依据地下水浅埋区植被蒸腾对地下水位变化十分敏感的特征,构建沙柳根系吸水条件下的水流方程,分析生态脆弱矿区植生长对地下水位下降幅度的阈限。通过原位监测获取气象要素、土壤水、地下水与沙柳蒸腾量的动态变化规律,建立地下水变化与植被蒸散发关系数值仿真模型并对模型进行求解,模拟沙柳蒸腾对煤炭开采区地下水位变化的响应。研究发现:沙柳的日蒸腾量有受气象要素控制的特点,并在正午12时前后出现2次极值,水位越浅变化越显著。地下水对沙柳蒸腾的贡献值随着地下水位埋深的增加而减少,当地下水位埋深15 cm时,贡献率为100%;地下水埋深215 cm时,贡献率为0。在地下水浅埋区,地下水是沙柳蒸腾的主要水源,潜水埋深超过215 cm后地下水不再对沙柳生长提供水源,这也是沙柳对煤层开采地下水位下降的阈限。

It is universally acknowledged that phreatophytic transpiration changes sensitively with groundwater level de- clining. The present study tries to find the groundwater level decline threshold limited to the vulnerable ecological con- ditions at Yushen mine. The methods include in-situ test and numerical analysis,firstly an experimental base was con- structed for collecting data,including meteorological factors,soil moisture,groundwater level and Salix psammophila transpiration,then a root water uptake model was derived to simulate the change of Salix psammophila transpiration during groundwater level declining. The results show that:Salix psammophila transpiration is strictly controlled by me- teorological factors,there appears two extremums before and after 12 noon,and Salix psammophila transpiration chan- ges more sharply with a shallow groundwater level. The contribution rate of groundwater to evapotranspiration declines with the groundwater depth goes deeper,which decrease from 100% to 0 with groundwater depth decreasing from 15 cm to 215 cm. Salix psammophila cannot utilize groundwater when the groundwater depth is more than 215 cm,that is the threshold of groundwater level decline limited to the vulnerable ecological conditions during coal mining in the study area. The results achieved above will enrich the coal mining technology at ecologically vulnerable coal mine.