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人类对土地的需求及开发日益增多,使其对河流岸线的侵占日益严重,导致河流岸边水土保持功能降低,面源污染物在降雨过程中随着径流和泥沙进入河流,对河流水生态功能造成严重影响[1-4]。河流生态缓冲带(本文主要探讨其中最主要的类型“河岸植被缓冲带”,后简称“缓冲带”)是保护河流水质的一道屏障,是具有改善河流水环境、控制面源污染和水土流失等重要作用的带状缓冲区域,可通过建立和恢复缓冲带来拦截面源污染[5]。近年来,国内外学者与管理部门加强了对缓冲带的研究与重视。我国先后颁布了《水污染防治法》《水污染防治行动计划》《重点流域水生态环境保护“十四五”规划编制技术大纲》等相关管理文件,对缓冲带保护与生态修复提出了新要求[5]。在实际应用中,如何合理确定植被缓冲带的宽度及构建方法,逐渐成为学者们与管理部门关注的热点之一。
国内外学者对缓冲带宽度的研究主要采用经验值和模型模拟计算2种方式[6]。其中,基于经验值的定量研究较少且适应性窄,难以推广应用;基于模拟计算的模型较多,主要包括VFSMOD模型、MANDER模型、REMM模型、SWAT模型等,模型模拟计算缓冲带宽度尽管所需参数较多、难度较大,但针对性较强,同等情景下可推广应用。其中,VFSMOD模型是一种用于模拟面源污染的田间尺度机制模型,模型参数获取相对简单,通过参数的设置与输入,可模拟计算不同情景下不同宽度的缓冲带对地表径流污染物的去除效率,取得了较好的效果并在国外得到了广泛的应用[7-12]。
大钱港是浙江省水生态保护与修复的重点示范水体,属于典型的平原河网型河流。平原河网型河流的水环境特点主要有:1)水系发达、河港纵横,水系成网状分布;2)地势平坦,水系水位落差小,水利闸坝较多,流向不定,水体流动性较差,水动力较弱;3)居住人口密集,水利水系变动较大,岸线被侵占问题突出;4)汊港水质一般较差,水体透明度较低,水环境承载力不足。对平原河网型缓冲带的划定,是指在地形坡度的基础上,结合汊港水体流向,综合考虑调整汇水分区,再结合土地利用状况、降水条件、土壤类型等现状条件,确定缓冲带的宽度。
本研究以浙江省湖州市大钱港为例,结合VFSMOD模型和大钱港流域自然和社会条件,沿干流及入河汊港两岸划定缓冲带,并选择典型区域构建缓冲带,以期为平原河网型缓冲带的划定与修复、水生态提升、水环境改善提供参考。
湖州大钱港(溇港)河流生态缓冲带的划定与构建
Delineation and construction of riparian ecological buffer zone in Daqiangang ( Lougang ) of Huzhou, China
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摘要: 河流生态缓冲带(后称“缓冲带”)对改善河流水环境、控制面源污染和水土流失等具有重要作用。如何确定缓冲带的宽度并对其进行合理构建,已成为学者与管理部门关注的热点之一。以浙江省湖州市平原河网型河流大钱港(溇港)为例,基于VFSMOD模型计算和地形坡度、水体流向、土地利用状况、降水条件、土壤类型等现状条件,确定了农田型河段、村落型河段、林草型河段的缓冲带宽度;针对城镇型河段,结合城市河道蓝线,确定了缓冲带的宽度。结果表明,大钱港干流左右岸缓冲带长度共约16.1 km,面积共约0.408 km2;同时,采用GIS对数据进行处理,并实现了缓冲带的可视化表达。结合农业农村面源污染负荷空间分析,筛选出高污染入河负荷区中的唐家浒自然村汊港段,并提出了缓冲带修复方案,以期为其他缓冲带划定与构建提供参考。Abstract: The riparian ecological buffer zone plays an important role in improving river water environment, controlling non-point source pollution and soil erosion. The delineation and construction of the riparian ecological buffer zone has been become a hot topic to many researchers and government regulators. This study took the river Daqiangang (Lougang) in Huzhou City, Zhejiang Province as an example for the buffer zone width determination of farmland-type river section, village-type river section, and forest-grass river section based on the current conditions such as terrain slope, water flow direction, land use status, precipitation conditions and soil types using VFSMOD model. The buffer zone width of the urban river section was determined according to the blue line of the urban river. Using GIS for data processing and visual expression, it was indicated that the length of the ecological buffer zone on the left and right banks of Daqiangang (Lougang) was about 16.1 km, and the total area was about 0.408 km2. The branch port section of Daqiangang near Tangjiahu Natural Village, as a high-pollution load area based on the spatial analysis of agricultural and rural non-point source pollution, was selected as a pilot for design of the buffer zone restoration plan, which would provide a reference for the delineation and construction of the ecological buffer zone of analogous rivers.
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表 1 河流生态缓冲带的宽度参照值
Table 1. Reference values of river ecological buffer width
河流类型 坡度/% 一般河流
最小宽度/m特殊河流
最小宽度/m堤防型河段 — 5 ~ 10 5 ~ 10 城镇型河段 — 城市河道蓝线 城市河道蓝线 农田型河段 1 25 45 农田型河段 3.5 30 60 农田型河段 9 35 80 农田型河段 30 70 125 村落型河段 1 20 35 村落型河段 3.5 25 45 村落型河段 9 30 60 村落型河段 30 70 120 林草型河段 — 15 15 注:堤防型河段的最小宽度参照水利部门河道管理范围5~
10 m;城镇型河段的最小宽度按城市河道蓝线划定范围确定。表 2 大钱港区域不同污染类型面源污染排放统计列表
Table 2. Statistics list of non-point source pollution emissions of different types of pollution in Daqian Harbor
t·a−1 污染
类型COD 氨氮 TP TN 排放量 入河量 排放量 入河量 排放量 入河量 排放量 入河量 农田径
流型547 109 109 22 7 1 126 25 农村生
活型1.8 0.36 0.44 0.09 0.05 0.01 0.55 0.11 合计 548.8 109.36 109.44 22.09 7.05 1.01 126.55 25.11 表 3 大钱港(干流)两岸缓冲带统计结果
Table 3. Characteristics of the buffer zone on both sides of the Daqian Harbor (main stream)
河流河段
类型左岸缓冲带 右岸缓冲带 宽度/m 长度/km 宽度/m 长度/km 城镇型 — 4.6 — 4.7 农田型 26 6.0 26 8.2 村落型 21 2.3 — — 合计 — 12.9 — 12.9 -
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