Local flow regulation and irrigation raise global human water consumption and footprint.

Fernando Jaramillo & Georgia Destouni, Stockholm University

This global study investigated the effects of flow regulation and irrigation using hydroclimatic observations from 1901-2008 in 100 hydrological basins situated throughout the world, covering about 35% of the global land area (excluding Antarctica)

For these basins, the results show that both flow regulation and irrigation lead to an increase in relative evapotranspiration, while flow regulation leads also to a decrease in temporal runoff variability. Evapotranspiration changes due to flow regulation and irrigation were found to be greater than changes due to climate change.

Comparing the time periods 1901-1954 and 1955-2008, the increase in evapotranspiration due to flow regulation and irrigation was 3563 ± 979 km3/year. These new results increase a recent estimate of the global water footprint for humanity by at least 18%, to 10,688 ± 979 km3/year. Also, it implies that human water consumption has passed beyond a proposed planetary boundary.

These results show how local water use has global impacts. Furthermore, given their impacts, the effects of flow regulation and irrigation should be accounted for in Earth-system modelling.

Jaramillo F, Destouni G, 2015. Local flow regulation and irrigation raise global human water consumption and footprint. Science 350(6265), 1248, doi: 10.1126/science.aad1010.