Location
States
CaliforniaIntroduction
The Stockton East Water District (SEWD) is located near Stockton, California, in San Joaquin County. SEWD provides water for agricultural, municipal, and industrial purposes from groundwater supplies and reservoirs. San Joaquin County relies heavily on groundwater to meet demand, particularly for agriculture, the dominant land use. Due to this reliance on groundwater, there has been a steady decline in the aquifer level since the 1970s. In response, managers added surface water through the construction of the New Hogan Reservoir, installed conveyance facilities to provide surface water from the New Melones Reservoir, and constructed a surface water treatment plant in 1979 to decrease the greater Stockton area’s reliance on groundwater.
To recharge water into the groundwater basin, SEWD initiated the Farmington Groundwater Recharge Program (Farmington Program) in 1997. The additional groundwater recharge was intended to act as a buffer for drought and climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change impacts. The Farmington Program recharges groundwater through excavated fields called spreading basins that allow water to percolate into the aquifer. It has been largely successful, recharging an average of 4,400 acre feet of water per year. More recently, SEWD decided to expand the Farmington Program into additional water district land called the Southeast Recharge Basin, in order to build on the success of the Farmington Program and increase groundwater recharge and management flexibility.
Key Issues Addressed
In the 1960s, the water table in San Joaquin County dropped below sea level. Subsequent groundwater measurements revealed that levels had been declining an average of 1.7 feet per year, with some areas dropping 100 feet below historic levels. From the 1970s until 1997, as groundwater was depleted, water was pumped further east of the City of Stockton in order to meet water demand. The Farmington Program was initiated in 1997 to replenish groundwater; however, expanding agricultural areas east of Stockton, which relied solely on groundwater, put further pressure on the groundwater basin as the source of water for the region.
In addition to local water usage drawing down the aquifer, current and increasing drought from climate change further threatens available water and increases future water supply uncertainties. California has experienced severe drought periods from 2015 to 2021. Particularly, 2015, 2016, and 2021 were designated as Exceptional Droughts, the most extreme drought designation, by the National Integrated Drought Information System. Without mindful water managers in San Joaquin County and SEWD, water allocations would not have reached urban populations after being utilized for agriculture.
In 1997, SEWD created the Farmington Groundwater Recharge Program in order to replenish the aquifer and protect water supplies for the future. However, the water treatment plant had to treat runoff during storms to meet demand. This could be problematic because of the potential pollution contained in runoff from storms. In response to the 2014 California Sustainable Groundwater Management Act, which identified the San Joaquin Basin as critically overdrafted, and to increase management flexibility, SEWD initiated the expansion of the Farmington Program to include the Southeast Recharge Basin.
Project Goals
- Improve drought resiliency by increasing groundwater supplies for use in years of limited surface water
- Recharge water into the aquifer to protect against potential saltwater intrusion
- Increase water storage to match production capacity of the water treatment plant
- Expand management flexibility of water sources through the addition of a groundwater recharge basin
Project Highlights
Habitat Bonus: In addition to providing groundwater recharge, the Southeast Recharge Basin creates seasonal wetland habitat for a multitude of birds, insects, and other animals.
- Zero-Waste Spreading Basin: Spreading basins are shallow ponds less than five feet deep that were excavated for the Southeast Recharge Basin site in order to capture stormwater and increase infiltration of precipitation to the groundwater. Construction of the spreading basin was balanced, meaning no material was moved in or out of the site, and was reused to form the concave shape of the basin. The construction of the spreading basin further supports groundwater recharge by accepting peak flows during storm events, and efficiently recharging water in large applications, making them effective in capturing water for groundwater recharge.
- Increased Water Storage and Water Quality: The groundwater recharge basin expansion significantly increased water storage and improved water quality. Since August 2019, the Southeast Recharge Basin has increased water storage by 16,000 acre feet per year, compared to an average recharge of 4,400 acre feet per year from the original 60-acre Farmington Program site. In addition, the recharge basin improves water quality by providing time for suspended solids to settle before water reaches the water treatment plant intake. Runoff can be received by the spreading basins and filtered through the soil, reducing the likelihood of excess nutrients causing concern for humans and wildlife.
- Flexible Operations: The addition of the Southeast Recharge Basin has increased water management flexibility for SEWD. With increased groundwater, SEWD can discharge or recharge specific groundwater basins or take them out of service for maintenance. Increased groundwater can now be pumped by the City of Stockton and for agricultural customers when surface water supplies are insufficient. Management flexibility is particularly useful because the shallow basins are prone to algal blooms during the peak of summer. When there is an algal bloom, water can be moved through the basin quickly in order to remove the algae. However, this could only be done previously based on water demands. With the additional Southeast Recharge Basin, basins experiencing algal blooms, requiring maintenance, or receiving excess runoff can now be taken out of service or treated by the water plant without compromising users’ water needs.
Lessons Learned
SEWD and other stakeholders surveyed potential spreading basin sites prior to project construction to evaluate the feasibility of groundwater recharge on the sites. The initial Farmington Program Study found that areas within SEWD would be capable of recharging excess surface water from floods and storage. Stakeholders later conducted surveys to assess the Southeast Recharge Basin site, which determined that this area is better connected to the aquifer than the original 60-acre Farmington Program recharge basin. Overall, these studies improved understanding of soil and hydrology of the basin sites, increasing investment security for constructing and maintaining the recharge basins.
Planners also considered multiple alternatives for recharging groundwater. Along with the construction of spreading basins, planners considered multiple basin configurations and reverse tile drain systems to increase recharge on nearby agricultural fields. Consideration for these alternatives has been effective in achieving the most efficient use of resources in San Joaquin County where land-use pressures are high.
SEWD implemented a “Design Build'' construction plan for the Southeast Recharge Basin to reduce costs. This process fostered collaboration among SEWD, the contractors, and the designers throughout the construction process by adapting the design as construction occurred. This was largely deemed successful, but finer details of the project, such as water meters, were eventually insufficient for SEWD’s needs. The selected water meters provided less accurate readings than was needed for large water circulations through the SEWD water reservoirs. Ultimately, using lower quality meters provided less accurate water measurements, and cost more because they needed to be replaced. Improving the success of future projects requires investing in more accurate water meters, and more generally, requires carefully balancing the benefits of investing in high-quality equipment with consequences that can come when reducing costs.
Next Steps
- Implement new groundwater recharge methods to further maximize land uses in San Joaquin County
- Replace current water meters with higher quality meters when funds are available
- Work with local and federal agencies to improve water management endeavors such as flood control improvements
Funding Partner
Resources
Contact
- Justin Hopkins, Assistant General Manager, Stockton East Water District: JHopkins@sewd.net
CART Lead Author
- Nicole Williams, CART Student Intern, University of Arizona
- Justin Hopkins, Assistant General Manager, Stockton East Water District
Suggested Citation
Williams, N. and Hopkins, J. (2022). “Protecting Future Water Supply Through the Southeast Recharge Basin Project.” CART. Retrieved from https://www.fws.gov/project/water-supply-southeast-recharge-basin.
