Abstract
Groundwater storage and level have declined rapidly in the Big Sunflower River Watershed (BSRW) of Mississippi Delta in recent years. Farmers in this region are beginning to save groundwater resources by increasing surface water usage for agricultural irrigation. In this study, we estimated the weekly amount of surface water available in ponds and streams, determined if the weekly surface water resources are sufficient for major crop irrigation demand, and assessed how much surface water can replace groundwater for agriculture irrigation in the BSRW. The SWAT (Soil and Water Assessment Tool) model was employed to simulate the weekly water resources for 23 sub-basins from the BSRW. Results showed that weekly stream water resources (SWR), stream evaporation (SE) and water loss from the channel via transmission through the side and bottom of the channel (stream transmission, referred as ST) for BSRW during the growing seasons ranged from 20.4 to 29.4 mm, 7.4 to 14.4 mm, 1.6 to 4.5 mm and 1.1 to 1.6 mm, while pond water resources (PWR) and pond evaporation (PE) ranged from 1.9 to 2.1 mm and 0.3 to 0.5 mm. The value of SWR − (ST + SE) and PWR − PE were positive in all sub-basins, indicating that there are net surface water resources available in this region. The percentages of total groundwater usage for irrigation that could be replaced by surface water in each sub-basin every week of each month from May to September ranged from 10% to 87%. Our studies suggested that the conjunctive use of surface and groundwater for agriculture irrigation is a feasible method for groundwater sustainable management in the Mississippi Delta.
Highlights
The Mississippi River alluvial plain in northwestern Mississippi (Mississippi Delta) is an important agricultural region in the United States with nearly 81% of the area being crop land including soybean, corn, cotton, and rice [1]
Our results indicated that weekly stream water resources (SWR) were higher in April, May and October than in the other months
Our results indicated that there was potential to reduce the groundwater use in Big Sunflower River Watershed (BSRW) if weekly ASWRR were used for irrigation
Summary
The Mississippi River alluvial plain in northwestern Mississippi (Mississippi Delta) is an important agricultural region in the United States with nearly 81% of the area being crop land including soybean, corn, cotton, and rice [1]. The average annual rainfall in this region is 1371 mm, approximately. Irrigation relies largely on groundwater in this region, especially in the Big. Sunflower River Watershed (BSRW) which is the most depleted aquifer in the Mississippi Delta [7]. According to Maupin and Barber [8], approximately 4.2 × 107 m3 per day of groundwater is withdrawn for irrigation from the Mississippi Delta aquifer. The groundwater level has decreased at least 12 m in the past 40 years [9]. Barlow and Clark [7] found that the groundwater level will continuously decline in the 30 years if no water-use conservation practices are employed
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