Globally, humans use about 4 trillion cubic meters of fresh water each year for everything from crop irrigation to cooling manufacturing equipment to generating electricity. In a recent study published in Earth's Future, Kåresdotter et al. modeled how our unquenchable demand for water affects four hydrological variables: runoff, evapotranspiration, soil moisture, and total water storage.

The researchers considered human water use with respect to eight objects and processes: interbasin transfers (systems that move water between river basins), dams, reservoirs, impervious surfaces such as roads, domestic and industrial water demand, livestock water demand, irrigated agriculture, and water "mining" (extracting groundwater for irrigation). They found that these eight factors alter all four hydrological variables, but different areas of the world experience different directions and magnitudes of change.