dws-ut-green-water-wold-map-countries-770pxWorldwide there's less rainwater available for nature and for the production of food, wood and plants for bioenergy. This is reported by researchers at University Twente in an online paper published by the National Academy of Sciences of the USA (PNAS).

By ignoring the limits of the use of rainwater for human activities, the world risks further loss of ecosystems and biodiversity. Such loss has an immediate effect on the productivity of agriculture, forestry and energy supply, the researchers warn.

dws-ut-green-water-allocations-400px Allocation of total green water flow from earth surface. Arrows represent flows from different sorts of land. Values are in 1,000 km3 y−1. (source: PNAS, February 2019)

Scarcity of ‘green’ water
In their paper the researcher use the term ‘green water’, as a classification for water in soils that can be absorbed by plants and evaporate into the air. Traditionally, the water scarcity debate is always about blue water in lakes and rivers.

The University Twente completes the picture of worldwide scarcity of limited freshwater by quantifying green water scarcity.

Limited potential per country
The new study shows that the total green water footprint of humanity is currently 56 percent of the world’s sustainably available green water flow.

To understand how green water scarcity (Wsg) constrains production of these human production of food, feed, fiber, timber and bioenergy, the limits to the green water footprint (Wfg) need to be considered, the green water flow allocated to human society.

By expressing green water scarcity (Wsg) per country as the ratio of the national aggregate green water footprint (Wfg) the study shows that countries facing scarcity are mainly found in Europe, Central America, the Middle East, and South Asia.

These countries have no or very limited potential remaining to increase rainfed food or biomass production.

The paper 'Limits to the world's green water resources for food, feed, fiber, timber, and bioenergy' by Joep F. Schyns, Arjen Y. Hoekstra, Martijn J. Booij, Rick J. Hogeboom, and Mesfin M. Mekonnen appears in the Proceedings of the National Academy of Sciences of the USA (PNAS).

(top illustration: Aggregated green water scarcity (Wsg) per country. Countries in black have fully allocated their sustainably available green water flow to human activities, source: PNAS, February 2019)

Read also on this website
New launched version of Water Footprint Assessment Tool provides easier access to data on global water use, 25 July 2014
University of Twente leads 4,5 million euro research programme on intelligent river management, 6 December 2013
Real water use of the average world citizens is an astonishing 4000 liter per day, 14 February 2012

More information
University Twente 
Department Water Engineering & Management (WEM) 
Enschede, the Netherlands 
+31 53 489 4320 

Water Footprint Network
Enschede, the Netherlands
+31 53 489 5383