Variation in annual runoff of the Wudinghe River as influenced by climate change and human activity

Response of river runoff to climate change and human activity is an important issue in hydrological sciences. Considering the Wudinghe River, a tributary of the middle Yellow River, a study has been made on the influence of climate change and human activity on annual runoff. Both the measured and natural annual runoffs showed a decreasing trend, and the areas of four types of soil and water conservation measures and water diversion increased. A comparison between the “base-line” period (1956–1971) and the “measure” period indicates that, for the former period, 78.6% and 72.9% of variations in the measured annual runoff and natural runoff respectively can be explained by variation in annual precipitation; but for the latter period, they lowered to 42.5% and 50.2%, indicating that after soil and water conservation measures, the control of precipitation on runoff generation became much weaker. There were close negative correlations between annual runoff and the areas of four types of soil and water conservation measures. Step-wise multiple regression analysis has been performed, and the contributions from water diversion, maximum 30-day cumulative precipitation, maximum 1-day precipitation, annual precipitation and the weighted average of the area of soil and water conservation measures to the variation in annual runoff were calculated as 37.5%, 26.9%, 9.4%, 14.5% and 11.8% respectively.