Understanding Hydrological Alteration

Abstract

Water enters the terrestrial phase of the water cycle when precipitation exceeds evapotranspiration at the land surface. Downstream drainage of this water via surface and subsurface flow paths including transient storage in snowpack, soils, aquifers, and lakes combine to produce the water regimes of freshwater ecosystems. Humans have altered these processes through changes in climate and atmospheric CO2 concentrations, modifications to the land surface including tree clearing and urbanization, construction of surface water impoundments that are generally operated for water supply, flood control or hydropower generation, diversion of surface water, extraction of groundwater, draining of wetla..