O i fO i f St tSt tOverview of Overview of StormwaterStormwaterEffects on WaterEffects on Water QualityQualityEffects on Water Effects on Water QualityQuality

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Stormwater Module 1Minnesota Pollution Control Agency

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Training Training goalsgoalsgg gg

Recognize the wide Identify how landRecognize the wide variety of pollutants in urban

Identify how land use, management practices, and

stormwater runoff that can impair

i i g t

natural factors affect pollutant l di greceiving waters loading

2Stormwater module 1: Overview of stormwater effects on water quality

What is What is urban urban stormwaterstormwater??

Water running off an urban land surface afterurban land surface after a rainfall or snowmelt event

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Urban areas have Urban areas have less infiltration and evaporation less infiltration and evaporation andand more runoffmore runoff than forested or grassland areasthan forested or grassland areasand and more runoff more runoff than forested or grassland areasthan forested or grassland areas

Two most important factors:p1. amount of impervious surface 2. connectedness of impervious surface

Source for figure: http://duluthstreams.org/understanding/stormwater_hydrology.html

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How do we affect the How do we affect the qualityquality of of stormwaterstormwater??stormwaterstormwater??

Chemicals that we apply to the l d i dlandscape are carried with runoff water to receiving watersreceiving waters

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What What environmental effects environmental effects are are associated withassociated with stormwaterstormwater runoff?runoff?associated with associated with stormwaterstormwater runoff?runoff?

Stormwater usually discharges to a lake, river/stream or wetlandIncreased runoff may cause floodingCh i l b t iChemicals may be toxic to organismsCharacteristics (habitat) of the receiving water body may changey g

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What water body What water body impairmentsimpairments are are associated withassociated with stormwaterstormwater??associated with associated with stormwaterstormwater??

Lakes nutrients (primarily phosphorus) and pathogens impair the lake for recreational use

Rivers/t

nutrients, sediment, chloride, pathogens, and temperature impair the river/stream for

streams aquatic vegetation, recreation, and habitat

t i t d di t i i tl d fWetlands nutrients and sediment impair wetlands for habitat

Stormwater module 1: Overview of stormwater effects on water quality 7

PhosphorusPhosphoruspp

Concentrations are greatest from lawns and residential areas with considerable tree canopyf ll d t lit t d d*from all areas exceed water quality standard*

2.0

2.5

L)

Lawns

1.5

ratio

n (m

g/L

Streets

Parking lots

0.5

1.0

Con

cent

r

Roofs

Water quality standard*

0.0* Standard varies with area of state and characteristics of lake

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Factors increasing phosphorus loadingFactors increasing phosphorus loadingg p p gg p p g

Increased impervious areaconnectivity of imper io s areaimpervious areaturfgrass and leaf contributionsconcentrations of soluble phosphorussoil erosionsoil erosion

Natural factors (rainfall, soil)

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SedimentSediment

Most pollutants are associated with finerMost pollutants are associated with finer sedimentConstruction is Freeways

Annual Sediment Load (lbs/acre)Ca major sourceVaries with Shopping Center

IndustrialCommercial

Freeways

precipitation characteristics

Large residential lotSmall residential lot

Multi-familyShopping Center

Affects biota0 200 400 600 800 1000 1

Parksg

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PathogensPathogensgg

Multiple urban sources,Multiple urban sources, including illicit discharges, residential,

10000

1000000

100000000

/100

mL

Standard

internal loading

Importance of different 1

100

10000Fore

stRoo

ftop

cial p

arking

lots

High tra

ffic str

eetde

ntial d

rivew

ayResi

denti

al law

nsLow

traffic

street

Basin o

utlet

Raw se

wage

Col

onie

s/

psources varies with precipitation

Commerc

ia HigResi

de Res Low

Affects recreational use

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ChloridesChlorides

Major source is roadMajor source is road saltHighest concentrations gin winterAffects biota

Data for Shingle Creek

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TemperatureTemperaturepp

VariesVaries with type of surface (e.g. ( gasphalt, concrete, grass)during a rain event

Effects biotaData for Miller Creek

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FlowFlow

Not an impairment byNot an impairment by itself, but a surrogate for other pollutantsA function of impervious surface and connectivity of drainage systemAffects loading of most

ll bpollutants; biota

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Metals, organics, nitrogenMetals, organics, nitrogen, g , g, g , g

Waters are currently notWaters are currently not assessed for theseConcentrations are elevated Cin urban runoffCharacteristics and effects vary with each pollutant

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SummarySummaryyy

Urban areas have moremore runoffrunoff andUrban areas have moremore runoffrunoff and less infiltration and evaporation less infiltration and evaporation than forested or grassland areasUrban runoff contains many pollutants contains many pollutants that can affect a receiving water bodyNatural and manNatural and man--induced factors affectinduced factors affect the amount of pollutant loading pollutant loading that results from

b ffurban stormwater runoff

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