| The construction of ecological civilization is related to the welfare of the people and is a major plan for the future of the nation,and is an important element in achieving the great rejuvenation of the Chinese race.Known as the source of many rivers in Asia,the Qinghai-Tibet Plateau provides water resources for many countries in Asia and is known as the "Water Tower of Asia".However,the protection of the source areas of rivers on the Qinghai-Tibet Plateau still needs to be strengthened.There are few studies on the source regionalization of rivers on the Qinghai-Tibet Plateau.Only a rough source area has been defined at the source of some large rivers,and most small and medium-sized rivers have not yet had a clear source area,which makes the ecological protection of this area lack of relevant support.The special climatic environment and landscape of the Qinghai-Tibet Plateau make the climate change and water circulation process in the region extremely complicated,so it is urgent to build a river source area zoning method that meets the characteristics of the Qinghai-Tibet Plateau,so as to provide methodological backup for the delineation of river source areas on the QinghaiTibet Plateau and offer technical support for the protection of river source areas on the Qinghai-Tibet Plateau.In this paper,we reviewed the research status of river source determination,the methods of river source regionalization,and the study of river source areas on the Qinghai-Tibet Plateau.By means of literature research,data collection and field investigation,the factors affecting the regionalization of the source area of the river are determined,and the specific regionalization indexes of each factor are clarified.Based on the characteristics of each index,the final index of the river source region regionalization on the Tibetan Plateau was selected,and the index system of the river source region regionalization on the Tibetan Plateau was constructed.Digital water systems under different thresholds were created by Arc Hydro Tools ArcGIS10.2,and the optimal water system was determined by means of mean-change point analysis and river network convergence difference method.Based on the sub-basins under the optimal threshold,the source area was preliminarily delineated based on the firstbranch method and the single-index method.The multi-index method of hierarchical cluster analysis of SPSS was used to delimit the final source area of Qinghai-Tibet Plateau river source area.The feasibility and rationality of the regionalization index system and the regionalization method constructed in this study were verified through the delineation of the source area of the Yarlung Zangbo River on the Qinghai-Tibet Plateau by using the cross and parallel comparison method.Finally,the Lhasa River,the largest tributary of the Yarlung Zangbo River,is selected as an example to delimit the source area of the Lhasa River.The principal conclusions from this investigation are as follows:(1)The constructed index system of the source area of rivers and streams on the Qinghai-Tibet Plateau includes the following indicators:along-range specific drop of hydrological and water resources;landform type,glacier and permafrost of topography and geomorphology;annual precipitation,average annual climate and annual evaporation of meteorology and climate;ecosystem type and water content of ecosystem;land use,population density and GDP per unit area of human activities and economic and social development.(2)The proposed methodology of river source area classification on the Tibetan Plateau is as follows:extracting water systems under different parameters based on DEM data;determining the optimal water system by mean-variance dot analysis;conducting mistake analysis between the optimal water system and the measured river grid to ensure the error between the extracted water system and the measured water system is within the allowable range;locating the source of the basin by using the optimal water method according to the principle of river source determination;initially delineating different source areas based on the first tributary method and the single indicator method;thus,using the initially defined source areas as the basis,the final delineation of the river source area boundaries is carried out by using the multi-indicator method.(3)The source area of the Lhasa River basin identified in the study is:the confluence areas above the section where the main tributary 4(Sangqu)and the main river converge are mainly located in Seni District and Jiali County of Naqu City,and a few of the headwaters are located in Biru County of Naqu City.The source area was between 91°44′～93°21′E and 30°11′～31°17′N,with an area of 8520 km2,accounting for 26.12%of the total basin area.The length of the main channel in the source area was 271 km,accounting for 44.29%of the total length of the main channel.The main channel drop in the source area was 797 m,accounting for 54.66%of the total channel drop.This research is the first to establish the index system for the source area zoning of rivers on the Qinghai-Tibet Plateau,propose the zoning method,and apply it to the Lhasa River basin for the first time,and its determined source area scope can also provide a reference basis for future conservation actions in the source area of the Lhasa River. |
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