90 YEARS OF NOURISHING THE VALLEY | Santa Clara Valley Water
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May 22, 2019
Page Groundwater Recharge Ponds

In almost a century, Valley Water has transformed a sinking valley of orchards with the help of a complex system involving reservoirs, percolation ponds, treatment plants, and vast pipeline networks, to support the world’s technology hub. And in our 90th year, we’re celebrating our proactive groundwater management, a core tenet of our founding. Groundwater accounts for almost half the water used in Santa Clara County, making it a critical lifeline for Silicon Valley.

The Santa Clara Valley Water District, now known as Valley Water, was founded in 1929 in response to overdrawn groundwater basins, land subsidence (sinking of the surface of the land), and the increasingly clear need for central water management and conservation. This effort was led by local farmers and business leaders who recognized the critical link between economic prosperity and a reliable water supply.

To address the sinking valley floor, early Valley Water leaders took swift action in finding a way to replenish groundwater. In the 1930s, the agency built six surface water reservoirs to capture stormwater (four additional reservoirs were constructed in the 1950s). Leaders also strategically built percolation pond systems in areas where natural gravel allows for water to easily seep down and refill aquifers. This was the start of something big — regional water reliability and groundwater recovery.

However, a surging valley population strained groundwater resources and subsidence continued. Between 1915 and 1969, downtown San Jose had permanently sunk by nearly 13 feet. The region’s water demands quickly outpaced existing supplies, so a contract with the State of California allowed Valley Water to start bringing water in from state-owned reservoirs outside of the county. In the 1960s and 70s Valley Water built two drinking water treatment plants to treat local and imported surface water, which helped reduce groundwater pumping and relieve pressure from aquifers.

By 1970 the agency had essentially halted permanent subsidence through an integrated water system that made use of imported and diversified local water supplies. In the next two decades, the agency would work to obtain additional imported water and build its third drinking water treatment plant.

Over the course of 50 years, Valley Water built a reliable and sustainable system with diverse sources and major valley pipelines that could convey surface water from reservoirs to treatment plants and percolation ponds. This unique and ingenious method of ensuring a reliable water supply while guarding against subsidence drew the attention of the American Society of Civil Engineers, which designated Valley Water’s system a Historical Engineering Landmark in 1976.

As a special district and not a direct water retailer nor a land use agency, Valley Water’s role in groundwater management is unique. To help protect groundwater quality, Valley Water regulates the construction, maintenance, and destruction of all wells in Santa Clara County. By providing free water quality testing and rebates for nitrate treatment for domestic wells, we help ensure well owners are empowered as community partners in protecting our groundwater resources

Just as critical as preserving our groundwater is fostering a close relationship with the community. Valley Water strives for transparency in groundwater operations. The annual rate-setting process engages the stakeholders and residents with an opportunity to learn and opine on the rates levied to protect and augment water supplies.

And to ensure our ability to continue protecting our groundwater resources and supporting a healthy life, environment and economy for the residents and businesses of Santa Clara County, Valley Water conducted a groundwater benefit zone study. The study reassesses areas benefitting from groundwater management activities to help ensure fair and equitable charges for well users. An independent panel of experts reviewed the study and the resulting proposed benefit zones that reflect the variance of benefits in the region. Experts commended the study and results. The proposed zones were presented this spring and will be implemented contingent on board approval. The Valley Water board of directors will be making a decision this summer. To learn more about the study and its potential impacts, visit: https://www.valleywater.org/gwbenefits

Ensuring a reliable water supply for nearly 2 million people requires a multi-faceted approach. Valley Water’s groundwater management programs have pioneered local water resource management for almost a century and are constantly evolving to meet the needs of our ever-growing valley.


Valley Water manages an integrated water resources system that includes the supply of clean, safe water, flood protection and stewardship of streams on behalf of Santa Clara County's 2 million residents. The district effectively manages 10 dams and surface water reservoirs, three water treatment plants, an advanced recycled water purification center, a state-of-the-art water quality laboratory, nearly 400 acres of groundwater recharge ponds and more than 275 miles of streams. We provide wholesale water and groundwater management services to local municipalities and private water retailers who deliver drinking water directly to homes and businesses in Santa Clara County.