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The water footprint of world’s artificial reservoirs

The water footprint of world’s artificial reservoirs

 

In our group, we try to keep track of all water flows that are appropriated for human use, be it for agriculture, industrial or domestic use. So far, however, the water consumpution of man-made reservoirs has been overlooked.

For centuries, humans have resorted to building dams to gain control over freshwater available for human consumption. Although dams and their reservoirs have made many important contributions to human development, they receive negative attention as well, because of the large amounts of water they can consume through evaporation from their surfaces.

WEM’s Rick Hogeboom, Arjen Hoekstra and Luuk Knook (MSc Student 2016) estimated the blue water footprint of the world's artificial reservoirs and attributed it to the purposes hydroelectricity generation, irrigation water supply, residential and industrial water supply, flood protection, fishing and recreation, based on their economic value.

We estimate that economic benefits from 2235 reservoirs included in this study amount to 265 × 109 US$ a year, with residential and industrial water supply and hydroelectricity generation as major contributors. The water footprint associated with these benefits is the sum of the water footprint of dam construction (< 1 % contribution) and evaporation from the reservoir's surface area, and globally adds up to 66 × 109 m y−1. The largest share of this water footprint (57 %) is located in non-water scarce basins and only 1 % in year-round scarce basins. The primary purposes of a reservoir change with increasing water scarcity, from mainly hydroelectricity generation in non-scarce basins, to residential and industrial water supply, irrigation water supply and flood control in scarcer areas.

The full paper is published (open access) in the journal Advances in Water Resources here.

Figure 1: The share of the global WF of reservoirs in river basins facing moderate to severe water scarcity during 0, 1-3, 4-6, 7-11 or 12 months per year (a); and the WF share per purpose located in basins facing moderate to severe water scarcity during zero (b), 1-3 (c), 4-6 (d), 7-11 (e) or 12 (f) months per year.