Decadal Precipitation Variations and Inflows into Fort Cobb Reservoir, Oklahoma

Changes in annual reservoir inflow and flood release volumes due to persistent multiyear dry or wet periods were investigated for the Fort Cobb Reservoir. A time-series analysis of the 1940-2004 annual precipitation revealed three dry and one wet period, called decadal variations. Corresponding strong variations were found in the reservoir inflow and flood release records. The sensitivity of watershed response, reservoir inflow and flood release volume to decadal precipitation variations suggested that water resources and water quality assessments in central Oklahoma should account for decadal precipitation variations. Along the same lines investigations based on numerical model simulations need to consider such climatic variations in the calibration, validation and application phase.