SINGAPORE ¨C Global reservoir volumes fell during the last 20 years despite a construction boom that drove up storage capacity, a new study showed, 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,¡± he 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 basin.

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

¡°As the climate gets more volatile, we will need more, not less, water infrastructure, with the bonus of much-needed low-carbon electricity,¡± it said.

China has also repeatedly said its enhanced ability to store and release water on the upper reaches of the Yangtze has alleviated downstream floods and droughts.

Unlike many regions, China¡¯s storage levels increased slightly over 1999 to 2018 as a result of higher run-off in major river basins, suggesting it will benefit from new reservoirs, Gao said.

¡°But this highly depends on future climate, especially since most regions have experienced decreasing run-off,¡± he said.