About two thirds of the 740,000 acres in the Sacramento-San Joaquin Delta (Delta) are in agriculture. The drained peat soils of the Delta have provided fertile soils for agriculture since the late 1800s when these lands were reclaimed from existing wetlands. Since then, the Delta environment has dramatically deteriorated as evidenced by subsidence. 2.5 billion cubic meters of peat soils have oxidized causing subsidence up to 20 feet or more below sea level on many Delta islands.

Subsidence has been indicative of other severe consequences: extensive greenhouse gas emissions, construction of a 110 mile levee network, risks to California’s water supply through the California State Water Project, degradation of water quality. If current agricultural practices remain unchanged, things will only get worse. Peat oxidation will continue resulting in further subsidence over decades; GHGs will continue to be emitted with an additional estimated 158 Mtonnes CO2eq of C and N2O will be lost to the atmosphere by 2050; levee failure risks will increase from deterioration and from increasing hydraulic gradients across the levees from the superposition of sea level rise and subsidence; and water quality will continue to be degraded. Clearly, agriculture needs to change in the Delta.

This project extends those previous efforts assessing the effects of growing rice in the Delta. The collaborative effort includes UCD, UCB, the USGS, the Delta Science Center, Stillwater Science and Tetra Tech and is funded through USDA. The primary long-term goal of this project is to demonstrate rice based cropping systems as an agricultural solution in the Delta with important environmental benefits: mitigating subsidence and concurrently mitigating GHG emissions and soil loss; reducing risks to California water supply, including the agricultural users throughout the San Joaquin Valley downstream of the Delta; and protecting water quality. Dr. Philip Bachand at Tetra Tech is the project manager, working with Professor William Horwath of UCD, the project director, to provide the vision, direction and focus on this project with regard to the stated grant goals and objectives. Tetra Tech and UCD are providing guidance on regionalizing data and results associated with environmental and agronomic effects to determine whether widespread rice production is sustainable and if it is environmentally and economically viable in the Sacramento-San Joaquin Delta. DAP and SWAT economic models, developed by UC Davis, are being refined and used by the team to assess the effects of rice on local, regional and state economics and to provide guidance for developing effective and cost-effective management strategies. Tetra Tech leads technical studies associated with surface water resources and their management; subsidence effects on levee stability and strategies to mitigate those risks; and environmental engineering.