DEVELOPING AN INTERACTIVE MODEL (DECISION SUPPORT SYSTEM) TO ADDRESS WATER MANAGEMENT POLICY ISSUES: AN EDWARDS AQUIFER EXAMPLE

The Edwards aquifer is a karstic aquifer that discharges naturally to springs that support a number of endangered aquatic species. Past and projected rates of development and urbanization are high as are the political stakes in managing regional growth and water resources sustainably. Key issues involve how can development occur or what type of development is acceptable to maintain critical spring flows, water quality, maximum pumping from the aquifer, and environmental quality with intergenerational equity? We are developing a decision support system (DSS) that links scientific and management models that incorporate community stakeholder input, optimization algorithms, and decision analysis tools. The Texas Water Development Board's groundwater availability model is the basis for the DSS. We scale the distributed parameter model (MODFLOW) into a systems dynamics model (POWERSIM©) with links to socio-economic data and stakeholder preferences. Key decision variables include: well distribution and pumping rates, impervious cover, water and sewage line distributions, and stream setbacks. Key outputs include spring flow and water table declines in drought years. Overcoming uncertainties in the relationships between land use, recharge, and aquifer performance is a significant challenge.

Understanding the interconnection between systems and hypothesis testing to bracket expected changes in recharge provide valuable information for groundwater management, which we are testing through stakeholder input, including narrative elicitation. The DSS allows comparison of hypotheses about spatial recharge distributions and communication with decision makers in a timely, policy-relevant format that is compatible with Texas policy for quantifying consensus and available yields. This research is being conducted at The University of Texas at Austin and Sandia National Laboratories.