Positive spring, summer water supply outlook for Santa Clara County, but Anderson Dam storage issues linger

Although local rainfall and statewide snowpack totals remain below average, the water supply outlook for spring and summer is more encouraging than one month ago. A recent series of storms soaked the region with beneficial rainfall and delivered several feet of snow across the Sierra Nevada, typically the source of about 50% of the water used in Santa Clara County.

At the end of February, the statewide snowpack measured at 39% of average. At that same time, reservoir levels in Santa Clara County were 49% of their restricted capacity. Five of our 10 reservoirs have seismic restrictions that limit the amount of water that can be stored in them.

On April 6, the statewide snowpack measured at 61% of average. A series of storms in March and early April also boosted reservoir levels across Santa Clara County.

On Jan. 2, 2020, mountain peaks are covered with snow near the Phillips Station meadow, where the California Department of Water Resources conducted a snow survey in the Sierra Nevada Mountains. A series of March storms boosted the statewide snowpack to 61% of average.
Ken James / California Department of Water Resources,

Local surface reservoirs are not the only source of water in Santa Clara County. Valley Water has a diverse water supply portfolio, which includes groundwater, imported water (both state and federal) and recycled water. As our community responds to the evolving Coronavirus (COVID-19) public health crisis, rest assured that Valley Water will continue to ensure a reliable supply of safe, clean drinking water.

Reservoir levels around California are also in good shape, hovering around average for this time of year.

Our ability to store water in Anderson Reservoir, which is already limited, will be further impacted this fall when Valley Water begins to empty it to comply with an order issued by the Federal Energy Regulatory Commission (FERC). Built in 1950 to the seismic and dam safety standards of the day, Anderson Dam could be damaged in a large earthquake.

Valley Water is working as quickly as possible to rebuild the dam in compliance with today’s seismic safety standards and regulations. Fixing Anderson Dam to protect public safety remains Valley Water’s highest priority.

Valley Water plans to put the water currently in Anderson Reservoir to beneficial use by sending usable water to our three drinking water treatment plants and recharging the groundwater basins. Anderson Reservoir may remain empty until the seismic retrofit project is complete.

In Santa Clara County, the largest water storage reservoir rests beneath our feet. Our local underground basins can hold more water than all 10 of Valley Water’s surface water reservoirs combined. Currently our groundwater basins are full and healthy.

In years when there’s a large Sierra snowpack, such as the 2016-17 and 17-18 water years, our local reservoirs are often at capacity. There are times when our share of available imported water from the Central Valley Project and State Water Project is more than we need and more than we can store in San Luis Reservoir in Merced County or locally in Anderson and Calero reservoirs.

When that occurs, we can send that surplus water down the California Aqueduct to a groundwater basin near Bakersfield for safekeeping. Currently, Valley Water’s portion of that Semitropic Groundwater Storage Bank in Kern County is full of 350,000 acre-feet of stored water. On average, one acre-foot of water supplies two households in Santa Clara County for one year.

Valley Water also supports the expanded use of recycled water to help meet Santa Clara County’s water supply needs. Our Silicon Valley Advanced Water Purification Center plant in Alviso produced more than 1.5 billion gallons of water in 2019 to augment local recycled water.

Today, recycled water purified at the Silicon Valley Advanced Water Purification Center is blended with the existing recycled water supply produced at the neighboring San Jose-Santa Clara Regional Wastewater Facility for non-drinking purposes. In the future, Valley Water is exploring using purified water for potable uses like groundwater recharge, or delivery to drinking water treatment plants.

While Valley water anticipates water supply conditions for this year are favorable, we will continue to actively track conditions as they evolve and will work to ensure continued water supply reliability.

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