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Global reservoir volumes have been decreasing over the past two decades, despite a construction boom that expanded storage capacity, Reuters reported.
According to satellite data analyzed in the study published in Nature Communications, water stored in 7,245 reservoirs worldwide declined from 1999 to 2018, even though the overall capacity increased by 28 cubic kilometers annually.
Lead author Huilin Gao from Texas A&M University emphasized that climate change played a critical role in reducing reservoir efficiency. However, she also noted that rising water demand was a contributing factor.
The decline in storage volumes was particularly prominent in the southern regions, particularly Africa and South America, where water demand has been rapidly rising while new reservoirs have not been filling up as anticipated.
Notably, the study did not factor in the impact of sedimentation, a persistent problem that is expected to reduce storage capacity by 25% by 2050, as highlighted in a January report by the United Nations University.
Prolonged droughts have raised concerns about the feasibility of large reservoirs. Last summer, China experienced a significant drop in hydropower output due to record-high temperatures in the Yangtze basin.
The International Hydropower Association recently stated that new dams and reservoirs play a crucial role in mitigating the effects of increasing climate extremes, as they enable better regulation of water flows.
The association emphasized that as climate volatility intensifies, the need for water infrastructure will only grow, providing the additional benefit of generating low-carbon electricity.
China has asserted that its improved capacity to store and release water in the upper reaches of the Yangtze River has helped mitigate downstream floods and droughts.
Unlike many other regions, China's storage levels showed a slight increase between 1999 and 2018, thanks to higher run-off in major river basins. However, Gao noted that this is highly dependent on future climate conditions, especially considering that most regions have experienced decreasing run-off.
(Writing by Alex Guo Editing by Harry Huo)
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