Aquifer storage and recovery (ASR) is a solution for regions experiencing groundwater shortages, but is unexplored in wet regions such as Louisiana, which is experiencing aquifer overdrafting at alarming rates. Surface storage reservoirs are infeasible in these low‐gradient environments, so ASR can provide an alternative to alleviate groundwater stress and prevent subsidence and saltwater intrusion. The purpose of this study was to assess the feasibility of ASR in the Chicot Aquifer in Southwest Louisiana. The study is based on a regional groundwater model combined with a geospatial analysis of the quantity and quality of surface water and groundwater resources and land use. A statistical distribution was used to rate each criterion and combine them into a suitability index (SI) that defines each watershed’s feasibility considering combinations of criteria determined by the user’s purpose for ASR and the availability of data. The SI was formulated as a hybrid additive‐multiplicative function to provide flexibility in specifying criteria that are deemed most constraining for ASR feasibility. The analysis identified the east‐central zone of the Chicot Aquifer, which is experiencing substantial groundwater stress from agricultural irrigation, as most suited for ASR operations. Besides the criteria on water availability and aquifer characteristics, the quality of the surface water and land‐use considerations were key factors in constraining the feasible watersheds.
This study identifies hydrogeologic characteristics of complex aquifers based on constructing stratigraphic structure with large, non-uniform well log data. The approach was validated through a modeling study of the irrigation-intensive Chicot aquifer system, which is an important Pleistocene-Holocene aquifer of the Coastal Lowlands aquifer system in the southwestern Louisiana. Various well log types were unified into the same data structure, prioritized based on data sources, and interpolated to generate a detailed stratigraphic structure. More than 29,000 well logs were integrated to construct a stratigraphy model of 56 model layers for the Chicot aquifer system. The stratigraphy model revealed interconnections of various sands in the system, where 90% of the model domain is covered by fine-grained sediments. Although the groundwater model estimated a slight groundwater storage gain during 2005–2014 for the entire region, groundwater storage in the agricultural area was depleted. Nevertheless, the quick groundwater storage recovery during the non-irrigation seasons suggests that the Chicot aquifer system is a prolific aquifer system. The groundwater modeling result shows that the gulfward groundwater flow direction prior to pumping has been reversed toward inland pumping areas. The large upward vertical flow from the deeper sands indicates potential saltwater migration from the base of the Chicot aquifer system.
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