Despite the construction of new reservoirs, global water reserves are dropping. 

A new study published in Nature Communications reveals that global reservoirs have experienced a significant decrease in water levels over the past two decades, despite an increase in total storage capacity due to the construction of new reservoirs. 

Researchers found that while reservoirs in the Global North have generally seen an increase in their reserves, those in the Global South, particularly in South America and Africa, have suffered a substantial decline.

Using satellite data, scientists led by Yao Li and Huilin Gao examined storage variations in 7,245 reservoirs worldwide between 1999 and 2018. 

They discovered that new reservoir construction contributed to an annual increase of approximately 28 cubic kilometres in global reservoir storage. 

However, the newly constructed reservoirs in the Global South failed to fill up as expected.

The findings carry significant implications for future water supplies, as water runoff is predicted to decrease while the demand for water is expected to rise. 

Building new reservoirs in the Global South may prove futile and wasteful in the face of these challenges. 

Instead, the researchers say there is an urgent need for new management strategies, particularly in reservoir regulation, to ensure universal access to water in the coming years.

The study sheds light on the complex relationship between reservoir construction, water availability, and socioeconomic benefits. 

It underscores the necessity of reevaluating the prevailing approach of relying solely on new reservoirs to address water resource limitations, highlighting the importance of sustainable management practices in overcoming the growing water demand and dwindling water availability in developing countries.