Assessment of the environmental effects of ecological water conveyance over 31 years for a terminal lake in Central Asia

Inland river terminal lakes help maintain the regional ecological environment. However, terminal lakes in arid regions have shrunk dramatically over the past 50 years. We extracted the water areas of Taitema Lake in the arid region of Central Asia and calculated the fractional vegetation coverage (FVC) of the surrounding areas based on Landsat images from 1989 to 2019. We analysed the evolution and driving factors of the FVC and lake area before and after implementing an ecological water conveyance (EWC) project in 2000. The contributions of the driving factors were derived using regression analysis, and the effect coefficients were calculated with a path analysis. Results showed that before EWC (1989-1999), Taitema Lake was dry, the proportions of medium and high FVC areas were small, and FVC varied moderately. The contributions of land use and inflow water from Qarqan River to the regional FVC were 57.4% and 45.3%, respectively, and the effect coefficients of temperature and precipitation on FVC were 0.09 and 0.02, respectively. Human-dominated land-use change was the main factor affecting FVC change. After EWC (2000-2019), the water in Taitema Lake was restored, and the average annual proportions of medium and high FVC were 9.5% and 2.7% higher than the pre-EWC period, respectively. The contributions of land use and river inflow to the water area were 39.1% and 60.9%, and those to FVC were 40.7% and 59.3%, respectively. Precipitation had a slightly stronger effect on the water area and FVC than the temperature in the study area, whereas the influence of river inflow on the water area and FVC was less evident than that of the EWC. EWC can replenish lake water quickly, which is essential for improving the ecological environment of terminal lake areas.