Susceptibility of Water Supply Reservoirs to Drought Conditions

Abstract

The knowledge of the behavior of a water supply system during hydrological drought events is useful to assess the risk of shortages and to undertake the necessary actions to reduce drought impacts. In the present paper relationships between performance indices of a water supply reservoir and severity of hydrological droughts identified using the concepts of runs have been studied. A linear relationship between water shortage index and mean intensity (or cumulative deficit) of droughts of the same length was derived analytically and verified by simulation. Simulation has been carried out during drought periods for two demand patterns by using either standard operating policy (SOP) or different hedging policies. Plots of performance indices versus drought characteristics show in some cases a definite pattern whereas in others the points present a relatively high scatter. When a hedging operating policy is applied, though the scatter of the points increases, some relationships still preserve a definite pattern. The slope of such patterns can be used to evaluate the ability of different hedging rules in reducing drought impacts.