Impact of human activities on the stream flow of Yellow River

The man-induced water diversion and consumption constitute a sub-system of the drainage basin water cycle system, namely, sub-system of side-branch water cycle.In this context, the main-stem water cycle is referred to as the water cycling processes including the runoff generation and movement from hill slopes and the diverse channels to the sea.Based on the data from the Yellow River, the man-induced side-branch water cycle and the main-stem water cycle are studied.The results show that since the late 1960s, the intensity of the side-branch water cycle and the ratio of the side-branch to the main-stem water cycles increase markedly, and the intensity of the main-stem water cycle decreases.Using the annual data, a number of multiple regression equations are established to express the relationship between the side-branch and main-stem water cycles and the influencing factors.The equations indicate that the contribution of variations in the irrigated land area, the annual precipitation and the annual temperature to the variation in the relative intensity of the side-branch water cycle are 86155%, 2118%, 11125%, respectively, and that the contribution of variations in the irrigated land area, the annual precipitation and the annual temperature and the area of soil-water conservation to the variation in the relative intensity of the main-stem water cycle are 57161%, 20178%, 11103%, 10157%, respectively.