Global perspective on hydrology, water balance, and water resources management in arid basins

Arid and semiarid regions comprise a large part of the world's terrestrial area and are home to hundreds of millions of people. Water resources in arid regions are rare and critical to society and to ecosystems. The hydrologic cycle in arid and semiarid regions has been greatly altered due to long-term human exploitation. Under conditions of global warming, water resources in these regions are expected to be more unstable and ecosystems likely will suffer from severe water stress. In the current special issue contributed to understanding ecohydrologic processes and water-related problems in arid regions of western China, this paper provides a global perspective on the hydrology and water balance of six major arid basins of the world. A number of global datasets, including the state-of-the-art ensemble simulation of land surface models by GSWP2 (Global Soil Wetness Project II, a project by GEWEX), were used to address the water balance terms in the world's major hydroclimatic regions. The common characteristics of hydrologic cycles and water balance in arid basins are as follows: strong evapotranspiration characterizes the hydrological cycle in arid basins; and in water use sectors irrigation consumes a large amount of water, resulting in degradation of native vegetation. From the ecohydrology viewpoint, a comprehensive study of hydrological and ecological processes of water utilization in arid basins is urgently needed. Copyright (C) 2009 John Wiley & Sons, Ltd.