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Assessing surface water use for irrigation in the Delta and its effects on groundwater
Proceedings of the 2020 Mississippi Water Resources Conference
Year: 2020 Authors: Brock M., Tagert M.L., Paz J.O., Krutz J.
Agricultural production in the Mississippi Delta region relies heavily on groundwater for irrigation due to insufficient rainfall during the summer growing season between May and September. As of 2019, more than 20,000 groundwater well permits for agriculture have been issued in the Delta. The Mississippi River Valley Alluvial Aquifer is the shallow subsurface aquifer underlying the Mississippi River Basin, and concerns persist over the dependence on and future supply of water in this aquifer. Surface water sources for irrigation include on-farm water storage (OFWS) systems implemented as a conservation practice for nutrient reduction with cost assistance from the NRCS Mississippi River Basin Healthy Watersheds Initiative. Consisting of storage ponds and tailwater recovery ditches that intercept irrigation and precipitation runoff from adjacent fields, these systems started being constructed in Mississippi in 2008 and have grown in prevalence in the following years. The goal of this study was to quantify the role of OFWS systems in irrigation and as an alternative to groundwater by examining the inventories of OFWS systems for selected years between 2007 and 2018. The size and number of OFWS systems were identified and recorded based on the geospatial data layers containing digitized polygons of the ditches and ponds that make up these systems. Inventory results show an increase in surface water storage from 22.37 ha in 2007 to 651.61 ha in 2018. Next, interpolated maps of saturated aquifer percentages were created using groundwater levels measured by the Yazoo Mississippi Delta Joint Water Management District and aquifer thickness values from the United States Geological Survey. These interpolated layers and inventories are being used to evaluate and define relationships and trends between surface water use and groundwater use for agricultural irrigation. This presentation will compare trends in groundwater decline between land with supplemental irrigation using surface water and land solely irrigated with groundwater.