The Sacramento-San Joaquin Delta system is an exceptionally rich area of agriculture and water supply for California. The impact of using this land for such resources has caused major subsidence to occur, increasing the possibility of salinity intrusion inward. Due to the reliance of Californians on this area, the development of a restored ecosystem by the U.S. Geological Survey (USGS) has allowed scientist to investigate ways to slow or even eliminate subsidence of the Delta islands. The restored Wetlands ecosystem is located on Twitchell Island, situated in the mid-western portion of the Delta, close to the confluence of the Sacramento and the San Joaquin Rivers. Twitchell Island is a good example of the majority of the islands found in the Delta with highly organic surface soils and land-surface elevations of five to seventeen feet below sea level.

In concurrence with the USGS studies on subsidence, our initial objective is to estimate evapotranspiration (ET) from the Wetlands ecosystem. The rate of ET can give estimations of how much water is lost through natural diurnal variation over both vegetation and open water surfaces. Our project includes the installment of an Eddy-Covariance (EC) system to directly measure the energy fluxes, including sensible heat and latent energy. Concomitantly, a Surface Renewal (SR) system has been set up near the EC system and two other SR systems will be placed in different locations in the Wetlands to measure the variability of ET over different vegetation types vs. open water. Other objectives to this experiment include determining the validity of the SR method, ecosystem productivity from carbon dioxide fluxes, and separating energy budgets for the different surfaces found in the Wetlands ecosystem.