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

Groundwater is an important water resource in arid and semi-arid regions. Therefore, this study aimed to assess groundwater's suitability for drinking and irrigation using the Water Quality Index (WQI) and the Irrigation Water Quality Index (IWQI). To this end, groundwater data were collected from 58 sites in 2019 (wet season) and 61 samples in 2020 (dry season) in the Meskala-Ouazzi sub-basin. The Piper diagram showed that Ca-Mg-Cl was the dominant groundwater facies type. The confinement due to COVID-19 has significantly improved the water quality of the Meskala-Ouazzi sub-basin. Instead, approximately 50% of sites showed improved water quality when calculating the WQI and IWQI. However, the sodium adsorption ratio (SAR) showed that most samples below 10 are found in all of the examined samples, which are mostly found, indicating excellent irrigation water, and the Wilcox diagram depicted 20.14% of samples lying in the unsuitable region. Stable isotopes (δ18O and δ2H) of groundwater reveal that local precipitation is the main source of recharge. However, groundwater recharge is affected by the evaporation process due to the different geological conditions caused by topographic differences in the study area. The present study is useful for proper planning and managing water resources available for consumption and irrigation.

Temporal and spatial assessment of groundwater contamination with nitrate using nitrate pollution index (NPI), groundwater pollution index (GPI), and GIS (case study: Essaouira basin, Morocco).

Groundwater aquifers in Morocco's coastal regions are under serious threat as a result of climate change. This study was conducted to evaluate and map the quality of water resources, by evaluating the level of pollution of the groundwater in the Meskala-Ouazzi sub-basin, a coastal area of Essaouira based on the physico-chemical analysis of 58 samples using a geographic information system (GIS) technique, analytical analysis, nitrate pollution index (NPI), and groundwater pollution index (GPI). The diagram piper of the study area is dominated by Cl-Ca-Mg, Cl-Na, HCO3-Ca-Mg, and SO4-Ca types. The concentrations of nitrate ranged from 2 to 175 mg/L. It was discovered that 22% of the groundwater samples had nitrate amounts greater than the World Health Organization's recommended maximum allowable level of 50 mg/L. The NPI ranged between - 0.9 and 7.8. According to the classification of NPI, 44.8% of the total groundwater samples represent clean water, indicating that the groundwater in the study area is suitable for irrigation. GPI values ranging from 0.6 to 3.7, with an average of 1.7, identifies 37.9% of all groundwater samples as low polluted. The inverse distance weighting (IDW) approach was used to generate a spatial distribution map, which indicates that appropriate groundwater is present in the sub-upstream basin's part. Overall, the forte concentration in groundwater samples detected in western and central areas showed that the nitrate originated from large amounts of nitrogen fertilizer used by humans in agricultural activities during periods of irrigation. The low tritium (δ3H) content shows that the aquifer recharge is stale water and excessive use of fertilizers leads to groundwater pollution faster over time.

Assessment of recharge and flowpaths in a limestone thermomineral aquifer system using environmental isotope tracers (Central Portugal).

We conducted chemical and isotopic analyses to develop and test a hydrogeological model of thermomineral water circulation in a limestone aquifer system at Caldas da Rainha (Central Portugal), contributing to future borehole-drilling and development strategies, with the aim of extracting waters with the best possible flow and/or temperature. The thermomineral waters (T approximately 33 degrees C) discharge from springs and boreholes located close to a locally N-S-oriented oblique fault (60 degrees E) that places loamy and detritic Upper Jurassic rocks and Hettangian-Rhaetian marls (and evaporitic deposits) in contact. (14)C determinations indicate a pmC content between 29.33+/-0.14 and 44.39+/-0.20 pmC. The presence of HCO[image omitted] , Ca(2+) (and Mg(2+)) are ascribed to water-limestone interactions, while Na(+), Cl(-) and SO[image omitted] concentrations are mainly associated with the dissolution of halite and gypsum lenses found along the regional syncline structure. The delta(18)O values of Caldas da Rainha thermomineral water were slightly lower than those of shallow groundwater from the Upper Jurassic rocks, suggesting the existence of two distinct aquifer systems. The different isotopic composition of water also indicates that the main recharge of the thermomineral waters likely occurs in the Middle and Lower Jurassic limestone formations of the Candeeiros Mountains. The presence of (3)H (from 1.1 to 2.8 TU) in some thermomineral borehole waters (showing rather similar geochemical signatures) suggests mixing of small amounts of shallow groundwater with thermomineral waters, as a result of leaking borehole casing construction or a recharge when the (3)H content in the atmosphere was higher than that at present. Caldas da Rainha thermomineral waters having delta(34)S(sulphate) and delta(18)O(sulphate) values between+14.9 and+19.1 per thousand and+11.1 and+16.2 per thousand, respectively, indicate that the sulphate is the result of water-rock interaction with evaporitic formations. The obtained chemical and isotopic data have informed the further development of a hydrogeological model that will be used by decision-makers, in order to contribute to the socio-economic development of the spa region.