OiOverview o f Stormwa ter Effects on Water Quality wq-strm7-81 Stormwater Module 1 Minnesota Pollution Control Agency Training goals Recognize the wide Identify how land variety of use, management pollutants in urban practices, and stormwater runoff natural factors that can impair affect pollutant receiigiving waters ldigloading Stormwater module 1: Overview of stormwater effects on water quality 2 What is urban 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 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? Chemicals that we apply to the ldlandscape are carr idied 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 Chem ica ls may be tox ic to organisms Characteristics (habitat) of the receiving water body mayyg change Stormwater module 1: Overview of stormwater effects on water quality 6 What water body impairments are associated with stormwater? nutrients (primarily phosphorus) and pathogens Lakes impair the lake for recreational use Rivers/ nutrients, sediment, chloride, pathogens, and temperature impair the river/stream for streams aquatic vegetation, recreation, and habitat nutitrien ts an d se dimen tit impa ir we tlan ds for Wetlands habitat Stormwater module 1: Overview of stormwater effects on water quality 7 Phosphorus Concentrations are greatest from lawns and residential areas with considerable tree canopy from all areas excee d wa ter qua lity stdd*tandard* 2.5 Lawns ) 2.0 LL Streets 1.5 Parking lots ation (mg/ r r 1.0 Roofs Water quality Concent 0.5 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 increasinggp phos phorus loadin g Increased impervious area connectivity of imperv iou s area 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) Construction is Freeways a major source Commercial Industrial Varies with Shopping Center precipitation Multi-family characteristics Small residential lot Large residential lot Affects biota Parks 0 200 400 600 800 1000 1 Stormwater module 1: Overview of stormwater effects on water quality 10 Patho g Multiple urbanens sources, including illicit discharges, residential, internal loading urban Im p sourcesortance varies withof different sources, precipitation Affects recreational use Stormwater module 1: Overview of 100000000 100 mL / 1000000 10000 Colonies 100 Standard 1 Forest Rooftop stormwater effects on water quality Commercial parking lots High traffic street Residential driveway Residential lawns Low traffic street Basin outlet Raw sewage 11 Chlorides Major source is road salt Highest concentrations in winter Affects biota Data for Shingle Creek Stormwater module 1: Overview of stormwater effects on water quality 12 Temperature Varies with type of surface ((ge.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 NotanimpairmentbyNot 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; biota Stormwater module 1: Overview of stormwater effects on water quality 14 Metals,,g organics, nitro gen Waters are currently not assessed for these Concentrations are elevated in urban runoff Characteristics and effects vary with each pollutant Stormwater module 1: Overview of stormwater effects on water quality 15 Summary 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--inducedinduced factors affect the amount of pollutant loading that results from urban stormwater runoff Stormwater module 1: Overview of stormwater effects on water quality 16.