塔里木河下游河岸带地下水埋深对生态输水的响应过程

Response process of groundwater table to ecological water conveyance in the lower reaches of Tarim River riparian zone

为了解塔里木河下游生态输水量与地下水埋深多年响应变化过程,得出地下水埋深对生态输水的响应变化规律,以塔里木河下游英苏断面为研究区,运用定性与定量分析方法,综合考虑不同输水差异(包括零输水年即2008年、输水极少年即2009年、输水较多年2011年等),对2000-2015年英苏断面1 050 m范围内地下水埋深数据进行了分析。结果表明:研究断面内地下水埋深在各年份总体呈现比较平稳的递减趋势,年内个别月具有较大的增幅,另外由于冻土消融等因素影响,地下水埋深在2~3月有一定的增幅;离河较近区域的地下水埋深变化对生态输水的响应具有时间同步性,而离河道较远地区的地下水埋深在响应时间上存在滞后性,本研究断面1 050 m范围内地下水埋深响应时间维持在1 a内;经过多年生态输水过程,英苏监测断面距离河道约750 m范围内地下水平均埋深维持在2~6 m范围内,基本达到植物生长所需地下水埋深水平;另外,综合分析研究断面多年输水引起的地下水位响应过程,为获得生态输水过程所带来的最大生态效益,生态输水不仅要保持一定的输水量,还要保持输水年周期的连续性。

Taking Yingsu-section in the lower reaches of Tarim River, Xinjiang, China, as the study area, using the methods of qualitative and quantitative analysis, the study considered different water conveyance conditions from the year of 2000 to 2015 （zero water conveyance of 2008, including water conveyance pole juvenile of 2009, and more water conveyance of 2011 ）, in order to investigate the relation between ecological water conveyance and the change process of groundwater table, and find the dynamic response laws of the groundwater table in the area. As the source of water conveyance, changes of the level of Bosten Lake directly affect the ecological water conveyance quantity. From 2000 to 2015, there have been sixteen water cycles and more than 20 stages of ecological water conveyance process in the lower reaches of the Tarim River, the cumulative water conveyance quantity was about 51.12 108 m^3, the total days of water supply was about 1 577. During the period, the level changes and the trend of ecological water conveyance were basically the same, showing a positive correlation. From 2000 to 2015, the groundwater table of Yingsu-section presented wave-type increase or decrease, and the overall trend was consistent with the ecological water conveyance. The deepest groundwater table was in 2009 and the highest groundwater table was in 201t, because 2011 was the year with the most water supply, but the ecological water conveyance in 2007-2009 was insufficient. The results indicate as follows： （ 1 ） The groundwater table overall showed a steady decline trend, but there was significant increase trend in individual months during a year, which mainly concentrated in the water conveyance time. In addition, there was also a certain increase of groundwater table during February to March due to the permafrost melting. （2） The response of groundwater table changes to ecological water conveyance showed obvious time synchronization near the fiver, especially within 60 meters away from the river, but there was a lag in the response time of the groundwater table which far away from the river. （3） With the increase of the distance to the fiver, the groundwater level exhibited a linear decreasing trend, the depth level was related to the ecological water conveyance and the lag time of each year. Owing to the ecological water conveyance, groundwater table maintained gradually at 2-6 meters within 750 meters away from the river. It is a reasonable level of groundwater that required by the growth of plants in Yingsu-section. What＇ s more, in order to obtain the maximum ecological benefit of ecological water transfer process, not only maintaining a certain amount of water transfer is necessary, but also maintaining the continuity of the water cycle is needed.