Impact Of Human Activity On Surface Water Resources On Digital Basin Platform

On the basis of raster Digital Elevation Model (DEM) data over the Laohahe River Catchment in the upper and west area of the Liaohe Basin within Inner Mongolia Autonomous Region, the Digital Elevation Drainage Network Model (DEDNM) is applied for assigning flow-vector directions over flat and depressional areas of the DEM, for identifying stream network and watershed divides, and for establishing spatial topological structure of subcatchments and stream network. Meanwhile, River network analysis Tools (RiverTools) and geographic information system software (ArcView) are used to display subcatchments and river network extracted from DEM data.On the platform of the digital basin built above, the Xin'anjiang model is selected for runoff simulation during the different periods. It is assumed that model parameters calibrated from measured precipitation-runoff data in a specific period, reflect the situation of land surface and the human activity in that period. Firstly, daily data of precipitation, pan evaporation, and discharge in 1960's are used to calibrate the parameters of the Xin'anjiang model. Then the parameters calibrated are applied to the computation of daily discharge from 1950's through 1990's, in which daily measured data of precipitation and pan evaporation are taken as the input of the Xin'anjiang model. The difference between computed and observed runoff becomes larger and larger from 1950's to 1990's. The mean annual precipitation is 400.65 mm in 1960's, and 474.14 mm in 1990's. However, the mean value of observed annual runoff is seventy million cubic meters less in 1990's than that in 1960's. It could be seen that the influence of human activity on stream runoff is very obvious.The quantity of downstream flow depends on precipitation over a catchment and withdrawal from the upstream. River runoff has a tendency towards decrease. The increase of the amount of water taken from river course is the direct cause why observed runoff decreases. As land cover forms the boundary between the atmosphere and the terrestrial sphere, changes in land cover may have significant implications on water resources. Some of them are very difficult to be estimated, such as an increase in water use induced by land-use change, soil conservation, modification of socioeconomic structure. The methodology is provided in this research for the separation of influence of human activity on water resources from that of climate change on hydrological regime.