Blue water supplies – those from rain water that flows over land and becomes surface water and groundwater – have been regularly studied and are fairly well documented. Green water supplies, however, aren’t as well studied.
Our friend and the father of the water footprint concept Arjen Hoekstra and his colleagues have gone a long way toward closing that knowledge gap by assessing green water supplies and scarcity throughout the world. They mapped out their results, which were recently published in the journal PNAS, and offered a regional and country-by-country analysis of green water use.
The study looked at green water supplies and uses by humans and nature and examined the potential limitations between the two. People typically use rainwater for food and fiber crops, timber, bioenergy resources and raising livestock. Human uses of water can often happen at the expense of the ecosystems that also rely on that water for biodiversity and survival.
According to the authors, ” The limit to our direct rainwater use has been reached or even exceeded in many places.”