Abstract
Best management practices (BMPs) are commonly used to reduce sediment loadings. In this study, we modeled the Fort Cobb Reservoir watershed located in southwestern Oklahoma, USA using the Soil and Water Assessment Tool (SWAT) and evaluated the impacts of five agricultural BMP scenarios on surface runoff, sediment yield, and crop yield. The hydrological model, with 43 sub-basins and 15,217 hydrological response units, was calibrated (1991–2000) and validated (2001–2010) against the monthly observations of streamflow, sediment grab samples, and crop-yields. The coefficient of determination (R2), Nash-Sutcliffe efficiency (NS) and percentage bias (PB) were used to determine model performance with satisfactory values of R2 (0.64 and 0.79) and NS (0.61 and 0.62) in the calibration and validation period respectively for streamflow. We found that contouring practice reduced surface runoff by more than 18% in both conservation tillage and no-till practices for all crops used in this modeling study. In addition, contour farming with either conservation tillage or no-till practice reduced sediment yield by almost half. Compared to the conservation tillage practice, no-till practice decreased sediment yield by 25.3% and 9.0% for cotton and grain sorghum, respectively. Using wheat as cover crop for grain sorghum generated the lowest runoff followed by its rotation with canola and cotton regardless of contouring. Converting all the crops in the watershed into Bermuda grass resulted in significant reduction in sediment yield (72.5–96.3%) and surface runoff (6.8–38.5%). The model can be used to provide useful information for stakeholders to prioritize ecologically sound and feasible BMPs at fields that are capable of reducing sediment yield while increasing crop yield.
Highlights
Sediments, originating from land use activities including farming and urbanization, constitute one of the major non-point source (NPS) pollutions and have impaired water bodies, reduced reservoir capacity and lifespan, threatened drinking water supply, increased water treatment cost, and reduced the overall ecosystem health globally (Abdulkareem et al, 2018; Falconer et al., 2018, FAO, 2013; Simon and Klimetz, 2008; Palmieri et al, 2001)
When contouring was applied in conservation tillage (S2), surface runoff reduced by 18.4% for cotton and grain sorghum and by 19.2% for winter wheat
We employed Soil and Water Assessment Tool (SWAT) model to estimate changes in surface runoff, sediment load and crop-yield under five different scenarios of agricultural best management practices (BMPs) in an agriculture-pasture intensive watershed located in southwestern Oklahoma
Summary
Sediments, originating from land use activities including farming and urbanization, constitute one of the major non-point source (NPS) pollutions and have impaired water bodies, reduced reservoir capacity and lifespan, threatened drinking water supply, increased water treatment cost, and reduced the overall ecosystem health globally (Abdulkareem et al, 2018; Falconer et al., 2018, FAO, 2013; Simon and Klimetz, 2008; Palmieri et al, 2001). In the United States of America (USA), more than 50% of water bodies are NPS impaired, with sediment ranking the sixth among the leading causes of water quality impairments The Great Plains region, characterized by highly intensive agricultural production system in the USA, is subject to water quality issues mostly due to agricultural NPS pollution (Osteen et al., 2012). Conservation Program provides financial and technical assistance as water quality protection activities in the Great Plains states to ranchers and farmers who adopt total conservation treatment of their entire operation. This approach has increased soil organic carbon in the Great
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