A new study published in National Science Review has provided the clearest picture so far of water storage in China's lakes. The findings show that the country's natural lakes hold about 1,174 km³ of water, including roughly 335 km³ of freshwater. However, only a limited share of these natural freshwater resources is directly accessible to the population centers in eastern China.

The study was led by researchers from the Nanjing Institute of Geography and Limnology (NIGLAS) of the Chinese Academy of Sciences.

"This study provides the most comprehensive assessment to date of China's natural lake freshwater resources," said SONG Chunqiao, a researcher at NIGLAS and first author of the study.

A nation's freshwater security is fundamentally shaped by the total volume and spatial distribution of its water resources. However, even this basic information remains highly uncertain at large scales. For China, which is home to one-fifth of the world's population but only 7 percent of its total renewable freshwater resources, closing this knowledge gap is especially critical.

Using nationwide lake survey data collected over the past three decades and advanced spatial statistical methods, the researchers conducted the first systematic national assessment of lake depth and freshwater‑saline lake types across China. They quantified water storage in 2,713 natural lakes larger than 1 km².

To enhance the reliability of the assessment, the team integrated data from nationwide lake surveys, scientific expeditions, and water resource investigations. They compiled high‑precision depth and bathymetric measurements from hundreds of lakes across the country and combined these with spatial statistical modeling.

The findings reveal a striking geographical imbalance in freshwater distribution. Nearly 65 percent of China's natural freshwater lake storage is concentrated in a small number of deep lakes in western inland basins, particularly on the Tibetan Plateau. This challenges the traditional view that freshwater lakes are mainly concentrated in eastern China.

In contrast, lakes in the eastern plains are generally shallower and store far less water. About 81 percent of China's population lives in the eastern regions, yet these areas have direct access to only about 23 percent of the country's natural freshwater lake storage. Water quality degradation in some eastern lakes further reduces the amount of safely usable freshwater.

The study also noted that China's extensive reservoir network plays an important role in supporting water availability and easing regional disparities in natural freshwater resources.

"By combining large‑scale field investigations with advanced statistical methods, we were able to move beyond traditional surface observations and better understand how much water China's lakes actually store and where freshwater resources are concentrated," SONG said. "The findings provide an important scientific basis for water resource management and long‑term water security planning."