地下河系统水动态监测网络优化对比分析:以桂林海洋-寨底地下河系统为例

基于我国南方地区岩溶发育极不均匀、水位水质动态变化快的特点,通过对信息熵法和防污性能法所得结果的对比,分析在缺少系列监测资料条件下,利用岩溶水系统防污性能评价结果快速布设地下河系统水动态监测网的可行性及其布设原则。根据防污性能评价结果,结合水循环特征,桂林海洋-寨底地下河系统水动态监测网需由17个监测站组成;采用信息熵法对现有35个监测站进行优化后,认为只需要12个监测站就可组成最优监测网,但这12个监测站点与采用防污性能评价法得到的点位完全重合,且均位于防污性能差的地区。对比分析认为,以地下水系统防污性能评价结果布设地下水动态监测网是可行性的,因为岩溶发育区既是防污性能差的地区,也是地下水动态变化快的地区,能充分反映地下河系统水质水量变化。采用防污性能评价法布设地下水动态监测网时,需要充分认识和了解地下河系统水文地质条件和地下河管道结构特征,且需要遵循以下原则:(1)在岩溶发育相对较弱的系统中部(基本上不存在防污性能差的地区)不设置监测站点;(2)在距离地下河出口较近的岩溶发育区内(即防污性能差的地区)监测站点可由地下河出口替代;(3)对于多支管道系统,岩溶发育相对较弱且距离较短的小型支管道上可以不布设监测站,由支管道与主管道交汇处的监测站代替。

Comparison and optimization of water dynamic monitoring network for underground river system:a case study of the Haiyang-Zhaidi underground river system,Guilin City

Based on the characteristics of the karst areas of southern China, i.e. uneven karst development and fast dynamic change of water level and water quality, and by comparison of the optimization results obtained by information entropy and vulnerability methods, we investigated the feasibility of rapid deployment of water dynamic monitoring network in underground river system using only the vulnerability results on the premise that monitoring data series are lacking. According to the partition of vulnerability assessment, the water regime monitoring network of the HaiyangZhaidi underground river system needs 17 monitoring stations. After optimizing the existing 35 monitoring stations by information entropy method, we determined that only 12 are needed to form an optimal monitoring network. These 12 monitoring stations, however, were among those identified by the vulnerability assessment method, and all of them are located in the areas of high vulnerability. Our comparative analysis showed that it is feasible to set up groundwater regime monitoring network based on vulnerability assessment. This is because the karst development area not only has high vulnerability, but also subjects to fast groundwater regime change, which can fully reflect the changes of water quality and quantity in underground river system. However, when using the vulnerability assessment method to set up the monitoring network, one needs to fully recognize and understand the characteristics of underground river systems hydrogeological conditions and pipeline structures, and adhere to the following requirements: 1) In the middle of the river system where karst development is relatively weak and high vulnerability areas almost non exist, monitoring stations are not needed; 2) In karst development areas (areas with high vulnerability) near the outlet of underground rivers, monitoring stations can be replaced with underground rivers outlets; and 3) For small and short pipeline branches in a multiple pipe system, where karst development is relatively weak, monitoring can be done instead by monitoring stations at the intersection of branch and main pipelines.