Change of Groundwater Quality and Restoration of the Forests of Populus euphratica under Transfusing Stream Water to the Lower Reaches of the Tarim River ——A Case Study along Yengisu Section

In this paper, the chemical properties of groundwater are studied during four times of transfusing stream water to the lower reaches of the Tarim River for regenerating the ecology so as to reveal the temporal and spatial response of chemical properties of groundwater to implementing the project of transfusing stream water along the Yengisu section. The results show that, spatially, the affecting extent of transfusing stream water to the chemical properties of groundwater is continuously enlarged, the affecting extent was within 250 m in distance away from the river channel after transfusing stream water of first time, extended to 450m after second time, and did not exceed 1 000 m after 4 times; temporally, the response of mineralization and chemical properties of groundwater to each time of transfusing stream water is sensitive, that is the groundwater mineralization was obviously increased at the early stage of stream water transfusion, then it was decreased rapidly but slowly in the late stage. The importance of the time of transfusing stream water to the regeneration of the forests of Populus euphratica, the dominant plant species in the lower reaches of Tarim River, is emphasized because the sprouting of seedlings of Populus euphratica requires the regime of groundwater with high quality, and it is also emphasized that the key of regenerating the forests of Populus euphratica is to strengthen the rehabilitation of river channel in the lower reaches of the Tarim River.