Drought and management effects on biophysicochemistry in a rapidly-flushed reservoir

Bellinger BJ, Richter A, Porras A, Davis SL. 2017. Drought and management effects on biophysicochemistry in a rapidly flushed reservoir. Lake Reserv Manage. 34:182—198.During a recent drought period, a municipal reservoir was affected by increased duration and magnitude of cyanobacterial blooms, deep water hypoxia, and abundant Hydrilla verticillata growth. We analyzed over 20 yr of water quality data from sources monitoring Lake Austin, Texas, USA, to relate changing hydraulic pulsing rates during periods of water surplus and deficit to system biophysicochemistry. During the drought period, average daily discharges through the reservoir system were significantly reduced to conserve water supply. In response, growing season hydraulic residence times in Lake Austin, typically a run-of-river system with residence of about 10 d, increased 2– to 8–fold. Nutrient loadings to Lake Austin decreased during low discharge, but only total phosphorus (TP) concentrations declined appreciably in the reservoir. ...