Simulation of the Impact of Climate Fluctuation and Land - cover Changes on Runoff in the Qu - chan River

摘要

Human activities have been widely acknowledged to be the main cause for the runoff decrease in the Yellow River basin. Of the two crucial reasons for runoff decrease, climate fluctuation and land cover change, which one on earth acted as the leading factor? In order to probe this issue, the Qu — chan River in the middle reaches of the Yellow River basin was chosen as a study area. About thirty years' climate fluctuation and land cover changes in the Qu — chan River were analyzed. According to three decades land - cover maps, the primary land cover changes are that forestland turned into sparse and shrub by forestland, and the shrubby and sparse forestland turned into grassland. A monthly water balance model was adopted to simulate the impact of climate fluctuation and land cover change on runoff discharge and to determine their contributions to runoff. The runoff depth in the 1970s decreased by 7.25% compared with that in the 1960s. Among them, about 3/4 -runoff change was caused by land — cover changes and 1/4 — runoff change was caused by climate fluctuation. In the 1980s the runoff depth decreased by 46.43% compared with that in the 1960s. Among them, about 1/3 - runoff change was caused by land — cover changes and 2/3 - runoff change was caused by climate fluctuation. So it was concluded that in the 1970s the land — cover changes is the main force on the runoff changes, but in the 1980s the climate fluctuation acts as the leading factor for the runoff decrease.