VARIATIONS IN GROUNDWATER CHEMISTRY AND RELATED FACTORS IN THE MIDDLE REACHES OF TARIM RIVER

Based on the three monitoring sections: Shazihe section,Usman section and Archihe section,the variation in groundwater chemistry during 2001—2005 was collected and the regulation of groundwater chemical variation influenced by the embankments was analyzed.The results indict that spatial variations in groundwater at Shazihe section is: the nearer to the embankments,the higher concentrations of ions in groundwater,which is opposite to the normal.The changes of groundwater chemical properties were not significantly,but the salt accumulation in topsoil are severe comparing with that before building the embankment.At the Archihe section,the change of groundwater hydrochemical properties caused by building the embankment is complicated.Generally,the content of major ions is lower in flood season than that in dry season at both the Usman section and Archihe Section.However it is opposite at the Shazihe Section.The contents of groundwater chemistry and their variations have close relations to the different environmental factors of the monitoring sections.About Shazihe Section,there had not been water overflowing from the watercourse since the embankments constructed.In contrast,ecological brakes were set in both Usman and Achihe sections,the water supplying in flooding period is relative plenteous.In general,total dissolved solids(TDS) and the concentrations in major ions are determined by the depth of groundwater,they increase directly with the groundwater level going down.