Estimating Freshwater Lens Volume based on Island Circularity

Freshwater lenses (FWLs) are an important source of drinking water on many islands in the world. Thus, it is important to study their volumes. Many case studies have already been carried out on real world islands to approximate the FWL volume of the respective islands. Also, generic studies on FWLs exist that consider idealised island shapes such as circular or strip islands. However, to the authors’ knowledge there is no study so far that describes the general relationship between the island’s shape and the freshwater volume of its lens. Here we show that there is a relationship between these two quantities. In our approach, we characterized the shape of the islands using a circularity parameter; the volume was approximated using this shape and a simple numerical steady-state Ghyben-Herzberg approach. While we found a strong relationship between island shape and FWL volume, the relationship between the island shape and the depth of the FWL was less clear. The findings of this study can help to estimate the FWL volume on islands for which there are no case studies available.