Preparing municipal water system planning for a changing climate: Integrating climate-sensitive demand estimates

Seasonality and a changing climate exert strong influences on supply and demand in the western United States, challenging municipal water system (MWS) management. Although supply and demand exhibit characteristics of nonstationarity, the commonly used econometric-based models to estimate demands discount the influences of climate variability and trends in seasonal MWS vulnerability assessments. Given the projected impacts of climate change on water resources, we use the documented performance of a real-world MWS with a calibrated systems model to investigate how demands modeled with and without the influences of climate impact system vulnerability indicators—determined by the exceedance of historical daily mean imported water—for MWS planning guidance. Neglecting climatic influences on MWS demands, the model overestimates the volume of imported water by up to 50% and misclassifies vulnerabilities during supply-limiting conditions. The climate-sensitive demand estimates reduced model error (i.e., <3% error) and correctly categorized vulnerabilities. Moreover, the MWS exhibited an average threefold greater sensitivity to percent changes in demand relative to percent changes in supply. The sensitivity to variances in demand emphasizes the need to account for factors influencing supply and demand when investigating the impacts of a changing climate, suggesting future research to examine the coupled influences of modeled supply and demand accuracy on MWS performance.