This study looked at how water quality varies in the Xiaohe River basin. They found that the main river, Songta River, has good water quality (grade Ⅲ), while a tributary, Baima River, has poor quality (grade Ⅴ), mainly affecting the basin's water quality. Pollution from local sewage and untreated industrial wastewater is a big problem. The study also showed that certain pollutants decrease from upstream to downstream, suggesting the Xiaohe River can clean itself to some extent, though not great. They discovered a link between water's ability to clean itself and how fast the river flows.