Assessing Hydrologic Drought Risk Using Simplified Climate Model

Water resources systems operation requires drought risk estimates to mitigate possible drought-related damages. Drought risk assessment is complicated by the nonlinear interaction of the atmospheric hydrologic and oceanic systems where highly varied hydrologic system responses to similar drought-forcing phenomena can occur. A methodology capable of assessing drought risk associated with hydroclimatic events by using a simplified climate model is presented. Ensemble mean and standard deviations of hydrologic water storage represent the expected hydrologic system response to the hydroclimatic event. Relative frequency histograms and cumulative distribution functions characterize the range of hydrologic system responses that can occur and are used to obtain the spatially and temporally evolving drought risks. The methodology is presented in a framework suitable for application to resources management. An outline of the approach, description of the simplified climate model used in this study, and an illustrative example using a La Nina type event as the drought-forcing mechanism are given. Simulation results, the methodology, and future directions are discussed.