Kansas Water Science Center
USGS Water Science Centers are located in each state. ![]() |
The Value of Continuous Turbidity Monitoring in TMDL ProgramsBy Teresa J. Rasmussen, Andrew C. Ziegler, Patrick P. Rasmussen, and Thomas C. Stiles AbstractThe Federal Clean Water Act requires States to establish total maximum daily loads (TMDLs) to meet water-quality criteria and to attain designated beneficial uses for each water body. Sediment and sediment-associated constituents, such as total nutrients and bacteria, are among the most common water-quality impairments in the Nation. The load of a contaminant introduced to a water body varies with both concentration and streamflow, requiring reliable information for both when implementing an effective TMDL program. In most TMDL programs, discrete water samples collected at periodic intervals are used to determine whether established criteria are being met and to determine loads from contributing sources. However, discrete samples do not adequately describe daily, monthly, or annual variability in load characteristics because both concentration and streamflow can fluctuate substantially between samples. The ability to continuously measure water-quality constituents such as sediment, nutrients, and bacteria frequently is limited by technical and financial constraints. However, turbidity, which often is strongly correlated with sediment, nutrients, and bacteria, can be measured in-stream and on a continuous basis. By developing regression models to establish statistical relations between laboratory-analyzed samples and in-stream turbidity measurements, it is possible to provide continuous estimates of concentration and load under changing streamflow and seasonal conditions.
Rasmussen, T.J., Ziegler, A.C., Rasmussen, P.P., and Stiles, T.C., 2006, The value of continuous turbidity monitoring in TMDL programs, in Proceedings of the Eighth Federal Interagency Sedimentation Conference, April 2-6, 2006, Reno, Nevada: Subcommittee on Sedimentation, CD-ROM, 8 p. Additional information about continuous water-quality monitoring studies in Kansas can be found at: http://ks.water.usgs.gov/studies/qw/KSRTMDLs/ To request a paper copy of this journal article, email: rasmuss@usgs.gov |