A Scenario Based Assessment of Future Ground Water Resources in the Phoenix Active Management Area

The availability of future water supplies in central Arizona depends on the interaction of multiple physical and human systems: climate, hydrology, water and land-use policy, urbanization, and regulation.  The problem in assessing future water supplies requires untangling these drivers and recasting the issue in a way that acknowledges the inherent uncertainties in climate and population growth predictions while offering meaningful metrics for outcomes under alternative scenarios.  The drivers, policy options, and outcomes are spatially heterogeneous – surface water supplies, new urban developments and changes in land-use will not be shared uniformly across the region.  Consequently, different geographic regions of the Phoenix Active Management Area (AMA) will be more vulnerable to shortages in water availability, and these potential vulnerabilities will be more or less severe depending on the robustness of each water provider’s portfolio.
The primary method of analysis will be a sensitivity analysis that follows the XLRM framework developed by Lempert, Popper and Bankes (2002, 2003).  Two existing models will be connected: WaterSim, developed at ASU’s Decision Center for a Desert City, will generate the X, L, and R components; and the Salt River Valley--1983 groundwater model, developed by the Arizona Department of Water Resources using MODFLOW, will produce the M component.  I use groundwater drawdown levels for each square mile grid-cell of the Phoenix AMA, for the outcome metric.  
Results of the vulnerabilities and sensitivity analysis will be portrayed as graphs of groundwater drawdown (at specific geographical points) as a function of climate change, population growth, groundwater policy and other variables in the X and L components.  This research provides a spatial metrics of water vulnerability and a novel approach to provider level groundwater analysis using the XLRM framework.