ADAPTING TO CLIMATE IMPACTS ON THE SUPPLY-AND-DEMAND FOR WATER

The prospect of climate change adds to future water supply and demand uncertainties and reinforces the need for institutions that facilitate adaptation to changing conditions and promote efficient management of supplies and facilities. High costs and limited opportunities for inc reasing water supplies with dams, reservoirs, and other infrastructure have curbed the traditional supply-side approach to planning in recen t decades. Although new infrastructure may be an appropriate response to climate-induced shifts in hydrologic regimes and water demands, it is difficult to plan for and justify expensive new projects when the m agnitude, timing, and even the direction of the changes are unknown. O n the other hand, evaluating margins of safety for long-lived structur es such as dams and levees should consider the prospect that a greenho use warming could produce greater hydrologic variability and storm ext remes. Integrated river basin management can provide cost-effective in creases in reliable supplies in the event of greenhouse warming. With water becoming scarcer and susceptible to variations and changes in th e climate, demand management is critical for balancing future demands with supplies. Although regulatory and voluntary measures belong in a comprehensive demand management strategy, greater reliance on markets and prices to allocate supplies and introduce incentives to conserve w ill help reduce the costs of adapting to climate change. Federal water planning guidelines allow for consideration of plans incorporating ch anges in existing statutes, regulations, and other institutional arran gements that might be needed to facilitate water transfers and promote efficient management practices in response to changing supply and dem and conditions.