Spatial And Temporal Variations Of The Surface Water Chemical Components Of The Lower Reaches Of Tarim River After Ecological Water Conveyance

As being an essential part of the global water cycle, rivers plays important role in theelement’s geochemical cycle. The features of water chemistry not only reflect the localgeology, geography and meteorology at the same time; it also reflects the surfaceweathering erosion and human activity impacts on river ecology. Based on previousstudies about aquatic chemistry of Tarim river Basin, and in order to improve theenvironment of the basin,11years of ecological water transport to lower reaches of theTarim river action evaluated. Comprehensive research on water chemistry of the basin hasbeen done and according to the principles of aquatic chemistry, several sources for mainions in the lower reaches of the river, like human activity and weathering, were analyzed.Obtained through research, generally, the amount of cations in the downstream ofTarim follows the order as Na⁺>Ca²⁺>Mg²⁺>K⁺; while as anions amount follows the orderof content size sequence for Cl^->SO₄^2->HCO₃^-. On the air, changing amounts of SO₄^2-, K⁺and Na⁺resulted the change in the order at some areas. During summer season, wateramount in the lower reaches of the river reaches it’s lowest as ion concentration reaches itshighest level. Along with the gradually rising of the waterbed, ion concentration willincrease; chlorinated water is the man subject to the aquatic chemistry, by August sulfuricwater become dominant. In the lower reach water shows alkaline, pH value range from7.8to8.65. Minimum value will appears during winter, as highest alkaline value shows in thesummer when flow stops. The order of mineralization degree in different times as: lateperiod of summer water drain> early period of summer drain> late period of winter waterdrain> winter water late period. From the Da Xi Hai Zi reservoir to Tail-end-lakes TetimaLake, the water in the river gets saltier, from some parts of Tetima lake brine also exits.The river water belongs to soft to hard water;. The analysis about major ion sourcesexplained that sea last chemical substances plays really small role on the water chemistryof the river. The discharges from human activities are main reasons for Cl^-, SO₄^2-ions;main source for HCO₃^-is weathering and decomposition while dissolution. By analyzingthe influence of weathering on water chemistry has great importance to explain for theCa²⁺, Mg²⁺ions in the lower reaches mainly comes from the carbonate, silicate weathering and decomposing/evaporation salt rocks. Na⁺mainly comes from silicate decompositionand evaporation. Salt desolations is the important source for K⁺ion.Comparison of Tarim river downstream aqueous chemistry in2011with the earlytimes of bring water project explained that there is no difference on the ionic order, whileconcentration of every ions higher that the year of2000; because Tarim River itself has arich salt content, ecological water bring project just helped to decline the concentration butdid not lower the general amount of salt; only through the integrated watershedmanagement, through the incensing the amount of the downstream water level, by strictlyprohibit the upper and middle stream drainage into the mainstream, and by strictlycontrolling the ion content of the downstream in the proper concentration range, theecology of the lower reaches can be effectively restored.