Disentangling Impacts
of Climate & Land Use Changes
on the Quantity & Quality of River Flows
in Southern Ontario
by
Trevor Dickinson & Ramesh Rudra,
Water Resources Engineering
University of Guelph
Acknowledgements
 Agencies
 NSERC, OMAF & Environment Canada
 Personnel
 Barry Smith - Retired Program Manager, Water
Survey of Canada
 Golmar Golmohammadi – Post Doctoral Research
Fellow
 Arezoo Amili – Former Graduate Student
 Akul Bhatt – Undergraduate Student Assistant
River Flows Have Changed
Average Monthly Flow Hydrographs
1916-1925
2004-2013
120
100
Flow
80
60
40
20
0
Dec
Jan
Winter
Feb
Mar
Apr
Spring
May
Jun
Jul
Summer
Aug
Sep
Oct
Fall
For Rural Watersheds like the Moira River at Foxboro:
winter flows have increased, spring flows have decreased,
& summer flows have remained unchanged.
Nov
Average Monthly Flow Hydrographs
2004-2013
1916-1925
1963-1972
8
7
6
Flow
5
4
3
2
1
0
Dec
Jan
Winter
Feb
Mar
Apr
Spring
May
Jun
Jul
Summer
Aug
Sep
Oct
Nov
Fall
For a highly Urbanized Watershed like the Don River at Todmorden:
winter flows have increased, spring flows have decreased,
& summer flows have greatly increased.
Monthly & Annual Precipitation
has remained unchanged.
Average Annual Precipitation (mm)
1200
1000
800
600
400
200
0
1940
1950
1960
Nith at New Hamburg
Moira near Foxboro
Linear (Cedar Creek at Woodstock)
1970
1980
Grand at Brantford
Linear (Nith at New Hamburg)
Linear (Cedar Creek at Woodstock)
1990
2000
Cedar Creek at Woodstock
Linear (Grand at Brantford)
Linear (Moira near Foxboro)
2010
What’s Going On?!
Possible causes of changes in the river
flows include:
- Changes in Climate, and/or
- Changes in Land Use
i.e. Urban Development
How Has Our Climate Changed?
Temperatures Have Risen
- mostly in the Winter
Annual Temperature Trends
Changes in Winter Mean Minimum Daily Temperature
Annual Temperature Trend Slopes
Rates of Increase in Temperatures
Celsius degrees per 100 years
Extreme Daily Minimum - 3.5 to 4.0
Mean Daily Minimum
-
2.0
Mean Daily
-
1.5
Mean Daily Maximum
-
0.5
Extreme Daily Maximum - 0 to – 0.5
Temperature Trends
So …
Temperatures have been increasing
somewhat steadily in Ontario,
- perhaps for up to and at least 150 years!
Winter temperatures have been rising at the
greatest rate, suggesting that winter
hydrology may have been impacted more
than summer hydrology.
The Frequency of Frost – Free Days
has Increased Exponentially
Frost-Free Days
Number of Frost-Free Days versus Mean Daily Minimum
Temperature per Winter for 7 Weather Stations
Number of Frost-Free Days per Winter
1200
80
1000
800
600
400
200
0
70
60
+ 15 days in
60 years
50
40
+ 5 days in 60
years
30
+ 1 day in 60
years
20
WMDMT
10
y = 115.67exp(0.1729x)
R² = 0.9496
0
-25
-20
-15
-10
Winter Mean Daily Minimum Temperature (°C)
-5
0
Frost-Free Days
 As winter mean daily minimum temperatures
have been rising steadily, frost-free days have
been increasing exponentially.
 Might snowmelt, which is related to degree-days,
also have been increasing exponentially?
There Has Been a Shift
in Winter Precipitation
from Snowfall to Rainfall
Changes in Winter Rainfall
Changes in Snowfall
Changes in Winter Precipitation
Total Precipitation
Rainfall
Snowfall
Total Precipitation
Snowfall
Rainfall
Total Precipitation
Rainfall
Snowfall
Increased
Winter
Temperature
Shift from Snowfall to Rainfall
(i.e. fewer Snow Days & Less
Snowfall,
& more Rainy Days & Winter
Rainfall)
Increased
Number of
Frost-Free
Days
What about Impacts on Snowpacks,
Winter Runoff & Infiltration
Likely Impacts I
Rising Winter
Temperatures
Increased Winter Snowmelt
Increasing
Number of
Frost-Free
Days
Likely Impacts II
Increased
Winter
Snowmelt
Increased Winter Surface
Runoff and/or Increased Winter
Infiltration
Increased
Winter
Rainfall
More Impacts I
Increased
Winter Tile Flow
Increased Winter
Infiltration
Increased Winter
Groundwater
Recharge
More Impacts II
Increased
Winter Surface
Runoff
Increased Winter Streamflow
Increased
Winter Tile Flow
& Recharge
And More
Increased
Winter
Snowmelt
Decreased
End-of-Winter
Snowpack
Decreased
Snowfall
Decreased
Snowmelt
Floods
Average Daily Flow Hydrographs
1916-1925
2004-2013
160
140
100
80
60
40
20
0
Dec
Dec
Dec
Jan
Jan
Jan
Feb
Feb
Mar
Mar
Mar
Apr
Apr
May
May
May
Jun
Jun
Jun
Jul
Jul
Aug
Aug
Aug
Sep
Sep
Oct
Oct
Oct
Nov
Nov
Flow (cms)
Flow (cms)
120
Winter
Spring
Summer
Moira River at Foxboro
Fall
Rural Streamflows
So …
for Ontario Rural Watersheds,
changes in winter climate have:
- increased winter streamflows
and
- decreased spring runoff/freshettes.
Water Quality Impacts
What about Water Quality Impacts
Are we now seeing more frequent and greater:
- Field & Streambank Erosion,
- Stream Sediment Loads, and
- Nutrient Loads.
in rural watersheds during the winter?
Have these loads become smaller and less
frequent during spring snowmelt events?
What about Impacts of
Urban Development?
Average Monthly Flow Hydrographs
2004-2013
1916-1925
1963-1972
8
7
6
Flow
5
4
3
2
1
0
Dec
Jan
Winter
Feb
Mar
Apr
Spring
May
Jun
Jul
Summer
Aug
Sep
Oct
Nov
Fall
For a highly urbanized basin like the Don River, winter flows
have increased & spring flows have decreased likely as a
result of both Climate Change & Urban Development.
In addition, the summer flows have increased significantly in
volume …
Average Daily Flow Hydrographs
1915-1925
1963-1972
2004-2013
35
30
Flow (cms)
25
20
15
5
0
Dec
Dec
Dec
Jan
Jan
Jan
Feb
Feb
Feb
Mar
Mar
Mar
Apr
Apr
May
May
May
Jun
Jun
Jun
Jul
Jul
Jul
Aug
Aug
Aug
Sep
Sep
Sep
Oct
Oct
Nov
Nov
Nov
Flow (cms)
10
Spring
Summer
Fall
… and in frequency on the Don River at Todmorden.
What’s going on?!
Mean event runoff coefficient
Runoff Coefficients
1.0
0.8
0.6
0.4
0.2
0.0
April
May
Before Urbanization

June
July
Initial Urbanization
August
September
October
Significant Urbanization (50%)
Streamflow Volumes
So …
in Ontario urban watersheds:
- urban development has augmented the winter
and spring climate change impacts; and
- summer flow volumes have increased
dramatically, in volume and frequency, these
impacts being completely due to urban
development.
Impacts of Urbanization on
River Water Quality
Are we seeing more frequent flushes and greater
volumes of:
- streambank erosion
- suspended sediment loads
- Chlorides and other pollutants
- sewage bypasses
???
Conclusions
River flows have changed in Southern Ontario:
- in winter and spring, primarily due to climate
change; and
- during the summer, primarily due to urban
development.
Questions
Water Management Questions
What do we do about the changes in river flows
- in urbanized and urbanizing watersheds?
How have these changes modified water quality,
and what do we do in that regard?
Questions
???
Monthly Average Flow Hydrograph
1916-1925
2004-2013
120
100
Flow
80
60
40
20
0
Dec
Jan
Winter
Feb
Mar
Apr
Spring
May
Jun
Jul
Aug
Summer
Moira River at Foxboro
Sep
Oct
Fall
Nov
Monthly Average Flow Hydrograph
2004-2013
1916-1925
1963-1972
8
7
6
Flow
5
4
3
2
1
0
Dec
Jan
Winter
Feb
Mar
Apr
Spring
May
Jun
Jul
Aug
Summer
Don River at Todmorden
Sep
Oct
Fall
Nov
Dec
Dec
Dec
Jan
Jan
Jan
Feb
Feb
Mar
Mar
Mar
Apr
Apr
May
May
May
Jun
Jun
Jun
Jul
Jul
Aug
Aug
Aug
Sep
Sep
Oct
Oct
Oct
Nov
Nov
Flow (cms)
Flow (cms)
Daily Average Flow Hydrograph
1916-1925
Winter
Spring
2004-2013
160
140
120
100
80
60
40
20
0
Summer
Moira River at Foxboro
Fall