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.

Climate change impacts on agricultural watersheds are highly variable and uncertain across regions. This study estimated the potential impacts of the projected precipitation and temperature based on the downscaled Coupled Model Intercomparison Project 5 (CMIP-5) on hydrology and crop yield of a rural watershed in Oklahoma, USA. The Soil and Water Assessment Tool was used to model the watershed with 43 sub-basins and 15,217 combinations of land use, land cover, soil, and slope. The model was driven by the observed climate in the watershed and was first calibrated and validated against the monthly observed streamflow. Three statistical matrices, coefficient of determination (R²), Nash-Sutcliffe efficiency (NSE), and percentage bias (PB), were used to gauge the model performance with satisfactory values of R² = 0.64, NS = 0.61, and PB = +5% in the calibration period, and R² = 0.79, NSE = 0.62, and PB = −15% in the validation period for streamflow. The model parameterization for the yields of cotton (PB = −4.5%), grain sorghum (PB = −27.3%), and winter wheat (PB = −6.0%) resulted in an acceptable model performance. The CMIP-5 ensemble of three General Circulation Models under three Representative Concentration Pathways for the 2016–2040 period indicated an increase in both precipitation (+1.5%) and temperature (+1.8 °C) in the study area. This changed climate resulted in decreased evapotranspiration (−3.7%), increased water yield (23.9%), decreased wheat yield (−5.2%), decreased grain sorghum yield (−9.9%), and increased cotton yield (+54.2%) compared to the historical climate. The projected increase in water yield might provide opportunities for groundwater recharge and additional water to meet future water demand in the region. The projected decrease in winter wheat yield—the major crop in the state—due to climate change, may require attention for ways to mitigate these effects.

Best management practices (BMPs) are commonly used to control sediment yields. 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 agricultural five different BMP scenarios on surface runoff, sediment load, 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 NS (0.61) in the calibration period and a good model performance (R² = 0.79; NS = 0.62) in the validation period 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. 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 system 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 significant reduction in sediment yield (72.5-96.3%) and surface runoff (6.8-38.5%). The model was capable of providing precise information for stakeholders to prioritize ecologically sound feasible BMPs at fields that are capable of reducing overland soil erosion and sediment delivery to channels while increasing crop yield.

Best management practices (BMPs) are commonly used to control sediment yields. 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 agricultural five different BMP scenarios on surface runoff, sediment load, 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 NS (0.61) in the calibration period and a good model performance (R² = 0.79; NS = 0.62) in the validation period 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. 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 system 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 significant reduction in sediment yield (72.5-96.3%) and surface runoff (6.8-38.5%). The model was capable of providing precise information for stakeholders to prioritize ecologically sound feasible BMPs at fields that are capable of reducing overland soil erosion and sediment delivery to channels while increasing crop yield.

Best management practices (BMPs) are commonly used to control sediment yields. 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 agricultural five different BMP scenarios on surface runoff, sediment load, 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 NS (0.61) in the calibration period and a good model performance (R² = 0.79; NS = 0.62) in the validation period 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. 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 system 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 significant reduction in sediment yield (72.5-96.3%) and surface runoff (6.8-38.5%). The model was capable of providing precise information for stakeholders to prioritize ecologically sound feasible BMPs at fields that are capable of reducing overland soil erosion and sediment delivery to channels while increasing crop yield.

Best management practices (BMPs) are commonly used to control sediment yields. 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 agricultural five different BMP scenarios on surface runoff, sediment load, 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 NS (0.61) in the calibration period and a good model performance (R² = 0.79; NS = 0.62) in the validation period 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. 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 system 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 significant reduction in sediment yield (72.5-96.3%) and surface runoff (6.8-38.5%). The model was capable of providing precise information for stakeholders to prioritize ecologically sound feasible BMPs at fields that are capable of reducing overland soil erosion and sediment delivery to channels while increasing crop yield.