Impact of phosphorus and nitrogen concentrations on the biological integrity of Wisconsin streams

Science Center Objects

The USGS and Wisconsin DNR collected water-quality and biological data from 240 wadeable streams and 40 nonwadeable rivers throughout Wisconsin to evaluate the potential environmental benefits of enforcing nutrient criteria and standards for streams and rivers if they better reflected regionally defined, scientifically defensible thresholds to biotic response.

Photo of a rural wadeable stream in Wisconsin

Photo of a rural wadeable stream in Wisconsin.

Problem:

Excessive nutrient (primarily phosphorus and nitrogen) loss from the watershed is associated with water-quality problems in Wisconsin's streams and lakes. Implementation of WDNR's agricultural performance standards and prohibitions should decrease the risk of excessive nutrient loss from croplands and livestock operations. In addition, establishing phosphorus criteria and developing site-specific TMDLs would also reduce the problems caused by excessive nutrient concentrations. Expected water-quality improvements due to the application of phosphorus criteria and other standards may vary due to differences in nutrient responses dependent upon where the site is located. There would be more confidence in the potential environmental benefits of enforcing nutrient criteria and standards for streams and rivers if they reflect regionally defined scientifically defensible thresholds to biotic response. Defined nutrient criteria and thresholds for biotic indices would enable the use of monitoring data to identify rivers and streams affected by excessive nutrients and would be useful to water-resource managers in directing rehabilitation efforts.

 

Objectives and Approach:

The USGS and Wisconsin DNR collected water-quality and biological data from 240 wadeable streams and 40 nonwadeable rivers throughout Wisconsin and described the environmental characteristics of their watersheds to:

  1. Describe how nutrients and biotic-community structure vary in streams and rivers throughout the State;
  2. Determine which environmental characteristics are most strongly related to nutrient concentrations;
  3. Determine reference water-quality and biotic conditions for different areas of the State;
  4. Determine how biotic communities respond to changes in nutrient concentrations;
  5. Determine the best regionalization scheme to describe patterns in reference conditions and responses in water quality and the biotic community;
  6. Identify thresholds or breakpoints in the biological response between nutrient concentrations and biotic indices; and
  7. Provide information for the Wisconsin DNR and U.S. Environmental Protection Agency to set nutrient criteria for Wisconsin's streams and rivers. 

 

Photo of Wisconsin Department of Natural Resources personnel collecting fish with electrofishing gear.

Wisconsin Department of Natural Resources personnel collecting fish with electrofishing gear. (Photo by Wisconsin Department of Natural Resources)

 

 

 

 

 

 

 

 

 

 

 

 

Web Links:

U.S. Environmental Protection Agency Nutrient Criteria Web Page
http://water.epa.gov/scitech/swguidance/standards/criteria/nutrients/index.cfm

Wisconsin Department of Natural Resources Phosphorus Rules 
http://dnr.wi.gov/topic/surfacewater/phosphorus.html