Salinization and improvement ways of water quality of Tarim River, Xinjiang, China

The stream water of Tarim River was fresh before 1958,and its mineralized degree was below 1.0 g/L at all the river sections and at all seasons.However,the average monthly mineralized degree of the water at all the river sections are over 1.0 g/L in the whole year except the flood season in August.At Aral Hydrometric Station at the upper reaches of Tarim River,the monthly mineralized degree of the water is 1 to 3 g/L,3 to 5 g/L and over 5 g/L for 5,4,and 2 months respectively every year,and the highest value comes to 6.3 g/L in May.The proportion of fresh water at Aral is lower than 35% of the annual runoff volume.The stream water at Kara at the lower reaches is totally sub-salt water1 The main causes resulting in the high mineralization of the stream water of Tarim River are the irrational irrigation and drainage,increase of the water consumption for irrigation at the upper reaches,which decrease in the annual fresh water volume of the mainstream of Tarim River from 5 billion m³ before 1960 to 4.2 billion m³ after 1990,except the effects of natural factors,such as arid climate,great evaporation,and high salt content in soil.Meanwhile, large amounts of the drained water from farmlands is discharged into Tarim River,brought the salt of 4.674 million t into the river every year.In order to improve the stream water quality of Tarim River,it is suggested to reduce the volume of the drained water from farmlands,separate the salt water and fresh water,with-drew from farming to reforesting and grass-planting,properly exploit groundwater in the areas of the three tributaries so as to maintain an annual discharged water volume of 4.6 billion m³/a to the mainstream from those tributaries of Tarim River.