塔里木河下游荒漠河岸林地下水蒸散发

Groundwater Evapotranspiration in Desert Riparian Forest in the Lower Reaches of the Tarim River

通过对塔里木河下游4个观测点地下水位的监测和地下水蒸散发的估算,分析荒漠河岸林地下水位月和日的波动、地下水蒸散发(ET_g)的时空变化及其主要影响因素。结果表明:①在生态输水前(7月21日至8月12日),4个观测点地下水位呈整体下降趋势;而生态输水后,水位保持稳定上升趋势。在整个观测期内,地下水位都表现出明显的昼夜波动现象。②ET_g均呈现出单峰变化特征,08:00开始快速增加,在12:00-16:00维持在一个较高水平上,18:00以后快速下降,最高值出现在当地时间14:00。③ET_g随着植被类型、覆盖度的不同而存在显著差异,同时又受地下水位埋深的影响。④太阳辐射、温度和饱和水气压差是影响塔里木河下游地下水蒸散发日变化的主要因素,风速对其无显著影响。

In this study,the groundwater level at four observation sites in the lower reaches of the Tarim River was monitored,and the values of groundwater evapotranspiration were estimated. The purposes of the study were to analyze the fluctuations of groundwater level and the groundwater evapotranspiration( ETg ) as well as their main affecting factors. The results showed that: ① A drawdown of groundwater level occurred holistically at the four observation sites before implementing the project of ecologic water conveyance;after implementing the project from July 21 to August 12,however,the groundwater level was in a steady rising trend. There was a diurnal-nocturnal fluctuation of groundwater level during the study period;② The curve of ETg was unimodal,ETg began to rapidly increase from 08: 00,maintained at a high level from 12: 00 to 16: 00,and rapidly decreased after 18: 00. The highest value appeared at 14: 00 local time;③ ETg varied significantly with different vegetation types and coverage,and was also affected by groundwater depth;④ Solar radiation,temperature and vapor pressure deficiency were the main factors affecting the daily variation of groundwater evapotranspiration in the lower reaches of the Tarim River,and the effect of wind speed on it was not significant.