Morocco is one of the Mediterranean countries currently experiencing intense demographic, social, cultural, economic and environmental changes. Water resources in the countries around the Mediterranean are limited and unequal. The Mediterranean bassin regroups 60% of the water-poor world population with water capital/inhabitants less than 1000 m3/inhabitant/year, in Morocco, it is less than 650 m3/inhab/year (Sinan et al., 2009 ; Ouzerbane et al, 2021a). Resources are already overexploited in many places and the growth in water needs will remain very strong with population growth in the southern Mediterranean basin, the development of tourism, industry and irrigated land. The scarcity of water resources in the Kingdom is not an exceptional concept. It stems from the peculiarities of the geographical and climatic context of the region. The various processes, cited above, will exacerbate the problems of availability of this resource in quantity and quality. This will accentuate the tension between supply and demand (Calow et al., 2010 ; Jamaa et al., 2020). Such situations will recur in the future and perhaps even more frequently if they are linked to the phenomenon of desertification which affects West Africa and to the extent of climate change on a planetary scale. This water crisis is aggravated by the dynamic interaction of several processes that act at the local, national and global level (Bahir et al, 2002, Ouzerbane et al, 2021b). Globally, the total volume of groundwater resources is difficult to measure, but one estimate puts it at around 10.5 million km³ (Shiklomanov and Rodda, 2003), with groundwater resources remaining the main source of water fresh water on Earth, with more than 90% of fresh water immediately available (PNUE, 2008; Boswinkel, 2000). Aquifers are increasingly in demand, as modern capture technologies are becoming widespread, while surface water resources, which are more accessible, are gradually being overexploited with 50% for domestic use; 40% in industry; and 20% in irrigation water supply (Zektser and Everett, 2004). Groundwater is essential for securing water supplies in arid and semi-arid regions and is a factor of resilience in the face of climate change (Bahir et al., 2001 ; Karroum et al., 2017 ; Ouhamdouch al., 2019).
Faced with these problems, it’s necessary to put in place mechanisms and actions aimed at recognizing, preserving and safeguarding water resources. The study area is represented by the coastal part of the Essaouira basin which is part of the Moroccan Atlantic coast with an arid to semi-arid climate. It’s a space that is given a heavy responsibility in the socio-economic development of Morocco (Chamchati et al., 2013 ; Ouzerbane et al., 2014; Ouhamdouch et al., 2016b ; Bahir et al., 2019 ; Jamaa et al., 2020). This development implies a significant increase in water needs in the years to come, both for drinking water supply and for irrigation and industry (Ouhamdouch et al., 2018b ; Chafouq et al., 2018 ; Jamaa et al., 2020). The Essaouira basin has experienced, like other regions of Morocco, a significant decrease in water inflows in quantity and quality. This situation has led to a reduction in agricultural productivity and the degradation of several ecosystems. However, this basin has an aquifer system made up of a set of aquifers of unequal importance. These aquifers can provide a natural regulating capacity that makes them valuable for safely ensuring a steady supply. The reserve also makes it possible to meet seasonal needs thanks to temporary overexploitation insofar as reconstitution is possible. The overexploitation of aquifers, especially in arid and semi-arid regions, leads to environmental problems, an increase in pumping costs and above all the depletion of the resource for future generations (Urish and Frohlich, 1990; Sherif et al., 2006; Attwa and Zamzam, 2020 ; Shah et al, 2007 ; Ouzerbane et al, 2021c). Water quality is essential for the well-being of the inhabitants of the coastal zone of Essaouira, the maintenance of healthy aquatic ecosystems and the activities of the primary sector, in particular agriculture, tourism and aquaculture. Quality problems rendering water unusable only exacerbate scarcity (e.g., Calow et al., 2010; Ouzerbane et al., 2014 ; Manu et al., 2016 ; Ouhamdouch et al., 2016a). With an increasing demand for water and an often insufficient resource, the Tenssift hydraulic basin agency (ABHT) and the National Office for Drinking Water and Electricity (ONEE) still favor the development of supply. So, the exploitation of groundwater, hydraulic developments and the use of non-conventional water are the means implemented to meet drinking water needs, particularly for agriculture. The integrated and participatory management of water resources and demands has been selected as the first area of action for decision-makers in the province of Essaouira, with water demand management issues of a different nature, in some places, the qualitative aspects of the resource prevail, as well as the interest in maintaining, or even restoring, ecosystems, thereby lowering the cost of water supply (Ouarani et al., 2021 ; Ouzerbane et al., 2021a). The coastal zone of Essaouira is tightening between a limited water resource and strongly increasing demands, the challenge is still above all quantitative. It is fundamental not only to consider water as a resource, but also to understand its importance for the functioning of complex ecological systems (Chamchati et al., 2013 ; Ouzerbane et al., 2019 ; Ouarani et al., 2020; Ouzerbane et al., 2021a; Ouzerbane et al., 2021b).
Local solutions, based on field knowledge, are necessary for the sustainable integrated management and protection of ecosystems. In this context, the geophysical study presented here aims to define the geometric characteristics of the superficial aquifer (Eluwole et al., 2018), in order to better understand the geological structure and plan the judicious location of groundwater exploitation boreholes (Souid, 1983; Medina, 1994; Piqué, 1994; Broughton and Trépanier, 1993; Piqué and Laville, 1996 ; Piqué et al., 1998 ; Hafid, 2000; Mader et al., 2017). The study by electrical soundings (VES) and electrical tomography (ERT), as well as hydrogeological mapping, and the collection of agricultural and socio-economic data are all data that must be integrated in digital form to obtain land classification maps that can be easily used by developers and planners in the Marrakech-Safi region and to plan the judicious location of groundwater exploitation boreholes (e.g., Bhattacharya and Patra, 1968 ; Bose and Ramkrishna, 1978; Urish and Frohlich, 1990; Devi et al., 2001; Sainato et al.,, 2003; Owen et al., 2005; Sharma and Baranwal, 2005; Singh et al., 2005; Yadav and Singh, 2007; Francese et al. 2009; Kumar et al., 2010, 2014; Chandra et al., 2012; Ebraheem et al., 2012; Zaidi and Kassem, 2012; Anechana et al., 2015; Manu et al., 2016; Sikah et al., 2016 ; Himi et al., 2017 ; Essahlaoui et al., 2003 ; Wafiq et al., 2019). In this regard, the use of a geographic information system (GIS) is necessary. The geological information collected also made it possible to facilitate the choice of geophysical methods best suited to the context of the study and to better implement the geophysical measurement grids (Ouzerbane et al., 2018b).