The salt-water body in the Northern part of Yarkon-Taninim aquifer: Field data analysis, conceptual model and prediction

The salinization processes of the Yarkon-Taninim aquifer (Israel) were investigated for many years, and so far little was known about the saline water body prevailing in the North-Western margin of the aquifer. The salinity of the water in this water body is close to that of seawater. Recently, in drilled wells in the Northern part of the aquifer, it was found that the freshwater and the saltwater are in direct contact, with no geological separation. A relatively thin transition zone, separates the freshwater from the saltwater beneath them. A conceptual model is proposed, based on the field findings: the freshwater flows above the saltwater due to the different density and some mixing takes place around the thin transition zone, which can be approximately modeled as a sharp interface. The saltwater body is connected weakly with the sea, so that the freshwater body mainly determines the pressure and the resulting water head in the saltwater body. The flow in the saltwater body is very slow compared to the flow in the freshwater body. Using water level measurements by monitoring wells, we were able to estimate the position of the interface as a function of time. In the last 50 years the interface elevation was continuously rising at an average rate of 2.8 m per year. This study is a first attempt to derive a model of the saltwater body in the Yarkon-Taninim aquifer that is based on quantitative considerations.