Water Quality
Sediment, nitrogen, and phosphorus are the leading nonpoint source pollutants in Iowa. Sediments commonly come from cropland tillage, livestock in pastures and feedlots, and woodlands. Urban sources such as construction sites also contribute to sediment loads in streams. Erosion of streambanks and lake shorelines add to the sediment loads as well.
Nutrients can come from commercial fertilizer applied to agricultural land or residential lawns and golfcourses and from organic sources such as manure and human sewage.
The 303(d) listing is composed of those lakes, wetlands, streams, rivers, and portions of rivers that do not meet all state water quality standards. These are considered "impaired waterbodies" and states are required to calculate total maximum daily loads (TMDLs) for pollutants causing impairments.
Total maximum daily load is a calculation that determines how much of a pollutant can enter a specific stream or lake in one day and still allow the lake or stream to meet the state's water quality standards.
Impaired Waters (303d) List
Iowa 303d Map
Iowa 303d Detailed Regional Maps
Iowa DNR Designated Use website
The site explains methods for assigning designated uses for Iowa streams and rivers.
Use the designated use searchable database to search for the designated use of a stream (http://programs.iowadnr.gov/uaa/search.aspx). Choose from the left bar menu to search by stream, facility, or city name.
