Analysis on Surface Water Quality in the Upper Reaches of the Ogan River Basin

Rising in the southern piedmont of the Tianshan Mountains,the Ogan River(41°06′～42°42′N,80°40′～84°10′E) was one of the headstreams of the Tarim River,which is converged by 5 tributaries including the Muzat River,Karbsyran River, Tailwankuk River,Karasu River and Hezil River,in which the Muzat River is the main tributary of the Ogan River.The Muzat River is 242 km in length,and its fall,maximum slope and catchment area are 1 637 m,23.7‰ and 16 716 km~2 respectively.In this paper,the actuality of surface water quality in the upper reaches of Ogan River and its tributaries as well as Hezil Reservoir is discussed based on the water quality data measured by more than 7 hydrological stations since recent more than 20 years,a case study on annual and seasonal change of water quality along the Ogan River is carried out,and the change characteristics of water quality of the mainstream of Ogan River are analyzed using the water quality data.The results show that the water quality is dominated by HCO_3~-and Ca~(2+),and the background values of the upper reaches of the Ogan River and its tributaries are low.The water mineralization in Hezil Reservoir has been increased with an increase rate of 10.5 mg·L~(-1)·a~(-1) since recent 20 years,and the compound concentration of HSO_4~(2-),Cl~-+ S~(2-) and mineralization has been significantly increased since recent 24 years.The results also reveal that the water quality in the upper reaches of the Ogan River can satisfy the water quality standards of all water consumption purposes if serious water pollution does not occur.