The lower reaches of the Tarim River is a region with fragile ecology and significant environmental problems in an arid area of Western China. The local ecological environment has experienced tremendous degradation over the decades, due to water resource deficits from human activities and climate change. In the year 2000, the Tarim River Basin Administration Bureau (TBAB) initiated the Ecological Water Conveyance Project (EWCP) in an attempt to restore the downstream ecosystem. By the end of 2017, 18 water delivery projects had been completed, totaling 6.3 billion m~3. Understanding the effect of water delivery on the ecological environment in the lower reaches of the Tarim River is of environmental importance. This paper monitors and analyses regional environmental changes and ecological responses before and after water conveyance from surface water (lakes, rivers and wetlands), groundwater and vegetation cover, using multi-source remote sensing and long-term series data. Wetland information and updated maps were produced using thematic map plaque knowledge transfer technology. Regional wetlands mapping and area change statistics were then completed for the years 1990, 1995, 2000, 2005, 2010 and 2015. Finally, regional wetland and vegetation change characteristics were analyzed pre-EWCP period (before 2000) and post-EWCP (after 2000). Results indicate that: (1) Pre-EWCP period (1990-2000), the regional ecological environment in the lower reaches of the Tarim River continued to deteriorate (almost half of the swamp wetlands in the basin disappeared and the regional vegetation coverage decreased significantly). (2) Post-EWCP period (2000-2017), the regional ecological environment has been significantly improved. This was indicated by a "V" type reversal in the lakes and wetlands of the basin. In addition, the areas containing medium and sparse vegetation coverage had a significant increasing trend, and the ecological environment of wetland was gradually restored. Furthermore, the long-term dry and shut-off state of the downstream river channel has been changed. In particular, the Tail Lake (Taitema Lake) gradually regained its vitality after 30 years of becoming dry (area reached 147.87 km~2 in Aug. 2017). This research showed that the EWCP played a key role in the rescue and control of the ecological environment in the lower reaches of the Tarim River and hence, the regional ecological environment is gradually recovering. These findings are critical for environmental effect assessments by the EWCP and future ecological restoration effort in the lower reaches of the Tarim River. They may also provide useful technical support and decision-making references for ecological engineering construction and performance evaluation.