Assessment of Warm-Season Rainfall Variability and Trends over the Lower Mississippi River Alluvial Valley

The lower Mississippi River alluvial valley (LMRAV) is characterized by abundant rainfall and a long growing season, and as a result agriculture plays a major role in land cover and hydrologic processes. Although irrigation is prevalent, a large portion of the agricultural land relies on rainfall for crop sustainability, leading to an increased sensitivity of crop production to atmospheric processes. In addition, the level of irrigation necessary to sustain current crop production is no longer feasible given the stress placed on the regional alluvial aquifer. Due to complex surface-atmosphere interactions leading to meteorological modifications in the region, along with continually changing anthropogenic needs on the groundwater system, it is difficult for water resource managers to make sound decisions for future water sustainability. As a result, it is critical to quantify the frequency and distribution of warm-season precipitation over the LMRAV to determine current and near-future water resource guidelines for planning and management purposes. This research will address this issue through an assessment of historical precipitation variability over the region, utilizing multi-sensor precipitation estimates from the NEXRAD system to maximize the spatial resolution of rainfall observations. Using these data at monthly and seasonal scales, a principal component analysis will be applied to determine the primary modes of rainfall distribution while a trend analysis will be used to quantify changes in rainfall amount over the past 15 years. This information will be used to estimate current and future precipitation availability over the region, which will aid in determining the natural limits to water resource availability, as well as the relationship between regional precipitation and groundwater variability.