A project summary: Water and energy budget assessment for a non-tidal wetland in the Sacramento-San Joaquin Delta

In the spring of 2002, a micrometeorological tower containing an eddy-covariance (EC) and a surface renewal (SR) system began measuring evapotranspiration rates to complete the water budget for a non-tidal wetland. Water budget assessment for the non-tidal wetland is a project involving the United States Geological Survey (USGS) and the Regents of the University of California, Davis (UCD) and is part of an overall CALFED funded project to restore ecological health and improve water quality in the Bay-Delta system. An additional goal is to investigate the mitigation of subsidence that is occurring on the Delta islands. The location of the non-tidal wetland, on 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.

The project summary will contain findings from the summers of 2002 through 2004, where weather conditions varied from year to year. The EC system is orientated over the wetland to capture most of the wetlands energy budget, with minimum loss to winds from areas other than the wetland. Information about fetch and source area will be a topic for discussion. Furthermore, due to the heterogeneity canopy of the wetland we use the SR system to capture individual components to quantify contribution of each area to the overall system. Another important aspect of the project is to get an accurate estimate of the heat stored in the water of the wetland. We have investigated different ways to increase accuracy for this energy budget term.