Modeling the Optimal Management of Land Subsidence Due to Aquifers Overexploitation
33 Pages Posted: 10 Aug 2023
Abstract
The study of land subsidence has recently been expanded due to its increased occurrence worldwide. Many groundwater systems around the world face overexploitation with serious associated quality and quantity problems. However, one important problem that is still underrepresented in scientific studies, especially from an economic point of view, is land subsidence. The occurrence and magnitude of land subsidence suggests better knowledge of its impacts, and the policies to address it. This paper develops and applies an optimal control model of groundwater extractions under conditions of land subsidence. We include, in a traditional groundwater management model, two types of negative externalities associated with land subsidence: damage to infrastructure and to economic activities, and the loss of aquifer storage capacity. The model is characterized by two sub-problems corresponding to the phase before and after the occurrence of subsidence, when the two externalities dictate the behavior of the optimal path of groundwater withdrawals. The model is applied to the Alto Guadalentín over-exploited aquifer in the Segura River Basin of Spain. The results suggest that regional net present value of welfare over the planning period, under the two land subsidence scenarios, is reduced by nearly 1–5%, compared to the no land subsidence scenario. Furthermore, under subsidence, even with relatively small impacts of both types of externalities, groundwater optimal extractions are kept at levels that avoid these externalities. These outcomes clearly call for government intervention in order to curtail groundwater withdrawals in aquifers with propensity to face undesirable subsidence effects.
Keywords: land subsidence, Groundwater, water overdraft, two-stage optimization, Pontryagin backward-solving problem, Guadaletín aquifer.
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