The study looked at why the amount of water flowing in the Yellow River source area has decreased since the 1990s. They found that changes in rainfall patterns, including where it falls, how much falls, and how intense it is, are the main reasons for the decrease in water flow. The area is also getting warmer, but this doesn't seem to directly affect how much water evaporates. Changes in the land surface, caused by both climate change and human activities, have also played a role in reducing the amount of water in the river.