Understanding global hydrology

Abstract

In this chapter we set out to discuss surface hydrology at the global scale and in doing so we will place emphasis on surface runoff, both direct and as baseflow, since this is the harvestable part of the hydrologic cycle. Of all the freshwater on Earth, only about 0.3% is surface water while the rest is frozen in the ice caps and glaciers or in the groundwater (Gleick, 1996). Yet it is this surface water that we are most familiar with and that, globally, provides 83% of the water we use (2030 Water Resources Group, 2009). It is runoff that constitutes the water resource. Part of the flow of rivers can come from groundwater (as baseflow) and in particular locations groundwater can be the mos..