The Sacramento-San Joaquin

Why We Work Here: 

While our more mature programs in Oregon are busy on the ground, we’re starting on the ground floor in California. Here, the mantra “you can’t manage what you don’t measure” is coming to the fore. The state enacted sweeping legislation to collect critical information on surface water and groundwater use to support new and more sustainable water management plans. However, these initiatives are “siloed,” run by different program offices. The data are often never aggregated, decreasing overall effectiveness. TFT is stepping in to connect the dots and ensure this opportunity for innovative solutions leads to real results. 

The state’s long-term drought has provided the opportunity to consider new approaches to dealing with the challenges of groundwater sustainability, surface water management and irrigation efficiencies. 

All of these concerns overlap geographically in the Sacramento-San Joaquin River basin. The Freshwater Trust is currently working in three geographies within the basin 

Northern Delta:

The Northern Delta is an area rich with natural resources and a history that includes more than a century of sustainable farming and wildlife stewardship. Much of this area was transferred from federal land to California in 1850 as a part of the Swamp and Overflow Act, where it was reclaimed for agriculture. This region has ample, naturally high water tables, which results in groundwater near the surface. It has an extensive levee system, which conveys surface water to local crops and drinking water as far as the San Francisco Bay Area. 

Solano Subbasin:

The Solano Subbasin (part of the Sacramento Valley Groundwater Basin) covers the eastern half of Solano County and extends into the Northern Delta. It is the primary source of groundwater used for municipal, agricultural and domestic supply in Solano County.

South American and Cosumnes Subbasins: 

The South American Subbasin is bounded on the west by the Sacramento River, on the north by the American River, and on the south by the Cosumnes and Mokelumne Rivers. These perennial rivers interact strongly with groundwater in the basin. The Cosumnes River, southeast of Sacramento, begins in the Sierra Nevada Mountains and empties into the Sacramento-San Joaquin Delta. The Cosumnes Subbasin contains rich agricultural lands as well as some of the largest remaining wetlands and riparian areas in the Central Valley.

Progress to Date:

Since 2016, TFT has built multiple programs in the basin. In response to Senate Bill 88, we developed a measurement method for surface water diversion that addresses the unique qualities of the Northern Delta region. In 2018, 174 surface water diversions covering more than 40,000 farmed acres in the region — including wine grapes, pears, corn, alfalfa, safflower, tomatoes and wheat — had enrolled in our five-year study. 

For groundwater concerns in the same area, we helped support the formation of the Northern Delta Groundwater Sustainability Agency. This means 17 local agencies formed into one integrated agency and have begun work on a unified plan for sustainably managing groundwater use. These agencies are understaffed, so TFT provides the capacity to gather and analyze data and develop effective sustainability measures. 

In the Solano Subbasin, we are also supporting the Solano Joint Powers Agency in developing their Groundwater Sustainability Plan (GSP). TFT secured a grant to integrate our BasinScout prioritization method into the GSP and to collaborate with severely disadvantaged communities. 

In 2017, we began working with the Sacramento Regional County Sanitation District (Regional San), which provides wastewater treatment services, on a range of surface water and groundwater management initiatives.

TFT supported the preparation of an application for funding through the state’s Water Storage Investment Program for a groundwater storage project. This project would create a sustainable, drought-proof, and climate-change resistant water supply to agriculture as well as wetlands and forest conservation lands.

By the end of 2017, this project proposal was one of the highest ranked applications. In 2018, Regional San received full funding of $280.5 million from the California Water Commission and TFT is now supporting the development of the Ecological Plan and program design optimization to improve Chinook and Sandhill crane habitat, and restore and enhance wetlands, riparian forests, and vernal pool complexes.

Irrigated farmland in northern California available to migratory birds

In 2018, TFT also received funding from the Betty and Gordon Moore Foundation and The Water Foundation to prototype the first blockchain-enabled platform developed for sustainable groundwater management, in partnership with IBM Research and IoT sensor company SweetSense, Inc. As allocations are set on groundwater use, markets will emerge as a management tool for groundwater users to exchange shares of groundwater in dry and wet years while meeting basin-scale sustainability goals. The prototyping process includes installing a network of IoT sensors on private, agricultural production wells within the Solano Subbasin in the Sacramento Valley. The sensors transmit real-time water extraction data through a satellite network to a blockchain-enabled platform, which anonymizes, encrypts, and records data into a ledger. Together with local stakeholders and project partners, TFT will develop a dashboard for users to exchange and track groundwater shares while integrating mechanisms to protect groundwater-dependent ecosystems and vulnerable communities.

Over time, our experience, fine-tuned models, and ability to bring together multiple stakeholders will establish our leadership in sustainable surface and groundwater planning and management in California.


In 2015 California passed Senate Bill 88, which made it mandatory for those diverting more than 10 acre-feet of surface water per year to accurately measure the amount of water used. In most cases, SB 88 requires meters for surface water diversions. However, in the Northern Delta, it is technically and logistically challenging to meter the diversions. Instead, most people use gravity-fed siphons, which are unpowered pipes that bring water from the rivers that are at higher elevations to the farms on the Delta islands. TFT is a partner in a scientific consortium to find more accurate and cost-effective methods of measuring water use.

In many locations, groundwater mixes with water in a river channel through the porous sediment surrounding a river. This is a natural process called hyporheic exchange. Rivers recharge the groundwater and, in some cases, rivers are depleted by declining groundwater. While many streams can naturally "lose" water, it is particularly the over-pumping of groundwater in much of California that has led to stream flows being significantly depleted.

For example, in south Sacramento County, a drop in the groundwater table of 30 feet in one area has jeopardized multiple other surrounding water resources – from irrigation wells to wetlands and forests to rivers that support migrating salmon.

TFT is working on several initiatives related to groundwater sustainability in northern California. It is working with the Northern Delta Groundwater Sustainability Agency (NDGSA) and its 17 member agencies to provide administrative support, analytical services, and grant-writing assistance as the NDGSA prepares their Groundwater Sustainability Plans (GSPs).

On a broader scale, TFT is developing user-friendly tools that provide information about water savings, the costs to implement savings, and, most importantly, how to add more water through conservation practices such as cover cropping and winter recharge with surface and stormwater.

In lieu recharge is where surface water is used as a substitute for pumping from a groundwater source. The substituted water is a renewable supply, such as excess surface water or treated wastewater. In lieu recharge allows for "conjunctive use," where surface water is used by persons that could otherwise extract groundwater in order to leave groundwater in the basin. This practice can help improve water reliability in California.

Groundwater is important to everyone, from farmers growing crops to local communities that rely on groundwater as their source of drinking water. Therefore, regional Groundwater Sustainability Plans (GSPs) need to consider the needs and concerns of all water users. In eastern Solano County, TFT is working with local partners to reach out to disadvantaged communities (where incomes are less than 80% of the state’s median household income) to actively engage them in the decision-making process about the future of the resource.