Engineering researchers at the University of Arkansas have developed an innovative system for obtaining important water-quality information on a near real-time basis and at much less expense than current methods. Using photographic images from a satellite and hand-held multispectral camera, researchers in the College of Engineering’s department of biological and agricultural engineering have built mathematical models that accurately predict sediment loads and nutrient content in Beaver Lake, the source of drinking water for more than 280,000 people in Northwest Arkansas.
“Remote sensing technology provides several advantages for any group responsible for the ecological health of a body of water,” said Indrajeet Chaubey, UA associate professor of biological and agricultural engineering. “Now we can monitor the entire lake, not just one area where you take a water sample. We can do this with much less expense because we don’t have to process hundreds of thousands of water samples through the traditional lab process. Until now, we’ve had very limited capability to monitor what is happening on a real-time or near real-time basis.”
Chaubey leads a team of UA ecological engineering researchers and students who for many years have traveled to remote locations on the lake to gather water samples, which must be taken to a laboratory for analyses of pollutant concentrations. Results of those analyses are often not available until a week after the sample is taken. As Chaubey said, the new technology should help researchers gather information without physically taking water samples from every nook and cranny of a river, reservoir or lake.
Reading the content of the photographs is tricky, but the process works because certain constituents—sediment, chlorophyll and organic carbon in the water—interact with light. The photos reveal nitrogen and phosphorous levels within sediment. Nitrogen and phosphorous are essential plant nutrients that in excess can accelerate eutrophication, which reduces oxygen in water and harms plant and animal life. Also, high concentrations of chlorophyll mean a source of energy must be present, which again indicates the presence of nitrogen and phosphorous.
“If you see high concentrations of chlorophyll,” Chaubey said, “chances are there are high amounts of nitrogen and phosphorous. If there weren’t, algae would not be growing.”
Chaubey knew algae were present because his researchers continued to draw water samples at the exact locations captured in the photographs. They compared lab results from the samples to predictions based on the photographs.
So far, their predictions of the concentration of nutrient levels at various locations on Beaver Lake, based on images provided by satellite and multispectral camera photography, have been 98% accurate.
Beaver Water District, the public entity charged with treating water from the lake and providing it to most northwest Arkansans, will be able to use this technology to overlay snapshots that will help them identify water-quality trends in the lake over time.