| Real-Time Estimation of Taste-and-Odor Occurrences in Cheney Reservoir, Kansas |
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Deployment of an in situ nitrate sensor in Cheney Reservoir, Kansas. Photo credit: Trudy J. Bennett, USGS
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Cheney Reservoir, Kansas is one of the City of Wichita’s primary drinking-water supplies. Cyanobacterial-related taste-and-odor events in the reservoirs are a concern because of aesthetics and water-treatment costs. Since 2000, the U.S. Geological Survey, in cooperation with the City of Wichita, has operated real-time water-quality monitors on the North Fork of the Ninnescah River, the main tributary to Cheney Reservoir, and in Cheney Reservoir. Real-time water-quality variables measured since 2000 include water temperature, specific conductance, pH, dissolved oxygen, turbidity, and chlorophyll fluorescence (an estimate of algal abundance). Data collected during 2001-2003 were used to develop a real-time water-quality model to estimate Cheney Reservoir geosmin (an earthy odor compound) concentrations in real time. Multiple regression analysis was used to develop a relation between geosmin concentrations and the real-time measured sensor variables turbidity and specific conductance. The resulting model is used to provide hourly estimates of geosmin concentration on the World Wide Web at https://nrtwq.usgs.gov/ks/. Evaluation of the model indicates that, within existing model limits (turbidity of < 36 formazin nephelometric units, specific conductance of 790-915 microsiemens per centimeter), geosmin estimates are conservative (overestimates are more likely than underestimates). However, model probabilities for exceeding the human detection limit of 10 ng/L are fairly robust (probabilities were accurate for 76% of measured geosmin values during 2001-2008). Several additional real-time sensors have been installed in Cheney Reservoir since the development of the initial geosmin model including: wind speed and direction, light, nitrate, and phycocyanin fluorescence (an estimate of cyanobacterial abundance). These new variables may facilitate additional model development and enhance understanding of the factors driving cyanobacterial bloom development and taste-and-odor occurrence. Ongoing studies at Cheney Reservoir will refine the relations between reservoir and inflow conditions and taste-and-odor occurrences and develop similar models for the cyanobacterial toxin microcystin. The City of Wichita currently uses the real-time geosmin estimates, along with other variables measured in real time, to make management decisions that have helped decrease water-treatment costs.
See the project Web page: The Cheney Reservoir and Watershed Study
For more information contact Jennifer L. Graham, Kansas Algal Toxin Research Team.
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