Interpreting sustainable yield of an aquifer using a fuzzy framework

Reliable estimates for how much water can be safely withdrawn from aquifers without harming the environment is crucial for identifying new water supply sources and fostering sustainable growth. Methodologies to estimate groundwater availability that are rooted in science and yet accomplishable with minimal data are particularly useful for effectual aquifer management. Also, as groundwater management is increasingly becoming a participatory process, these methodologies must be transparent and easily understood by a wide range of audiences. In addition, proposed approaches must also reconcile imprecision and uncertainties arising from lack of data, differences in stakeholders' perceptions and limitations associated with incomplete aquifer characterization. In this study, the fundamental concept of water balance is coupled with fuzzy regression to develop a scheme for assessing regional-scale groundwater availability. Using the mass-balance approach, anthropogenic water demands (municipal, industrial and agricultural) and ecological demands (baseflows to rivers) can be incorporated into the availability estimation process. The use of fuzzy regression enables the specification of decision makers' preferences to the adopted procedure and renders the parameter estimation to be more robust in the presence of extreme values. The methodology is illustrated by using it to estimate groundwater availability in the Gulf coast aquifer, underlying Refugio County, TX, USA.