Within an area of about 5 km2, 25 wells were drilled to depths of about 90 m for groundwater observation. The wells were sampled and analyzed, and from the results it could be concluded that the ionic composition is controlled by equilibrium between water and solids. The dominating weathering product is Ca-montmorillonite.
Establishing equilibrium takes approximately ten years. On higher grounds, equilibrium is far from being reached, and these waters are only a couple of years old. In lower positions of the terrain, sea water from glacial times is retained. Turn-over time of water is thus in the order of hundreds to thousands of years. The degree of washing out of the salt water is correlated to the transmissibility of the tectonic zones by which the water is found.