The Interplay Between Water Resources Management and Hydroclimate Variability in the Semi-Arid Southwest U.S.

Effective management of water resources is a critical global issue, particularly in the arid and semi-arid regions which constitute nearly 1/3 of the world's land mass. At least three issues place special stresses and added uncertainties on water resources and conservation strategies in semi-arid regions. First, rapid population growth is occurring in almost all semi-arid regions of the world. In the U.S., this growth is largely due to immigration of people seeking a mild climate and related quality of life attributes. Second, growing prosperity over the last few decades has impacted per capita water consumption rates and created new water demands. For instance, many semi-arid urban regions of the western United States are transitioning from agriculture, mining and industrial economies to new information- and recreation-based economies, and as result water diversions for the former needs are declining. However, the new prosperity is increasing the demand for urban requirements (e.g. landscaping, water-based recreation) and other in-stream uses. Third, and perhaps most relevant to this session is the additional water management uncertainties resulting from global and local climate changes and their potential impacts on the hydrologic cycle in these regions. Example from the Southwest US, where changes in land cover and timing of snowmelt already are impacting the water balance (both, in terms of quantity and quality) in the desert areas will be provided. Limitations and the uncertainties associated with climate forecast over semi-arid regions, in the context of recent droughts in the Western US, will also be shared.