Observational evidence from all continents and most oceans shows that many natural systems are being affected by anthropogenic climate changes. One of those affected systems is the hydrological cycle which encompasses water availability and water quality as well as water services (IPCC, 2007). Adaptation to climate change is, consequently, of urgent importance. The impacts will certainly vary considerably from region to region and even from basin to basin. This poses serious challenges for water resources management.
A particular challenge for water resources management is connected to the fact that many river basins and groundwater systems are transboundary; i.e. the basin is shared by two or more countries. Recent studies identify a total of 279 international river basins (Bakker, 2006), covering almost half of the world’s total land surface (Wolf et al., 1999).