Response of land use/coverage change to hydrological dynamics at watershed scale in the Loess Plateau of China

In this study Qiaozidong and Qiaozixi watersheds in Loess Plateau were selected as the case to investigate the effects of land use/coverage change on hydrological dynamics. The results showed that the runoff coefficient of controlled watershed reduced by about 50%, 85%, 90%, respectively, in wet, normal and dry years in comparison with that of uncontrolled watershed. The average runoff coefficient reduced by 73.6% during the period of 1995–2004 compared with that in the previous period of 1986–1994 for land use in controlled watershed. And the impacts of land use and vegetation changes on runoff were strengthened in response to the increasing rainfall. Additionally, the impacts of land use/coverage change on runoff yield are characterized by seasonal fluctuation. The maximum monthly runoff reduction in the both watersheds occurred in May, which was consistent with the period of the maximum land coverage appeared. Finally, when the rainfall intensity reached a certain threshold, the variance of flood peak in two watersheds reduced, which showed that the effects of forest on flood weakened. The flood peak discharge frequencies indicated that peak discharge would respond to the land use and vegetation change obviously on condition that there were the same frequencies of rainfall intensity in the earlier and later periods.