3D numerical model for the Yarqon-Tanninim groundwater basin, Israel: challenges and advantages

3D numerical model for the Yarqon-Tanninim groundwater basin, Israel: challenges and advantages

The Yarqon-Taninim groundwater Basin (YTB), is one of the major sources of freshwater in Israel, supplying ~400 MCM/yr. The hydrogeological knowledge regarding the YTB was accumulated step by step, over the last five decades, and was lately re-conceptualized by Dafny [1,2] to accommodate the latest findings and controversies, including stratification of the water column, and allegedly imbalance of the water budget.

The major tool of this study was a 3D numerical flow model, developed using FEFLOW. The model’s setting and calibration process were challenged by complexity of:
- High Relief;
- Extreme inclined geological strata and gradients;
- Facies changes and hydro-stratigraphy variability;
- Faulting;
- Multiple water tables;
- Structural dictated flow paths;
- Lateral shift from confined to unconfined conditions;
- Density-driven stratification.
The model had to accommodate also connection with the sea (interface) and variable outflow through two large springs. In addition, head map for the phreatic part of the basin, to assist with calibration process was not available.
Consequently, a single-layer static model was set and calibrated at the first stage and a three-layer, geological base model was set only after achieving a correlated head map for the entire domain. The 3D transient model was calibrated for 16 years and verified for the following 5 years [2]. This model was linked to a dedicated hydro-meteorological model [3]. Calibration process was very complicated, but very precise, because of the tens of observations points, each has been monitored during tens of years [1,2].

The newly developed model successfully serves to test on-going salination processes at different locations within the YTB and to bridge hydrogeological uncertainties [2,4]

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