ABSTRACT
Arizona is “doubly exposed” to the dual challenges of climate change and rapid growth (Wilder et al. 2010, Leichencko and O’Brien 2008, Ray et al. 2007; and Scott et al. and Garfin, this volume). These challenges will require new, adaptive strategies for managing water resources. Many water scarce regions, including Arizona, have access to substantial, minimally used water supplies, but the supplies are of such impaired quality that they were not historically considered for potable and agricultural purposes. This is obvious for coastal regions, where seawater is accessible, but it is also true for inland water scarce areas where brackish water (defined here as supplies with total dissolved solids between 1,000 and 15,000 mg/L) and/or wastewater are often available. In fact, the global volume of brackish and saline groundwater exceeds the summed volume of all non-frozen fresh water supplies (Shiklomanov, 1993). If one were to include brackish groundwater, along with the salinity impaired non-marine surface water resources and wastewater discharges, there would be sufficient water quantity (but not quality) to meet demand in many areas currently considered water scarce or limited. However, the economic and environmental cost of raising the water quality to the necessary use standards and disposing of the waste residuals are key limiting factors.
