基于云模型的干旱扬水灌区地下水环境状态综合评价

Cloud model-based comprehensive evaluation of groundwater environmental status in arid pumping irrigation area

为解决干旱扬水灌区地下水环境状态受多因素耦合影响而难以定量化描述的难题,以甘肃省景电一期灌区为例,基于灌区多级地下水水文驱动主导因素构建复合评价指标体系,运用CM-AHP和因子分析法对评价指标进行指标赋权。通过最小二乘法优化组合权重模型得到指标综合权重,将评价矩阵与综合权重矩阵相乘得到综合评价云模型。最终以云数字特征的形式对研究区2009年、2014年及2018年的地下水环境风险状态进行了可视化表达。研究结果表明:研究区各时期地下水环境风险状态综合评价云分别为R_(2009)=(0.775 1,0.034 2,0.003 4)、R_(2014)=(0.796 7,0.034 2,0.003 4)、R_(2018)=(0.818 3,0.033 9,0.003 3),各时期地下水环境风险状态分别为"较高(Ⅳ级)"—"中等(Ⅲ级)""较高(Ⅳ级)"趋近于"中等(Ⅲ级)""中等(Ⅲ级)"—"较低(Ⅱ级)",地下水环境状态呈良性演化态势。浮动云的熵值、超熵值均较小,表明评判结果可靠度较高,能够客观揭示研究区实际地下水环境风险状态演化过程。该方法可为指导研究区及相似研究区定量揭示地下水环境风险状态及探寻水环境生态响应平衡机制提供有益参考。

In order to solve the problem that the groundwater environment status in arid pumping irrigation area is difficult to be quantitatively described due to the multi-factor coupling effect, Jingdian Phase-I Irrigation District is taken as a study case herein for building up a composite evaluation index system based on the dominant driving factors of the multi-level groundwater hydrology within the irrigation district, and then the relevant evaluating indexes are weighted with CM-AHP and factor analysis method. Through optimizing the combined weight model by least square method, the comprehensive weight of the indexes is obtained, and then a comprehensive evaluation cloud model is obtained by multiplying the evaluation matrix and the comprehensive weight matrix. Finally, the groundwater environment risk statuses of the study area in 2009, 2014 and 2018 are expressed through visualization in the form of cloud digital characteristics. The study results show that the comprehensive evaluation clouds of the groundwater environment risk statuses in all the periods of the study area are R_(2009)=(0.775 1,0.034 2,0.003 4), R_(2014)=(0.796 7,0.034 2,0.003 4), R_(2018)=(0.818 3,0.033 9,0.003 3) respectively, while the groundwater environmental risk statuses in all the periods are higher(Ⅳ) ~ medium(Ⅲ), higher(Ⅳ) and tending to medium(Ⅲ), medium(Ⅲ) ~ lower(Ⅱ) respectively, thus the groundwater environment status therein exhibits a benign evolution trend. Both the entropy and the hyper-entropy of floating cloud are smaller, which indicate that the reliability of evaluation result is higher and can objectively reveal the evolution process of the actual groundwater environment risk status in the study area. This method can provide a useful reference for guiding the study area and similar study area to quantitatively reveal the environment risk status of groundwater and explore the ecological response balance mechanism of water environment therein.