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United States Department of Agriculture

Agricultural Research Service

Research Project: CONSERVATION EFFECTS ASSESSMENT IN THE SOUTH GEORGIA LITTLE RIVER Title: Water Quality Effects of Simulated Conservation Practice Scenarios in the Little River Experimental Watershed

Authors
item Cho, Jaepil
item Vellidis, George -
item Bosch, David
item Lowrance, Robert
item Strickland, Timothy

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2010
Publication Date: November 1, 2010
Citation: Cho, J., Vellidis, G., Bosch, D.D., Lowrance, R.R., Strickland, T.C. 2010. Water Quality Effects of Simulated Conservation Practice Scenarios in the Little River Experimental Watershed. Journal of Soil and Water Conservation Society. 65(6):463-473.

Interpretive Summary: Conservation Effects Assessment Project (CEAP) was initiated in 2003 to quantify the environmental benefits of USDA conservation practices. Long-term hydrology and water quality data have been measured for more than 30 years within the Little River Experimental Watershed (LREW), which is one of ARS benchmarking watersheds for CEAP, representing typical a Coastal Plain Watershed. Here we examined the water quality effect of two suites of upland conservation practices – one targeting erosion and the other targeting nutrients, along with the impacts of riparian forest buffers. The study indicates that implementing CPs in subwatersheds with the largest nonpoint source pollution loads results in the most rapid water quality improvements. Prioritizing CPs based upon nonpoint source pollutant load yields greater (nonlinear) improvements when CPs are introduced on the subwatersheds with the greatest nonpoint source pollution while the other implementation schemes yield linear returns. The results are useful for setting expectations of the expected benefits of conservation practices across the landscape and at the watershed scale.

Technical Abstract: In this study, we evaluated the water quality effects of alternative conservation practice scenarios using the SWAT model in the Little River Experimental Watershed (LREW), a representative coastal plain watershed located in southern Georgia. We simulated the water quality effect of two suites of upland conservation practices (CPs) – one targeting erosion and the other targeting nutrients. We also simulated the impact of riparian forest buffers. Finally, we evaluated three different management scenarios for implementing the upland CPs – using a random approach, using subwatershed stream order as a prioritization criterion, and using subwatershed nonpoint source pollutant load as a prioritization criterion. The study indicates that implementing CPs in subwatersheds with the largest nonpoint source pollution loads results in the most rapid water quality improvements. Prioritizing CPs based upon nonpoint source pollutant load yields greater (nonlinear) improvements when CPs are introduced on the subwatersheds with the greatest nonpoint source pollution while the other implementation schemes yield linear returns. The suite of CPs targeting erosion resulted in the greatest reductions of sediment and total phosphorus from upland crop areas. The suite of CPs targeting nutrient reduction resulted in the greatest total nitrogen reductions. Overall, riparian forest buffers offered the most comprehensive reduction of nonpoint source pollutant loads. Simulation results indicate that the current level of riparian forest cover in the LREW may be the single greatest contributor to nonpoint source pollutant reduction.

Last Modified: 11/27/2014