Kansas Water Science Center
Period of Project: 2001 - present
During 2001-03, the U.S. Geological Survey, in cooperation with the city of Wichita, Kansas, conducted a study to develop reliable tools to estimate the onset of cyanobacterial-related taste-and-odor occurrences in Cheney Reservoir, one of Wichita’s primary drinking-water supplies. The study combined discrete sampling with real-time continuous water-quality monitoring in an effort to relate the concentration of the taste-and-odor compound geosmin to environmental variables measured in real time (specific conductance, pH, temperature, turbidity, dissolved oxygen, and chlorophyll). Geosmin was detected in 92 percent of discrete water-quality samples (n=25), and concentrations ranged from < 3 to 113 nanograms per liter (median = 6 ng/L). Multiple regression was used to develop a relation between geosmin concentrations in discrete water samples and the real-time variables turbidity and specific conductance (r2=0.71, p<0.01, n=18), and the resulting model was used to provide hourly estimates of geosmin concentration. The model consistently indicated when geosmin concentrations would exceed the human detection limit of 10 ng/L. Real-time estimates of geosmin and the probability that concentrations will meet or exceed the human detection limit are available on the World Wide Web at http://nrtwq.usgs.gov/ks/. Ongoing studies at Cheney Reservoir will refine the relations between reservoir and inflow conditions and taste-and-odor occurrences. The city of Wichita plans to use these models, along with other variables measured in real time, to aid the management of the resource and decrease water-treatment costs.
A diverse range of physical, chemical, and biological factors may potentially limit algal growth, and no single variable stands out as an unequivocal link to cyanobacterial bloom formation. As a result, the relations between environmental variables and cyanobacterial by-products, such as taste-and-odor compounds and toxins, are invariably complex and may vary considerably over time (hours-weeks). Understanding the factors driving algal community dynamics is critical to the development of reliable models predicting the occurrence of taste-and-odor episodes. Current research in Cheney Reservoir is focused on characterizing the physicochemical, hydrological, and biological processes in Cheney Reservoir with respect to both watershed inputs and in-reservoir processes.
1. Assessment of annual and seasonal water-quality conditions and description of taste-and-odor and other algal-related by-products that occur in Cheney Reservoir
2. Description of the water-quality dynamics in the photosynthetic zone of the water column to provide an understanding of algal growth, diurnal movement, and production of taste-and-odor compounds associated with algae in Cheney Reservoir
3. Use of the latest technology in water-quality instrumentation to continuously monitor variability and potentially relate that information to observed algal-population dynamics and taste-and-odor episodes
4. Determination of relations between algal community structure dynamics and the production of taste-and-odor producing algal compounds (geosmin/MIB) and potential algal toxins such as microcystin
5. Providing a long-term data base with which to verify and refine previously determined relations between easily monitored water-quality variables and constituents related to the use of Cheney Reservoir as a water-supply source for the city of Wichita.
Photos of Interest