Buffer type identification and water quality status of inflow rivers under different buffer patterns in Lake Erhai

Focusing on the buffer zones of Lake Erhai, and using combined methods of on-site investigation, spatial analysis and data survey, the buffer types of Lake Erhai were identified and the water quality of the inflow rivers under different buffer patterns were analyzed. The results indicated that the buffer structure of Lake Erhai is unreasonable, with excessive proportion of farmland-type and village-type buffer zones. In addition, both the area and shoreline of the village buffer patterns close to the inner parts accounted for over 60% of the buffer zones of Lake Erhai, which mainly located in the western part of the lake. The water quality of main inflow rivers was generally poor, being Class Ⅳ and inferior Ⅴ. The buffer zones of the Tao stream and the Luoshi River were typical “outer cycle-village-farmland-village-inner circle” and “outer cycle-farmland-village-farmland-inner circle” respectively, with inferior Ⅴ class of surface water quality, mainly affected by non-point source pollution such as agricultural non-point sources, residential sources, and tourism pollution. In Lake Erhai buffer zones, the village-type buffers have a large number of external pollution load inputs, while the non-point sources from farmland-type buffers with high fertilization rates and highly polluted decentralized livestock and poultry have direct impacts on the river water quality. Therefore, the area of village-type and farmland-type buffer zones nearby Lake Erhai should be strictly controlled and non-point source pollution from village residential sources, farmland sources and tourism sources should be reduced.