Lakes provide humans with many different types of ecosystem goods and services that are necessary to sustain human livelihoods. In the past several decades, humanity has substantially increased its efforts to produce desired ecosystem goods from lakes, such as fish, food, and ornaments. However, these efforts have ignored other important ecosystem services from lakes such as water storage and damage mitigation from floods and droughts because lakes are important in regulating the hydrological cycle. The major impacts on the water regulation function of lakes are lake reclamation, returning croplands to lakes, and climate change by impacting the hydrological cycle. Scientific research on measuring the current status and dynamics of lakes in terms of their water regulation capacities can help improve lake ecosystem management in China by filling an important scientific blank. Managers want quick but effective evaluation methods to assess the water regulation capacity of lake ecosystems to clarify the vital role lakes play in supporting human well-being. In this paper, we try to address this scientific need by first conducting a regression analysis to construct a primary water regulation model that connects available water storage capacity to lake area, based on data from the book titled "Records for Chinese Lakes". We then evaluated the biophysical quantity of water regulation across China's five lake zones and the temporal changes across the time-series based on the constructed models using regulation capacity and regulation efficiency indicators. From our analysis we had three main findings. First for lakes bigger than 1 km² in area, the water regulation capacity totaled 1500.02×10⁸ m³. The water regulation capacity of the Eastern Plain and the Tibetan Plateau were the highest among the five lake zones identified in this paper. The Eastern Plain and the Tibetan Plateau occupied 44.46% and 43.63% of the total capacity respectively. Second in terms of water regulating efficiency, the Eastern Plain was the highest among all five lake zones with a regulating efficiency of 310.19×10⁴ m³/km² followed by the Northeast China Plain and Mountain, which was 191.19×10⁴ m³/km². Lake reclamation (opposite efforts return croplands to lakes) would significantly weaken (strengthen) the water regulation capacity for lakes in these zones. Third in recent decades, the water regulation capacity for China's lakes displayed a slight increasing trend of an absolute increase of 9.76×10⁸ m³ and a growth rate of 0.65%. Four lake zones (Inner Mongolia-Xinjiang was only zone not applicable) showed an increase in water regulation capacity with the largest absolute increase in the Eastern Plain, and the highest growth rate in the Northeast China Plain and Mountain. This paper lays the groundwork for creating a quick monitoring and assessment method to evaluate the water regulation capacity of China's lakes. Also it is applicable to management by providing a means to assess the influence of land-use change on the water regulation capacity of lakes to buffer against flood and drought disasters. Lastly, this paper provides a basis for analyzing the trade-offs among ecosystem goods and services, thus it has real-world implications for managing lake ecosystems in China.