Projecting Storage in Highland Lake Reservoir System

Abstract

The probability distribution of storage in the Highland Lakes reservoir system on the Lower Colorado River in Central Texas is projected up to six years into the future. Projections are based on simulation using historical hydrologic data, initial storage conditions, expected water demands, and system operation policy. Results are compared with those obtained by application of Gould's probability matrix method, which assumes annually uncorrelated hydrologic data. Although serial correlation of combined annual inflows is not statistically significant, it is demonstrated that persistence in the annual data reduces the expected system storage under steady‐state conditions from 86.5% to 81.7% of the active storage capacity. Mechanisms are illustrated for evaluating the effect of reductions in contracted water supply on future reservoir storage levels.