Estimating Land Subsidence Induced by Groundwater Extraction in Unconfined Aquifers Using an Influence Function Method

This article presents a new method based on the influence function approach to predict complex ground movement patterns arising from multiple groundwater pumping stations. The method makes use of the experience and prediction techniques that are used by the mining industry for land subsidence estimation. The analysis of land subsidence induced by groundwater extraction involves the evaluation of factors that are often rather complex and practically difficult to assess. Existing approaches to the land subsidence issue are limited in their ability to address effects of geological variation, multiple pumping, and making use of monitoring data. In this article, simplified key input parameters such as equivalent extraction thickness and angle of draw are discussed in relation to the effects of a typical groundwater drawdown profile. The similarities of land subsidence between underground mineral extraction and groundwater extraction are hypothesized, and the application process of using the methodology for horizontal movement as well as vertical settlement calculation is described. Examples are presented to demonstrate the flexibility and adoptability of the method in comparison with other existing methodologies, including presentations of vertical subsidence contours, horizontal movement vectors, and principal strain distributions over the entire affected area. This article shows that the new method is an invaluable tool in assessing groundwater-extraction-related subsidence effects on proximal surface structures and utilities.