关键词: 东居延海, 湿地恢复, 生态输水, Landsat

Abstract:

As vital components of lower reaches of inland river basins, terminal lake wetlands provide ecosystem services, e.g., conserving water resources, preventing soil desertification, protecting biological diversity and productivity, regulating local microclimate and improving ecology and environment functions, etc. However, the drying of terminal lakes has been accompanied by a series of serious ecological problems (e.g., soil desertification, vegetation degradation, declination of water table, forming sources of sand storms, etc), which is considered as an important signal of ecological and environmental degradation in the watersheds of inland rivers in arid regions. Such issues have been widely raised in inland arid basins of northwestern China, e.g., Tarim, Heihe, and Shiyang river basins. To restore the delicate ecological environment and rebuild the balance between natural environment and human-being society in these basins, the Chinese government implemented the Inland Watershed Water Division Plan in 2000. East Juyan Lake, the terminal lake of China's second largest inland river Heihe River, shrunk continually for lacking surface water recharge and dried up completely in 1992. The ecological degradation was so severe that it had aroused great concerns around China. As a result of the implementation of environmental water transfer project, the East Juyan Lake had water flowing into it again in 2002. In order to understand wetland restoration process of the lake, this paper provides detailed information of wetland area dynamic changes by interpreting 137 Landsat images with the method of ratio algorithm, and analyses monthly wetland areas, pure water body areas and water vegetation areas from 2000 to 2015. The results show that: (1) There was a rising trend of wetland area in the study period. Before 2009, with more than 94% of pure water body, wetland expanded at an annual rate of 3.7 km². After 2010, wetland area increased slightly and maintained an area of around 55 km². Till 2015, wetland contained more than 9 km² of water vegetation and its area, 54 km², is almost twice as much as that of 2002. (2) Wetland has not dried up seasonally since 2004, and wetland area is the biggest in October or November and the smallest in July or August in a year, while water vegetation booms from June to September. (3) Wetland area and its change are closely related to water volumes and the implementing time of environmental water transfer project, which ensures the health of the East Juyan Lake.

Key words: East Juyan Lake, wetland restoration, environmental water transfer, Landsat