
40
40
20
20
Percent abundance
0
0
BC BG BB CC C GS LB M NP P
R RB SB W WS YP
BC BG BB CC C GS LB M NP P
60
R RB SB W WS YP
60
Long Reach
Ottawa Reach
40
40
20
20
0
0
BC BG BB CC C GS LB M NP P
R RB SB W WS YP
BC BG BB CC C GS LB M NP P
R RB SB W WS YP
Legend
BC – black crappie
BG – bluegill
BB – brown bullhead
CC – channel catfish
C – common carp
GS – golden shiner
LB – largemouth bass
M – muskellunge
NP – northern pike
P – pumpkinseed
R – redhorse species
RB – rock bass
SB – smallmouth bass
W – walleye
WS – white sucker
YP – yellow perch
Figure 11 Percent abundance of fish species in 6 reaches along the Rideau River
(1997-2000 sampling period).
Sources: MNR, 2000; RMOC, 2000
Limitations
Sampling methods may be biased for certain species of fish. Comparison of CUE between different
systems is not possible unless identical methods are used. Different reaches are sampled in different years;
results may reflect conditions such as water levels in a given year.
1
3.4 Biological Indicator: Restrictions on fish consumption
Background
Many contaminants in freshwaters accumulate in the flesh of fish, although the amounts are variable
depending on the contaminant, the species of fish and their position in the food chain. The fish most likely to
contain high contaminant concentrations are predatory species and large fish. The Ontario Ministry of the
Environment, in partnership with the Ministry of Natural Resources, monitors the concentrations of harmful
pollutants in sport fish across Ontario, and publishes the results every 2 years in the Guide to Eating Ontario
Sport Fish. Changes in this indicator over time may indicate changes in overall environmental health.
Fish consumption restrictions are based on concentrations of a variety of contaminants, and vary
depending on the species and size of fish. More than 99% of restrictions on the consumption of sport fish from
inland locations, such as the Rideau River, are due to contamination with mercury. In contrast to the Great Lakes,
very few inland locations have been exposed to discharges of pesticides or other organic compounds in sufficient
quantities to cause fish consumption restrictions.
Mercury occurs naturally but is usually found at very low levels in water. Inputs from industry have
declined since the 1970s when actions to reduce mercury entering aquatic systems were initiated. Consumption
restrictions are put in place when the concentration of mercury in fish flesh exceeds 0.45 ppm, and total restriction
is recommended at 1.57 ppm. Children under 15 and women of childbearing age are advised to eat no fish
containing over 0.45 ppm mercury, and only 4 meals per month of fish with less than 0.45 ppm mercury.
The fish used to calculate consumption restrictions for the Rideau River are collected during fisheries
assessments conducted by the Surface Water Quality Branch of the City of Ottawa (formerly RMOC) and the
Kemptville District Office of the MNR. Separate fish consumption advisories are provided for fish from 3 reaches
of the Rideau River: from Smiths Falls to Merrickville, from Merrickville to Manotick, and from Manotick to Ottawa.
Some fish species were tested for mercury only, while others were tested for mercury, PCBs, mirex/photomirex
and pesticides.
Results
For most species tested, the maximum recommended number of meals per month was 8, regardless of
fish size (Table 7). However, restrictions of 4 or fewer meals per month were applied to larger specimens of
northern pike, largemouth bass, walleye, smallmouth bass, rock bass and yellow perch in some or all of the
reaches of the Rideau.
Overall, these consumption guidelines are similar to (or in some cases slightly more restrictive than) those
for fish of the same species and size in Upper Rideau Lake and the Trent River. For example, a maximum of 4
meals per month is recommended for northern pike (18” or larger) in the lower Rideau River, while the same
1
restriction does not apply to pike of any size in the Trent River, and only to larger pike (over 22”) in Upper Rideau
Lake. However, the consumption guidelines for the Rideau River are less restrictive than those for the Ottawa
River below Arnprior. For example, in the Ottawa River, restrictions of 4 meals per month are recommended for
12-14” walleye, smallmouth bass and black crappie, while in the Rideau, the same restrictions only apply to larger
smallmouth bass and walleye (and never to black crappie).
Trends in mercury concentrations in fish from the Rideau River vary between species. There appears to
have been a decrease in mercury concentrations in northern pike and smallmouth bass since the mid-1970s
(RMOC 1999). However, mercury levels in brown bullhead, walleye and largemouth bass have not declined
during this period.
Table 7 Fish consumption recommendations for the Rideau River, 2000-2001.
Reach
Species
Smiths Falls to
Merrickville
Northern Pike (1)
Largemouth Bass (2)
Rock Bass(1)
Yellow Perch (1)
Pumpkinseed (1)
Brown Bullhead (2)
6-8
Merrickville to
Manotick
Manotick to
Ottawa
Walleye (2)
Northern Pike (2)
Smallmouth Bass (2)
Largemouth Bass (2)
Rock Bass (2)
Yellow Perch (2)
Pumpkinseed (1)
Bluegill (1)
Black Crappie (2)
Brown Bullhead (2)
Carp (2)
Walleye (1)
Northern Pike (2)
Smallmouth Bass (2)
Rock Bass (2)
Yellow Perch (1)
Bluegill (1)
Black Crappie (2)
Brown Bullhead (2)
Carp (2)
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
Maximum recommended number of monthly meals
Fish Size (inches)
8 - 10 10 - 12 12 - 14 14 - 18 18 - 22 22 - 26 26 - 30
8
4
8
8
4
4
8
8
8
8
8
8
4
8
8
8
8
8
8
4
4
8
8
4
8
2
4
8
8
8
8
8
4
4
8
4
8
8
8
8
8
8
8
8
8
8
8
4
4
4
2
4
4
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
(1) tested for mercury only (2) tested for mercury, PCBs, mirex/photomirex and pesticides
Source: Guide to Eating Ontario Sport Fish, 2000-2001 (MOE, 2001)
1
>30
8
8
Limitations
Consumption guidelines may be based on different combinations of contaminants, making comparisons
between different sites or time periods difficult.
Guidelines are not available for all species at each site.
Information on trends in specific contaminant concentrations is limited, based on small sample sizes, and
available over different time periods for different sites.
3.5 Biological Indicator: Aquatic plant diversity and abundance
Background
Aquatic plants are critically important in river ecosystems. They slow currents and decrease wave action,
protecting shorelines. They play an important role in the recycling of nutrients, and some species remove
contaminants from water, through uptake or by promoting sedimentation. Aquatic plants create wetlands and
lake-like environments within rivers, providing food, shelter and sites for reproduction for fauna including
zooplankton, insects, molluscs, fish, reptiles, amphibians, waterfowl and semi-aquatic mammals.
Shallow eutrophic (nutrient-rich) lakes and rivers may exist in either of two stable states: one is a clearwater state associated with abundant aquatic plants, and the other is a turbid state with high algal biomass. Of
these two alternate states, the plant-dominated state is preferred, and considered to be indicative of a healthier
ecosystem.
Results
The Rideau River supports a rich community of aquatic plants. Between Smiths Falls and Ottawa,
approximately 70% (by area) of the Rideau River is less than two metres in depth, and these shallow areas
support dense beds of plants. Fifty-five species of submerged, floating-leafed and emergent aquatic plants were
found in the Rideau River by researchers involved in the recent 3-year Rideau River Biodiversity study.
Six permanent, long-term monitoring plots were established along the Rideau River in 1998 by
researchers at the Canadian Museum of Nature. A total of 30 species of submerged and floating aquatic plants
was found during 1998 and 1999, although the number of species found at each plot ranged between only 5 and
17 (Figure 12). There was considerable variation in plant species found at the different sites (Figure 13).
1
St.
t.
tric
Pa
S
nk
kS
le
tre
en
vil
rC
ck
rri
xte
Ba
Ba
Me
t.
15
k
c
Lo
's
nd
mu lls
Ed
a
sF
ith
Sm
20
1999
1998
10
5
Aquatic Macrophytes (# of species)
0
100
80
60
40
20
0
Distance above Rideau Falls (km)
Figure 12 Aquatic plant species richness, 1998-1999.
Source: Canadian Museum of Nature
Overall, the most common species were Vallisneria americana (Tape grass), Elodea canadensis
(Common waterweed), Ceratophyllum demersum (Coontail), Zannichellia palustris (Horned pondweed), Lemna
trisulca (Star duckweed), Nymphaea odorata (Fragrant white water lily), and Potamogeton richardsonii
(Richardson’s pondweed).
Myriophyllum sibiricum (Northern water milfoil) and Myriophyllum spicatum (the
invasive Eurasian water milfoil) were not generally abundant in the long-term monitoring plots. However, these
species of milfoil, as well as various pondweed species, particularly the introduced Potamogeton crispus (curly
pondweed), are extremely common in other parts of the Rideau River, particularly in the deeper navigation
channel. In fact, aquatic plants are so dense in the navigation channel that they are harvested every summer at
some sites.
Limitations
The permanent sampling sites are located in shallow areas only, and therefore do not reflect conditions in
deep areas in the navigation channel.
Plant abundance is described by percent cover rather than biomass so it
is difficult to compare the abundance of different plant species.
1
100
Smiths Falls
75
50
25
0
100
Edmund's Lock
75
50
25
0
100
Merrickville
75
50
25
0
100
Baxter Centre
75
Percent cover
50
25
0
100
Bank St.
75
50
25
0
100
St. Patrick St.
1998
1999
75
50
25
0
water lily
White
duckweed
Star
Pondweed
Horned
Tape grass
pondweed
Richardson's
Waterweed
Common
Coontail
Figure 13 Percent cover of dominant aquatic plants, 1998-1999.
Source: Canadian Museum of Nature
1
3.6 Biological Indicator: Aquatic plant harvesting
Background
Eurasian water milfoil (Myriophyllum spicatum) is an invasive introduced species, native to Europe, Asia
and North Africa. It was first recorded in Canada in Lake Erie in 1961 and was present in the Rideau Canal by
the late 1960s. This species of milfoil can grow in deeper water than most other species of aquatic plants. It is a
perennial plant, which spreads readily, and can become established from branch fragments.
Mechanical
harvesting and boat traffic may encourage its spread, by creating fragments that can colonize new areas.
Eurasian water milfoil produces thick growth at the water surface, forming dense floating mats that shade out
native plant species, and interfere with navigation and recreation.
Curly pondweed (Potamogeton crispus) is another introduced plant species, native to Eurasia, Africa and
Australia. It is commonly found in waters that are alkaline and high in nutrients, and spreads by producing burrlike winter buds that are distributed by water currents. Curly pondweed, like Eurasian water milfoil, produces
dense growth that interferes with navigation and recreation. When curly pondweed dies off in mid-summer,
decaying plants may sometimes result in drastic decreases in dissolved oxygen, and large releases of nutrients.
Although this invasive submergent plant is widespread in the Rideau River, the densest growth occurs in the
southern end of the Cataraqui portion of the Rideau Canal (above Kingston Mills).
The amount of plant material harvested annually from the Rideau River may be used as an indicator of
the extent of Eurasian water milfoil and curly pondweed problems in the Rideau. These invasive species are both
considered major “nuisance” aquatic plants along the Rideau Canal. Dense aquatic plant growth has been
removed from a few select areas of the navigation channel of the Rideau River for decades. In the past, (until
1991) the herbicides Reglone ‘A’ (diquat dibromide) and Aqua Kleen (2,4-D) were used to control plant growth in
some locations.
Parks Canada contracted out the annual cutting and removal of aquatic plants to the RVCA
(from 1971 to 1985) and has used private contractors since 1986. In addition, landowners and municipalities may
obtain permits from Parks Canada and hire contractors for plant removal, and unofficial harvesting (and probably
a limited amount of illegal herbicide use) occurs around private waterfront.
Results
Currently, submergent aquatic plants are cut and removed once or twice each summer, in 4 navigation
channel locations along the Rideau River (totalling 8 hectares) primarily between Smiths Falls and Burritts Rapids
(the “central sector”). Another six sites (about 45 hectares) are located in the “Ottawa reach”, the man-made
canal cut in downtown Ottawa between Hartwell locks and the Laurier St. bridge (including Dow’s Lake).
European water milfoil and curly pondweed dominate the plant material removed from the “central sector”
of the Rideau River (Figure 14).
In this region, the amount of plant matter harvested annually ranged
1
from 13 to 28 tons (or between 1.6 and 3.5 tons/hectare) between 1996 and 2000 (Figure 15). By contrast, no
harvesting of aquatic plants was necessary in the “Ottawa reach” until 1999. Dense growth of Eurasian water
milfoil was first noted there in 1998 and plant harvesting began in 1999. The amount of plant material removed
from the Ottawa reach is considerably higher; 349 tons of plant matter were harvested in 1999 and 173 tons were
harvested in 2000 (7.8 and 3.9 tons/hectare respectively). Areas of dense plant growth in the Ottawa reach were
almost entirely dominated by Eurasian water milfoil, although more than 10% of the total plant harvest was
actually composed of algae. The harvest of aquatic plants in the Ottawa reach was lower in 2001; although
figures are not yet available, it is estimated that the amount of plant material harvested dropped by about 40%
from 2000, possibly due to the effects on plants of the harvesting in the previous two years.
100
1999
80
60
40
20
0
100
2000
Percent of harvest
80
60
40
20
0
Smiths Falls
Detached
Smiths Falls
Combined
Old Sly's
Burritts
Rapids
Myriophyllum sp.
Potamogeton crispus
Vallisneria americana
Other
Figure 14 Dominant aquatic plants harvested from the navigation channel, 1999-2000.
Source: Parks Canada, Eastern Ontario Field Unit
Prior to 1999, when plant harvesting started in the Ottawa reach, Parks Canada’s annual budget for
aquatic plant removal on the entire waterway was less than $20,000. In 1999, more than $65,000 was spent for
harvesting in the Ottawa reach alone. Currently, the projected minimum annual budget for aquatic plant removal
is $100,000, of which $50,000 to $75,000 is for the Ottawa reach.
The sudden increase of aquatic plant growth (particularly milfoil) in the downtown canal cut (Ottawa
reach) may be linked to zebra mussel colonization, which has led to increased water clarity (and possibly higher
concentrations of available nutrients) in the lower Rideau. Warmer weather in the early spring and summer may
also play a role in this increased aquatic plant growth. The dominance of milfoil in this section may also be
1
partially attributed to winter draw down of the Rideau, which is thought to discourage other plant species. This is
somewhat speculative, however, as draw down is also considered to be a possible method of controlling milfoil
growth.
8
7
Figure 15 Annual aquatic plant harvest, 1996-2000.
Source: Parks Canada, Eastern Ontario Field Unit
Central sector
Ottawa sector
6
5
4
3
2
Plant harvest (tons per hectare)
Limitations
1
0
1996
1997
1998
1999
2000
This indicator may show general trends in the distribution or abundance of these invasive species, but
there is considerable yearly variation in aquatic plant growth due to differences in weather conditions. The amount
harvested might reflect changing management practices, such as the timing of harvesting, rather than real
differences in plant abundance. In addition, only one of the two contractors harvesting plants in the Rideau River
reports the composition of the harvest in any detail, making comparison of the two sections difficult.
3.7 Biological Indicator - Non-native species: Zebra mussels
Background
The zebra mussel (Dreissena polymorpha), is native to the Caspian Sea. It was likely transported to North
America in a ship’s ballast water, and was first identified in 1988 in Lake St. Clair, southern Ontario. Zebra
mussels are sedentary, and feed by filtering bacteria, algae, zooplankton and other organic particles from the
water. The zebra mussel multiplies rapidly, colonizes many different habitats, is tolerant of extremes of
temperature and dessication, and has few natural predators except a few species of shellfish-eating fish and
diving ducks. Zebra mussels also have effective dispersal methods. They are transported easily by natural water
currents, or by attaching to boats. This combination of traits has enabled the zebra mussel to spread rapidly,
producing dense colonies in freshwaters throughout much of eastern North America.
1
While some have suggested zebra mussels have a positive effect on lakes and rivers, because they
increase water clarity, these exotic mussels have numerous negative impacts. Apart from obstructing water
intake pipes and engines on motor boats, zebra mussels may have adverse effects on aquatic ecosystems. Zebra
mussels have been found to replace native mussels, to biomagnify toxic organic contaminants, and to cause
substantial oxygen depletion in some systems. Intense and selective filter feeding on natural phytoplankton
communities can result in an increase of other, possibly toxic algal species, and shifts in food webs which are
detrimental to fish populations.
Results
In 1990, the first occurrence of zebra mussel was reported in the Rideau River at Mooney’s Bay. Since
1993, zebra mussel distribution and density has been monitored by staff at the Canadian Museum of Nature, at
10 lockstations and 3 additional sites in the Rideau River (Figure 16). Between 1993 and 1995, the abundance of
zebra mussels on hard surfaces in the lower section of the Rideau between Kars and Ottawa increased by up to a
million-fold. Zebra mussel density has remained high in these areas since then, and the distribution and
abundance of zebra mussels may be increasing upstream of Kars.
3
5
9 24 29 35 61 74 83 88 89 91 98
100
2
1
1993
1000000
10000
1995
100
1
1000000
10000
1997
100
Number of mussels per m
1
*
1000000
10000
1999
100
1
*
a
w
tta
ls
O
el
tw
ck
ar
H
Ba
y
's
Ba
og
H
y'sids
neapd
oo Rn
M k la
acIs a
n
Bnl g ari
s
Lo M
id
rs
ap
Ka lson R
s
ho itt e
ic rr ill
N Bucdksv
rni
eor
Mmlys
EdS
ld
lls
O
Fa
ith
Sm
Figure 16 Zebra mussel distribution and density along the Rideau River, 1993-1999.
* no data available. Source: Martel et. al, 2001 (in press)
1
Since zebra mussels appeared in the Rideau, there has been a dramatic decline in populations of native
freshwater mussels. Zebra mussels colonize any available hard surface, including other mussel species (which
cannot survive heavy buildups of zebra mussels). Three native mussel species, which were commonly found in
the Rideau River have been virtually eliminated in a 30 km section that has been studied since 1993 (Martel et al.,
2001, in press). There is also evidence that zebra mussels are responsible for the decline in chlorophyll a
(suspended algae) which has been observed in the lower Rideau, downstream of Kars, in recent years.
3.8 Biological Indicators - Summary
While total species diversity is fairly high in the Rideau River (comparable to other rivers such as the
Trent), aquatic communities are typically dominated by a relatively small subset of species at any given location.
There are a number of rare species in the Rideau, but we know little about the size and condition of their
populations. Several introduced invasive species are of particular concern. Zebra mussel colonization has
caused a dramatic decline in native clam populations in the lower Rideau, and may have contributed to a decline
in suspended algae, and a sudden increase in the density of Eurasian water milfoil in the last few years (by
increasing water clarity in the deeper main channel).
•
Species diversity
The Rideau River supports a diversity of wildlife. The recent 3-year Rideau River Biodiversity Study identified 314
species of phytoplankton, 59 species of aquatic plants, 8 species of native clams, 28 species of amphibians and
reptiles, 34 species of fish and 23 species of aquatic birds.
•
Species at risk
Two species found along the Rideau River are considered “at risk’: the black tern and least bittern (rare, and
vulnerable in Ontario). Ten other species on the Rideau are considered rare in Ontario, although not at risk.
•
Fish diversity and abundance
Fisheries assessments indicate that the Rideau River is dominated by relatively few species of fish. Between
1997 and 2000, index netting in the six reaches along the river captured a total of 21 species of fish, but only 13
or 14 species within any reach. All reaches were dominated by a handful of species. Bluegill and pumpkinseed
dominated the 3 upstream reaches, while pumpkinseed, rock bass and smallmouth bass dominated the 3
downstream reaches. Fish abundance was highest in the wide, shallow Kilmarnock reach between Smiths Falls
and Merrickville.
•
Restrictions on fish consumption
The recommended consumption of most fish in the Rideau River is restricted to 8 meals per month, with the
exception of larger specimens of northern pike, largemouth and smallmouth bass, walleye, rock bass and yellow
perch, for which 4 meals per month or fewer are recommended. In general, these recommendations compare
favourably to those for fish in the Ottawa River, but are similar or slightly more restrictive than those for Upper
Rideau Lake and the Trent River.
1
•
Aquatic plant diversity and abundance
Thirty species of aquatic plants were found in 1998 and 1999 at six shallow sites along the Rideau River. Only 5
to 17 species were found at any one site, and a relatively few species dominated each site. The most abundant
species were tape grass, common waterweed, coontail, horned pondweed, star duckweed, white water lily and
Richardson’ pondweed.
•
Aquatic plant harvesting
Eurasian water milfoil and curly pondweed, two invasive introduced plant species, dominate deeper areas of the
Rideau River, and are harvested annually in a few locations to keep the navigation channel open. The amount
harvested between Smiths Falls and Burritts Rapids ranged from 13 to 28 tons between 1996 and 2000. Prior to
1999, no harvesting was carried out in the Ottawa region of the Rideau Canal. Since then, explosive growth of
Eurasian water milfoil has made harvesting necessary (349 tons in 1999 and 173 tons in 2000), increasing the
annual budget for plant removal by at least 5 times.
•
Non-native species: zebra mussels
Zebra mussels have rapidly colonized the Rideau River since they were first found in 1990. Their density remains
high in the lower section of the river, between Kars and Ottawa, and they continue to increase in abundance in
the upper section of the river between Smiths Falls and Kars. The colonization of the Rideau by zebra mussels
has been accompanied by the elimination of the native mussel species previously found there, and an increase in
water clarity due to a steep decline in the concentration of phytoplankton.
1
4.0 Stress Indicators - Introduction
__________________________________________________________________________________________
A wide range of human activities affect conditions on rivers, either directly or indirectly. Some are directly
associated with the river, such as boating, fishing, and other recreational activities. Other activities such as
urbanization, farming, industry, mining and logging are closely linked with conditions on rivers, although they may
occur some distance away in the watershed. Generally, these activities increase as human populations grow,
creating greater negative impacts on the health of rivers. The negative impacts of these various activities or
“stressors” include degradation of water quality due to discharges of nutrients or toxic compounds, deterioration of
natural shorelines due to shoreline development or heavy boat traffic, and detrimental effects on aquatic
communities due to water level manipulations.
A first step in improving conditions on a river such as the Rideau is to identify and monitor various human
activities that may put stress on the health of the river. A number of such “stress indicators” have been included in
this report. Trends in population growth and urban growth, permits for surface water withdrawals, boating traffic,
and water level manipulation (draw down) are presented. Information is also included on wastewater treatment
and agricultural activities along the Rideau River.
4.1 Stress Indicator: Population growth
Background
Population growth has a direct effect on the state of the environment. For rivers such as the Rideau,
increased population in the surrounding watershed leads to increased water use such as water withdrawal for
municipal water supply, industry and agriculture. Liquid wastes from wastewater treatment plants, urban
stormwater and industrial effluents are discharged to rivers in higher quantities. Shoreline property is developed,
leading to increased runoff of nutrients and toxic chemicals, and damage to near-shore aquatic habitats.
Recreational activities, such as fishing and boating also increase with population growth.
Results
In 1996, 822,116 people lived in municipalities entirely or partially within the Rideau River watershed
(Appendix 9). This represents a 6.8% increase in population since 1991. Approximately 88% of this population
lived in municipalities in the RMOC (now the City of Ottawa), through which the Rideau River flows.
Population figures from City of Ottawa assessment records give a more detailed picture of population
growth trends (Appendix 10). Between 1992 and 1997, the population of RMOC grew from 680,170 to 740,897,
an increase of 8.9%. Approximately 90% of this population growth was in urban areas of Ottawa. However, 55%
of the growth of RMOC population occurred in urban centres outside the Greenbelt. These urban centres outside
the Greenbelt (Kanata, Orleans, and the South Urban Centre) were designated in 1974, in the City of Ottawa’s
1
Regional Official Plan, to accommodate future urban growth. Between 1992 and 1997, 15% of Ottawa’s
population growth was in the South Urban Centre (in the area around the Rideau River). In this 5-year period, the
population of the South Urban Centre grew from 21,199 to 30,243, an increase of 43%.
Overall, the population of Ottawa is projected to increase by 61% between 1997 and 2021, to 1,193,000.
About 89% of this population will be located in urban areas of Ottawa.
Limitations
Population is reported at the municipal level; while some municipalities are entirely within the watershed,
others are only partially inside the watershed. Canadian census data are only collected every 5 years (and 2001
data is not yet available). Municipal boundaries have changed since the 1996 census (with the creation of larger
amalgamated municipalities) so comparisons with future population data may be difficult.
4.2 Stress Indicator: Urban growth and density
Background
The density of urban development can have important implications for the impacts of human population
on the environment.
Compact urban development uses existing infrastructure and land resources more
efficiently than dispersed urban development. Farmland and natural land, including forests and wetlands, is lost
as urban development spreads. The extent of urban development is not simply a reflection of population growth.
The growth of urban areas, which are largely residential, is related to the number of households (which is
dependent on population age structure as well as population size) and dwelling unit density.
Urbanization creates a number of stresses on the Rideau River, including shoreline encroachment, and
pollution from urban wastewater, runoff from paved roads and waste snow. Since most of the population of the
Rideau River watershed resides within the City of Ottawa, changes in the pattern of urbanization in this
municipality are an important indicator of potential stress on the Rideau River.
Results
The area of urbanized land in the City of Ottawa has increased more than ten-fold over the last century
(Figure 17,18). When the Greenbelt was established in 1961, almost half of the land within it was undeveloped
(Figure 17). By 1999, most of the land inside the Greenbelt had been developed. While most of the City of
Ottawa’s population is still located inside the Greenbelt, this proportion has been declining, and the proportion in
urban centres outside the Greenbelt has been increasing.
1
We apologize, but Figure 17 (showing urban development) is temporarily unavailable.
1
40000
30000
20000
10000
11
20
91
19
84
19
67
19
55
19
25
19
06
19
RMOC urban area (hectares)
0
(de
sig
)
ted
na
Figure 18 Urban area in the City of Ottawa (formerly RMOC), 1906-1991 (and designated for 2011).
Source: RMOC 1998
The largest land use in Ottawa is housing. In 1991, housing occupied 44% of the urbanized area in the
City of Ottawa, and about 80% of this residential land was occupied by single-detached homes. Commercial,
institutional and industrial land use made up 6.5%, 9.9% and 7.3% of Ottawa’s area respectively. Paved road
covered 13.1%, and 17.6% of Ottawa's area was open space or recreational areas.
The number of persons per household in the City of Ottawa declined from 4.8 in 1901 to 2.6 in 1991. As
a result, it takes more dwelling units to house Ottawa’s population, and therefore more urban land. Thus, while
population and urban development continue to increase, urban density is declining (Figure 19).
80
70
60
50
40
Persons per hectare
30
20
1900
1920
1940
1960
1980
2000
2020
Figure 19 Urban density in the City of Ottawa (formerly RMOC), 1906-1991 (and projected for 2011).
Source: RMOC 1998
1
If urban density in Ottawa had remained at the same level as in 1906, Ottawa’s urban population could
have been housed inside the Greenbelt until past the year 2011. The inevitable impact of decreasing urban
density is increased impacts, per capita, on the environment.
4.3 Stress Indicator: Permits to take water
Background
Demands on freshwater supplies in Ontario increase yearly with population increases and economic
growth. Water use has to be balanced against the goal of protecting aquatic ecosystems, and the needs of all
users must be considered. Permits to take water (PTTW) from both groundwater and surface water sources are
managed under the Ontario Water Resources Act (OWRA). Any water taking in excess of 50,000 litres per day
requires a permit, except for water taken for livestock or poultry, domestic use, or emergency fire fighting. Water
takings can be limited in the event of drought or severe water shortages.
Results
The number of active permits to take surface water from the Rideau River, or from its tributaries or lakes
within its watershed (for purposes other than wildlife conservation) has increased steadily since 1964, reaching 36
in 2000 (Figure 20).
40
30
20
10
0
# active permits to take surface water
1965 1970 1975 1980 1985 1990 1995 2000
Figure 20 Growth in the number of permits to take surface water from the Rideau watershed
(excluding conservation purposes) , 1964-2001.
Source: Ministry of the Environment
Currently, permits have been issued to allow the withdrawal of over 20 million litres of water per day, from
the Rideau River and its tributaries and other source bodies of water. However, about 84% of this water is
permitted to Ducks Unlimited, for wildlife conservation. Ducks Unlimited has 36 current permits that allow it to
1
maintain water levels in wetlands throughout the watershed, by means of water control structures such as low
earth dikes.
Water permits for other uses have increased from 318,220 litres per day in 1965 to 3,428,718,002 litres
per day in 2001 (Figure 21). Current permits in 2001 were for uses such as drinking water supply, storm water
management, road building, various commercial enterprises including quarries, slurry production and pipeline
testing, and agricultural and golf course irrigation.
1000
100
10
(millions of litres)
Maximum water withdrawals per day
1
1965 1970 1975 1980 1985 1990 1995 2001
Figure 21 Total volume of water permitted to be taken daily from the Rideau River, and tributaries or lakes
in the watershed (excluding wildlife conservation permits) 1965-2001. Note that the scale is logarithmic.
Source: Ministry of the Environment
Limitations
Permits to take water do not necessarily mean that the permitted quantity of water is actually taken.
Some permits are issued for the entire year, while others are for a limited number of days annually. Only users
taking more than 50,000 litres per day are required to obtain permits. Many of the permits are for water which is
held back to maintain water levels in wetlands, and so is not actually removed from the system.
4.4 Stress Indicator: Boat traffic
Background
Recreational boating has become increasingly popular in recent years. Greater numbers of motorized
boats creates demand for larger marinas and docking facilities, which results in more development of natural
waterfront. Boat traffic creates a number of adverse environmental impacts, such as waste emissions, disruption
of wildlife by noise and wake, shoreline erosion and subsequent hardening due to wake damage, and
resuspension of sediments and nutrients by propeller wash in shallow areas. Boat traffic is impeded by aquatic
1
vegetation in shallow areas; as a result, plant removal is necessary in some navigational areas, which may result
in the spread of invasive aquatic plant species. Boats are also involved in the spread of other invasive species
such as zebra mussels.
In a waterway such as the Rideau Canal, boat activity originates from local shoreline residents, marinas,
public boat ramps, as well as vessels navigating through the entire canal system from the Great Lakes through to
the Ottawa River. One method of assessing trends in boating traffic in such a waterway is to compare the
number of vessels passing through the various locks throughout the boating season.
Results
Overall, there is heavy boat traffic on the Rideau River, particularly during the peak summer months of
July and August. In recent years, there has also been high weekend boat traffic (from local boat use) early in the
season in some river sections. Based on data collected over the past 20 years, there does not appear to be an
overall trend towards higher boating traffic through the locks. However, the lock system is operating at or near full
capacity at times during the peak summer season, which may be acting as somewhat of a constraint to boat
traffic on the Rideau.
Between 1980 and 2001, there was considerable yearly variation in the total number of vessels passing
through locks on the entire Rideau waterway from Kingston to Ottawa (Figure 22). Boating traffic through locks
was higher between 1982 and 1990 than in the past decade. Declines in boating traffic in some years may be the
result of fee increases, gas price increases, lock closures, poor weather conditions, and changes in the general
economy.
105000
100000
95000
90000
85000
80000
# boats (annual total)
75000
70000
65000
1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000
Figure 22 Total annual boat traffic through all locks on the Rideau Canal, 1980-2001.
Source: Parks Canada (Eastern Ontario Field Unit)
1
In the north-flowing section of the waterway, between the Rideau Lakes and Ottawa, the total number of
vessels passing through locks has varied between 38,253 and 42,559 over the past 5 years (Figure 23). There
was an increase in boating traffic between 1996 and 1999, but total boat traffic dropped somewhat in 2000.
44000
42000
40000
38000
36000
Total number of boats through all locks
1996
1997
1998
1999
2000
Figure 23 Total boat traffic through northern Rideau canal locks, 1996-2000.
Source: Parks Canada (Eastern Ontario Field Unit)
4000
1996
1997
1998
1999
2000
3000
2000
a
taw
Ot
s
ell
rtw
ck
Ha
Ba
gs
s
Ho
pid
Ra
ck d
n
Bla Isla
s
ng
pid
Lo
Ra
inttss
lsror
s hBou
wNeic
Clo
le
vil
ck k
c
rri
Me arno
m s
Kilond
m
Ed lys
dS
d
Ol
ine
mb
Co hed
tac
lie
ma
De
a
on
Po
Number of boats through lock
Figure 24 Boat traffic through individual locks in northern Rideau Canal, 1996-2000.
Source: Parks Canada (Eastern Ontario Field Unit)
Some lockstations report substantially higher boat traffic than others (Figure 24) and boat traffic is lower
at the Ottawa locks, indicating that a considerable amount of boat traffic through locks on the Rideau River
originates within the river (and is not travelling through the entire canal system).
1
There are more than a dozen marinas and wharfs located on the Rideau River, between Smiths Falls and
Ottawa, offering services such as fuel, transient dockage, launching ramps and waste water pumping.
Limitations
The number of vessels passing through locks likely represents only a proportion of the total number of
boats using the river.
4.5 Stress Indicator: Water level manipulation – effects on fish
Background
Parks Canada manages water levels along the Rideau River, in order to provide a navigable channel and
to prevent serious flooding problems. Control structures with stop logs are located along the river at various lock
stations. During the navigation season (from the Victoria Day weekend in May, to mid-October), water levels are
controlled to maintain a water depth of at least 1.5 m in the navigation channel. At the end of the navigation
season, water levels are drawn down between Poonamalie (above Smiths Falls) and Hog’s Back in Ottawa. The
section between Long Island and Hog’s Back is “de-watered”, by dropping the water level by approximately 3 m.
The reason for this draw down is that it is not possible to remove the stop logs from the control structures during
winter and early spring (if necessary to prevent flooding) so they are removed prior to freeze-up. The river is then
refilled again in the spring, in preparation for the navigation season.
Fall draw down on the Rideau River has adverse effects on aquatic communities, due to the destruction
of littoral zone habitats in the river between Manotick and Ottawa. The over-wintering capability of fish, reptiles,
amphibians and aquatic mammals may be affected, particularly in areas where the draw down exceeds 2 m.
Aquatic plant survival may also be affected in areas where the riverbed becomes exposed. Fall draw down may
encourage spread of the introduced Eurasian water milfoil, which has become a problem for navigation in the
Rideau. The rate at which the water level is dropped in fall can affect the survival of fish, and the time at which
the river is refilled can affect spawning success for fish species that spawn in early spring. The Region of OttawaCarleton (now the City of Ottawa) began monitoring the fall draw down process in 1995, at 7 sites between Blacks
Rapids and Hog’s Back. This monitoring involved measuring the rate of water level change, and counting the
number of dead fish at each site.
Results
Since monitoring by the City of Ottawa began in 1995, the rate of fall draw down in the Rideau has varied
considerably (Table 8). In 1995, when the draw down occurred over a 24-hour period, there was high fish
mortality, particularly at Blacks Rapids. Following this finding, Parks Canada agreed to extend the draw down to
between 7 and 10 days. This resulted in a substantial reduction in fish deaths, particularly in 1997 when the draw
down took place over 16 days. However, in 1996 and 1999 there were short periods over which draw down was
rapid, and these periods were associated with high fish mortality. In 1999, a significant fish kill occurred in
1
Mooney’s Bay, with thousands of young-of-the-year pumpkinseed, bluegill and yellow perch left stranded in mats
of exposed vegetation as the water dropped. It is possible that higher fish kills went undetected in 1996 and
1998, as monitoring did not take place over the weekends, and large numbers of dead fish may have been eaten
by gulls and waterfowl.
The timing and rate of spring refilling of the river may have adverse effects on fish spawning. However,
the extent of this impact is not known. If the river is not refilled before the water warms up to the appropriate
temperature for fish spawning, fish such as northern pike, walleye and yellow perch may not be able to reach their
spawning areas along the shoreline, up creek tributaries, or in riffle areas. If flow is particularly rapid, fish such as
walleye, which are not strong swimmers, may be prevented from spawning. Also, in the area of the river below
Hog’s Back, some spawning shoals may be left out of the water, when water levels drop after the Hog’s Back dam
is closed in the spring.
Table 8 Fall draw down and related fish deaths in the Rideau River (between Blacks
Rapids and Hog’s Back), 1995-1999.
YEAR
DRAW DOWN
PERIOD
DRAW DOWN RATE
NO. OF SITES
WITH FISH KILLS
NO. OF FISH
MORTALITIES
1995
24 hours
300 cm/day
7
1469
1996
9 days
30 cm/day (first 2 m)
100 cm/day (last 1 m)
3
821
1997
16 days
15-30 cm/day
1
12
1998
9 days
35-50 cm/day
2
213
1999
9 days
avg 41 cm/day,
100 cm/day on day 6
n/a
12300 *
* Estimated
Sources: RMOC 1998, 1999, and 2000.
Limitations
Information is limited on the effects of fall draw down on the fish community. The effects of draw down on
other aquatic organisms have not been investigated. Monitoring has taken place only during weekdays, so fish
mortality may be underestimated.
1
4.6 Stress Indicator: Population served by wastewater treatment
Background
Municipal wastewater is one source of nutrients and toxins to surface waters. As many as 200 chemicals,
originating from human waste, industrial by-products, household detergents and general cleaners, have been
found in municipal sewage. In 1999, 73% of Canadians were served by municipal sewer systems. Most of these
sewage systems provided at least primary wastewater treatment, and the level of treatment is improving as
municipalities upgrade their wastewater treatment facilities.
The various levels of wastewater treatment are:
•
primary treatment – removes suspended solids, using physical processes
•
secondary treatment – removes suspended solids, and uses biological processes to break down organic
matter
•
tertiary treatment – in addition to secondary treatment, advanced biological or chemical methods are used to
reduce nutrient concentrations and remove some persistent toxic chemicals.
However, up to 25% of Canadians rely on septic systems to treat their sewage. In many areas, there are too
many septic systems for the land base, and many have been built too close to shorelines, or in unsuitable soil
conditions. In addition, many septic systems are faulty and poorly maintained. Septic system discharges can be
a source of groundwater (and ultimately surface water) contamination.
Results
In the Rideau River watershed, various types of wastewater treatment facilities serve approximately 82%
of the total population. The great majority are served by a tertiary treatment facility (Table 9), which typically
removes about 93% of phosphorus from the effluent. Most of this effluent is discharged to the Ottawa River, from
the R.O. Pickard tertiary sewage treatment plant that treats wastewater from Ottawa.
Table 9 Population served by wastewater treatment facilities in the Rideau
River watershed, 2000.
TYPE OF WASTEWATER
TREATMENT
Primary
Secondary
Tertiary (discharging to Ottawa R.)
Tertiary (discharging to Rideau)
No municipal wastewater facilities
POPULATION
SERVED
% OF TOTAL
POPULATION
200
7199
616,221
13,058
139,582
0.03%
0.9%
79.4%
1.7%
18%
Source: Environment Canada, Municipal Water Use Database (MUD)
1
Smaller facilities discharging into the Rideau or its tributaries include a small primary treatment facility at
Elizabethtown, two secondary treatment facilities located in Merrickville and Perth, and another small secondary
treatment plant serving the correctional facility at Burritts Rapids. Smiths Falls and North Grenville (Kemptville)
upgraded their wastewater facilities to provide tertiary treatment in 1993. However, many rural residents,
approximately 18% of the watershed population, have no municipal wastewater treatment, relying instead on
septic systems.
The performance of these wastewater treatment facilities varies (Table 10).
In general, much of the
phosphorus is removed from the wastewater (80.4% to 95.5%), and even higher proportions of suspended solids
and BOD (a measure of organic matter) are removed. Between 1995 and 2000, the average phosphorus
concentrations in effluent from the different facilities varied between 0.2 and 1.0 mg/L.
Table 10 Wastewater treatment plant performance, 1995 – 2000.
WASTEWATER
FACILITY
Perth
Smiths Falls
Merrickville
Burritts Rapids
Kemptville
POP’N CAPACITY
SERVED
X1000
3
M /D
6000
9000
924
275
3278
5.91
14.70
0.50
0.50
4.51
AVERAGE
FLOW
3
(X1000 M )
AVERAGE
REMOVAL
(%)
Daily Annual
P
SS
AVERAGE
EFFLUENT
CONCENTRATION
(MG/L)
BOD
P
SS BOD
6.58 2010.0
13.60 4940.8
0.48 177.2
0.11
38.8
2.71 978.5
80.4
95.5
93.0
87.4
95.4
86.4
96.4
91.7
94.0
98.0
83.3
96.8
93.9
95.1
98.9
0.4
0.3
0.2
1.0
0.2
19.1
10.2
10.9
18.3
2.1
14.7
4.7
6.3
14.5
0.8
NONCOMPLIANCE
(% MONTHS)
P
SS
BOD
0
25
0
40
3
5
19
3
17
0
8
7
0
10
0
Source: Ontario Clean Water Agency
Over this period, the Kemptville wastewater facility discharged the cleanest effluent (as measured by
average phosphorus, suspended solids and BOD concentrations) and almost always complied with the effluent
criteria for a plant of its type. The Burritts Rapids facility, by contrast, discharged effluent with the highest
phosphorus concentration, and frequently did not comply with effluent criteria. However, the amount of water
discharged from this facility is small by comparison with the other wastewater treatment plants.
Limitations
This indicator is based on municipal population, and some municipalities are only partially within the
Rideau River watershed. Urban wastewater treatment is not necessarily a guarantee that the treated wastewater
is free of contamination.
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4.7 Stress Indicator: Agricultural activities
Background
Agricultural activities can have a number of impacts on aquatic systems. Improper management of
manure, commercial fertilizers and pesticides can lead to increased nutrients entering waterways, as well as
contamination by bacteria, viruses, trace elements and organic substances. Poor agricultural practices can also
lead to soil erosion, affecting shorelines and aquatic ecosystems. Agricultural pollution originates from both point
sources and diffuse sources. Point sources of agricultural pollution arise from specific, identifiable sources, such
as manure from livestock allowed access to rivers. However, most agricultural sources of pollution are diffuse,
and harder to identify (and regulate). Diffuse agricultural pollution originates from farmland as a whole, through
surface runoff and groundwater.
Results
In 1996, there were 3525 farms, covering 326,901 hectares (40% of the total land area), in municipalities
at least partially within the Rideau River watershed. Almost half of this farmland, 144,539 hectares, was found on
1709 farms in the 13 municipalities bordering the Rideau River (below Smiths Falls) or its major tributaries the
Jock River and Kemptville Creek (Appendix 11).
Within these 13 municipalities (which are most closely associated with the Rideau River as it flows
between Smiths Falls and Ottawa), farmland covered 40% of the total land area (Appendix 14), and
approximately half of the farmland was planted with crops, and one-quarter was used for pasture (Figure 25).
Figure 25 Land use on farms in municipalities bordering the Rideau River and its tributaries, 1996.
Source: Statistics Canada Agriculture Census, 1996
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Commercial fertilizer was applied to approximately 30% of the total farmland, while manure was applied
to approximately 10% of the land. (Figure 26). Herbicides were used on approximately 20% of the farmland, but
insecticides and fungicides were used on a relatively small area (roughly 4% and 1% of the land, respectively).
Irrigation was rare: less than 700 hectares were reported as being irrigated.
Figure 26 Area of farmland on which fertilizers, pesticides and irrigation were used in
municipalities bordering the Rideau River and its tributaries, 1996.
Source: Statistics Canada Agriculture Census, 1996
Sixty percent of the livestock raised in these municipalities were cattle. Pigs and sheep made up 17%
and 18% of the total livestock, while horses accounted for only 6% (Figure 27). Overall, 53% of farms in these
municipalities raised cattle, with an average of 30 cows per farm (Appendix 15). About 24% of farms reported
owning horses (approximately 6 horses per farm). Pigs and sheep were raised on far fewer farms (5% and 8%
respectively), but the number of animals per farm was considerably higher (90 pigs per farm, and 59 sheep per
farm, on average). The density of pigs per farm varied considerably between municipalities. Farms with pigs in
Nepean and Osgoode reported high animal densities (320 and 240 pigs per farm on average, respectively), while
seven municipalities (Beckwith, Gloucester, Kitley, Montague, Oxford-on-Rideau, S. Gower and Wolford)
averaged less than 10 pigs per farm.
Cattle continue to graze to the water’s edge on some farmland along the Rideau River. This practice
contributes to pollution of the river with both nutrients and potentially harmful microorganisms. However, the full
extent of this problem will not be known until a shoreline characterization study is carried out along the Rideau.
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Grants are currently available to rural residents in the City of Ottawa (through the Rural Clean Water Program), to
assist with projects for animal waste management and fencing to restrict livestock access to watercourses.
However, information on grants that have been awarded is considered confidential information, so it may be
difficult to assess the impact this program has on water quality in the Rideau River.
Figure 27 Number of livestock in municipalities bordering the Rideau River and its tributaries, 1996.
Source: Statistics Canada Agriculture Census, 1996
Limitations
Agricultural census data are collected at the municipal level, and not all municipalities are entirely within
the watershed. In addition, recent municipal amalgamations will create difficulties for comparisons between this
baseline data and future census data. Agriculture census data is not available free of charge. The most recently
available data is from the 1996 census.
Stress Indicators - Summary
________________________________________________________
Human population is increasing within the Rideau River watershed, particularly within the City of Ottawa
along the lower Rideau. The proportion of Ottawa’s population living in urban areas outside the Greenbelt is
increasing, and urban density is decreasing. As a result, the impacts of human activities on the health of the
Rideau may increase in the future, as more of the watershed is developed. However, these impacts will depend
on many factors, such as the type and quality of development that occurs. Improvements in planning and in
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urban infrastructure such as sewage treatment and storm water management may mitigate some of the
environmental impacts associated with population growth.
A limited number of stress indicators is included in this report. The choice of indicators is a reflection of
the availability of information within a short time frame, and does not imply that these indicators are necessarily
those that have the greatest impacts on conditions in the Rideau River. For some of these indicators, such as the
various agricultural activities in the watershed, historical trends are not given; the information provided serves as
a starting point, or “baseline” against which we can compare conditions in future reports on the state of the
Rideau River. In most cases, more information is required about these stress indicators, or the links between
them and conditions on the Rideau River.
•
Population growth
The population in municipalities within the watershed increased by 6.8% between 1991 and 1996. About 88% of
this population lived within the City of Ottawa. In a similar period, the population of the City of Ottawa grew by
8.9%, and it is projected to rise by 61% between 1997 and 2021.
•
Urban growth and density
Within the City of Ottawa, urban development has occurred primarily outside the Greenbelt, since 1999. The
population in the South Urban Centre of Ottawa grew by 43% between 1992 and 1997. Urban density is
declining, so it takes increasingly more land to house a given population size.
•
Permits to take water
The number of permits to take surface water from the Rideau watershed is increasing. Water uses include
drinking water supply, irrigation, and various commercial enterprises. Many of the permits issued to take water
from the Rideau watershed, however, are for water which is held back for wetland conservation purposes.
•
Boat traffic
There is heavy recreational boat traffic on the Rideau during the summer, although boat traffic through the
lockstations does not appear to be increasing.
Much of the boat traffic appears to originate along the shores of
the Rideau, from more than a dozen wharfs and marinas between Smiths Falls and Ottawa, as well as properties
along the river.
•
Water level manipulation (draw down)
Rapid draw down of the Rideau River in the fall has been found to cause high fish mortality in the lower section of
the Rideau River. Fall draw down likely has negative effects on other aquatic wildlife, but these (as well as the
effects of refilling the river in spring on fish spawning) remain to be investigated.
•
Population served by wastewater treatment
Nearly 80% of the population within the Rideau River watershed is served by one tertiary wastewater treatment
facility, which discharges into the Ottawa River. Less than 3% is served by other wastewater facilities that
discharge into the Rideau River or its tributaries. However, many rural residents (about 18% of the watershed
population) rely on septic systems to treat wastewater.
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•
Agricultural activities
About half of the farmland in the Rideau River watershed is located in the municipalities bordering the Rideau
River. In 1996, this agricultural land covered about 40% of the total land area. About 50% of the farmland was
used for crops, and about 25% was used for pasture. Over 40% of the land had commercial fertilizer or manure
applied to it, while about 20% had herbicide applications. Cattle continue to have access to the shoreline in
some areas along the Rideau River.
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Data Gaps
A number of potential indicators that were originally selected for inclusion in this report, were omitted
because data was not available. In some cases, this was due to the short time available for the preparation of
this report and in other cases the research still needs to be carried out. Some of these data gaps are listed
below:
Water Quality/Quantity Indicators
•
Water clarity
The Canadian Museum of Nature measures water clarity by taking Secchi depth readings, as part of their water
quality sampling program. However, these data were not available within the time frame of this report.
•
Groundwater quality and quantity
The Ministry of the Environment has monitored a number of groundwater wells in the Rideau watershed in the
past, but no data are available on these historical monitoring wells. However, a new Provincial Groundwater
Monitoring Network is currently being set up. Ten monitoring wells are being established within the Rideau River
watershed. Daily water level data will be accessible on-line, and water quality testing will be done twice yearly.
Biological Indicators
•
Individual species
Apart from invasive species (zebra mussels, Eurasian water milfoil and curly pondweed), no individual species
have been listed as biological indicators. A few species were considered and rejected, because they were too
rare, too common, or not present throughout the system. These included:
- Common loon - common in some areas, non-existent in others;
- Bull frog - not restricted by habitat, number may be more related to poaching, therefore not a good indicator of
habitat conditions;
- Western chorus-frog - not sufficiently common or widespread;
- Two-lined salamander - too rare due to limited habitat along the Rideau;
- Painted turtle - too common;
- Northern water snake - too common.
•
Species at risk
There is limited information available on the conditions of species at risk in the Rideau River.
Aquatic and Shoreland Habitat Indicators
•
Acreage of wetlands of various classes along the river, percent of watershed that is forested
Wetlands and forest cover have been mapped in Ontario by MNR, which has provided these maps to RVCA.
However, neither organization was able to extract area data for the Rideau River watershed from their GIS in
order to provide it for this report (due to time and budget constraints).
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•
Shoreline characterization
Shoreline development has been identified as one of the main stressors on the Rideau River.
Shoreline
development reduces the diversity and quality of riparian habitats as well as shallow littoral zone habitats within
the river. The number of households/buildings along the Rideau shoreline was suggested as an indicator. This
information is not currently available. The Rideau Waterway Land Trust Foundation keeps a database listing
every piece of waterfront property along the waterway and its features, but could not provide any information for
this report. The RVCA is expected to begin a shoreline characterization study along the Rideau River in the
spring of 2002.
Recommendations
The scope of the report
One of the chief difficulties encountered in the preparation of this report involved differences in the scale
of the various indicators. Some indicators, such as water quality parameters, are clearly measurable within the
boundaries of the Rideau River. However, others are not so easily constrained to within the banks of the river.
Some species for example, require both aquatic habitat found within the river, and some portion of the land along
its shores. Many stress indicators, such the area of land used for urban or agricultural development should be
considered at a much larger scale.
Since rivers are so closely linked to their surroundings, it is clearly appropriate to consider the
surrounding land area and connecting water bodies. An important goal should be to integrate the monitoring and
reporting on the state of the Rideau River with that of the Rideau Lakes, the Tay and Jock Rivers and Kemptville
Creek. Therefore, the Rideau River SOE report should be eventually expanded to encompass the entire Rideau
River watershed.
A number of other recommendations arose during the preparation of this report. They range from general
suggestions for the gathering and management of data, to specific ideas for additional indicators that should be
included in future reports, and areas of research and monitoring that should be given high priority:
Data coordination, storage and management
•
Work out agreements whereby the various organizations that perform research and monitoring provide
information for selected indicators on an on-going basis, and arrange for the information to be organized and
expressed in a manner that is consistent with the SOE reporting format. For example, rather than supplying a
large database of raw data, organizations could provide a summary report, figure or table.
•
Establish a location (and identify a host organization) which can house data and updated it on an on-going
basis. This organization would ideally have a Geographic Information System (GIS) in which ecological and
biogeographical information can be collected and analyzed.
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•
Coordinate timing of Rideau SOE reports to allow the incorporation of data from other source reports (ex.
Fisheries Assessment 5-year summaries; Canadian Census).
Additional indicators
•
Continue to investigate the use of individual wildlife species as indicators. Assessing the condition of key
indicator species, or rare species populations found in the Rideau could help to pinpoint areas requiring
protection.
•
Future SOE reports should incorporate information on management responses such as:
- Implementation of watershed management plans
- Creation of protected lands
- Fish habitat protection or restoration work
- Stormwater management
- Storm sewer replacement
- Changes to canal operational procedures
- Programs such as the Rural Clean Water Program
•
Investigate the possible use of composite indices for future SOE reports. For example, the Canadian Council
of Ministers of the Environment is currently developing a composite metals index, which might simplify
comparisons between different periods, and between different systems.
•
Expand the Rideau River SOE report to include social and economic indicators.
Research and monitoring
Research and monitoring along the Rideau River should be integrated with work being done on the other
water bodies within the watershed. A number of areas requiring further research and monitoring were identified
during the preparation of this report. Some of the key projects that should be given priority include:
•
Shoreline characterization survey.
•
Increased research, monitoring of algae, particularly in shallow littoral zone areas (toxic algae, mat-forming
algae), and associated concerns such as dissolved oxygen depletion during decay of algal mats and plants.
•
Research into changes in aquatic plant community in the lower Rideau (monitoring of plant growth in
navigation channel; better reporting of composition of harvested plants).
•
Research into effects of water level manipulations on fish spawning, and on overwintering of aquatic wildlife.
•
Nutrient apportionment study, to identify the major sources of nutrients to the Rideau River.
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