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
Pe
rcen
t o
f A
nn
ua
l L
oa
d
0
20
40
60
80
100
Large POTWsStormwater 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 waterHighly variableMany sources and influencing factors
Effective management requires tools to increase our understanding MonitoringSource characterization and identificationModel developmentBMP siting and design
Today’s Talk
Take home messages from 20 yrs of SCCWRP stormwater research
Emerging issues
Thoughts on management approaches
Potential Sources
AnthropogenicLand usesMobile sourcesAerial deposition
NaturalBackground
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
0
1000
2000
3000
4000TSS
Mea
n S
torm
Flu
x(k
g/k
m2 ±
SD
)
D E F H G B C A
Me
an
Sto
rm F
lux
(g/k
m2 ±
SD
)
0
50010001500200025003000
Total Copper
Main Messages on Wet Weather RunoffMain sources vary
by constituent
Natural areas contribute low background levels, may be substantial for some constituents
– Atmospheric sources may play role
Flo
w-w
eigh
ted m
ean
conce
ntra
tion
(ug
/L)
0.01
0.1
1
10
100
1000
As
Cu Pb
Se
Zn
NaturalDeveloped
Wet weather metal
concentrations
– natural versus developed
Main Messages on Wet Weather RunoffMain 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
Mas
s E
mis
sio
ns
To
tal P
AH
s (k
g)
0
2
4
6
8
10
12
14
16
Early Season StormsLate Season Storms
R2
= 0.81
What About Dry Weather Runoff?
Los Angeles River - Dry Season Flow
Year
1930 1940 1950 1960 1970 1980 1990 2000
Ann
ual D
ry S
easo
n V
olum
e (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 RunoffCan 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
% o
f to
tal
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
Con
cen
trat
ion
(m
g/L
)
0.001
0.01
0.1
1
10
100
1000
10000
NH3
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 includedStream algaeOverall 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 S
core
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 ConceptsMinimize runoff
Maximize infiltration
Avoid building in floodplains
Education
ApproachesBetter 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: [email protected]
Martha Sutula: [email protected]