image: Contrary to the traditional "saline west, fresh east" perception, the study uncovers four freshwater lake hotspots across China, with approximately 65% of the natural lake freshwater stored in the western interior, primarily on the Tibetan Plateau.
Credit: Science China Press / Chunqiao Song et al.
A nation's freshwater security is fundamentally constrained by the total volume and spatial distribution of its water resources. For China, home to one-fifth of the world's population but possessing only 7% of its total renewable freshwater, assessing the true distribution of these resources is critical. While satellite observations have long tracked lake surface areas, the crucial third dimension (water depth) has remained largely unknown at a national scale, precluding a robust assessment of actual water storage.
To bridge this knowledge gap, a collaborative research team led by researchers from the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, conducted the first national-scale bathymetric and typologic assessment of all 2,713 natural lakes (>1 km2) in China.
The researchers compiled a massive dataset of high-precision field surveys covering 588 lakes, which account for about 78% of the national lake area and 87% of the total estimated storage. Combined with region-specific geo-statistical models, the team successfully established a definitive baseline for China's lacustrine water resources.
The study revealed a profound east-west bathymetric divide. The total water volume of China's natural lakes is approximately 1,174.3 km3. Deep lacustrine systems are concentrated in the western interior, shaped by active tectonic subsidence and glacial processes. In contrast, lakes in the eastern and northern plains are uniformly shallow, largely due to riverine sediment infilling.
Contrary to the traditional “saline west, fresh east” perception, the study uncovered unexpected freshwater hotspots. Of the nation’s 334.9 km3 of natural lake freshwater, approximately 65% is stored in a few large, deep, open lakes in the western interior, primarily on the Tibetan Plateau. The Tibetan Plateau lake zone alone holds a freshwater volume that significantly surpasses the densely populated eastern plains.
This natural distribution creates a severe spatial imbalance between water and demographic distribution. While 81% of China's population resides in the east, they have direct access to only 23% of the natural lake freshwater storage. This results in a nearly 330-fold difference in per capita freshwater availability between the Tibetan Plateau and the eastern plains. Furthermore, widespread eutrophication in eastern basins further compromises the actual accessible supply of good-quality freshwater.
To address this immense spatial disparity, China’s vast network of artificial reservoirs, holding approximately 1000 km3 of capacity, plays a transformative role. Spatially concentrated in the water-stressed eastern and southern monsoon regions, these engineering-driven impoundments effectively rebalance the distribution of surface freshwater.
The researchers propose a "dual-governance strategy" to manage national water resources. They suggest adopting a conservation-oriented approach to maintain the deep, high-quality lakes of the west as protected strategic reserves, while implementing an efficiency-oriented approach by combining demand-side management with the conjunctive use of surface and groundwater for the populous eastern regions.