NUMERICAL MODELING OF INLAND FRESHWATER LENS FORMATION AND EVOLUTION IN DRYLANDS

In arid environments, brackish to saline groundwater encourages the development and sustainability of horizontally oriented, biconvex-shaped, inland freshwater lenses (IFLs). Recharge occurs after high-intensity and short duration rainfall. IFLs supply limited drinking water throughout the Arabian Peninsula (e.g. Kuwait, Saudi Arabia) and other drylands, but their position and longevity through time is underinvestigated. The aim of this study is to simulate the formation and sustainability of IFLs in SEAWAT, a three-dimensional finite difference model designed to solve groundwater flow and transport problems in a variable-density environment. The model represents a scaled representation of the Raudhatain IFL in northern Kuwait. We calibrated vertical and horizontal hydraulic conductivity, specific storage, and specific yield with observations made from physical laboratory simulations and data within the literature. The model adequately matched observed IFL water table elevations along the horizontal profile at four static locations through time [R² = 0.89]. The volume of available freshwater (< 1000 mg/L) was obtained from the numerical transport calculations under varying recharge rates through time. Improved understanding of IFL dynamics provides opportunities for water resource exploration in drylands with shallow, unconfined brackish to saline groundwater.