Nature and Environment
4. Hai River
Another of China's rivers, the Hai, comes in at number 4. It connects two of China's most populous metropolitan areas, Tianjin and Beijing, before flowing into one of the world's busiest shipping lanes, the Bohai Sea. The 10 river systems share traits, says the study. One is that they are located in densely populated areas with a lack of waste infrastructure and little awareness of recycling.