Runoff: Sources, Emerging Issues and

kayakjokeMécanique

22 févr. 2014 (il y a 2 années et 9 mois)

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Water Quality Associated with Urban
Runoff: Sources, Emerging Issues and
Management Approaches

Martha Sutula and Eric Stein

Biogeochemistry and Biology

Departments

Southern California Coastal Water Research Project

Increased Focus on Stormwater, As Point
Sources Are Reduced

Figure 2.
Relative contribution to combined metals emissions from major sources between 1971
and 2000.
1970
1975
1980
1985
1990
1995
2000
Percent of Annual Load
0
20
40
60
80
100
Large POTWs
Stormwater Runoff
Annual Load

Total Combined Metals to the SCB

Origins of Storm Water Pollution
-

Urbanization

LA River
-

1938
Flood

Challenges of Managing Storm Water


Difficult to understand and predict all the factors that
influence storm water


Highly variable


Many sources and influencing factors



Effective management requires tools to increase our
understanding



Monitoring


Source characterization and identification


Model development


BMP siting and design

Today’s Talk


Take home messages from
20 yrs of SCCWRP
stormwater research



Emerging issues



Thoughts on management
approaches

Potential Sources


Anthropogenic


Land uses


Mobile sources


Aerial deposition




Natural


Background

SCCWRP Studies Contributing to
Understanding of Stormwater Sources


Wet weather sampling of land use sites



Monitoring and modeling of dry weather runoff in LA Region



Sources associated with natural landscapes


Wet and dry weather concentrations and loads
-

bacteria, metals and
nutrients



Atmospheric deposition of metals and organics



Studies of fire
-
related effects on stormwater





Main Messages on Wet Weather Runoff


Main sources vary by
constituent


Metals


industrial


PAHs


aerial
deposition


Bacteria


recreation
and agriculture


Nutrients


agriculture
and residential



Industrial
Agricultural
Recreational
Open Space
Transportation
Low Density Res.
Commercial
High Density Res.
0
1000
2000
3000
4000
TSS
Mean Storm Flux
(kg/km
2
± SD)
D
E
F
H
G
B
C
A
Mean Storm Flux
(g/km
2
± SD)
0
500
1000
1500
2000
2500
3000
Total Copper
Main Messages on Wet Weather Runoff


Main sources vary
by constituent



Natural areas
contribute low
background levels,
may be substantial
for some
constituents


Atmospheric sources
may play role



Flow-weighted mean concentration (ug/L)
0.01
0.1
1
10
100
1000
As
Cu
Pb
Se
Zn
Natural
Developed
Wet weather metal
concentrations



natural versus
developed



Main Messages on Wet Weather Runoff


Main sources vary by
constituent



Natural areas
contribute low
background levels, but
may be substantial for
some constituents



Important to
understand factors
driving variability


Affects strategy for
managing stormwater
as a resource


Cumulative Rainfall (cm)
0
10
20
30
40
Mass Emissions
Total PAHs (kg)
0
2
4
6
8
10
12
14
16
Early Season Storms
Late Season Storms
R
2
= 0.81
What About Dry Weather Runoff?

Los Angeles River - Dry Season Flow
Year
1930
1940
1950
1960
1970
1980
1990
2000
Annual Dry Season Volume (m
3
)
2e+7
4e+7
6e+7
8e+7
1e+8
Source: USGS


Region has on average
345 dry days per year


Main Messages on Dry Weather Runoff


Can be as major load,
particularly during
dry years





Dry Season Cu Load
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
10%
25%
50%
75%
100%
Rainfall %-ile
% of total load
Contribution of Dry Weather Load (30
-
year simulation


Ballona

Creek)


Main Messages on Dry Weather Runoff


Can be as major load,
particularly during
dry years



Again, natural
loadings can be
substantial for some
constituents




Dry Weather Concentrations of
Nutrients


Natural Versus Developed


Concentration (mg/L)
0.001
0.01
0.1
1
10
100
1000
10000
NH
3
Nitrate+Nitrite
TP
TSS
Natural
Developed
Emerging Management Issues


Biological quality of streams



Hydromodification



Contaminants of emerging concern



Recycled water


Effects of Watershed Urbanization Go
Beyond Water Quality


Water quality/toxicity



Physical structure



Habitat condition



Water quantity/


hydrodynamics

Increased Focus on Biological Endpoints in
Assessing Effects of Urban Runoff


SWRCB working on
development of biocriteria for
streams, eventually estuaries



Benthic invertebrates first, but
over time, other lines of
evidence may be included


Stream algae


Overall habitat condition



Benthic Invertebrates

Stream Algae

In
-
stream and
Riparian Habitat

Early Messages From Stream Bioassessment


Large percentage of
stream miles with
measureable effects
in region





Biological condition:
SoCal
IBI
Non
-
reference
High
-
reference
Low
-
reference
Early Messages From Stream Bioassessment


Large percentage of
stream miles
impacted in region



Lowest invertebrate
IBI scores near urban
and
ag

lands




Land use
Region
Agricultural
Open
Urban
IBI Score
0
20
40
60
80
100
Non
-
Reference
Near reference
Early Messages From Stream
Bioassessment


Large percentage of
stream miles
impacted in region



Lowest invertebrate
IBI scores near urban
and
ag

lands



Nutrients, physical
habitat disturbance
are top stressors


Relative Risk
0.1
1
10
Toxicity to reproduction
Sediment deposition
% eroded or vulnerable banks
Selenium
Copper
Invasive species
Embeddedness
Cadmium
Total N
Riparian vegetation
Chloride
Riparian disturbance
Channel alteration
Total P
% sands and fines
Physical habitat
Biology
Water
chem
Nutrients
Toxicity
Risk of Low
Invertebrate IBI
score associated
with stressors

Effect of Increased Impervious Cover
-

Hydromodification

Hydromodification


Infrastructure damage


Instream

habitat loss


Coastal erosion

SCCWRP is Developing Modeling Tools To
Support Management of Hydromodification


1.
Which streams are at the greatest risk of effects of
hydromodification
?
Screening Tool


2.
What are the anticipated effects in terms of increased erosion,
sedimentation, or habitat loss, associated with increases in
impervious cover?
Modeling Tools


3.
What are some potential management measures that could
be implemented to offset hydromodification effects?

Management Tools

What Can We Do?



Adverse effects of hydromodification and urban runoff
must be addressed at watershed scale

General Concepts


Minimize runoff



Maximize infiltration



Avoid building in floodplains



Education

Approaches


Better Site Planning



On
-
site control of runoff



Biotechnical stream stabilization



Stream restoration


These General Principles Will Improve Physical and Biological
Condition, and Ameliorate Water Quality

THANK YOU

For more information contact:


Eric Stein: erics@sccwrp.org

Martha Sutula: marthas@sccwrp.org