MISSION OF THE BASIN: Improve regional water supply reliability and protect groundwater-dependent ecosystems.
The Sacramento and San Joaquin River basins extend nearly 500 miles across northern and central California. Their streams and rivers, such as the Cosumnes, are connected to vital underground aquifers, forming a network of natural habitats and farmed land dependent on connections between groundwater and surface water.
In 2016, TFT began working with the Sacramento Regional County Sanitation District to secure a massive state grant that allows the utility to send clean, recycled water to a stressed subbasin south of Sacramento. Farmers there will use the recycled water to irrigate fields and reduce the demand for pumped groundwater. TFT designed the program’s conservation plan that will secure, protect, and enhance more than 4,000 acres of sensitive habitat for decades. This $600 million program, called Harvest Water, is expected to restore groundwater levels, thus increasing drought resilience for the entire system, and benefiting irrigators, at-risk drinking water supplies, and fish and wildlife species.
Since opening its Sacramento office in 2016, TFT has put an integrated strategy in motion to further bolster the basins. For example, TFT helped form a Groundwater Sustainability Agency to create a unified plan for sustainably managing groundwater. We are using our BasinScout® Analytics to identify and prioritize on-farm conservation actions for replenishing groundwater. By designing and implementing strategically located projects to replenish groundwater and enhance streamflows, we have also successfully engaged corporate partners in their commitments to replenish more water than they consume. True to TFT’s strengths in finding win-win solutions, we have also addressed the region’s surface water by developing a practical measurement method for farm diversions in the Northern Delta and reducing barriers to state reporting requirements for agricultural communities.
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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.
