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Numerical model of the unconfined aquifer of the Triffa Plain (Morocco)
Jebbari, I.; Lebbe, L. (1999). Numerical model of the unconfined aquifer of the Triffa Plain (Morocco), in: De Breuck, W. et al. (Ed.) Proceedings of the 15th Salt-Water Intrusion Meeting Ghent (Belgium), 25-29 May 1998. Natuurwetenschappelijk Tijdschrift, 79(1-4): pp. 55-61
In: De Breuck, W.; Walschot, L. (Ed.) (1999). Proceedings of the 15th Salt-Water Intrusion Meeting Ghent (Belgium), 25-29 May 1998. Natuurwetenschappelijk Tijdschrift, 79(1-4). Natuurwetenschappelijk Tijdschrift: Gent, Belgium. 307 pp., more
In: Natuurwetenschappelijk Tijdschrift. L. Walschot/Natuur- en Geneeskundige Vennootschap: Gent. ISSN 0770-1748, more
Peer reviewed article  

Available in  Authors 
    VLIZ: Proceedings D [27353]
Document type: Conference paper

Keywords

Authors  Top 
  • Jebbari, I.
  • Lebbe, L., more

Abstract
    A three-dimensional finite-difference model of the steady and unsteady groundwater flow in a part of the Triffa plain is elaborated. The model treats the interaction between the unconfined aquifer and the wadi Cherraâ. The base of the unconfined aquifer is drawn by means of lithostratigraphical cross-sections and recent borehole descriptions. The recharge of the unconfined aquifer is estimated by means of a water balance of the unsaturated zone based on hydrometeorological data. In the numerical model, the unconfined aquifer is subdivided in 3 layers, 50 columns, and 65 rows. So, 9750 finite-difference cells are considered with a square base plane that has a side of 200 m. The observation period runs from 1972 to 1992. The simulated hydraulic head of the steady-state flow is compared with the average values of the observed hydraulic head. Here, the horizontal and vertical conductivities of the unconfined aquifer are estimated for the first time. The steady-state flow is also calibrated with the discharge rate of the springs Ras Elma and Ain Beida for short periods. The transmissivity is about 4000 to 8000 m²/d in the central part of the studied area and less than 4000 m²/d in the other parts. Hereafter, the simulated fluctuations of hydraulic head are compared with the observed ones. Here, the specific yield was the most important parameter to adjust, so that the simulated amplitudes of the fluctuations would correspond to the observed ones. The specific yield varies between 0.001 and 0.09 in the central part and between about 0.09 and 0.33 in the other parts. The estimated average total discharge rates of the springs Ras Elma and Ain Beida for the simulation period are respectively 22055 m³/d and 9648 m³/d. These rates are considerably lower than the average discharge rate of the wadi Cherraâ, which is 73267 m³/d.

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