R. Spell, A. Lewis, R. Kempka, F. Reid
Landscape changes in California have seriously impacted the state's wetland resources. For example, U.S. Fish and Wildlife Service calculations suggest that of the original five million acres in the Central Valley of California, only 319,000 wetland acres remain (Dahl, 1990). More recent work with satellite imagery implies there may even be less than 260,000 acres remaining, based on satellite imagery collected from 1986-1989 (Kempka et al., 1991). This project also found that beyond the wetlands, there are substantial acreages of flooded small-grain fields that are used as habitat by wildlife. The drastic wetland loss has stimulated efforts to restore seasonal wetlands and enhance harvested agricultural ground for waterbird use. The remaining wetlands in the Central Valley, along with the seasonally-flooded and non-flooded agricultural land, support up to 60 percent of the Pacific Flyway's waterfowl (10-20 percent of U.S wintering waterfowl). Flooding harvested rice (with a base of 600,000 acres) offers an opportunity to supplement restored wetland acreage for wildlife values. The importance of the Central Valley to waterfowl has made this region a priority area for the North American Waterfowl Management Plan (NAWMP). Resource agencies, conservation organizations, local governments, as well as agricultural interests require accurate, up-to-date wetlands inventory information for use in planning, protecting, and mitigating landuse actions and the impacts to wildlife. The purpose of this project is to develop techniques to inventory and monitor flooded ricelands of the Central Valley of California during the winter season. Ducks Unlimited Inc., Pacific Meridian Resources, NAWMP Central Valley Habitat Joint Venture (CVHJV), and U.S. Bureau of Reclamation are partners in this project. Recent Landsat Thematic Mapper (TM) scenes of the Sacramento Valley were used to classify rice agriculture. A series of satellite images (Landsat TM) collected from winter and summer of 1988 and 1993 were processed to determine the extent of change in winter flooded ricelands. The results indicate that nearly 133,000 of the total 404,222 acres of rice were flooded in 1988 and over 142,000 of the total 424,811 acres of rice were flooded in 1993. The increased acreage of flooded rice in winter 1993-94 was related to only a small increased percentage of inundated stubble.
