Document Type


Publication Date


Faculty Mentor

Bethany Neilson

Exhibition Venue

Utah State University Student Showcase; Research on Capitol Hill (Utah)

Funding Agency

Washington County Water Conservancy District


Limited water resources in Southern Utah with the competing interests of humans and native fishes require careful management. High instream temperatures resulting from low flows are a consideration in managing the Virgin River for two endangered fish species. Throughout these periods, fish behavior changes have been observed during those high turbidity. One hypothesis was that high turbidity decreased the amount of solar radiation in the water column due to increased reflection at the water surface resulting in reduced instream temperatures. To quantify the extent of changes in incoming energy to the river, a water tank was constructed to measure the effects of turbidity on solar radiation reflection off the water surface and attenuation with depth. We found that increases in turbidity led to a linear increase in solar radiation reflection for specific turbidity ranges. We also found that attenuation of solar radiation increased linearly as turbidity increased for specific turbidity ranges. The effects of turbidity on solar radiation behavior were translated into changes in instream temperatures through the use of an instream temperature model. The results indicated during summer low flow conditions that turbidity increases from 30-500 NTU decreased instream temperatures 1 degree Celcius on average with maximum increases of 2 degrees Celcius.



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