Ecological Water Conveyance Influences the Groundwater table and Vegetation Characteristic in the Lower Reaches of the Tarim River

In the arid regions, groundwater plays a vital role in the development of vegetation especially the desert riparian vegetation due to the limited precipitation and high evaporation. Understanding the response mechanism of desert riparian vegetation to groundwater dynamics is important for the sustainable development of environment in the arid regions.

The Tarim River, located in the northwest arid area of China, is the longest inland river in China with the length of 1,321 km. The lower reaches of the river start from the Daxihaizi Reservoir in Yuli County and end in Lop-nor lake in Ruoqiang County. Recent years, groundwater levels in the lower reaches of the Tarim River dropped sharply as a result of over-exploitation. To protect the environment in this area, the ecological water conveyance project (EWCP) has been implemented since 2000. This project provides a valuable opportunity to reveal the mechanism of hydro-ecological processes in this area.

Based on the NDVI time series data, the water flow and groundwater depth data of the EWCP, the vegetation data and the meteorological data from 2000 to 2012, Dr. HAO Xingming et al. analyzed the effects of ecological water conveyance on groundwater dynamics and vegetation recovery in the lower reaches of the Tarim River.

The results showed that the groundwater table decreased with the increase of the (longitudinal) distance between wells and the water source of the EWCP. The ecological water conveyance significantly influenced the individual number of herbs and shrubs but did not affect the individual number of trees or the total species number.

In the lower reaches of the Tarim River, variation of groundwater depth significantly influenced vegetation phenological characteristics, such as the start time of the herb growing season and the length of the growing season. Since the implementation of the EWCP, the vegetation cover in the lower reaches of the Tarim River was significantly improved. Vegetation cover gradually increased and reached the maximum value in 2005, and decreased from 2006 to 2008 due to the decreasing of recharged water volume. Further, vegetation cover increased again since 2008 with the increasing of recharged water volume.

The findings have been published in Environmental Monitoring and Assessment in November 2014.

Contact

HAO Xingming

State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences

E-mail: haoxm@ms.xjb.ac.cn