Effects of land use change on hydrological dynamics at watershed scale in the Loess Plateau-A case study in the Lüergou watershed, Gansu Province

Predicting hydrological effects of land use change is a currently focus in the field of hydrology. Land use change impacts the water resources available to watershed by changing the runoff process. As we all know, the Loess Plateau is limited in water resources, and sensitive to hydrological environment. In order to understand the effects of the change in land use on water resources and provide planners and managers with theoretical bases, this study compared the runoff production during two periods of 1982-1988 and 1989-2000 in the Lüergou watershed in the Loess Plateau. The results showed that land use change had effects on annual runoff production, which decreased by 27% to 100% during land use period with more forest land or good land cover, and runoff coefficient decreased by 57%. The effects of land use on runoff production had been found to be seasonal, i.e. the significant differences between the good land cover and the poor one only could be found in growth season. Although the runoff coefficients of the previous and the later land use periods had demonstrated different trends in low water season, it should be noted that it did not represent the runoff production capacity for low water season. The authors deduced that this difference was to some extent relevant to the amount of precipitation. Flood peak discharge frequencies had indicated that peak discharge would response to the land use and vegetation change obviously, provided the same frequencies of rainfall intensity of the earlier and later periods existed.