Study: Global Water Reservoir Volumes Decline

SINGAPORE (Reuters) — Global reservoir volumes fell during the last 20 years despite a construction boom that drove up storage capacity, a new study showed on June 13, suggesting that new dams will not be enough to solve growing strain on the world’s water supplies.

Satellite data showed that water sequestered in 7,245 reservoirs across the world fell from 1999 to 2018, despite a 28-cubic-kilometer annual increase in capacity, a study published by Nature Communications said.

Climate change was a “critical factor” in reducing reservoir efficiency, said lead author Huilin Gao of Texas A&M University, but rising water demand also played a role.

“Even if temperatures stop rising, increasing demand and new construction are likely to continue,” she added.

The decline in storage volumes was concentrated in the south, especially Africa and South America, where water demand increased rapidly and new reservoirs didn’t fill up as quickly as expected.

The study did not account for the impact of sedimentation, a persistent problem that is predicted to cut storage capacity by a quarter by 2050, according to a January paper by the United Nations University.

Lengthy droughts have raised questions about the feasibility of large reservoirs. China saw hydropower output plummet last summer as a result of record-high temperatures across the Yangtze River basin.

The International Hydropower Association said that new dams and reservoirs played a “crucial mitigating role in an era of increasing climate extremes,” making it easier to regulate water flows.