关键词: 地下水动态, 潜水位下降, 植被退化, 额济纳绿洲

Abstract: Erjina oasis is a alluvial plain of lower reaches of Heihe River in Erjina Banner of lower reaches of Heihe River. Affected by natural and human factors, vegetation of the oasis degenerated greatly ,and its ecological function declined ,which made the oasis being at the edge of collapse.Based on the research achievements of the major project Groundwater Exploration and Ecological Environment and Geological Investigation in Erjina Plain of Northwest groundwater Special Plan from the original Geology and Mineral Department and the major project of Study on Ecological Environment Comprehensive Control and Moderate Use in Erjina Desert Oasis from the Science and Technology Department, the paper gave rounded analysis to groundwater dynamics and groundwater balance characters: groundwater recharge capacity is less than discharge capacity and groundwater storage capacity reduced 92.5×10⁶m³ making it to be negative balance ;recharge in middle and deep layers is not obvious while phreatic fluctuation is complicated resulting a general decline of groundwater level which some places declined 1～2 m. Compared the area from the result of Forest Resources Investigation 2002 with the area 30 years ago, Diversifilious Popular forest reduced 20 600 hm², reaching 29 400 hm²now, and Chinese Tamarisk forest and Saxaul forest reduced significantly .Meanwhile, other desert plant species such as Mongolian Calligonum, Siberian Nitraria and Desert Wormwood died in large areas, leading to a 20%～50% decline of vegetation coverage.The main natural factors causing vegetation degeneration in the oasis are groundwater dynamics changes and groundwater table decline originated from the reduced discharge capacity of Heihe River and the balance irregularity of groundwater .Thus keeping a certain amount of river discharge capacity is the base of stability and rehabilitation of the oasis vegetation for the Erjina Plain groundwater system dependent mostly on the outer runoff recharge as well as effective measures of changing the using way of water resources and regulating groundwater dynamics.

Key words: groundwater dynamics, decline of the phreatic table, vegetation degeneration, Erjina Oasis