洱海缓冲带模式识别与不同模式下入湖河流缓冲带段水质

以洱海缓冲带为研究区,利用现场调查与ArcGIS分析相结合的手段,识别洱海缓冲带模式,分析不同模式下主要入湖河流缓冲带段水质。结果表明:洱海缓冲带共分7种模式,其中模式1面积最大,占洱海缓冲带总面积30.46%;模式4岸线最长,占洱海岸线总长度37.14%;村落紧靠缓冲带内圈的模式,其面积和岸线均占洱海缓冲带60%以上。不同模式下入湖河流缓冲带段水质为GB 3838—2002《地表水环境质量标准》Ⅳ类~劣Ⅴ类,流经模式1即外圈—农田—村落—内圈缓冲带的桃溪、流经模式3即外圈—农田—村落—农田—内圈缓冲带的罗时江、流经模式5即外圈—村落—内圈缓冲带的白鹤溪,主要受缓冲带内农田面源、农村生活源、旅游污染等的影响,水质均为劣Ⅴ类。洱海缓冲带内村落与景区、高施肥种植农田、分散式畜禽养殖产生大量的污染,直接影响入湖河流缓冲带段水质。洱海湖岸线系数为2.28,沿岸生物多样性相对较低,易受外源污染输入的影响。应治理临近洱海的村落和农田型缓冲带,削减缓冲带内污染负荷量,减轻对洱海的污染。

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.