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 Northern region of the Sacramento-San Joaquin 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. 

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 2017, 148 surface water diversions covering more than 29,000 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. 

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.

Irrigated farmland in northern California available to migratory birds

By applying our analytical approaches and building on our StreamBank database, we are gaining experience and the opportunity to fine-tune our models for groundwater and surface water management. Over time, our ability to bring together sustainable surface and groundwater planning and management will give us a substantial foothold in the California market and establish TFT’s technical leadership for the state’s most important water legislation.


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.