Spatial and Temporal Variations of the Groundwater Chemical Characteristics under Ecologic Water Conveyance in the Lower Reaches of Tarim River

Based on the monitoring data of groundwater chemistry and groundwater level influenced by the intermittent water conveyance in the lower reaches of Tarim River from May 2000 to November 2002,the variation of the groundwater chemistry was studied in this paper.It is found that the groundwater chemistry in the whole lower reaches has changed a lot.The groundwater chemistry at the sections near the Daxihaizi Reservoir was influenced earlier than that beyond it.The varying scope of the total dissolved solid(TDS) and the major ions in groundwater is obvious near the Daxihaizi Reservoir.At Yinsu Section,the range influenced by the water conveyance was continual enlarged,it was about 200 m from the channel during the first water conveyance,about 400 m during the second conveyance,about 700 m during the third conveyance,and about 1000 m during the fourth conveyance.As for the groundwater chemistry in a certain site,TDS and the major ions in groundwater increased at the beginning of the conveyance,then it can be interpreted as follows: at the beginning water brought the salt to channel from the place nearby,when more and more water came,the solute was diluted,so TDS and the major ions in groundwater decreased,and the decreasing process was fast in speed at the beginning,then slowed down.In addition,it is assumed that the water conveyance has not removed any salinity in this region,but diluted it.To reduce the salinity in the groundwater and soil,a series of measures on ecology,engineering and management should be carried out.