The dynamic groundwater flow field at the central Yarqon-Taninim basin, Israel: a 3D geological-based numerical model

The hydraulic gradient at the confined part of the Yarqon-Taninim (YT) basin, Israel, slightly declines along the main flow-lines from south to north, towards the outlets.  Nevertheless, a local dynamic water divide that is developed during rainy winters at the foothills of the Judea Mountains, temporally alters groundwater flow direction. The exact location of this water divide and the mechanism of its appearance and disappearance are demonstrated using a 3D numerical model of groundwater flow in conjunction with hydrometeorological model.
    Using a calibrated numerical groundwater flow model, we reconstructed the dynamic flow field at the YT basin between 1987 and 2008, and detected the water divide apex near the Ajur wells-field, at the central part of the basin. Its location is determined by the flow field at the mountainous phreatic part of the basin, which itself is controlled by the geological structure. Major folds, comprising the mountainous area, force flow paths to converge into the in-between synclines. In this manner, most of the recharge from the Jerusalem Mountains converges into the narrow southwestern edge of the En-Karem structural low, known as the “Ajur entrance”. At this area, heads
respond quickly to recharge events, resulting in relatively high seasonal fluctuations, mounding, and creation of a dynamic water divide in the confined part of the basin.  The water divide prevails usually for 5–7 months during the winter and spring, and diminishes thereafter.