Surface water use to counterbalance groundwater withdrawals in Southwest Louisiana

David M. Borrok, School of Geosciences, University of Louisiana at Lafayette, Lafayette, LA 70504: dborrok@louisiana.edu; Emad Habib, Department of Civil Engineering, University of Louisiana at Lafayette, Lafayette, LA 70504: habib@louisiana.edu; Whitney P. Broussard, III, Institute for Coastal Ecology and Engineering, University of Louisiana at Lafayette, Lafayette, LA 70504: Wbroussard@louisiana.edu; JoAnne DeRouen, Department of Sociology, University of Louisiana at Lafayette, Lafayette, LA 70504: derouen@louisiana.edu; Durga Poudel, School of Geosciences, University of Louisiana at Lafayette, Lafayette, LA 70504: poudel@louisiana.edu; Ning Zhang, Department of Civil, Chemical, and Mechanical Engineering, McNeese State University, Lake Charles, Louisiana 70609: nzhang@mcneese.edu 

The Chicot aquifer, covering over 9,000 mi² of the Southwestern part of Louisiana, is the most-used source of fresh water in the state. Demand for Chicot aquifer water is dominated by agricultural users, primarily for the irrigation of rice. The aquifer is currently over-drafted by about 350 million gallons per day. The focus of our project is to evaluate whether surface water in the region could be used as an alternative to groundwater in order to achieve sustainability. We are creating a Geographic Information Systems (GIS)-based tool that will be capable of examining various scenarios of surface water management. The first step involves disaggregating water supply and demand data spatially and temporally within the GIS framework. Initial supply data are taken from existing surface water runoff model outputs. Because the quality of water can additionally influence its availability, we also will develop indices of key water quality indicators using a database linked to the GIS framework. Another critical component of this work is a social survey of water users, which will better define user needs and decision making. Finally, we are undertaking a climate assessment for the region so we can better predict future precipitation and evapotranspiration amounts and variability. This includes a carbon isotope investigation of tree rings to extend the current historical climate record.

To date we have created the GIS framework for our modeling tool and have incorporated and disaggregated water demand data. Using these data we completed a statistical assessment of the distribution of groundwater users relative to the proximity of useable surface water sources in the study area. Surface runoff data are currently being processed. We have created an easily searchable water quality database for our region that combines U.S. Geological Survey and Environmental Protection Agency data into a single platform. Our initial social assessment work indicates that the key water quality parameter of concern for most users in the region is salinity. Hence, we have created a salinity index linked to the database for characterizing surface water bodies. Finally, we are analyzing existing climate models with respect to our region and we recently completed coring of several old-growth pines for analysis of C isotopes.