Effect of Drought on Urban Water Supplies. II: Water‐Supply Analysis

Using a water‐resource‐system model, the water‐supply system of the City of Fort Collins, Colorado, which consists of five river basins, was simulated for selected drought periods to determine the yield of the city's existing water supplies and for other potential water‐supply sources. The paper outlines approaches for estimating yields of various water‐supply sources from adjacent basins during projected drought conditions. A water‐rights model (MODSIM) is used to simulate allocations of water supplies based on existing and future water‐rights ownership scenarios for the city. Safe demand levels are determined to assure adequate water availability during extreme drought events. The results of the study indicated that although water supplies for the city are adequate at the present time, policies should be adopted to assure that supplies are adequate to meet future demands during drought periods. The study provided a tool to use in evaluating the drought sensitivity of new water sources for meeting future water demands. The approach presented in this study has widespread application to evaluation of droughts on western urban water supplies.