Securing a Robust Water Supply for Zone 7

 

Various words have been used to describe the characteristics of what we want in a water system. Reliability—consistently providing high-quality water. Resilience—recovering quickly from difficult conditions. Robustness—maintaining performance under stress. These overlap somewhat, but the bottom line is that we want sufficient high-quality water in both wet years and dry years, which means storage in reservoirs and aquifers.

 

We all remember drought years when we were supposed to decrease our water use by 20% or so. Some of that reduction was for discretionary uses, including letting landscaping die, but some was by one-time upgrades in appliances and landscaping, so future reductions become more difficult and impinge upon quality of life for those who have already invested in conservation. Most of us want a water supply chain that stores more water in wet years for use in dry years, so we don’t suffer sacrificial water-conservation restrictions.

 

Three important factors are at the root of our challenge

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(1) California naturally has highly variable precipitation.

This is due largely to the contribution of atmospheric rivers originating thousands of miles away in the Pacific Ocean. Variability in annual precipitation ranges from 4-6 depending on geographical area, and less is being stored as snow because of warmer temperatures. For us, variability is important both locally and in northern California, because most of our water comes from the State Water Project (SWP), which moves water from Northern to Southern California. The Tri-Valley is actually more dependent on the SWP than Southern California. The SWP infrastructure is aging and in need of upgrades.

 

(2) Zone 7 population has grown but SWP deliveries have shrunk.

Zone 7 was formed in 1957 when the Tri-Valley population was about 20,000, primarily in Livermore. Groundwater levels were dropping as usage exceeded natural recharge. Zone 7 joined the new SWP in 1961 to address this shortage of rainfall in our drainage basin. Zone 7’s population is now close to 260,000, and our dependence on the SWP has grown to nearly 80% of consumption. However, water allocations have shrunk due a combination of climate changes and regulations (Figure 1). We can capture more of our drainage basin runoff, but not nearly enough to solve our problem.

 

(3) PFAS contamination shut in three Pleasanton municipal wells.

Perfluoroalkyl substances (PFAS) are a national water contamination problem. The technology for cleaning them out of our water is well established, but it takes time and money. Zone 7 is well on its way to adding more cleanup capacity, but the contamination of the now inactive Pleasanton wells puts more demand on Zone 7 to supply the difference, and the capacity challenge is greatest in the dry years when the SWP allocation is the smallest. Zone 7 is working with Pleasanton to replace that groundwater capacity.

 

The solutions to these challenges are straightforward in principle but complex in detail: encourage reasonable conservation, add more total supply, and add more storage to save water from wet years to be used in dry years. The complexity is that there are multiple possible projects to address the supply shortages, and they involve technical and financial tradeoffs. We need Directors who are dedicated to solving the problem and not pushing a narrow political agenda.