The Physical and Economic Impact of Aquifer Over-Exploitation at Hangu, China

During the second half of this century, the deep unconsolidated sedimentary aquifer under the coastal city of Hangu has been heavily exploited by the local industry, agriculture and domestic users. This has caused large piezometric head reductions and has resulted in significant land subsidence. The proximity of the sea makes this particularly undesirable. In order to better understand the relationship between the groundwater abstraction and the aquifer compaction, a computer model of the aquifer system which simulated the settlement was created. The nature of the local geology which included thick, slow-draining, clayey aquitards meant that the compaction was delayed in relation to the reduction in pressure in the more transmissive, sandy layers. The reproduction of this delay required the development of a special model package. The modelling indicated that a significant reduction in abstraction was required to restrict the amount of future subsidence to an acceptable level. In parallel with the specific hydrogeological investigation of subsidence, a wider socio-economic study of aquifer over-exploitation used the Hangu situation as a case study. This concluded that water scarcity threatens future regional development, but that more efficient water allocation and efforts to manage groundwater demand might go some way towards putting water use on a more sustainable footing and reduce the need for supply augmentation.