The Influence of Groundwater on Vegetation in the Lower Reaches of Tarim River,China

Results of the analyses of the monitored data of the 4 times of stream water conveyance to the river section where the stream flow was cut-off more than 30 years, of the nine groundwater-monitoring sections and 18 vegetation plots in the lower reaches of the Tarim River from 2000 to 2002, show that the composing and type of vegetation, the distribution and the way vegetation is growing closely related to the depth of groundwater; the continuously decreasing of the groundwater and the loss of soil water are the main factors for the degradation of vegetation in the lower reaches of the Tarim River; the 4 times of stream water conveyance to the dry up of the lower reaches of the river plays an important role in raising the groundwater level, which is close to the watercourse. The groundwater was raised gradually. The transverse response scope of groundwater level was gradually enlarged to about 1,000 m after the fourth conveyance and the lift range of groundwater level is the highest in the upper section (84%), median in the middle section and the lowest in the lower section (6%) longitudinally. The natural vegetation in the lower reaches is saved and restored along with the rise of groundwater level, the response scope of vegetation is gradually enlarged, i.e., from 200-250 m in width after the first conveyance to 800 m after the fourth conveyance.