The evaluation of conservation practice placement in the Little River Experimental Watershed using geographic information systems

Abstract

The Conservation Effects Assessment Program Watershed Assessment Study is a joint effort between the USDA Natural Resources Conservation Service (NRCS) and the USDA Agricultural Research Service to evaluate the effectiveness of federally funded conservation programs. In response to this initiative, a 26-year history of NRCS conservation practice placement (1980 to 2006) was evaluated for the Little River Experimental Watershed (LREW) in the southeastern coastal plain of Georgia. To accomplish this task, currently available geographic databases were integrated and queried to assess levels of commonly adopted practices and to evaluate factors affecting practice placement. Databases included (1) USDA NRCS Conservation Practice Database for the LREW, (2) USDA NRCS Soil Survey Geographic Database (SSURGO), and (3) 30 m (98 ft) digital elevation maps. Nearly 50% of all cropland fields in the LREW were delineated as having participated in conservation programs. Practices were predominantly used for water quality and erosion control. Sixty to 65% of the fields (77% of land area) implemented soil erosion and/or water quality control practices in high resource concern areas. Results showed that hydrologic group and proximity to a water body, rather than slope class, were the predominant factors in conservation practice placement. Using a subwatershed database having complete field coverage of four LREW subwatersheds (with and without USDA NRCS assistance), geographic information system databases were queried to evaluate the adoption and placement of erosion control practices that were visible in a 2005 digital orthoquad. Forty-seven percent of all fields in the subwatershed database had implemented visible erosion control–specific conservation practices. and implementation was linearly related to slope class (r² = 0.64, p < 0.10). Fields identified as having participated in federally funded conservation programs coincided with high resource concern areas 35% of the time.