Water agencies across the San Bernardino Valley depend on San Bernardino Valley Municipal Water District to provide them with supplemental water from Northern California as well as ongoing water security.

That security is based not only on Valley District’s ability to import supplemental water supplies from the State Water Project and other sources, but on the district’s ability to effectively forecast the future water supply needs of local agencies. These forecasts enable Valley District to quantify how much water it needs to import to ensure local agencies never run out of water, even during periods of extended drought.

But what if the assumptions and forecasts that Valley District and other local water agencies make about future water needs are wrong?

Valley District and other water agencies are required to provide the state Department of Water Resources (DWR) with a collaborative Urban Water Management Plan every five years. The plan, the latest of which will be submitted to DWR this year, includes local water agencies’ best estimates on future water demands within their respective service areas. The plan also identifies the specific water sources that agencies plan to use to meet these demands, taking into account potential offsets in water demands resulting from water conservation efforts.

Given the wide swings in the availability of State Water Project water from year to year as well as the possibility of even more severe and lasting droughts, Valley District hired The Rand Corporation to independently analyze the long-term demand forecasts of local waters. The Rand study, completed in 2019, took into account a variety of drivers of future water demand, including patterns of urban development and population growth. Valley District uses a 10 percent reliability factor in its forecasts, meaning it increases its highest future water demand projections by an additional 10 percent to offset any unforeseen changes in demand.

Rand concluded that the 10 percent reliability factor is a good start, but more analysis is needed.

“Our analysis suggests that the existing 10 percent reliability factor utilized by Valley District to account for uncertainty is likely to be sufficiently broad to address the range of uncertainties in the drivers of demand, including climate warming, efficiency improvements and population growth,” Rand wrote in the analysis.

However, Rand also cautioned that future demands of the water agencies Valley District serves could be higher than projected if temperature and population growth increase more than projected over time and if water use efficiency is less than projected.

“The results of the study showed that in a single dry year, demands could be about equal to planned supplies,” Rand wrote. “This also means that the reliability factor, intended to account for uncertainty in demand and supply, is fully used up by demand alone. This leaves no margin for error.”

Rand, therefore, suggested that Valley District perform a similar analysis, looking specifically at the reliability of the water supply portfolios of both Valley District and its water agency customers.

“The Valley District could also perform a similar time-series analysis to understand the cumulative impact of drought conditions and increased temperature on multiple dry years,” the Rand study continued, adding, “Analysis of the plausible range of multiple dry year supplies would give the Valley District a better understanding of how often demand may exceed supply.”

Valley District has hired Rand to complete such an analysis, looking at the reliability of local agencies water supplies. The results of this second phase of the Rand study are expected to be released later this year.

In the meantime, Rand’s analysis found that additional investments in water use efficiency could be worthwhile and that demand management strategies can also help shield Valley District from unforeseen increases in demand. Valley District is already taking steps in this regard.

In addition to funding ongoing water conservation and water education efforts, Valley District has established a Local Resource Investment Program to provide financial support and incentives to local agencies for securing supplemental water each year, most likely in the form of recycled water.

The first agency to take advantage of this program is East Valley Water District in Highland, which is building a recycled water facility that will produce up to 11,000 acre-feet of recycled water per year. The facility, called the Sterling Natural Resource Center, is expected to begin producing recycled water in 2021.

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