Research Of Distributed Hydrologic Modeling In A Typical Large Scale Watershed In Longxi Loess Plateau Of China

Land-use readjustments and ecological restoration in Chinese Loess Plateau are the most important stratagems for the social and ecological development. Land Use and Land Cover (LULC) and the precipitation variations in this have brought spatial and temporal changes in hydrological and environmental factors such as storm characteristics, flood process, soil erosion, and so on. To spatially quantify the changes in aforementioned factors, a spatially-distributed hydrological modeling should be adopted. Spatially-distributed hydrological modeling takes a full consideration of spatial heterogeneity of all factors that contribute to the concerned hydrological issues. This research focuses on Zuli River basin, a typical watershed in the Chinese Loess Plateau, to spatially model the runoff generation and routing processes. The followings are the main conclusions of this dissertation:1. With GIS support, the spatial distribution of the hydrological modeling-required parameters can be easily obtained based on point-station observations. The spatially-distributed parameters can be effectively partitioned into the well-established hydrological models and the accuracy of the water-balance calculation can be considerably improved2. SCS model is used for simulating the impact of land-use and land-cover changes on hydrologic processes under different soil conditions. By taking consideration of spatial variability in LULC and soil conditions in SCS model, the runoff generation and water interception and retention in soil-plant systems can be more accurately estimated.3. This research demonstrates that the unit hydrograph (UH) method is suitable for conflux calculation on a regional scale. The geomorphologic instantaneous unit hydrograph (GIUH) is suitable for a short-time step hydrologic simulation, while for long-time step hydrologic simulation, the Clark UH method is more suitable.4. This research also demonstrated that the temporal and spatial variations in precipitation have very complicated and profound impact on runoff-generation processes and the gross runoff production. The ultimate water contributions to the outlets of hydrological stations have been declining since 1970s primarily because various engineering measures have been taken to alleviate the water loess in the watershed.To sum up, this research validated the suitability of the SCS model for long-step time hydrologic simulation. This research successfully incorporated the time-area curve (TAC) into GIS platform and this empowered TAC method with GIS-supported spatial analysis functions. As a result, the precision and efficiency of the TAC computation for regional-scale runoff production are effectively improved. The most pronounced feature of this research is GIS-assisted spatial modeling of watershed-scale runoff production. This approach utilized DEM as the datum in GIS environments to spatially distribute the point-observed data with a full condition of the spatial heterogeneity of all parameters that contribute to the watershed runoff production. This lays a solid foundation for future studies of water resources and water-resource management in this regions and other hydrologically similar regions.