more from nhk world's -- >> reporter: kuming has been nicknamed spring city. residents enjoy clean air thanks to the high elevation. the community is growing in size and people are relocating here. in the south of the city is this lake. it's a popular tourist spot but until a few years ago, this fresh water lake was severely polluted with algae -- was born and grew up near the lake. he used to run a pig farm here but decades ago he noticed the water he was using for feed was rapidly disappearing. he looked into the problem and told the authorities the chemical fertilizer plant was releasing sulfuric acid into the lake. >> translator: i gathered evidence and sued the company that was polluting the lake. i won the case and the plant was forced to stop operations. people were grateful for what i did. >> reporter: local officials took measures to improve the water quality and their efforts paid off. over the past five years the amount of algae lessened and the water became much clearer but just as the situation was improving a new problem arose. there are a lot of