Sensitivity of Water Clarity to Drawdown in Reservoirs Across the Climatic 100th Meridian

Abstract Reservoirs provide key water storage in regions facing projected water scarcity and population growth. Many reservoirs experience water level fluctuations including periods of drawdown tied to drought. To examine sensitivity of water clarity to drawdown, we compiled 30 years of water level and Secchi depth measurements in southern Great Plains reservoirs ( n = 84) positioned across a climate gradient from the arid west to the wetter east. Mixed‐effect models incorporated reservoir‐specific coefficients relating Secchi depth to water storage volume. Predictions from the best model indicated that many reservoirs lost more than half of their Secchi depth as water levels approached their recorded lows. Reservoirs in west and central Texas tended to experience more severe drawdown and more pronounced loss of water clarity during drawdown. These results show that droughts can cause a dual setback in which the loss of water quantity coincides with loss of water quality in reservoirs.