| Water environment change is one of the main parts of global changing environments. Human activities inevitably contact with water, due to water is essential to human living. Numerous processes related to the human activities, such as population growth, economical progress, agricultural development, urban area's enlargement, industrial structure change, and irrigation works construction, not only influence river hydrological process, but also affect water quality by discharging pollutants to river. Therefore, to study river water environental change related the human activity attracts a lot of scholars. The study area is located at main stem of Aksu River and Upper reaches of Tarim River in Southern Xinjiang, where is irrigation area of Aksu river. The aim of research is to study water environment characteristics, its variation, and its influencing factors at Aksu River and Upper reaches of Tarim River.In this paper, the spatial and temporal variations of river water quality was studied by using multivariate statistical techniques as variance analysis, clustering analysis and factor analysis on the basis of field investigation, sample analysis and extensive collecting materials. And the trend study was performed using the Mann-Kendall Seasonal Test to the main water parameters during 1996-2004(2007) period. The influencing factors mainly anthropogenic and their impacts on water quality were investigated. The results of this research show that:(1)The tributary and main stream of Aksu river is HCO—Ca type river just like the Northern Hemisphere rivers, proportion of ions changes from upper reaches to lower reaches, the proportion Cl and Na gradually rises. At Xidaqiao station, mineralization rate is generally stable, but it grows all along during past 50 years at Aral station in upper reaches of Tarim river, and the trend is slowed down from the beginning of this century. These all changes owe to human activity in this region.(2) The characteristics of water quality of three large plain reservoirs in Aksu River basin were determined at dry and flood seasons. Water quality was improved than 70-80's last century, because of better irrigation and drainage conditions. Water quality of these three large plain reservoirs, Shanyou reservoir, Shengli reservoir, and Duolang reservoir, has differences and it correlated to the Aksu river water quality.(3) The river water quality has evident spatial and temporal differences, especially between stations at Aksu river and staions at upper reaches of Tarim river. Multivariate statistical techniques help us to determine pollution source type and main pollutants. The water quality of Aksu river belongs to I grade (clean water) (GB3838-2002) in all months of a year,and it is I grade for July, August, September, October, V grade(highly contaminated water) in other months of one year. So The water quality of upper reaches of Tarim river could be divided clean water period and contaminated water period in a year.(4) Comparative analysis of NH3-N,CODMn, Cl, SO4, F, TH at Xidaqiao station and Aral station between 1998-2001 and 2002-2005 show, TH and F concentration is higher in 2002-2005 than 1998-2001,concentration of other water quality parameters is lower in 2002-2005 than 1998-2001.(5) The results of Kendall Seasonal Trend test to concentration and load of pollutants showed that water quality of Aksu River at Xidaqiao and Longkou station was stable than of Tarim River at Aral and 14tuan station. Observed values, flow regulated concentrations and pollutant Loads of CODMn, NH3-N had significant downward trend. TH, Cl,SO4 which had deep relations with agricultural activities had no downward trend,instead TH had upward trend.(6) The impacts of human activities to river water environment include alteration of flow distribution yearly and monthly in a year, oasis water consumption and its influence, changing in cultivated land and irrigation drainage, municipal domestic sewage and its influence,etc.①CV of flow was 0.154 at Xidaqiao station, and 0.224 at Aral station. Monthly variation coefficient was also higher at Aral station than at Xidaqiao station. Runoff of Aksu river was an increasing trend, but it was decreasing trend at Aral station (Tarim river) for the past 50 years. All these indicates the river was interfered by human activities.②Agricultural water consumption accounted for the most part of oasis water consumption in the study area. It could be seen when oasis water consumption proportion was relatively high in March and November, flow at Aral station was the least.③Cultivated land was growing gradually, and there was some newly reclaimed wildland areas every year. Increasing cultivated areas lead in more total sown areas, and this caused more oasis water consumption and more farmland drainage. Salty farmland drainage discharges was also increasing in amount, especially spring and winter irrigation periods, when river water flow was low.④The river had also received municipal domestic sewage from Aksu City which could impact the water quality. The influence of waste water treatment plant on river water quality need further study.The research results would help us to understand surface water environment in the study area, and to recognize characteristics of water parameters and its influecing factors. At the same time, The research results might have instructive role on reasonably distribution of water resources and maintaining healthy river ecosystem.
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