Location: Crop Production Systems ResearchTitle: A modeling approach to develop hydrological relationships between groundwater & ET in the lower Mississippi river alluvial plain Author
Submitted to: Journal of Ground Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2013
Publication Date: N/A
Citation: N/A Interpretive Summary: Traditional agricultural production practices have negatively impacted ground water resources. By changing crop management practices, such as reduced tillage and crop rotations, farmers can improve soil and water resources and enhance crop yield and economic return. A collaborative research team of scientists from Mississippi State University and USDA-ARS explored mechanistic relationships between water movement through the crop (evapotranspiration) and soil, and the resultant impact on ground water in the Mississippi Delta. The Soil and Water Assessment Tool (SWAT) was used to simulate crop, soil and water parameters within the Yazoo River Basin of the Lower Mississippi River alluvial plain. Standard statistical parameters determined good model performance for both hydrologic and crop model calibration and validation. Identified areas of ground water overuse can be used to indicate areas particularly sensitive to crop production choices. The results support realistic changes that can be implemented in current farm production practices, and the impact of these changes on surface and ground water resources.
Technical Abstract: Agriculture management practices change the hydrological budget of watersheds. Changes in surface runoff can be easily identified using the intensive USGS stream gage network. However, changes to the groundwater table are poorly understood due in part to inherent difficulties in obtaining accurate, detailed measurements. This research was designed to develop relationships among evapotranspiration (ET), percolation (PERC), groundwater discharge to the stream (GWQ), and depth to the groundwater table through a modeling approach. The Soil and Water Assessment Tool (SWAT) hydrologic and crop models were applied for the Big Sunflower River watershed (BSRW; 7,660 km2) within the Yazoo River Basin of the Lower Mississippi River alluvial plain. Hydrologic part of the model was calibrated and validated for the period from 1999 to 2009 using USGS monthly stream flow data. The crop model was calibrated and validated for the same period using corn and soybean yield data from the research plots. Results showed good to very good model performances with the coefficient of determination (R2) and Nash-Sutcliff Efficiency Index (NSE) from 0.4 to 0.9 respectively during both hydrologic and crop model calibration and validation. An empirical relationship of ET, PERC, GWQ, and groundwater level changes was able to predict 64% of the groundwater level variation in the alluvial plain in this study. Thematic maps were developed to identify areas with overuse of groundwater, which can help watershed managers to develop water resources program.