| Abstract: | ABSTRACT: Effects of aquatic macrophytes are not considered in most standard water quality models. This study used field measurements and water quality models to help determine the effects of aquatic macrophytes on dissolved oxygen (DO) concentrations in a shallow tailwater reservoir. Installation of a hydropower plant and macrophytes (primarily Potamogeton and Chara) in a large shallow portion of the lake are possible causes of reduced DO levels in the tailwater reservoir. A water quality model (WASP5) was used to quantify the various DO sources and sinks and to evaluate the effects of the hydropower operations on DO levels in the lake. It was found that the macrophytes in Lake Ogallala had a significant effect on the DO levels in the lake. At an average macrophyte density of about 6,360 g/m2 (wet weight) in 2000, the DO fluctuated daily from about 3 mg/l to about 12 mg/l. At an average macrophyte density of about 2,120 g/m2 (wet weight) in 2002, the DO fluctuated from about 5 mg/l to about 9 mg/l daily. The model predicted that the DO would remain near 5 mg/l without macrophytes. The photo‐synthetic and respiration rates developed in the model (4.4 mg/g‐hr and 1.4 mg/g‐hr, respectively) agree well with literature values. |
