Potential Hydrogeological, Environment and Vulnerability to Pollution of the Plio-Quaternary Aquifers of the Coastal Basin of Essaouira (Morocco)

The Essaouira synclinal area is part of the semi-arid areas of Morocco which are subject to the impacts of climate and anthropogenic pressures. It is also expected to experience an important agro-industrial development. Water requirements are important for the development of all these activities. Although the situation is not yet alarming, the fact remains that the quality of groundwater resources is constantly put to the test because of the growth sources as diffuse pollution that point. To prevent pollution of groundwater, one approach is the knowledge of especially vulnerable areas. It is for this reason that this study was initiated to produce a map of intrinsic vulnerability of aquifers in the region. The method used to make the card is the numerical rating DRASTIC method (Aller et al. 1987). In the case of this coastal area, which includes two main aquifers superimposed; the Plio-Quaternary and Turonian, the resulting vulnerability is compounded by the risk of infiltration navy. The Rainfall in the area does not exceed 300 mm year-1, the average temperature hovers around 20 ° C. The results indicate that the region is dominated by the class of high vulnerability (61%) followed by the class of very high vulnerability (20%), then the class medium vulnerability (15%) and the class of low vulnerability (4 %). Class very high vulnerability is located in the western coastal area. The center of the basin is dominated by the class of high vulnerability to the east, past the middle and low class. Almost throughout the Oued Ksob is particularly dominated by the class of high vulnerability. Keywords: basin of Essaouira; aquifer; semi-arid regions; hydro geochemistry;  stable isotopes; recharge; vulnerability, pollution, DRASTIC, management, protection of water resource

Recharge and Hydro-geochemical Evolution Groundwater in Semi-Arid Zone (Essaouira Basin, Morocco)

Arid and semi-arid areas are threatened by desertification, and thus the degradation due to various factors, including drought, of course, but also the exploitation of resources. They are, in fact, already in a state of stress (resources less than 500 m3 per year per capita) with important disorders induced by climate change. These make an impact on the hydrological cycle, with longer droughts and increased flooding. These disorders will strengthen the already observed degradation of ecosystems, which are often overexploited. Essaouira synclinal area is part of the semi-arid areas of Morocco that are subject to the impact of climatic and human pressures. In the case of this coastal area, which includes two main aquifers superimposed; the Plio-Quaternary and Turonian, the resulting vulnerability is compounded by the risk of infiltration navy. The Rainfall in the area does not exceed 300 mm year-1, the average temperature hovers around 20 °C, the piezometric map of Essaouira synclinal basin was made, different water samples have been collected from October 2009 after exceptional rainfall, all waters are sodium-chloride facies, interpretation of mineralization indicates power by the Ksob Wadi in the northeast and increasing levels of chlorides in the central part generated by the Essaouira diaper hidden. Excessive levels of nitrates have been identified, as well as chlorides after rains of winter 2009. The electrical conductivity and concentrations of 18O and 2H were measured, a local meteoric water line was determined according to the Atlantic origin of precipitation. However, the water Turonian, characterized by significant resources, demonstrates a very low charging current; its vulnerability would be more related to human pressure than changes in climatic conditions. The Essaouira Basin is more vulnerable to drought because its climate is entirely dependent on recharge meteoric waters. Keywords : Basin of Essaouira; Aquifer; Semi-Arid Regions; Drought; Hydro-geochemistry;  Stable Isotopes; Recharge.

Isotopic Tool and Problematic of Recharge in Semi-Arid Area: The Case of the Coast Zone of Essaouira Basin (Morocco)

The Essaouira coastal zone is one of the Moroccan semi-arid areas with annual rainfall not exceeding 300 mm/year. This area contains several main aquifers such as: The Plio-quaternary aquifer consisting of sandstones, the Turonian aquifer composed of chalk-dolomitic rocks, the Barremian-Aptian aquifer content in calcareous clay formations, fossil limestone and sandstone and the Hauterivian aquifer housed formations of marl clay alternating with hard siliceous limestone and calcareous marl. The study had framework on the most important aquifers of the Eassouira coast zone, while having as principal objectives the dating of underground waters of the region and the sampling of main water points that supply drinkable water to the city as well as to the rural agglomerations. Different water samples were collected from drillings, sources and wells belonging to the Plio-quaternary, Turonian, Barremian-Aptian and Hauterivian aquifers of the studied region. Their electric conductivity, pH and temperature were measured in situ and water samples were collected for 18O, 2H and 3H determinations. A meteoric local line was determined and compared to the world meteoric line.The apparent radiocarbon ages of the studied aquifers were evaluated. The recharge to the main aquifers of the studied region was investigated. It has been shown by this study that the recharge rate to the deep Turonian aquifer is very low. This may cause a shortage in water supply to the Essaouira city and its surrounding region. Among the concerned aquifers, the Turonian provides more than 50 % of drinkable water to Essaouira city and rural villages and must therefore be subject to a rational and durable exploitation of the groundwater resources. Keywords: Essaouira basin, semi-arid, 18O, 2H, 3H and 14C isotopes, aquifer recharg

Using Geochemical and Isotope Investigations for Groundwater Management Strategies Under Semi-Arid Area: Case of the Wadi Ouazzi Basin (Morocco)

The characteristics of Essaouira basin water resources are a semi-arid climate, which is severely impacted by the climate (quantity and quality). Considering the importance of the Essaouira aquifer in the groundwater supply of the region, a study was conducted in order to comprehend this aquifer groundwater evolution. The Essaouira aquifer is a coastal aquifers located on the Atlantic coastline, southern (Morocco), corresponding to a sedimentary basin with an area of near 200 km2.A water sampling from twenty wells, drillings and sources belonging to the Plio-quaternary and Tu-ronian aquifers was realized (what was realized). Samples examined from the ground for electric conductivity and temperature, determined waters belonging to the Plio-quaternary and Turonian aquifers present very variable electric conductivities from 900 µs/cm to 3880 µs/cm. In spite of this variability, they form the same family and are characterized by sodium-chloride facies. There exists, however, a good correlation between the electric conductivity and chloride and sodium contents. Therefore the lower electric conductivities are situated in the North quarter immediately in the south of the Wadi Ouazzi. Keywords: Management, Wadi Ouazzi, Drought, Strategies, Semi-arid, Turonian, Plio-Quaternary

The Assessment of the Groundwater Quality in the Coastal Aquifers of the Essaouira Basin, Southwestern Morocco, Using Hydrogeochemistry and Isotopic Signatures

Because of anthropogenic activity and seawater intrusion, coastal aquifers worldwide frequently face a threat to their water supply due to salinization. This paper investigates the assessment of the groundwater quality in coastal aquifers of the Hauturivien aquifer in the Essaouira basin. In this study, 56 groundwater samples collected from the Hauturivian aquifer across four campaigns in 2017, 2018, 2019, and 2020 were subjected to multivariate analyses involving principal component analysis (PCA) and cluster analysis (CA) using SPSS software. Among the three main water types, the mixed Ca-Mg-Cl classification was predominant in the investigated aquifer. In addition to the natural processes (such as the water–rock interaction, ion exchange, dissolution/precipitation dynamics, and evaporation) that govern groundwater quality, current land use practices have increased salinization in this poorly drained semi-arid area. Based on assessments using Water Quality Index (WQI) and Irrigation Water Quality Index (IWQI), the water quality is suitable for human consumption, but its use for irrigation is limited to crops that can tolerate high salt levels. The stable isotopes (δ2H and δ18O) of groundwater demonstrated that local precipitation is the primary recharge source. Nonetheless, the evaporation process, influenced by various geological conditions, affects groundwater recharge, regardless of the topographical differences in the study area

Dam effect on groundwater characteristics from area under semi-arid climate: case of the Zerrar dam within Essaouira basin (Morocco)

Morocco has 140 large dams with a total capacity of 17 Gm3. The amount of potential fresh water is decreased by sedimentation of clays and/or soil in the dam’s reservoirs. It is estimated at 70 million m3, surface evaporation and water loss by the banks and foundations. In this study, the environmental stable and radioactive isotopes together with geochemical and piezometric data were used to assess the impact of Zerrar dam on groundwater in Essaouira basin (western Morocco). The water facies has been determined and has evolved from Na–Cl type (before the establishment of the dam) to Mg–Cl and Ca–Cl type (after establishment). The dissolution of evaporates and ion exchange reactions are the main processes affecting groundwater composition. Groundwater level has been measured and shows a decline. 2H–18O diagram revealed that the aquifer recharge has assured by precipitation of oceanic origin without evaporation and by infiltration from Ksob Wadi. 3H and 14C content shows that this recharge is generally recent and the age of the waters ranges between modern and 2.3 BP (ka). However, the Zerrar dam indirectly influences the groundwater quality of the study area, because this one decreases the flow of the Ksob Wadi that is the main recharge source of the aquifer during rainfall. In addition, this Wadi flow suffers the effect of climate change, which decreases the flow of the Ksob Wadi (river) that adds to the effect of the dam

Impact du changement climatique sur la ressource en eau en milieu semi-aride : exemple du bassin d'Essaouira (Maroc)

Comme les bassins des zones arides et semi-arides, le bassin d’Essaouira est susceptible d’être à haut risque de pénurie d’eau en raison du changement climatique. Le bassin d’Essaouira qui fait l’objet de cette étude est situé sur la façade atlantique du Maroc au sud-est de la ville d’Essaouira. Il se caractérise par un climat semi-aride avec des précipitations moyennes annuelles de l’ordre de 300 mm et des températures moyennes de 20 °C. Vu l’importance de ce bassin dans l’approvisionnement en eau de la ville d’Essaouira et des agglomérations avoisinantes, cet article tente d’étudier l’effet du changement climatique sur la ressource en eau dans cette zone. Une série de cartes piézométriques ont été réalisées (1990-2016). L’étude hydrochimique montre que celles-ci présentent un faciès de type Na-Cl en 1990, 1995 et 2009 et de type Mg-Ca-Cl en 2015. Cette évolution est due aux précipitations exceptionnelles de 2015 ayant déclenché le processus d’échange de bases. Des clichés isotopiques (18O, 2H, 3H, 14C) ont été réalisés lors des campagnes de 1996, 2006 et 2007. La droite météorique locale proche de la droite météorique mondiale caractérisant les précipitations d’origine océanique a été déterminée. Les résultats de ce travail montrent : i) l’existence d’une dépression du niveau piézométrique pendant les années sèches (ex. 1995) et une modeste remontée au cours des années pluvieuses (ex. 2004 et 2009), ii) une dégradation de la qualité des eaux en s’éloignant de l’oued Ksob (source d’alimentation de l’aquifère) et iii) la recharge de l’aquifère dépend des précipitations.As is the case for basins of arid and semi-arid zones, the Essaouira Basin is likely to be at high risk of water scarcity due to climate change. The Essaouira Basin, which is the subject of this study, is located on the Atlantic coast of Morocco, southeast of the city of Essaouira. It is characterized by a semi-arid climate with annual rainfall of around 300 mm and average temperatures of 20°C. Looking at the importance of this basin for the groundwater supply of the Essaouira City and neighbouring clusters, this article considers the potential effect of climate change on water resources in this area. A series of piezometric maps was prepared (1990-2016) and the hydrochemical study of the water shows that they have a Na-Cl type facies in 1990, 1995 and 2009 and Mg-Ca-Cl type in 2015. This evolution is the result of cation exchange following the exceptional precipitation of 2015. The isotopes 18O, 2H, 3H and 14C were analyzed during the campaigns of 1996, 2006 and 2007. The local meteoric water line close to the global meteoric water line characterizing precipitation of oceanic origin was determined. The results of this work show: i) the existence of a depression in the piezometric level during dry years (e.g. 1995) and a modest recovery during wet years (e.g. 2004 and 2009), ii) a deterioration of the water quality away from the Wadi Ksob (recharge zone of the aquifer), and iii) that the recharge the aquifer depends on rainfall

Land suitability evaluation to optimize land management of small-scale farms in the Gerado catchment, North-Eastern Ethiopia

Biophysical and socio-economic constrains, and sub-optimal utilization of soil and water resources have resulted in progressive reduction of land productivity in Ethiopia. This study investigated the suitability of land mapping units of the Gerado catchment for subsistence rainfed cultivation of wheat (Triticum aestivum L.), maize (Zea mays L.) and teff (Eragrostis tef Zucc.). A land resource survey was conducted and it identified nine different land mapping units (LMU). The FAO maximum limitation method was used to assess LMU and determine land suitability subclasses. The study indicated that soil erosion, soil wetness, soil fertility status, and soil workability were the main limiting factors affecting land quality within the catchment. We suggest that drainage using traditional ditches may be a cost-effective method to reduce the incidence of waterlogging conditions. Long-term fertility management requires the implementation of suitable fertilization programmes that consider the use of organic materials such as manure and compost. Such programmes need to account for nutrient budgets over the entire crop rotation to maximize use efficiency and minimize environmental losses. Soil erosion may be mitigated through stone terracing, soil bunding and by adopting a more conservative approach to agriculture, that is, by matching land use with land capability based on the correct assessment of land suitability. Implementation of the proposed approach to optimizing land management in the Gerado catchment will deliver a range of socio-economic and agri-environmental benefits to the local communities