O
Overview
i
off Stormwater
St
t
Effects on Water Quality
wq strm7 81
wq-strm7-81
Stormwater Module 1
Minnesota Pollution Control Agency
Training
gg
goals
†
Recognize the wide
variety of
pollutants in urban
stormwater runoff
that can impair
receiving
i i g waters
t
†
Identify how land
use, management
practices, and
natural factors
affect pollutant
l di g
loading
Stormwater module 1: Overview of stormwater effects on water quality
2
What is urban stormwater
stormwater??
Water running off an
urban land surface after
a rainfall or snowmelt
event
Stormwater module 1: Overview of stormwater effects on water quality
3
Urban areas have less infiltration and evaporation
and more runoff than forested or grassland areas
Two most important
p
factors:
1. amount of impervious surface
2. connectedness of impervious surface
Source for figure: http://duluthstreams.org/understanding/stormwater_hydrology.html
Stormwater module 1: Overview of stormwater effects on water quality
4
How do we affect the quality of
stormwater??
stormwater
Chemicals that we
apply to the
l d
landscape
are carried
i d
with runoff water to
receiving waters
Stormwater module 1: Overview of stormwater effects on water quality
5
What environmental effects are
associated with stormwater runoff?
†
†
†
†
Stormwater usually
discharges to a lake,
river/stream or
wetland
Increased runoff may
cause flooding
Ch i l may b
Chemicals
be ttoxic
i
to organisms
Characteristics
(habitat) of the
receiving water body
mayy change
g
Stormwater module 1: Overview of stormwater effects on water quality
6
What water body impairments are
associated with stormwater
stormwater??
Lakes
Rivers/
streams
t
Wetlands
nutrients (primarily phosphorus) and pathogens
impair the lake for recreational use
nutrients, sediment, chloride, pathogens, and
temperature impair the river/stream for
aquatic vegetation, recreation, and habitat
nutrients
t i t and
d sediment
di
t iimpair
i wetlands
tl d ffor
habitat
Stormwater module 1: Overview of stormwater effects on water quality
7
Phosphorus
p
Concentrations
† are greatest from lawns and residential areas with
considerable tree canopy
† from
f
all
ll areas exceed
d water
t quality
lit standard*
t d d*
Concentrration (mg/L
L)
2.5
2.0
Lawns
Streets
1.5
Parking lots
1.0
Roofs
0.5
Water quality
standard*
0.0
* Standard varies with area of state and characteristics of lake
Stormwater module 1: Overview of stormwater effects on water quality
8
Factors increasing
gp
phosphorus
p
loading
g
Increased
impervious area
† connectivity of
imper io s area
impervious
† turfgrass and leaf
contributions
† concentrations of
soluble phosphorus
† soil erosion
†
Natural factors
(rainfall, soil)
Stormwater module 1: Overview of stormwater effects on water quality
9
Sediment
Most pollutants are associated with finer
sediment
Annual Sediment Load (lbs/acre)
†C
Construction is
Freeways
Commercial
a major source
Industrial
† Varies with
Shopping Center
Multi-family
precipitation
Small residential lot
characteristics
Large
g residential lot
Parks
† Affects biota
†
0
200 400 600 800 1000 1
Stormwater module 1: Overview of stormwater effects on water quality
10
Multiple urban sources,
including illicit
discharges, residential,
internal loading
†
Importance
p
of different
sources varies with
precipitation
†
Affects recreational use
100000000
1000000
10000
Standard
100
1
Fo
re
Co
st
m
m
R
er
o
of
ci
to
al
p
pa
rk
i
ng
H
ig
lo
h
ts
tra
Re
ffi
sid
cs
en
tre
tia
et
ld
riv
Re
ew
sid
ay
en
tia
ll
Lo
aw
w
ns
tra
ffi
cs
tre
et
Ba
sin
ou
tle
Ra
t
w
se
w
ag
e
†
Colonies//100 mL
Pathogens
g
Stormwater module 1: Overview of stormwater effects on water quality
11
Chlorides
Major source is road
salt
† Highest
g
concentrations
in winter
† Affects biota
†
Data for Shingle Creek
Stormwater module 1: Overview of stormwater effects on water quality
12
Temperature
p
Varies
† with type of
surface (e.g.
( g
asphalt, concrete,
grass)
† during a rain event
Effects biota
Data for Miller Creek
Stormwater module 1: Overview of stormwater effects on water quality
13
Flow
Not an impairment by
itself, but a surrogate
for other pollutants
† A function of impervious
surface and connectivity
of drainage system
† Affects loading of most
pollutants;
ll
biota
b
†
Stormwater module 1: Overview of stormwater effects on water quality
14
Metals,, organics,
g
, nitrogen
g
Waters are currently not
assessed for these
†C
Concentrations are elevated
in urban runoff
† Characteristics and effects
vary with each pollutant
†
Stormwater module 1: Overview of stormwater effects on water quality
15
Summaryy
Urban areas have more runoff and
less infiltration and evaporation
than forested or grassland areas
† Urban runoff contains many pollutants
that can affect a receiving water body
† Natural and manman-induced factors affect the
amount of pollutant loading that results from
urban
b stormwater runoff
ff
†
Stormwater module 1: Overview of stormwater effects on water quality
16