Predicting Diel Dissolved Oxygen Dynamics in the Carson River, Nevada

The Carson River originates in eastern Alpine County California, flows northeast into western Nevada through Carson City, and terminates in the Carson Sink. Elevated nutrient levels from agricultural return flows allow for excess attached algal (periphyton) growth. Periods of low flow, coupled with an abundance of periphyton, harbor an environment capable of producing dissolved oxygen concentrations less than 5 mg L-1. Algal biomass sampling, water quality constituent sampling, and YSI Sonde deployments were performed during low flow months of 2003 and 2004 to investigate dissolved oxygen dynamics and relative amounts of periphyton present in a 33 kilometer reach of the Carson River. A significantly augmented version of the Water Quality Analysis and Simulation Program (WASP5) was calibrated and verified. Preliminary results from this version of WASP5 track observed periphyton biomass and dissolved oxygen data fairly consistently throughout both the temporal and spatial model domains. Dissolved oxygen calibration was constrained through the use of observed periphyton biomass, water quality constituents, and temperature data. Finally, the calibrated input file will also be used as an input file for an updated version of the EPA water quality model, WASP7, and a comparison of the simulated periphyton biomass and dissolved oxygen dynamics from these models will be accomplished. The uniqueness of this study stems from the coupling of algal biomass, water quality constituents, temperature, dissolved oxygen field data and the comparison of results from two water quality simulation models, in order to understand the underlying reasons for observed dissolved oxygen variations.