An investigation of seasonal precipitation patterns for rainfed agriculture in the southeastern region of the United States

Authors: Sohoulande, Clement; Stone, Kenneth - Ken; Szogi, Ariel; Bauer, Philip

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2019
Publication Date: 8/20/2019
Citation: Sohoulande Djebou, D.C., Stone, K.C., Szogi, A.A., Bauer, P.J. 2019. An investigation of seasonal precipitation patterns for rainfed agriculture in the southeastern region of the United States. Agricultural Water Management. 223. https://doi.org/10.1016/j.agwat.2019.105728.
DOI: https://doi.org/10.1016/j.agwat.2019.105728

Interpretive Summary: The Southeastern region of the United States has encounter cases of rainfall irregularity during the last decades. Even though the region regularly receives a high total annual rain, the irregularity of rainfall events during crop seasons is a threat for rainfed agriculture which is common practice in the Southeastern US. With this situation, deep understanding of the pattern of rainfall irregularity is needed to support the local agriculture. Thus, this study aims to address the phenomenon by delineating precipitation regions for an area spanning the states of South Carolina, North Carolina, and Georgia. The regions were delineated using both seasonal rain total and seasonal number of rainfall events data over the period 1960 to 2017. Data were collected from 208 rainfall stations across the studied region. Finally, three precipitation regions were delineated based on statistics and similarity criteria. The precipitation pattern in these three regions were different from each other. Tables of precipitation probabilities were created for each region. These tables of probability may provide information about the chances of precipitation deficits or excesses relatively to a crop and henceforth be useful for agricultural water planning.

Technical Abstract: Over the last decades, signs of precipitation irregularity were frequently reported across the Southeastern United States (US). Even though the region receives a relatively high annual precipitation, the precipitation events are not equally distributed in the time and space. Hence, rainfed agriculture which is common practice in the region is threatened by changes in precipitation frequencies during the crop growing seasons. With this situation, a better understanding of the actual patterns of precipitation irregularity is needed to support the local agriculture. This study uses a spatial regionalization approach to delineate precipitation regions for an area spanning the states of South Carolina, North Carolina, and Georgia. The data used include time series of seasonal precipitation totals and seasonal numbers of precipitation events greater than 5 milimeters (mm) over the period 1960 to 2017. A regionalization method which combines principal components and cluster analyses was applied to 208 precipitation stations selected across the study region. Finally, three precipitation regions were delineated based on statistics and similarity criteria. A comparative analysis of these three regions shows significant differences in the seasonal precipitation totals and the seasonal number of precipitation events. In addition, the differences were examined using a probabilistic approach. As a result, tables of probabilities and seasonal precipitation characteristics (precipitation totals and number of events greater than 5mm) were generated for each region. These tables could provide information about the chances of precipitation deficits or excesses relatively to a crop and henceforth be useful for agricultural water planning.