Abstract
The understanding of hydro systems is of great importance in monitoring quantitative and qualitative changes in water resources. The Essaouira region at the edge of the Moroccan Atlantic Ocean is subject to a semi-arid climate. The decrease in rainfall as a result of climate change and the increase in the exploitation of surface and groundwater have disrupted the stability of these resources and threaten the socio-economic and environmental balance in the area under investigation. Climate scenarios estimate that precipitation will decrease by 10–20% while warming increases by 3 °C over the next 30 years. The physico-chemical parameters studied show that the evolution of the pH and temperature of the groundwater remained stable with a neutral (pH ≈ 7) and a hypothermal character (T < 30 °C). For the electrical conductivity, it showed an increasing trend from 2017 to 2020. A hydrochemical approach showed that the groundwater mineralization was controlled by the dissolution of evaporites and carbonates, by cation exchange processes, and by seawater contamination. A groundwater assessment for drinking use was made by comparing the concentrations of the chemical elements with the standards set by the World Health Organization. The results obtained show that the groundwater from the aquifers studied requires treatment before being consumed, in particular for Cl− and SO42−. Furthermore, the groundwater quality for irrigation was evaluated based on the parameters Na% and Sodium Adsorption Ratio (SAR). The results showed that the groundwater was adequate for agricultural purposes, especially for the plants that adapt to high salinity. The monitoring of surface water by processing the satellite images via the calculation of the normalized difference water index (NDWI) showed an increase in water surface areas in the region following the commissioning of two large dams (Zerrar and Igouzoullene). Despite the installation of these hydraulic structures, a drop of 4.85 km2 in water surface area was observed beyond 2016. This situation requires intervention in order to preserve this vital resource.
Highlights
In coastal environments in arid and semi-arid climates, groundwater pollution, including groundwater salinization, becomes a major topic since a series of circumstances favors the introduction of excess salts dissolved from different origins in these waters
This study aimed to investigate and monitor the state and spatiotemporal evolution of surfaces and groundwater based on piezometric and hydrochemical approaches by using the results of the campaigns carried out in 2017, 2018, 2019, and 2020, as well as geographic information system (GIS) techniques
The Essaouira basin belongs to areas with a semi-arid climate with very irregular temperatures and precipitation in space and time that do not exceed annual averages of 20 ◦ C and 300 mm, respectively
Summary
In coastal environments in arid and semi-arid climates, groundwater pollution, including groundwater salinization, becomes a major topic since a series of circumstances favors the introduction of excess salts dissolved from different origins in these waters. The phenomenon of salinization is one of the main threats to groundwater in coastal areas [1,2,3,4,5,6]. This salinization is mainly due to the effects of climate change, marine intrusion, and agricultural and industrial activity [7,8,9,10,11]. Research on water resources indicates that Africa in general and Morocco in particular will reach an extremely high level of water stress by 2040. According to the United Nations, Morocco is already classified as a water-stressed country, with only
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