The study looked at how the amount of water in major rivers in China has changed from 1956 to 2018. They found that most rivers had less water flowing through them over time, except for one on the Yangtze River. The Yellow River seemed to be a dividing line, with rivers to the north having significant decreases in water flow compared to those in the south. Overall, China's total surface water decreased by about 12.2 billion cubic meters from 1956 to 2018. This reduction in water resources in certain areas has made it harder to meet the growing demand for water in those regions.