The water environmental risk evaluation of watershed control units based on the risk source-acceptor-response framework
Received date: 2016-06-25
Request revised date: 2016-10-02
Online published: 2016-12-23
Copyright
Small areas within watersheds, known as control units, have been designated in China to improve water resources management, and the definition of these control units is a government priority. As yet, there is no consensus on how to identify "risk defensive priority", "water quality maintained priority" and "water quality improved priority" control units. Hence, the definition of risk defensive priority control units was the focus of this study. The risk source-acceptor-response framework was applied to establish a comprehensive water environment risk evaluation system with quantitative and qualitative indexes. Different methods were used to calculate the weighting coefficient for each type of index: for the quantitative index, the coefficient was determined using the entropy value method; for the qualitative index, the coefficient was determined using a fuzzy hierarchy analysis method. Finally, the risk level for each control unit was ascertained by calculating the risk scoring, and four levels of risk were established: "high", "medium", "low" and "extremely low". The high-risk units were defined as risk defensive priority control units, and the medium-risk units were defined as early warning units. A case study of the Zhejiang province in the Taihu watershed was conducted using 2011 data. Five categories of risk and 20 indexes were selected to construct the three-level water environmental risk evaluation system. In all, 35 control units were dispersed across 13 counties of the research area. Four high-risk (risk defensive priority) control units were identified, which were located in the downstream portion of the basin, including all of Jiashan County and part of Pinghu County. These units suffer from "self-contamination" risk and from "upstream accumulated pollution" risk, and should receive much remedial attention. In addition, 17 medium-risk (early warning) control units were identified, which were distributed in 12 towns (excluding the town of Jiashan County). In conclusion, it is feasible to identify risk defensive priority units and early warning units by distinguishing their risk rankings. This study provides an important theoretical benchmark for objective definition of risk defensive priority control units.
Key words: risk; control unit; source; acceptor; response
XIE Rongrong , PANG Yong , JIANG Caiping , WANG Feifeng . The water environmental risk evaluation of watershed control units based on the risk source-acceptor-response framework[J]. GEOGRAPHICAL RESEARCH, 2016 , 35(12) : 2363 -2372 . DOI: 10.11821/dlyj201612014
Fig. 1 Schematic representation of the control unit, control cross-section, the water hydrographic network and water quality in the research area图1 研究区域控制单元、控制断面及主要水系水质类别简图 |
Tab. 1 Water environmental risk evaluation system for control units based on the risk source-acceptor-response framework表1 控制单元水环境风险源体—受体—响应综合评价体系 |
| 一级 指标 | 二级 指标 | 三级指标 | 等级 | |||
|---|---|---|---|---|---|---|
| 高风险 | 中风险 | 低风险 | 极低风险 | |||
| 风险源体(S) | 点源(S1) | 主导行业(S11) | 石油加工、炼焦和核燃料加工业,化学原料和化学制品制造业,医药制造业。 | 纺织业,造纸及纸制品业,金属冶炼及压延加工业、金属表面处理及热处理加工,皮革、毛皮、羽毛及其制品和制鞋业,橡胶和塑料制品业,化学纤维制品业。 | 设备制造业,交通运输、仓储和邮政业,建筑业,采矿业。 | 其他 |
| 污水排放量(m3/d)(S12) | ≥2000 | ≥1000 | ≥200 | ≥0 | ||
| 污水水质复杂程度(S13) | 复杂 | 中等 | 简单 | 不排放 | ||
| 主导行业工艺水平(S14) | 国内落后 | 国内平均 | 国内先进 | 国际先进 | ||
| 面源(S2) | 氮肥施用强度(kg/hm2)(S21) | >364 | >225 | >120 | ≥0 | |
| 磷肥施用强度(kg/hm2)(S22) | >104 | >46 | >10 | ≥0 | ||
| 畜禽养殖数量(折算成猪,头)(S23) | ≥6000 | ≥3000 | ≥1200 | ≥0 | ||
| 生活污水接管率(%)(S24) | ≤70 | ≤80 | ≤90 | ≤100 | ||
| 风险受体(A) | 控制断面水环境(A1) | 断面控制类别(A11) | 国控 | 省控 | 市控 | 县控及以下 |
| COD(A12) | >40 | >30 | >20 | ≥0 | ||
| NH4-N(A13) | >2.0 | >1.5 | >1.0 | ≥0 | ||
| TN(A14) | >2.0 | >1.5 | >1.0 | ≥0 | ||
| TP(A15) | >0.4 | >0.3 | >0.2 | ≥0 | ||
| 功能区划目标水质(A16) | Ⅰ、Ⅱ | Ⅲ | Ⅳ | Ⅴ | ||
| 流量(m3/s)(A17) | ≤5 | ≤15 | ≤150 | >150 | ||
| 区域水生态(A2) | 鱼类多样性指数(A21) | ≤0.4 | ≤0.6 | ≤0.8 | >0.8 | |
| 底栖动物多样性指数(A22) | ≤2 | ≤3 | ≤4 | >4 | ||
| 风险响应(R) | 政府公众响应(R1) | 应急响应能力(R11) | 无 | 低 | 中 | 高 |
| 政策法规贯彻力度(R12) | 极低 | 低 | 中 | 高 | ||
| 公共环保意识(R13) | 无 | 低 | 中 | 高 | ||
Tab. 2 Criteria for the comprehensive risk evaluation表2 综合风险等级评分分级表 |
| 项目 | 综合评价值 | |||
|---|---|---|---|---|
| xmin<ESI≤xmin+0.25△ | xmin+0.25△<ESI≤xmin+0.5△ | xmin+0.5△<ESI≤xmin+0.75△ | xmin+0.75△<ESI≤xmax | |
| 风险等级 | 极低风险 | 低风险 | 中风险 | 高风险 |
注:△=xmax-xmin。 |
Tab. 3 Relative importance of factor values in the priority relation array表3 优先关系矩阵数量标度[20] |
| 评价指标A和 B的相对权重 | 定义 | 说明 |
|---|---|---|
| 0.5 | 同等重要 | ai,aj对目标具有同样的贡献 |
| 0.6 | 稍微重要 | ai比aj稍微重要 |
| 0.7 | 明显重要 | ai比aj重要 |
| 0.8 | 重要的多 | ai比aj明显重要 |
| 0.9 | 极端重要 | ai比aj非常重要 |
| 0.1,0.2,0.3,0.4 | 反比较 | rji=1-rij |
Tab. 4 Examples of the calculation matrix using the entropy method and the fuzzy evaluation method表4 熵值法和模糊层次分析法计算矩阵构建实例 |
| 熵值法 (以面源层为例) | 判断矩阵 | 归一化矩阵 | ||
|---|---|---|---|---|
| 模糊层次分析法 (以点源层为例) | 优先判别矩阵 | 模糊一致判别矩阵 | ||
| B2 | 高风险 | 中风险 | 低风险 | 极低风险 |
| B21 | 364 | 225 | 120 | 0 |
| B22 | 104 | 46 | 10 | 0 |
| B23 | 6000 | 3000 | 1200 | 0 |
| B24 | 70 | 80 | 90 | 100 |
| B2 | 高风险 | 中风险 | 低风险 | 极低风险 |
| B21 | 0 | 0.382 | 0.670 | 1 |
| B22 | 0 | 0.558 | 0.904 | 1 |
| B23 | 0 | 0.5 | 0.8 | 1 |
| B24 | 0 | 0.333 | 0.667 | 1 |
| B1 | B11 | B12 | B13 | B14 |
| B11 | 0.5 | 0.1 | 0.3 | 0.3 |
| B12 | 0.9 | 0.5 | 0.7 | 0.7 |
| B13 | 0.7 | 0.3 | 0.5 | 0.5 |
| B14 | 0.7 | 0.3 | 0.5 | 0.5 |
| B1 | B11 | B12 | B13 | B14 |
| B11 | 0.5 | 0.3 | 0.4 | 0.4 |
| B12 | 0.7 | 0.5 | 0.6 | 0.6 |
| B13 | 0.6 | 0.4 | 0.5 | 0.5 |
| B14 | 0.6 | 0.4 | 0.5 | 0.5 |
Tab. 5 Weighting coefficients in the water environmental risk evaluation system表5 控制单元水环境风险评价体系指标权重系数结果表 |
| 一级指标 | 一级权重 | 二级指标 | 二级权重 | 三级指标 | 三级权重 |
|---|---|---|---|---|---|
| 风险源体 (S) | 0.35 | 点源 (S1) | 0.55 | 主导行业(S11) | 0.183 |
| 污水排放量(m3/d)(S12) | 0.317 | ||||
| 污水水质复杂程度(S13) | 0.250 | ||||
| 主导行业工艺水平(S14) | 0.250 | ||||
| 面源 (S2) | 0.45 | 氮肥施用强度(kg/hm2)(S21) | 0.249 | ||
| 磷肥施用强度(kg/hm2)(S22) | 0.251 | ||||
| 畜禽养殖数量(折算成猪,头)(S23) | 0.249 | ||||
| 生活污水接管率(%)(S24) | 0.251 | ||||
| 风险受体 (A) | 0.4 | 控制断面水环境 (A1) | 0.6 | 断面控制类别(A11) | 0.141 |
| COD(A12) | 0.142 | ||||
| NH4-N(A13) | 0.142 | ||||
| TN(A14) | 0.142 | ||||
| TP(A15) | 0.142 | ||||
| 功能区划目标水质(A16) | 0.141 | ||||
| 流量(m3/s)(A17) | 0.150 | ||||
| 区域水生态 (A2) | 0.4 | 鱼类多样性指数(A21) | 0.500 | ||
| 底栖动物多样性指数(A22) | 0.500 | ||||
| 风险响应 (R) | 0.25 | 响应 (R1) | 1 | 应急响应能力(R11) | 0.483 |
| 政策法规贯彻力度(R12) | 0.283 | ||||
| 公共环保意识(R13)) | 0.234 |
Tab. 6 Comprehensive risk evaluation results and identification of control units in the case study表6 控制单元综合风险等级评分及等级确定表 |
| 序号 | 图示码 | 综合风险评分 | 综合风险等级 | 序号 | 图示码 | 综合风险评分 | 综合风险等级 |
|---|---|---|---|---|---|---|---|
| 1 | 101 | 2.681 | 低风险 | 19 | 208 | 3.025 | 中风险 |
| 2 | 102 | 2.969 | 中风险 | 20 | 209 | 2.537 | 极低风险 |
| 3 | 103 | 2.863 | 中风险 | 21 | 210 | 2.468 | 极低风险 |
| 4 | 104 | 2.702 | 低风险 | 22 | 211 | 3.045 | 中风险 |
| 5 | 105 | 2.897 | 中风险 | 23 | 212 | 2.798 | 低风险 |
| 6 | 106 | 2.516 | 极低风险 | 24 | 213 | 2.896 | 中风险 |
| 7 | 107 | 2.543 | 极低风险 | 25 | 214 | 3.008 | 中风险 |
| 8 | 108 | 2.860 | 中风险 | 26 | 215 | 3.006 | 中风险 |
| 9 | 109 | 2.965 | 中风险 | 27 | 216 | 2.906 | 中风险 |
| 10 | 110 | 2.600 | 极低风险 | 28 | 217 | 3.006 | 中风险 |
| 11 | 111 | 2.795 | 低风险 | 29 | 301 | 2.922 | 中风险 |
| 12 | 201 | 3.217 | 高风险 | 30 | 302 | 2.827 | 低风险 |
| 13 | 202 | 3.179 | 高风险 | 31 | 303 | 3.058 | 中风险 |
| 14 | 203 | 2.982 | 中风险 | 32 | 304 | 2.970 | 中风险 |
| 15 | 204 | 3.112 | 高风险 | 33 | 305 | 2.758 | 低风险 |
| 16 | 205 | 3.079 | 高风险 | 34 | 306 | 2.758 | 低风险 |
| 17 | 206 | 2.659 | 低风险 | 35 | 307 | 2.829 | 低风险 |
| 18 | 207 | 3.052 | 中风险 |
Fig. 2 Schematic of the comprehensive risk evaluation result for the control units in the case study图2 控制单元综合风险等级示意图 |
The authors have declared that no competing interests exist.
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