流程691公里，这里的出境水质为何优于入境？

Group 1 - The ecological restoration project of Gaodong River in Chongqing's Changshou District has improved water quality from Class IV to Class III, showcasing successful environmental management efforts [1] - Long-term efforts in protecting the Yangtze River's ecology have resulted in the water quality of the Yangtze River in Chongqing reaching Class II standards for eight consecutive years since 2017 [2] - The transformation of the former tailings pond of Zhonghua Chongqing Fuling Chemical Co. into a green park demonstrates the shift towards sustainable industrial practices, with over 3 billion yuan invested in modernizing operations [2] Group 2 - Chongqing's modern manufacturing industry, focusing on new energy vehicles and advanced materials, is projected to produce over 950,000 electric vehicles in 2024, marking a 90.5% increase [3] - The shift from coal mining to eco-tourism and specialty agriculture in Fengjie and Wushan counties highlights the region's commitment to sustainable development and ecological preservation [3] - The "Bayu Water Management" system integrates data from over 20 departments, significantly improving pollution analysis and response times from 10 days to 2 days [4] Group 3 - Collaborative ecological protection agreements with neighboring provinces have established a comprehensive ecological compensation mechanism along the Yangtze River [4] - The implementation of over 140 environmental governance projects reflects a strong commitment to improving water ecological conditions in the region [4] - Chongqing aims to play a demonstrative role in promoting green development along the Yangtze Economic Belt, emphasizing its responsibility as an upstream region [4]