Safe pumping in areas prone to karst collapses: A case study of the urban emergency water source of the Guanghua basin in the Pearl River Delta

How to realize safe pumping by control in areas prone to karst collapses is an urgent problem for groundwater managers and scientific and technical personnel of the urban emergency water source. Taking the Guanghua basin of Pearl River Delta as an example, this paper presents a comparative analysis of pumping in the field and critical hydraulic gradient tests in the laboratory to determine the control conditions for safe pumping. The results show that the karst collapse can be prevented and controlled by proper choice of the depth of the water level. The probability of sinkhole collapse is greatly reduced when the water level is lower than 9 meters. This result can be directly used as the control index of groundwater safety exploitation by enterprises and the decision-making index of safety management and control by government management departments. At the same time, it is pointed out that due to the differences of geological conditions, in the process of actual groundwater exploitation, it is not possible to rely mechanically on a single control index of groundwater level drawdown. The depth of groundwater level should be controlled according to the influence radius of pumping water and the different critical hydraulic slopes in different regions, or the mining method should be changed to make full use of groundwater resources. It is suggested that emergency disaster plan should be made during the actual pumping period, groundwater monitoring should be strengthened, and groundwater and other influencing factors should be monitored in real time.