Simulating potential weekly stream and pond water available for irrigation in the Big Sunflower River Watershed of Mississippi Delta
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.