Assessing upland reservoirs using a daily flow model

Abstract

A procedure is given for analyzing multisite upland reservoir storage for water supply at a downstream point. Synthetic monthly streamflow for six sites replicates mean, standard deviation, and lag correlation coefficient of historic data; a matrix of spatial correlations interrelates the sites. Factors translate flow to seven reservoirs operated in two modes and one use point. The Thomas-Fiering formula, using lag-one correlation and coefficient of variation of historic daily flows and a random gamma variable, converts monthly flow to daily supply at the use point. Results comprise probabilistic analyses of deficiencies and reservoir performances. Results of a study of the Washington, D. C., requirements for 1985 indicate that six upland reservoirs reduce the duration of a deficiency occurring once in a hundred years and that a smaller volume of nearby storage is an alternative or can be used for standby. Results indicate that sophisticated operation of upstream reservoirs should enhance recreational values while concurrently satisfying supply requirements at Washington.