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

Per

cent

of A

nnua

l Loa

d

0

20

40

60

80

100Large 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 St

orm

Flu

x(k

g/km

2 ± S

D)

D E F H G B C A

Mea

n St

orm

Flu

x(g

/km2 ±

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

Flow

-weig

hted

mea

n co

ncen

tratio

n (u

g/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 Em

issi

ons

Tota

l PA

Hs

(kg)

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

Year1930 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 l

oad

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

cent

ratio

n (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: erics@sccwrp.org

Martha Sutula: marthas@sccwrp.org