Impact of Different Ratios of Surface Water and Groundwater for Row Crops Irrigation on Groundwater Level in Mississippi Delta

Author(s): Gao, F.; Feng, G.; Dash, P.; Ouyang, Y.

Groundwater resources in Mississippi Delta have been overexploited for agricultural irrigation for a number of years. Over 700,000 hectares of row crops in this region was irrigated by using groundwater. As a result, groundwater level has declined > 6.5 m (20 ft) since 1970, which threaten the sustainability of irrigated agriculture in this region especially in Big Sunflower River Watershed. Surface water resources can be used as an alternative source for irrigation. Limited information was reported regarding groundwater level as affected by different ratios of surface water and groundwater for irrigation in this region. The objectives of this study were to employ a coupled SWAT-MODFLOW model and simulate the change in groundwater level and storage as affected by a) no irrigation scheme; b) conventional irrigation scheme; c) water-saving irrigation scheduling by using different percentages of surface and ground water. An analysis from 2000 to 2016 showed practically achievable reductions in weekly pumping (<22%) and replacement by surface water for irrigation would stabilize the groundwater levels in the Mississippi Delta. This study suggested that the conjunctive use of surface water in addition to groundwater can be a sustainable way for future to continuously grow major row crops soybean, corn, cotton and rice in the Mississippi Delta.

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