The Effects of Lake Precipitation and Evaporation on Reservoir Modeling

Abstract

This paper explores the effects of lake evaporation and precipitation, reliability levels, and streamflow probability distribution on reservoir capacity and average release. A series of reservoir-analysis deterministic and stochastic models of increasing complexity are employed to examine these effects, which are illustrated using a mid-sized reservoir in Santa Barbara County, California. The deterministic reservoir models show evaporation dominating reservoir water balance, and, for the most part determining optimal reservoir capacity and annual releases, whereby comparatively larger reservoirs are required to compensate for the water lost to evaporation. The more complex stochastic models use chance constraints and bootstrapped reservoir inflow probability distributions, and suggest that optimal capacity and annual releases are dominated by reliability levels, with very large optimal reservoir capacities and annual releases required when the reliability levels approach one.