Characteristics and Impact of Human Activities of Surface Water Hydrochemical in the Shuodugang River Basin from the southeastern edge of the Qinghai Tibet Plateau

　　This paper is the result of geological survey engineering.
　　ObjectiveShuoduogang River Basin is located in the southeast margin of Qinghai-Tibet Plateau, with fragile ecological environment, abundant hydropower and tourism resources, and underdeveloped local economy. In order to serve the strategy of rural revitalization and rational development and utilization of water resources, surface water hydrochemistry has been studied. MethodsOn the basis of systematic investigation of hydrological and geological conditions of the basin, the main and branch water samples of Shuoduogang River were collected, and the hydrochemical composition, spatial distribution, recharge sources and main control factors of surface water in the basin were studied by comprehensive use of ion ratio analysis, PMF source analysis and geographical detector. ResultsThe pH value of the surface water in Shuoduogang River Basin ranges from 7.52 to 8.66, and the TDS value ranges from 65.00 to 744.00mg/L. The cations are mainly Ca²⁺ and Mg²⁺, with the characteristics of Ca²⁺>Mg²⁺>Na⁺>K⁺, while the anions are mainly HCO₃^- and SO₄^2-, with the characteristics of HCO₃^->SO₄^2->Cl^->NO₃^-. The saturation index of calcite and dolomite minerals gradually increases from order 1 to order 4 river streams, and reaches saturation in all order 4 river streams. The coefficient of variation of Na⁺, K⁺, Cl^- and SO₄^2- in surface water is high, showing strong spatial variability. The hydrochemical type is mainly HCO₃-Ca type, affected by hydropower station, and some water samples are Cl-Na type. δD ranges from -120 to -103‰, δ¹⁸O ranges from -15.9 to -14.1‰, and surface water is mainly supplied by atmospheric rainfall from the ocean. In surface water, NO₃^- is mainly affected by agricultural and animal husbandry activities and weathering of carbonate rocks; Ca²⁺, Mg²⁺, Na⁺, HCO₃^-, SO₄^2- and TH are mainly affected by weathering of limestone, dolomite and silicate rocks; Cl^-, PO₄^3- and pH are mainly affected by animal husbandry; K⁺, NH₄⁺ and TDS are mainly affected by agricultural activities. ConclusionsThe contribution rates of rock weathering, animal husbandry, agriculture, interaction between agricultural and animal husbandry activities and carbonate weathering to water solute in the basin are 33.8%, 24.6%, 22.1% and 19.5%, respectively. Among them, hydropower station enhances the influence of agricultural and animal husbandry activities; It can be seen that human activities have a significant impact on solute in the water of Shuoduogang River Basin.