Despite a construction surge that increased storage capacity, global reservoir volumes have declined over the past two decades, according to a new study published on Tuesday, suggesting that new dams will not be sufficient to alleviate the increasing strain on the world’s water supplies.
The amount of water stored in 7,245 reservoirs across the globe decreased from 1999 to 2018, despite an annual capacity increase of 28 cubic kilometers, according to a study published in Nature Communications.
Climate change was a “critical factor” in diminishing reservoir efficiency, according to Texas A&M University’s Huilin Gao, the study’s primary author; however, increasing 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, particularly Africa and South America, where water demand rose sharply and new reservoirs did not fill as swiftly as anticipated.
Climate change was cited as a decisive factor.
The study did not account for sedimentation, a persistent problem that, according to a paper published in January by the United Nations University, is projected to reduce storage capacity by a quarter by 2050.
Long-lasting droughts have raised concerns regarding the viability of large reservoirs. As a consequence of record-high temperatures in the Yangtze basin last summer, China’s hydropower output plummeted.
Last week, the International Hydropower Association stated that new dams and reservoirs play a “crucial mitigating role in an era of increasing climate extremes” by making it simpler to regulate water flows.
“As the climate becomes more unstable, we will need more, not less, water infrastructure, as well as the much-required low-carbon electricity,” the report stated.
China has stated repeatedly that its improved ability to retain and discharge water on the upper Yangtze has reduced floods and droughts downstream.
In contrast to many regions, China’s storage levels increased marginally from 1999 to 2018 due to higher runoff in main river basins, indicating that the country will benefit from new reservoirs, according to Gao.
“However, this is highly dependent on future climate, especially since runoff has decreased in the majority of regions,” she said.