Neither population size nor the size of economies necessarily co-varies with river basin size, nor do conflicts over water or complexities of interactions over space.2 Variations in geography and human occupation of river basins are great. Some, such as those in Central Asia, are in semi-arid regions where water scarcities have become chronically severe and where cross-border governance has faced serious challenges in taking remedial actions. Others are facing the portent of their watersheds being below sea level as the oceans continue to rise from global warming.