Baseflow Separation And Characteristic Analysis In Wuding River Basin

River base flow is the replenishing part which is the infiltration of groundwater, and it is a primary source of stream flow in the drought period. To maintain a certain amount of base flow plays a crucial part in the riverway ecological protecting. Base flow separation means to separate the underground stream flow from its total flow, thereby to ascertain the ratio of the components in various stream flows. Base flow separation is often encountered in hydrological analysis and in the evaluation of regional water resources. But since it relates to climate, physical geography, and hydrogeology and so on, it is very difficult to break through compared with other technical analysis of hydrological water resources. Now that the definitions of direct stream flow and groundwater stream flow are quite arbitrary, separation methods also have the traits of artificial and arbitrary, while the consistence of methods in the whole separation process is of a great importance.There are a variety of ways of base flow separation. Among these segmentation methods, beeline separation is not only relatively reliable, but also requested in technical details, and it is the very separation method used in this paper. On the basis of the beeline separation, some AutoCAD drawing functions are also employed. Automatically generating stream flow curves and calculating as well as separating the area with AutoCAD, the findings could be more objectively reflecting the trends of changes of the base flow with little artificial work. It functions quickly and efficiently, making the results of separation more close to the actual situation.The Wuding River basin is the most serious branch in the middle of Yellow River valley in water and soil erosion. It is drought all the year. Base flow, accounting for a large proportion in the Wuding River Basin, is the main supply of the stream flow in the non-flood season. The change of the base flow will significantly affect the economic development and the ecological environment of the basin area. Exploring the change of the base flow has a great significance in studying the water cycling in the basin area. This paper takes the Wuding River Basin as the studying region, applying beeline separation method and the AutoCAD to the separation of the stream flow in Wuding River basin to obtain the base flow capacity and analyzing the changes and characteristics of base flow. The major studying contents and findings are as follows:(1) 11 representative hydrological stations in Wuding River Valley (Cao Ping, Dian City, the Han's Hilly, Yokoyama, the Ding's Canal, the Li's River, Ma Lake Valley, Qingyang Fork, Suide, the Bai's River, and Zhaoshiyao) are selected. After analyzing and proof-reading the existing data, representative years which meet the requirements are selected as research datas.(2) Beeline Separating method is employed in this base flow separation, and with some drawing functions of AutoCAD, 11 representative hydrological stations are conducted base flow separation.(3) Analyzing the changes of the base flow and the reflecting factors according to the base flow separation data of every representative hydrological station. The findings suggest:â‘ Baseflow accounts for a large proportion in Wuding River Basin.According to the features of landscape, Wuding River Valley can be divided into three districts: sandstorm district, riverhead gully, and loess plateau district. Baseflow takes a large proportion in all the three districts.â‘¡Every tributary throughout the watershed was significantly decreasing basically.In recent years, due to the impact of climate and human activities, the baseflows in the whole valley are declining, especially in the sandstorm area. The reduction of the baseflow will affect the analysis and use of water resources in the entire basin. So to strengthen the study of baseflow changes in the watershed is needed.â‘¢Base rate of flow in Wuding River basin is relevant to the structure of the underlying surface.On the one hand, the size of base rate of flow depends on the surface composition and surface infiltration conditions, such as soil composition, slope gradient, surface vegetation and so on, and on the other hand, it depends on the direction and geographical structure of underground impermeable layer, as well as the water supplies and others. It is a convergence process of greater scope and more profound longer-term. So the flow of areas with different landscape is different. The base flow accounts for a larger ratio in sandstorm areas of WuDing River Valley, and smaller in riverhead gully district and the loess plateau district.