Abstract: In this study,some surface water samples were collected from the mainstream and main distributaries of the Tarim River Basin in June 2010 to analyzed the hydrochemical components.The ionic concentrations of Koxkar glacier meltwater collected from the headwaters of the Tarim River were compared with those of the Heihe River,the second longest continental river in China.The results revealed that the main basic ionic concentrations in the Tarim River Basin were higher than those in the Heihe River.The concentrations of cations of mainstream of the Tarim River were in an order of Na⁺+K⁺＞Ca²⁺＞Mg²⁺，which were significantly different from those of its main distributaries,i.e.Na⁺+K⁺＞Mg²⁺＞Ca²⁺,and the main basic cations were Na⁺ and K⁺ but not Ca2⁺.The Na⁺+K⁺ concentrations of the mainstream and the south and north distributaries accounted for 68.6%,62.6% and 62.5% of the total basic cationic concentrations respectively.The mean ionic concentrations (except NO₃^-) of the north distributary were lower than those of the south one.Compared with the values in 1965,the ionic concentrations in the Tarim River Basin were significantly increased by 8 times in average,and especially,the Cl^- concentration was as high as 21.7 times of that in 1965,which were possibly related to the increase of both air temperature and precipitation in the Tarim River Basin in recent years.Moreover,river water in the Tarim River Basin was polluted due to the rapid industrial development and sewage discharge.

Key words: hydrochemical component, ion concentration, water quality variation, spatial characteristic, Tarim River Basin