Assessment of Spatial Rainfall Variability over the Lower Mississippi River Alluvial Valley

Abstract

large portion of the lower Mississippi River alluvial valley (LMRAV) relies on irrigation from the regional alluvial aquifer for crop sustainability, which is expensive both in terms of water resources and farmer expenditures because of the large volume of water necessary to maintain crop production. As a result, knowledge of the seasonal frequency and distribution of precipitation over the LMRAV is critical for water resources management, the development of irrigation strategies, and economic planning. This project addresses the need for a detailed assessment of regional precipitation patterns through the use of rotated principal component analysis (RPCA) of high-resolution gridded radar-derived rainfall data, which provides quantification of the spatial and temporal characteristics of rainfall over the LMRAV from 1996 to 2011. Results of the project show that precipitation depths over the LMRAV are generally lower and more variable than adjacent eastern areas throughout the year, although there is substantial variability between seasons. This pattern seems to be influenced more by variations during the cool season (January?March), which has a higher overall precipitation depth and lower spatial variability than the warm season (July?September). Results further indicate that warm season rainfall is generally lower and less predictable over the LMRAV as compared to the cool season, which may be detrimental to regional water resources since irrigation planning and permitting is heavily based on seasonal rainfall predictions.