Abstract: 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.

Key words: karst, underground river, information entropy, vulnerability assessment, regime monitoring network of groundwater