Estimation of Nutrient Loads Using Continuous Water-Quality Monitoring and Regression Analysis Compared to Other Load Estimation Methods

Abstract

A common way of estimating constituent loads employs a regression model calibrated to discrete water-quality samples, to relate constituent concentrations to daily value streamflow measurements. Today, several U.S. Geological Survey streamflow gaging stations in Kansas are equipped with water-quality monitors that provide relatively inexpensive, continuous measurements of specific conductance, pH, water temperature, dissolved oxygen, turbidity, and fluorescence. These measurements are useful indicators of a broader range of water-quality conditions and can be used with regression models to estimate real-time loads of selected constituents, such as nitrogen and phosphorus, in streams.

Between 1998 and 2001, about 20 discrete water samples were collected at each of four streamflow gaging stations throughout Kansas and analyzed for total organic nitrogen, total phosphorus, and other constituents of concern. Site-specific regression equations were developed relating nutrient concentrations in the discrete samples to the variables reported by the continuous water-quality monitors. Annual nitrogen and phosphorus loads were estimated using the continuous water-quality measurements and compared to estimates using continuous streamflow measurements and computer models. For more information on continuous water-quality monitoring in Kansas go to http://ks.water.usgs.gov/rtqw/

Christensen, V.G., Rasmussen, P.P., and Ziegler, A.C., 2002, Estimation of nutrient loads using continuous water-quality monitoring and regression analysis compared to other load estimation methods [abst.], in Proceedings of National Monitoring Conference, 2002, "Building a Framework for the Future," May 20-23, 2002, Madison, Wisconsin: Oklahoma City, Oklahoma, National Water Quality Monitoring Council, compact disk, track 5, no. 14, 1 p.

For additional information about Real-Time Water Quality in Kansas, please visit: http://ks.water.usgs.gov/studies/qw/

For additional information about this project contact:

Victoria Christensen
U.S. Geological Survey
4821 Quail Crest Place
Lawrence, KS 66049-3839
Telephone: (785) 832-3552
Fax: (785) 832-3500
Email: vglenn@usgs.gov

To request a paper copy of this abstract, email: GS-W-KS_info@usgs.gov