Development of the WEP-L distributed hydrological model and dynamic assessment of water resources in the Yellow River basin

Dynamic assessment of water resources becomes desirable to reflect water resources variations in the basins under strong human impacts. A physically based distributed hydrological model, WEP-L, which couples simulations of natural hydrological processes and water use processes, is developed for the purpose. Concepts of special water resources (i.e., surface water resources and groundwater resources) and general water resources (i.e., the special water resources plus the precipitation directly utilized by ecosystem) are proposed, and an approach for dynamic assessment of water resources is suggested. Basin subdivision, classification of land covers, and deduction of water use spatial/temporal distributions in the Yellow River basin are carried out with the aid of remote sensing (RS) data and geographic information system (GIS) techniques. The basin is subdivided into 8485 sub-watersheds and 38,720 contour bands, and the WEP-L model is verified by comparing simulated and observed discharges at main gage stations. Lastly, continuous simulations of 45 years (1956–2000) in variable time steps (from 1 h to 1 day) are performed for various land cover and water use conditions, and water resources assessment results under present condition of land cover and water use are compared with those under historical condition of land cover and water use. The study results reveal that: (1) the surface water resources reduced, but the groundwater resources non-overlapped with the surface water resources increased under the impact of human activities in the Yellow River basin; and (2) the special water resources reduced, but the general water resources increased accompanied with increase of the precipitation directly utilized by ecosystem in the basin.