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Estimating the ratio of pond size to irrigated crop land: A tool to conserve groundwater resources in Mississippi

Photo of A schematic diagram showing (a) the pond hydrological processes and water budget used in model development and (b) a photo of a pond in Macon, Mississippi used for model application. A schematic diagram showing (a) the pond hydrological processes and water budget used in model development and (b) a photo of a pond in Macon, Mississippi used for model application. Snapshot : Groundwater withdrawals in the Mississippi Delta region and around the nation have increased dramatically since the last century, resulting in the depletion of water resources from subsurface aquifers. Although more on-farm water storage ponds have been constructed in recent years to mitigate groundwater depletion in Mississippi, little effort has been devoted to addressing the question of how many hectares (1 hectare = 2.47 acres) of crop land can be irrigated with water from one hectare of agricultural pond. Forest Service scientists developed a computer modeling tool to address this need.

Principal Investigators(s) :
Ouyang, Ying 
Research Location : Macon, eastern Mississippi; Porter Bayou Watershed, Mississippi Delta
Research Station : Southern Research Station (SRS)
Year : 2017
Highlight ID : 1336

Summary

Groundwater levels in the Mississippi Delta have declined more than 6.4 meters (20 feet) since 1970 due to extraction to irrigate agricultural crops. More on-farm water storage ponds have been constructed in recent years in Mississippi, but the optimal ratio of pond size to irrigated crop land area was not known. It is crucial to know how many hectares (1 hectare = 2.47 acres) of crop land can be irrigated with one-hectare of pond water in order to cost-effectively construct the proper size pond, manage pond water for crop irrigation, and mitigate groundwater depletion in Mississippi and in other regions of the U.S. facing similar issues. Scientists from the Forest Service and the Agricultural Research Service, agencies within the U.S. Department of Energy, developed a modeling tool using the STELLA (Structural Thinking, Experiential Learning Laboratory with Animation) software to determine the ratio of pond size to irrigated soybean land for a pond that represented the average conditions in east Mississippi and the Mississippi Delta. One simulation shows that a reasonable ratio of pond size to irrigated soybean land is 1:18, if the scheduled irrigation rate is 2.54 centimeters (1 inch) per day, the average pond depth is 1.83 meters (6 feet), and the pond water level is drawn down to 0.38 meters (1.25 feet). A maximum ratio of 1:20 is possible if the pond water level is drawn to near zero. Using the ratio of 1:18, a one-hectare soybean field could save about 542 cubic meters (143,181 gallons) of groundwater each year. Results suggest that an on-farm water storage pond is a promising approach to conserve groundwater resources. The model and findings from this project could have substantial impacts on 1.82 million hectares (4.50 million acres) of crop land in Mississippi. Other regions of the U.S. with similar groundwater management challenges would also benefit from using this predictive tool.

Forest Service Partners

External Partners

 
  • Mississippi State University
  • USDA Agricultural Research Service