The scientists studied pollution in the Kuihe River caused mostly by residential waste, with industry and agriculture contributing less. They calculated the exact amounts of pollutants entering the river and developed a plan to address the residential pollution source. They found that living activities added about 89.3% of COD and 93.5% of ammonia-nitrogen to the river, while industry and agriculture played smaller roles. By focusing on controlling residential pollution, they showed how to ensure the water quality of a river that doesn't have natural runoff.