Valley Water releases draft master plan for water reuse

Each year record-setting temperatures and extreme weather alert us to the impacts of climate change. Unanticipated lightning storms in August 2020 incited wildfires across the Bay Area region impacting thousands of people. It has never been more evident that California’s changing climate threatens our natural resources. As the water resource manager for Santa Clara County, Valley Water works diligently to secure a safe, reliable water supply for Silicon Valley in a sustainable manner that protects our environment. That’s why water reuse is a critical strategy to the agency’s future water supply outlook.

This summer Valley Water released a draft of the Countywide Water Reuse Master Plan, a framework that outlines existing and potential opportunities to expand water reuse in Santa Clara County. Water reuse is the recycling of wastewater for potable (drinkable) or non-potable purposes, which includes landscape irrigation, agricultural and industrial uses such a cooling systems, firefighting and flushing toilets.  Potable reuse means recycled water is treated to drinking water standards using advanced purification technology, producing what is known as advanced purified water.

Water reuse allows us to be better prepared to face the looming impacts of climate change as a locally controlled and drought-resistant water source. By recycling water, we no longer have to rely on rain to meet our region’s water needs. Water reuse also helps reduce our dependency on imported water, water we bring in from outside of Santa Clara County, which accounts for 55 percent of water use in our area. Reusing water is a sustainable practice that also cuts back on energy and environmental costs of transporting these supplies.

Valley Water began developing the blueprint for water reuse in 2018.  We’ve been working with four wastewater partner agencies, 15 municipalities and 13 local water providers. The master plan looks at the best ways to take existing recycled water systems and expand water reuse for non-drinking purposes. It also looks at expanding purified water reuse with our partners to boost our drinking water supply.

In addition, the master plan identifies new sources, quantity and costs of wastewater for water reuse.  To make sure we have enough water for our future, Valley Water board of directors set a goal of providing 10 percent of our total countywide water demands with recycled water by 2028. The board also established a long-term goal of producing at least 24,000 acre-feet a year of recycled water by 2040 to bolster drinking water supplies. An acre-foot is approximately the amount of water used in a year by two families of five.

The draft master plan outlines a series of projects, referred to as portfolios, in North County and three additional ones in South County that would help meet the 24,000 acre-feet annual goal. In evaluating and ranking portfolios, Valley Water and its partners considered using and building on existing recycled water systems, including a combination of projects for both potable and non-potable reuse. Each of these includes obtaining wastewater from identified partner agencies, along with new projects that would help meet our 2040 goal.  

The draft master plan explores four different ways of expanding our local water supply through water reuse.  

  • Groundwater Recharge – replenishing the groundwater aquifer with purified water
  • Surface Water Augmentation – using purified water to increase water levels in our reservoirs
  • Raw Water Augmentation – sending purified water into a pipeline system that delivers untreated water to a drinking water treatment plant
  • Treated Water Augmentation – sending purified water directly into the drinking water system

Instead of recommending one path, the draft master plan allows for flexible options by presenting a menu of water reuse opportunities and comparing benefits, challenges, risks and costs. Valley Water and partners designed tools and criteria to evaluate priorities and risks for each. Projects were evaluated based on criteria such as costs, ease of obtaining permits from regulatory agencies, environmental impacts and benefits, the scale of construction and engineering feasibility, and potential risks to disrupt, delay or halt projects.

Potential projects in North County include:

  • Expanding the current Silicon Valley Advanced Water Purification Center to allow for water reuse through either groundwater recharge, raw water augmentation or treated water augmentation.
  • Building a purification facility to be used by the cities of Sunnyvale and Palo Alto to allow for groundwater replenishment.
  • Building separate purification facilities in both Sunnyvale and Palo Alto for groundwater recharge.

The additional projects in South County include:

  • Extending a pipeline to connect the South Bay Water Recycling system in San Jose to a new recycled water system in Morgan Hill.
  • A new purification facility in Morgan Hill for groundwater recharge or surface water augmentation.

Projects for both north and south county range from $70 to $795 million in capital costs and vary in the amount of purified water each would produce. To read more about the detailed projects outlined, including cost estimates for construction, maintenance and to produce purified water per acre-foot a year, you can access a copy of the draft water reuse master plan at:

The final Countywide Water Reuse Master Plan will be presented to the Valley Water board of directors in early 2021. 


  1. Are there plans to dredge Lake Anderson’s build up of silt now that the lake is mostly drained? Surely that would increase water storage capacity for the water district.


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