Critical regions: A model-based estimation of world water resources sensitive to global changes

Abstract

This paper presents a top-down approach for identifying regions whose water resources have higher sensitivity to global change than other regions. The aim of this approach is to provide an overview of regions that may justify special attention from the research and development assistance community, under particular global change scenarios. As a 'top-down' method it is best seen as a type of sensitivity analysis that can complement rather than replace other 'bottom-up' studies of the vulnerability of particular watersheds. An increase in 'water stress' is used as a measure of increasing sensitivity of watersheds to global change, and this stress is computed with the global water model, WaterGAP. Stress increases when either water withdrawals increase or water availability decreases. Since the criteria for determining criti- Aquatic Sciencescal regions is uncertain, they are calculated and compared for four different sets of criteria. To examine the difference in critical regions under different socio-economic and climate scenarios, they were also calculated for four distinctive scenarios. Under the scenario showing the largest increase in water stresses, the estimated area of critical regions (in 2032) ranges from 7.4 to 13.0 percent of total land area, depending on the criteria for identifying critical regions. As expected, the estimate of critical regions is very scenario-dependent, showing smaller areas under scenarios having smaller increases in water stress. However, some regions always appear as critical regions regardless of the scenario. These include parts of central Mexico, the Middle East, large parts of the Indian sub-continent, and stretches of the North African coast.

Resistance and Resilience of A Stream Salamander To Supraseasonal Drought

“…Those particularly at risk will be populations living in megacities, rural areas strongly dependent on groundwater, small islands, and in glacier-or snowmeltfed basins (more than one-sixth of the world's population live in snowmelt basins). Problems will be more critical in economically depressed areas, where water stress will be enhanced by socio-economic factors (Alcamo and Henrichs, 2002;Ragab and Prudhomme, 2002). [WGII 3.3.2,3.5.1]…”

L’Etat des Ressources En Eau au Maghreb En 2009

“…Le seuil de 40% est considéré comme un optimum d'utilisation de l'eau dans un pays (Alcamo et Henrichs, 2002). Tous les pays du Maghreb ont déjà franchi ce seuil, montrant une utilisation intensive des ressources en eau dans ces pays (Tableau 1).…”

Water stress and water wars

“…A final uncertainty about future water shortages arises from the impact of climate change on the availability and usage of freshwater in particular countries. I must leave for others, such as Alcamo and Henrichs (2002), to discuss these highly technical issues. One important study (Barnett, Adam, and Lettenmaier, 2005) also shows that the most important impacts of climate warming will not necessarily be the amount of precipitation in particular areas, but rather a change in the seasonal pattern of snow and glacier runoff to winter and early spring, away from late spring and summer when demand for water is highest, a phenomenon placing great strain on water storage capacity.…”