南水北调中线水源地缓坡型库岸生态屏障构建

Ecological barrier constructing in the gentle slope reservoir bank in the water source of Middle Route of South-to-North Water Diversion Project

丹江口水库缓坡型库岸农业生产强度大,面源污染对库区水质产生威胁。构建库岸生态屏障,是阻控库周面源,减少消落区土地无序利用,保障水库水质的重要手段。缓坡型库岸生态屏障构建的核心是消落区植被恢复和生态水系统建设。植被恢复将消落区划分为拦滤净化带(160~163.5 m)、固岸缓冲带(163.5~165 m)、保土持水带(165~167 m)和适度利用带(167~170 m),适度利用带能够解决消落区土地无序耕种的问题。生态水系统建设根据现场微地形特征,设计布局生态塘、近自然湿地、生态透水坝和生态沟道等措施。选择香花镇缓坡型库岸开展了应用实践,构建的生态屏障对TN、TP、TSS的预计削减量分别为3.94、0.23、315.79 t·a-1,各污染物去除率在75%以上。上述研究结果可为南水北调中线水源地缓坡型生态屏障构建提供依据,亦可为我国其他水库库岸生态建设提供借鉴和参考。

The agricultural production intensity in the bank of Danjiangkou Reservoir is high and the water quality in the reservoir area is threatened by non-point source pollution. The construction of ecological barrier is an important means to prevent and control peripheral non-point sources of the reservoir, reduce the disorderly use of land in the water-level-flucutation zone and guarantee the water quality of the reservoir. The core of the ecological barrier construction in the gentle slope reservoir bank is the vegetation restoration and ecological water system construction. Vegetation restoration divided the subsidence area into filter blocking and purification zone(160~163.5 m), shore solid buffer zone(163.5~165 m), soil retaining and water holding zone(165~167 m) and moderate utilization zone(167~170 m). Moderate utilization zone can solve the problem of land disordered cultivation in the water-level-flucutation zone. In the construction of ecological water system,measures such as ecological ponds, near natural wetlands, ecological permeable dams and ecological gullies are designed according to the site microtopographic characteristics. The gentle slope bank of Xianghua Town was selected to carry out the application practice. The estimated reduction amounts of TN, TP and TSS by the constructed ecological barrier were 3.94, 0.23 and 315.79 t·a-1, respectively, and their corresponding removal rates were above 75%. This study can provide the basis for the construction of gentle slope ecological barrier for water source in the middle route of South-to-North Water Diversion Project, and also provide reference for other reservoir bank ecological construction in China.