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Temporal areal changes of wetlands in the lower reaches of the Tarim River and their responses to ecological water conveyance |
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| Affiliation: | State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, ürümqi 830011, China University of Chinese Academy of Sciences, Beijing 100049, China Key Laboratory of GIS & RS Application Xinjiang Uygur Autonomous Region, ürümqi 830011, China Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100094, China |
| Abstract: | Aims Ecological water conveyance is of great importance for desert riparian wetland ecosystem. However, few studies have been focused on the quantitative evaluation of water conveyance to wetland restoration due to a lack of continous observation data. This paper analyzed the temporal wetland area changes between Yengisu and Alagan in the lower reach of Tarim River based on time series remote sensing data during 2000-2018, and evaluated the effects of ecological water conveyance on wetland restoration, so as to guide the ecological water conveyance and maintain the stability of the desert wetland ecosystem. Methods About 354 Landsat ETM+/TM/OLI, Sentinel 2 images during 2000-2018 were used to map the monthly wetland area changes in the lower reach of Tarim River, then their annual, seasonal and spaital areal changes were analyzed. The correlation between wetland area changes and ecological water conveyance, underground water levels were also evaluated based on Pearson correlation and cross-correlation methods. Important findings The wetland area has steadly increased in the last 19 years. The areal change rate was minor before 2011 while rapidly increased after 2011. The wetland expanded at a high rate during 2011-2013 and 2017-2018. Different ecological water volumes and water conveyance patterns (single channel or dual channel) can explain different areal changing rates at different stages. The correlation analysis between wetland area changes and ecological water volumes showed that the accumulative ecological water volume is the primary reason causing wetland expansion in recent years. In order to maintain a steady improvement of wetland vegetation, more than 350 million square meters of ecological water are conveyed to the downstream of the Tarim River through dual channel. When the groundwater depth is maintained between -5.0- -3.5 m, the wetland vegetation can sustain a good growth condition. |
| Keywords: | desert riparian wetlands time series ecological water conveyance effect temporal delay analysis lower reaches of Tarim River |
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