The impact of seasonal flow characteristics and demand patterns on required reservoir storage

Annual streamflow volumes, modeled by AR(1) and ARMA(1,1) processes, were generated and disaggregated to seasonal flow volumes and routed through a reservoir algorithm to determine the within-year capacity of a single reservoir needed to satisfy a specified demand sequence. Six seasons, each of two months duration, were used to investigate the impact of seasonal demand—seasonal flow variability coupling. Annual synthetic flows were disaggregated by a modified version of the disaggregation scheme which has been developed by Valencia and Schaake. Annual demand levels of 0.3, 0.5, and 0.7 of the mean annual flow were used. Three seasonal patterns representing relatively uniform demand, demand in phase with streamflow, and demand out of phase with streamflow were used. Modeling the skewed distributions of seasonal flows was shown to be important at all demand levels investigated.