Stream Ecology (NR 280)
Topic 13 – Human Impacts
Threats to rivers
Impacts of Urbanization
Consequences for Lake Champlain
Threats to Rivers
• Habitat alteration
– Altered hydrology: too little, too much
– Channelization: confined flow
• Pollution
– Point sources: WWTPs, industry
– Non-point sources: land uses
– Atmospheric deposition
• Invasive and nuisance species
• Exploitation
• Climate change
Index of Biotic Integrity
Framework for thinking about stream degradation
Urbanization
A case study in human impacts
Sprawl is dispersed, automobile-dependent
development outside of compact urban and
village centers along highways and in rural
countryside.
The US at Night (1993 vs 2001)
Dense 1993
Fringe 1993
Dense 2001
Fringe 2001
The National Geographic Society (2001)
Urban Sprawl in New England
• growth
• fragmentation
• corridors
The National Geographic Society (2001)
The value of natural areas…
…promotion of ‘infiltration’
Rain
ET
Infiltration
Surface runoff
Groundwater
Perspectives on impervious areas…
…rural (near Underhill, VT)
Perspectives on impervious areas…
…suburban (Butler Farm, S. Burlington)
Perspectives on impervious areas…
…commercial (University Mall)
Perspectives on impervious areas…
…urban (downtown Burlington)
Perspectives on impervious areas…
…where we are now!
Sprawl &
Impervious
Cover
Agriculture
Parks, golf courses, cemetaries
Open urban land
Residential (2 acre)
Residential (1 acre)
Residential (1/2 acre)
Residential 1/4 acre)
Residential (1/8 acre)
Institutional
Residential (townhouse)
Residential (multifamily)
Light Industry
Commercial
Mean
SE
0
20
40
60
80
Impervious area (%)
Center for Watershed Protection 2003
The problem of impervious areas…
…impediments to ‘infiltration’
Rain
ET
Infiltration
Surface runoff
Groundwater
Stream flow (cubic feet per sec)
Development & Stormwater Quantity
• Higher highs/lower lows
• Intensification/flashiness
• Flow regime modification
Rainfall
Runoff - undeveloped
Runoff - developed
Runoff – “managed”
Time (hours)
Runoff as a function of Imperviousness
Center for Watershed Protection (2003) after Schueler (1987)
Urban Stream Channel Evolution Process
Stage
I
II
(Incision)
III
IV
(Aggradtion)
V
Source: VTDEC (Vermont Department of Environmental Conservation). 2005. Stream geomorphic assessment handbook:
Phase 1 & 2 Protocols. Vermont Agency of Natural Resources Publication.
The problem of impervious areas…
…sources of pollutants
Fertilizers
Herbicides
Pesticides
E-Coli
Oil
Growth has been rapid
Sources of P to the Lake
Modified from Troy et al. (2007)
Phosphorus
concentration trends in
Lake Champlain
State of the Lake Report, 2012 (LCBP)
Typical
Pollutant
Concentration
Ranges
State of Maine (1995)
The “Urban
Syndrome”
Wenger 2008 (SUSE2)
Impacts of
Impervious
Area
Center for Watershed Protection (2003) as noted.
Generalized Framework
Sprawl, impervious area, & impairment
Thomas Schueler (2008)) Do not use without permission.
Effects of Development
• Impairment of freshwater resources
– Rivers: ~30% of 3.5 million miles (17% surveyed)
– Lakes: 37% of 41 million acres (42% surveyed)
• Sources of impairment (in priority order)
–
–
–
–
–
–
–
–
–
–
Agriculture (lakes)
Municipal point sources
Urban runoff/Stormwater
Unspecified NPS
Industrial point sources
Land disposal
Hydro/Habitat modification
Resource Extraction
Riparian disturbances
Forestry operations
US/EPA 1995, Burton and Pitt (2002)
Effects of Development
• Impairment of freshwater resources
– Rivers: ~30% of 3.5 million miles (17% surveyed)
– Lakes: 37% of 41 million acres (42% surveyed)
• Sources of impairment (in priority order)
–
–
–
–
–
–
–
–
–
–
Agriculture (lakes)
Municipal point sources
Urban runoff/Stormwater
Unspecified NPS
Industrial point sources
Land disposal
Hydro/Habitat modification
Resource Extraction
Riparian disturbances
Forestry operations
Urban-related
US/EPA 1995, Burton and Pitt (2002)
‘Natural’ Stream Form
Upper Allen and Sucker Brooks
Urban Stream Form
Englesby Brook
Healthy Stream Substrate
Impaired Stream Substrate
‘Natural’ Stream Biota
Impaired Stream Biota
Reasons for hope...
…recovery from urban impacts
Increasing Sheer Stress
Decreasing Sheer Stress
Fitzgerald et al. (2012)
What we know…
• Connected impervious area
is a major stressor on
freshwater resources
• Redistribution of runoff is a
major culprit
• Contaminant transport –
especially sediment –
worsens the problem
• It is possible to effectively
control water and
contaminant loading
Potash Brook (Alex Hackman)
…and what we’d like to know
•
•
•
•
How much is enough?*
How long will it take?
What will in cost?
How do we start?
*Tear et al. BioScience 55(10):835
Impacts of climate change
The Overarching RACC Question
How will the interactions of climate change and land
use alter hydrological processes and nutrient transport
from the landscape, internal processing and eutrophic
state within the lake, and what are the implications for
adaptive management strategies?
Figure 3
Integrated
Assessment
Model (IAM)
Question 3
Questions 1 and 2
The Core RACC Research Questions
• Q1: What is the relative importance of endogenous (inlake) processes versus exogenous (to-lake) processes to
eutrophication and harmful algal blooms?
• Q2: Which alternative stable states can emerge in the
watershed and lake resulting from no-linear dynamics
of climate drivers, lake basin processes, social behavior,
and policy decisions?
• Q3: In the face of uncertainties about climate change,
land use and lake response scenarios, how can
adaptive management interventions be designed,
valued, and implemented in the multi-jurisdictional
region?
Opportunities for Outreach,
Research & Management
• Fluvial geomorphology: sediment dynamics
• Eco-hydrology: impact thresholds
• Community ecology: recovery dynamics
• Economics: tradable development rights
• Sociology: stakeholder engagement
• Urban planning: transportation, energy, wastes
• Informatics: databases & visualization
• Cyber-infrastructure: sensors & monitoring
Extra Slides
“The Urban Syndrome”
Image credit: USGS (2010) http://water.usgs.gov/nawqa/urban/
Quote credit: Cottingham et al. (2003) CRC Report and Meyer et al. (2005) JNABS
Biotic condition vs Stressor Impact
A generalized framework
Impacts of channelization
Impacts of water withdrawals
Impacts of land use intensification
Sources of Atmospheric Pollutants
Acid Rain Revisited (HBRF)
Atmospheric
Deposition
LONG-TERM TRENDS IN STREAM CHEMISTRY
Hubbard Brook, NH
Acid Rain Revisited (HBRF)
Fewer fish species at lower pH
Acid Rain Revisited (HBRF)
Framework for species invasion
What’s wrong with one more species?
•
•
•
•
•
•
•
Often…nothing
Competes with native species
Predates on native species
Alters habitats & behavior of native species
Hybridizes with native species
Introduces new diseases and pathogens
Direct as well as indirect effects
Exploitation inland fisheries
BUT…
Variation among different watersheds
Index of Biotic Integrity (IBI)
100
80
60
40
20
0
0
10
20
30
40
Percent watershed impervious cover
50
Fairfax County (2001) in CWP (2003)
Index of Biotic Integrity (IBI)
Variation obscures potential differences
Total watershed impervious cover
Horner and May (1999) in CWP (2003)
-■- Urban -●- Rural
-■- Burlington-Winooski -●- Rest of Chittenden County
Source: Lake Champlain Basin Program
http://www.lcbp.org
Source: Vermont Forum on Sprawl
http://www.vtearthinstitute.org/sprawl.html#evidence
How fast are we growing?
Equivalent to a doubling in 20 years!
Burlington Municipal Development Plan, 2001
Trends in Lake Champlain
Total Phosphorus Load
Troy et al. (2007)
Total Discharge