Posted on 29 February 2012

GODALMING, UK — Water scarcity impacts at least 2.7 billion people in 201 river basins for at least one month each year, according to a new report published in the online journal PLoS ONE.

Global Monthly Water Scarcity: Blue Water Footprints versus Blue Water Availability, which analysed 405 river basins around the world, marks an advance on previous estimations of water stress by looking at monthly rather than annual averages of water availability and consumption.

“Where and when is something that really matters for water flows, water use and the continued health of our water sources,” said study co-author Ashok Chapagain, Senior Water Advisor at WWF-UK. “Annual averages can mask what is really happening in a basin.”

Researchers from the University of Twente, Water Footprint Network, The Nature Conservancy and WWF studied river flows in 405 river basins between 1996 and 2005.

Through detailed analysis of the total water consumption, or depletion, rather than water withdrawals, the study highlights how the water used to grow crops, sustain industry and provide drinking water has in many places exceeded sustainable levels of water use.

Rivers running dry – a situation experienced in increasing numbers of rivers including the Rio Grande in the Americas, the heavily populated Indus in South Asia and Australia’s vast Murray Darling – is only one consequence of the imbalances between water availability and use.

Others include potential extinction of freshwater fish, dolphins and other species, increasing conflict between water users and substantial economic disruption.

The levels of water scarcity estimated in the report correspond strongly with documented ecological declines and socio-economic disruption in some of the world’s most heavily used river basins.

“Freshwater is a scarce resource; its annual availability is limited and demand is growing,” said Arjen Hoekstra, professor in water management at the University of Twente and lead author of the report. “There are many places in the world where serious water depletion takes place: rivers running dry and dropping lake and groundwater levels.”

Ninety-two percent of humanity’s total water footprint is for agriculture, and irrigated agriculture depletes more water than cities and industries.

Study co-author Brian Richter, Director of The Nature Conservancy’s Global Freshwater Program, explained, “Cities use more water than crops on a per-area basis, but it's important to note that irrigated agriculture occupies four times as much land as cities do.

We need to help farmers implement state-of-the-science irrigation methods and improve the productivity of rain-fed farms as soon as possible. We are going to have to produce more food with less water.”

“In places with multiple months of scarcity, they are likely experiencing serious competition for water,” said Richter, “and during droughts they’ll have economic impacts in agriculture, power production or other industries.”

“This assessment gives a more detailed and complete view of the relationship between the water footprint – the amount of water consumed in the production of goods and services – and the growing problems of water scarcity and the resulting environmental, social and economic losses,” said Ruth Mathews, Executive Director of the Water Footprint Network.

“Through cooperation between governments, investors, companies, farmers and environmental organizations, we can take direct action to improve the sustainability, efficiency and equitability of water use, ensuring that we can feed people and sustain healthy ecosystems in the future.”