Continuous Monitoring and Regression Analysis
to Estimate Bacteria Loads

Abstract

To obtain timely and continuous water-quality information, the U.S. Geological Survey, in cooperation with State and other Federal agencies, has been using an innovative real-time monitoring approach for several Kansas streams. Continuously recorded data and data from periodic collection of water-quality samples are being used to develop surrogate relations between physical properties of water and constituents of concern. For example, regression equations were developed to estimate fecal coliform bacteria from continuous turbidity measurements collected from 1995 through 1998 on the Little Arkansas River in south-central Kansas. The equations were applied to data collected in 1999 to estimate constituent concentrations and loads. At one site, estimated fecal coliform bacteria densities exceeded contact recreation criteria (200 colonies per 100 milliliters of water) on 244 days during 1999. Estimated fecal coliform bacteria loads were 30,000,000 and 32,400,000 billions of colonies per year for the two sites in the study. Despite some large differences between instantaneous measured and regression-estimated loads, continuous monitoring of turbidity in streams may increase the accuracy of load estimates thay may be useful for calculating total maximum daily loads (TMDL's). The availability of this data in real time also may be useful for considering whole-body contact and recreation criteria, for adjusting water-treatment strategies, and for preventing adverse effects on fish or other aquatic life.

Additional information on the TMDL Program in Kansas can be found at: http://ks.water.usgs.gov/studies/TMDL/

Additional information on Real-Time Water Quality in Kansas can be found at: http://ks.water.usgs.gov/studies/qw/

Christensen, V.G., Rasmussen, P.P., Ziegler, A.C., and Jian, Xiaodong, 2001, Continuous monitoring and regression analysis to estimate bacteria loads, in Proceedings of TMDL Science Issues Conference, March 4-7, 2001, St. Louis, Missouri: Water Environment Federation, p. 405-411.

To request a paper copy of this proceedings article, email: vglenn@usgs.gov