Quantifying Water Use in the Mississippi Alluvial Plain

The Mississippi Alluvial Plain (MAP) is one of the most important agricultural regions in the United States with an estimated water-use demand for irrigation to be over 10 billion gallons per day. Crop productivity relies on groundwater irrigation from the Mississippi River Valley alluvial (MRVA) aquifer - an aquifer system that is not fully understood in terms of water-level response to pumping, sources of recharge and the water budget components. Withdrawals from the MRVA aquifer have resulted in substantial declines in groundwater-levels and reductions in stream baseflow, and a realization that continued rates of withdrawal may not be sustainable to maintain the aquifer as a source for irrigation in the region. To address this need in the MAP, the U.S. Geological Survey has initiated a regional water-availability study to improve characterization of the MRVA aquifer system. Understanding the water-use demands within the MAP region is imperative before questions of water availability and sustainability can be addressed. Water-use represents one of the largest components of the water budget and is significant variable in groundwater-flow models. The USGS plans to improve water-use estimates by establishing a regional water-use monitoring network and enhancing the existing State networks within the MAP region. These data along with multiple remotely-sensed (or GIS) data variables will be evaluated geostatistically to develop a dynamic irrigation water-use model to provide a consistent and improved estimate of water-use throughout the MAP. The irrigation water-use model will include variables such as; remotely-sensed data, climate data, crop types, soil types, and amount of irrigated acres to estimate water-use both spatially and temporally for the MAP region. Improving estimates of water use will improve groundwater-flow model predictions, and help guide management strategies to improve sustainability of water resources to meet the needs of humans and ecosystems.