Water agencies in California regularly evaluate the water supply reliability for their service areas in an Urban Water Management Plan which is updated every five years. These plans generally compare the total demand for the agency with the total anticipated water supplies available to the agency. A careful evaluation of supply and demand projections can be used to help identify any vulnerabilities and can be used by decisionmakers to make more informed decisions about investments in water use efficiency and new supplies. The San Bernardino Valley Municipal Water District (Valley District) is taking the first step in a comprehensive evaluation of its supplies and demands by evaluating the demand projections used in its service area. The RAND Corporation provided an independent evaluation of the long-term demand methodology and assumptions used by Valley District's retail agencies, and then developed a single consolidated approach that reflects additional drivers and accounts for uncertainties in these drivers. The study team then used this approach to develop new demand forecasts for each retail agency that reflect a range of plausible future drivers of demand, including climate, population growth and per capita water use. This broader range of plausible future water demands was then analyzed with the goal of helping the Valley District better understand how water demand could evolve in the coming decades. This report suggests that the Valley District incorporate the demand forecasting approach developed in this study in future Regional Urban Water Management Plans. The analysis presented in this report also shows that the Valley District could monitor the drivers of water demand, including population growth, water use rates and temperature, to ensure the Valley District plans for a sufficient buffer between supply and demand into the future. This report is also relevant to water management efforts more broadly, as water supply agencies in California and the Western United States face similar uncertainties around water demand that impact their planning and management decisions.
Table of Contents
Independent review of RUWMP demand forecasts
A standardized demand forecasting approach that adds additional demand drivers and considers uncertainty
Evaluation of the range of plausible future demand