Assessment of Groundwater Quality and the Main Controls on Its Hydrochemistry in a Changing Climate in Morocco (Essaouira Basin)

Abstract

Groundwater is essential for both water supply and environmental conservation, especially in semi-arid and desert areas. Managing groundwater resources requires a thorough understanding of groundwater characteristics and dynamics. The hydrogeochemical properties and evolution of groundwater in the Essaouira synclinal basin in northwest Morocco were studied in this research, with 105 water samples collected in 2009, 2017, 2018, and 2019. The Water Quality Index (WQI) and Irrigation Water Quality Index (IWQI) were developed to determine groundwater quality for consumption and irrigation purposes. The chemical evolution of groundwater is mainly dominated by evaporite, mineral carbonate dissolutions, and cation exchange. Contamination by nitrates is particularly severe in agricultural and tourist areas. The WQI of the 2019 campaign showed that 6.7% of groundwater samples are unsuitable for drinking; 76.7% are poor quality water; and 13.3% are very poor-quality water; while only 3.3% are drinkable. According to IWQI, the total study area has been split into 50% (good), 43.3% (bad), and 6.6% (unfit), respectively, and no excellent groundwater areas have been identified. Therefore, the water is suitable for agriculture but must be treated for drinking. The presence of evaporation and maritime intrusion and the contribution of recent precipitations to aquifer recharging were demonstrated by stable isotope content.

Combining stable isotope and WQI methods to study the groundwater quality: a case study in Essaouira city, Morocco

“…The link between stable chloride and water isotopes (δ 18 O, δ 2 H) is employed to provide a reliable interest by combining chemical and isotopic data to confirm the fundamental processes governing groundwater salinity. Many previous research studies [ 15 – 17 , 42 ] in arid and semi-arid areas have found that groundwater salinity is mainly determined by dissolution or evaporation. Indeed, the graph shows a significant increase in Cl − concentration and δ 18 O enrichment (Fig.…”

“…The Meskala-Ouazzi sub-basin has an average elevation of 382 m, with the lowest and the highest elevations of 4 m and 714 m, respectively. Two rivers cross the Meskala-Ouazzi sub-basin: Wadi Ouazzi and Wadi Igrounzar, whose natural outlet is the Atlantic Ocean [ 15 – 17 ].

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“…1 ). The Essaouira basin has a semi-arid climate with an annual rainfall of about 300 mm and temperatures between 20 and 30 degrees Celsius [ 15 – 17 ]. Four hundred thousand people live in this predominantly rural region.…”

“…Four hundred thousand people live in this predominantly rural region. The area of the Essaouira basin is 6000 km 2 and is characterized by scarce and irregular water resources [ 15 – 17 ].…”

Assessment of Groundwater Quality Using the Pollution Index of Groundwater (PIG), Nitrate Pollution Index (NPI), Water Quality Index (WQI), Multivariate Statistical Analysis (MSA), and GIS Approaches: A Case Study of the Mnasra Region, Gharb Plain, Morocco

“…Consequently, there has been increased global attention towards assessing groundwater quality to ensure its suitability for various applications. Various techniques, including binary plots, ionic ratios, Wilcox plots, Piper diagrams, Schoeller diagrams, USSL diagrams, and Gibbs diagrams have been employed to evaluate the hydrogeochemical behavior of groundwater [19][20][21][22][23]. Moreover, to ascertain groundwater suitability, hydrochemical characteristics and ionic concentrations are often assessed against the standards set by the World Health Organization (WHO) [24].…”