The Mamora coastal aquifer in northwest Morocco: Geophysical imaging of the aquifer, assessment of hydraulic parameters and attempt of simulating scenarios of projected recharge and discharge and their impact on saltwater intrusion
by
E. A. Toto
University of Ibn Tofail, F.S. Kenitra, Depart. Geol., Lab. of Exploration Geophysics and Environment
Coauthors: B. Ben Kabbour - University Cadi Ayyad, Faculty of Sciences and Techniques, Dep. Earth Sci.

Coastal aquifers, along the Atlantic coast of Morocco, provide the majority of water needs. One of these is the Mamora aquifer which is very likely the most important in the country because of its wide extent, good water-bearing properties, and generally excellent water quality. The Mamora aquifer provides almost all of the public domestic- and irrigation-supply water for the Wilayas (States) of Cherrard-Beni hasen and Zemmour-Zair, which have a population of about 3.000.000. In the last decade, the severe conditions of drought, the population growth and the substantially increased farming and industrial activities have made the groundwater withdrawals to increase continuously. Because quite a great number of the supply wells are located on the coastal plain of the Atlantic ocean and if the current trend in the decline in water levels is accounted for, saltwater intrusion and other surface pollution sources may pose a serious threat to the water quality in the Mamora aquifer. In fact, increasing chloride concentrations in water sampled from one of the coastal wells were reported higher than the drinking water standards.

In this investigation, most of the data were collected in the predominantly agricultural and industrial coastal Mamora because factors likely to impact water quality are concentrated in this area. So, the geographic scope of the study was limited the Mamora coastal aquifer, hydraulically connected to the ocean.

In attempting to better understand the subsurface hydraulic functioning of the study aquifer and to contribute to the development of coastal groundwater management and protection, a detetaile one-dimentional DC resistivity survey and a two dimensional numerical modelling study were carried out using the USGS Modflow code. In the first stream of simulations for both the steady and unsteady states, the aquifer shows an areal variability in hydraulic and water-quality properties that would strikingly correlate with the aquifer heterogeneity. Estimated values for the hydraulic permeability and the effective porosity (storage) coefficients range respectively from1.2E-04 m/s up to 2.25E-03 m/s and between 3% and 15%, an indication of possible good groundwater potentiality. In the second stream of simulations, projected future climatic and pumping scenarios simulated with the obtained ground-water flow model indicate water levels will substantially decline in the aquifer coastal area, thereby inducing the inland movement of saltwater into the aquifer. Consequently, to optimally exploit this seemingly fragile coastal aquifer, a plan of future actions to implement is proposed.

Date received: August 6, 2004

Copyright © 2004 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caon-24.