The study looked at annual natural runoff in the Yellow River basin from 1951 to 1998. They found that most stations showed a decrease in runoff starting in the early or mid-1990s, leading to water scarcity and ecosystem problems. This decrease was influenced by changes in precipitation patterns and human activities affecting the hydrological cycle. The researchers suggest two solutions: promoting water-saving practices in irrigation and implementing South-to-North water transfer projects. However, water scarcity issues are expected to persist in the future.