Hydrogeochemical Approach Research Articles

Analysis of the Spatial Distribution of Seawater Intrusion Using a Hydrogeochemical Approach: A Study of the Coastal Geology of Kebumen Regency, Indonesia

This study examines seawater intrusion in the southern part of Kebumen District, focusing on the impact of various geological formations on groundwater salinity. Groundwater samples were systematically collected from 11 locations representing alluvial, volcanic, coastal sediment, and karst geological conditions. The samples were analyzed for major ions, including calcium (Ca²⁺), magnesium (Mg²⁺), chloride (Cl-), and bicarbonate (HCO₃-), as well as Total Dissolved Solids (TDS). Ion ratios such as Mg²⁺/Ca²⁺, Cl⁻/HCO₃⁻, and Mg²⁺/(Mg²⁺+Ca²⁺), along with the Fraction of Seawater (fsea), were calculated to assess the extent of seawater intrusion. The study employed the Gibbs diagram method to identify the primary processes controlling groundwater chemistry, revealing that water-rock interactions are dominant in most samples, particularly in those affected by seawater intrusion. The results indicate significant seawater intrusion in alluvial and karst regions, especially at sampling points TP 2, TP 4, and TP 10, while volcanic and coastal sediment areas show minimal intrusion. These findings underscore the critical influence of geological conditions on seawater intrusion and highlight the need for targeted groundwater management strategies. Further research focusing on long-term monitoring is recommended to better understand and mitigate the impacts of seawater intrusion in this region.

Hydrogeochemical characteristics of shallow aquifers in Thanh Phu District, Ben Tre Province, Vietnam

Shallow aquifers in the Thanh Phu coastal area in Ben Tre Province are increasingly withdrawn for domestic and irrigation purposes. However, groundwater resources here are declining in quality due to the effects of seawater intrusion and anthropogenic activities. It requires an understanding of the groundwater origin and changes in water quality to protect local groundwater resources. By applying the hydrogeochemical approach, the origin and quality of groundwater here have been clarified. A total of 35 water samples were collected during the 2023 dry season. The laboratory analysis included 16 ions. The results show that the groundwater water types are Ca-Cl, Ca-Mg-Cl and Na-Cl, with the domination of the third pattern. Hydrochemical characteristics have shown evaporation, silicate weathering, cation exchange and marine effects as the vital processes governing the mineralization of regional groundwater. Most of the water samples are of poor quality, not adapting to domestic water standards according to the National Technical Regulation on Domestic Water Quality and WHO 2011. It requires water treatment before being used for domestic purposes. However, the SAR, Na%, PI, KR and EC values displayed that groundwater here was still acceptable for irrigation purposes, demonstrating the prospect of using groundwater for agricultural purposes in the study area.

Identifying Karst Aquifer Recharge Area Using Environmental Stable Isotopes and Hydrochemical Data: A Case Study in Nusa Penida Island

Identifying the recharge area of karst aquifers is scientifically challenging due to the complexity of karst groundwater flow characteristics. It is essential to identify the recharge zones to conserve the groundwater resources contained within these aquifers. This paper proposes a combined methods for identifying recharge area of karst aquifers on Nusa Penida Island using stable isotopes (18O and 2H) and a hydrogeochemical approach. Based on the analysis of δ18O and δ2H values and their spatial distribution, it is possible to retrace karst aquifer recharge areas using average isotope elevations. In the meantime, groundwater facies will be determined in the karst region of Nusa Penida using the hydrogeochemical approach with the Piper diagram. According to the calculation of water stable isotope results, the average elevation of the groundwater recharge area at the study site is between 62 - 450 meters. If applied to the location of the study, the recharge area is almost entirely distributed across Nusa Penida. In addition, based on the hydrogeochemical analysis, the groundwater type at the study site can be divided into three categories: Na-Cl, mixed, and Mg-HCO3. The water types indicate that the groundwater in Nusa Penida comes from a combination of old water stored from its internal geological formations and mix with modern rainwater.

Hydrogeochemical and isotopic assessment for characterizing groundwater quality in the Mitidja plain (northern Algeria).

Coastal aquifer overexploitation represents a concerning trigger for water salinization around the world and especially in arid and semi-arid regions along with urban growth and urbanization, as well as land use human-induced changes. This study aims to assess the groundwater quality in the Mitidja alluvial aquifer (northern Algeria) along with its suitability for domestic and agricultural utilizations. A hydrogeochemical approach, based on the interpretation of groundwater physiochemical parameters (EC, pH, dry residue, Ca2+, Mg2+, Na+, K+, Cl-, SO42-, HCO3-, and NO3-) collected during the wet and dry periods for the years 2005 and 2017 along with an isotopic characterization, including stable isotopes to identify the recharge sources for the samples collected in October 2017, has been proposed. The results show the presence of three dominant hydrochemical facies: (i) calcium chloride, (ii) sodium chloride, and (iii) calcium bicarbonate. Groundwater mineralization and salinization are so ascribable carbonates and evaporitic dissolution, especially during the dry periods, and to the presence of seawater. Ion exchange significantly affects groundwater chemistry along with human activities which directly or indirectly contribute in raising groundwater salts concentration. Specifically, NO3- concentrations are very high in the eastern portion of the study area which is exposed to fertilizers pollution where also the Richards classification pointed out the necessity of limit water utilization for agricultural use. The δ2H = f(δ18O) diagram indicates that the recharge origin for this aquifer is mainly due to the oceanic meteoric rainwater from the Atlantic and the Mediterranean Sea. The methodology proposed in this study can be applied in the similar worldwide coastal areas in order to contribute and sustainable water resource management in these regions.

A novel hydrogeochemical approach to delineate the origin of potentially toxic elements in groundwater: Sophisticated molar ratios as environmental tracers.

The occurrence, mobilization, and origin of Potentially Toxic Eelements (PTEs) in the environment is always a difficult research question that has not been fully addressed to date; solving this problem would be a major achievement for environmental science and pollution research, a significant scientific breakthrough, and an important contribution to environmental analysis and monitoring. The lack of a holistic methodology that uses chemical analysis to determine the origin of each PTE in the environment is the main motivation for this project. Therefore, the hypothesis tested here is to develop a scientific approach applied to each PTE to determine whether its origin is geogenic (i.e., water-rock interaction with dominance of silicate or carbonate mineral phases) or anthropogenic (i.e., agricultural practices, wastewater, industrial activities). A total of 47 groundwater samples from the Psachna Basin in central Euboea, Greece, were used and plotted on geochemical mole ratio diagrams (i.e., Si/NO3 vs. Cl/HCO3) and used to perform a robust geochemical modeling analysis. The proposed method showed that elevated groundwater concentrations of various PTEs in groundwater were mainly related to intensive fertilization (e.g., Cr, U), water-rock interaction (e.g., Ni), and saltwater intrusion. (i.e., As, Se). This work highlights that a comprehensive framework with sophisticated molar ratios combined with modern statistical methods, multi-isotope signatures, and geochemical modeling could provide answers to unresolved scientific questions about the origin of PTEs in water resources and improve environmental resilience.

Source apportionment of mine contamination across streamflows

Globally, metals released by mine waste represent a challenge for protecting water quality and ecosystems. Understanding metal dispersion in catchments is critical for developing efficient remediation strategies and reducing contamination from mining activities. Efforts to address the issue have been constrained by diffuse sources and variation of source contributions across streamflows. In the UK, metal source apportionment is typically addressed using monitoring strategies with low spatial resolution, which can underestimate the contribution of diffuse sources. In this proof-of-concept study, diffuse sources were accurately apportioned in a mining-impacted catchment in Mid-Wales (UK), using a hydrogeochemical approach with combined continuous tracer injections, gulp injections, and streambed sediment geochemistry. The continuous tracer injections identified a major Zn and Pb point source, diffuse sources due to mine waste tip runoff, and potential groundwater contributions. Variations in source contributions were estimated during high and low flow conditions, with Zn having similar sources and importance across streamflows and Pb being released mainly from overground tips during high flow conditions (22% Pb under low flow and 80% Pb under high flow). The distribution of metal-bearing sediment along the stream sheds light on metal release mechanisms across streamflow conditions. This hydrogeochemical approach for source apportionment, builds on common monitoring methods, and represents a substantial advance in accounting diffuse mine contamination sources, understanding potential metal release mechanisms, and designing remediation strategies.

Hydrogeochemical processes in rural coastal aquifer (Haha region, Morocco).

In arid and semi-arid regions, groundwater is the principal source of urban and rural water supply. Given that groundwater is the only source of water supply in the Haha region (Moroccan Atlantic coast), the evaluation of this vital resource, using the hydrogeochemical approach, is the main objective of this study. The interpretation of these analytical data showed that the chemical composition of the groundwater is of Ca-Mg-Cl, Na-HCO3, and Na-Cl, with the dominance of the first type. Hydrochemical characteristics using the bivariate diagrams of major (Ca2+, Mg2+, Na+, K+, HCO3-, Cl-, NO3-, and SO42-) and some trace elements (Br- and F-), mineral saturation indices, and statistical analysis show that the water-rock interaction, cation exchange processes, and marine effect are the main processes that control groundwater mineralization. Also, the majority of analyzed samples have concentrations above the thresholds for human consumption fixed by WHO, especially F-, NO3-, K+, Cl-, and HCO3- concentrations. This requires treatment of this groundwater before any consumption and domestic uses. For agricultural uses, the groundwater of the Haha region remains adequate, especially for plants, which can withstand water with electrical conductivity greater than 1000 µS/cm. However, the results obtained can be used as a basis for decision-makers for better water management in the Haha region.

Hydrogeochemistry of low agricultural soil yield in Sahelian and sub-tropical watersheds, Northern Cameroon

Bound to the north by the Sahara and to the south by the Sudanian savannah, watersheds in the African Sahelian belt supply food and water to an estimated 135 million people. Being one of the Earth's most vulnerable zones to climate change impacts, the Sahel covers a 3.1 million km2 corridor from the Atlantic Ocean in the west to the Red Sea in the east. It is predicted that decadal timescale migration of Sahelian arid conditions southwards, and associated changes in water-rock interaction patterns resulting from desertification and reduction in rainfall trends, would increasingly alter soil nutrients availability. In this pilot study, we developed a hydrogeochemical approach by linking local geology to elemental dynamics, while focusing on nutrient enrichment, depletion, mobility, flux, and exchange between bedrock and groundwater. This approach was successfully applied to two watersheds in Northern Cameroon: the Sahelian Douka Longo sedimentary watershed (SDLSW) and the tropical Bidou igneous watershed (TBIW). Comparative inorganic nutrient budgets and availability suggest that carbonates and plagioclases are prone to weak and intermediate chemical weathering, compared to stronger rates recorded for granite, basalt, trachyte, and sandstone. Collectively, these sources contribute to significant trace element nutrients enrichment of local water bodies within the watersheds. Non-isochemical dissolution produces highly mobile Ca, Mn, Na, Cu, Zn, K, Ni and Fe compared to elements not part of plant nutrients. Acidic groundwater recharged by rainwater through preferential flow pass has a Ca + Mg–NO3 and Ca + Mg–HCO3 chemical signature in the SDLSW and the TBIW, respectively. Both watersheds are characterised by distinct solute flux patterns, with lower annual nutrient loss rates associated with the TBIW. The data indicate that surface water runoff needs to be managed to control nutrient deficiencies and excesses, and that low-yield capacity in both watersheds appear to be partly linked to P, Fe, and Mo deficiencies.

Hydrogeochemical processes on inland aquifer systems: A combined multivariate statistical technique and isotopic approach

Groundwater is an important resource used for multiple purposes and should be protected, especially, in arid regions. The aim of this study is to assess the main processes on groundwater salinization from Menzel Habib shallow and deep aquifers, southeastern Tunisia, which could be applied to further groundwater quality assessment. Indeed, combined hydrogeochemical and isotopic fingerprints data approaches were used using multivariate statistical methods, highlighting, Hierarchical Clustering Analysis and Principal Component Analysis.A total of 36 groundwater samples were collected from the Menzel Habib aquifer system: 25 from shallow aquifer and 11 from deep aquifer. The obtained results from both stretches indicated three dominant hydrochemical facies: Chloride-sodic, Sulphated-sodic, and mixed water type. The determination of groundwater salinization origin, and the understanding of its hydrological and geochemical behaviors, were assessed by a combined statistical and hydrogeochemical approach. The study of correlations between major elements and Total Dissolved Solids is, thus, an important tool where dissolution of evaporites that can originate from the Triassic materials of Hadifa mountain, the precipitation and/or dissolution of carbonates, cationic exchange and inverse cationic exchange are the main processes associated to groundwater salinity increase.Moreover, the HCA has allowed to classify the groundwater samples into two clusters: the first one with low to moderate salinity and the second one with high salinity. In addition, the application of stable isotopes allowed a better understanding of the hydrodynamic functioning of this aquifer system. The isotopic data suggests a relatively high δ2H and δ18O values for groundwater samples located close to Global Meteoric Water Line that reflects recent recharge for the aquifer system by direct rainwater infiltration, respectively from bordered reliefs in the study area. It also showed a depletion in isotopic composition for almost groundwater samples that indicates the importance of evaporation on the hydrochemistry of the area.

Enrichment of High Arsenic Groundwater Controlled by Hydrogeochemical and Physical Processes in the Hetao Basin, China.

Based on 447 samples collected from a shallow aquifer (depths from 0 to 150 m) in the Hetao Basin, Northern China, an integrated hydrogeochemical approach was used in this study to conceptualize the enrichment of high arsenic groundwater in the Hetao Basin. An unconventional method of distinguishing hydrogeochemical and physical processes from a dataset was tested by investigating the cumulative frequency distribution of ionic ratios expressed on a probability scale. By applying cumulative frequency distribution curves to characterize the distribution of ionic ratios throughout the Hetao Basin, hydrogeochemical indicators were obtained that distinguish the series of hydrogeochemical processes that govern groundwater composition. All hydrogeochemical processes can basically be classified as recharge intensity of groundwater, evaporation concentration intensity, and reductive degree controlling the spatial distribution of arsenic. By considering the three processes, we found that the concentration of arsenic was more than 10 μg/L when the (HCO3-+CO32-)/SO42- ratio was over 4.1 (strong reductive area). As the evaporation concentration intensity increased, the median value of arsenic increased from 10.74 to 382.7 μg/L in the median reductive area and rapidly increased from 89.11 to 461.45 μg/L in the strong reductive area. As the river recharge intensity increased (with the intensity index increasing from 0 to 5), the median value of arsenic dropped from 40.2 to 6.8 μg/L in the median reductive area and decreased more markedly from 219.85 to 23.73 μg/L in the strong reductive area. The results provide a new insight into the mechanism of As enrichment in groundwater.

Coupled Hydrogeochemical Approach and Sustainable Technologies for the Remediation of a Chlorinated Solvent Plume in an Urban Area

The presence of chlorinated solvents polluting groundwater in urbanized areas poses a significant environmental issue. This paper details a thoughtful approach to remediate a tetrachloroethylene (PCE) plume in a district that is characterized by a complex hydrological context with a limited accessibility. Through a geodatabase-driven and coupled hydrogeochemical approach, two distinct remediation technologies were chosen for the management of a contaminant plume. On one hand, coaxial groundwater circulation (CGC) wells coupled with air sparging (AS) aspire to promote the in-situ transfer of PCE from the contaminated matrices into a gaseous stream that is then treated above ground. On the other hand, reagent injection has the goal of enhancing chemical reduction combined with in situ adsorption, creating contaminant adsorbent zones, and stimulating dechlorinating biological activity. The development of an integrated conceptual site model (CSM) harmonizing geological, hydrochemical, and membrane interface probe (MIP) data captures site-specific hydrogeochemical peculiarities to support decision-making. The hydrochemical monitoring reveals contamination dynamics and decontamination mechanisms in response to treatment, quantifying the performance of the adopted strategies and investigating possible rebound effects. The estimation of masses extracted by the CGC-AS system validates the effectiveness of a new and sustainable technique to abate chlorinated solvents in groundwater.

Understanding the geochemical evolution of groundwater in Central Gujarat, India: an integrated hydrogeochemical and multivariate statistical approach

Understanding the geochemical evolution of groundwater in Central Gujarat, India: an integrated hydrogeochemical and multivariate statistical approach

Multivariate statistical assessment of groundwater in cases with ultramafic rocks and anthropogenic activities influence

Multivariate statistical analysis has been proven an invaluable tool for environmental studies. In the present hydrogeochemical study of Eastern Central Greece and NW Euboea (Evia) Island, several statistical tools were applied, i.e. one-way analysis of variance (ANOVA), cluster analysis and principal component factor analysis alongside the classical hydrogeochemical approach in order to assess the hydrogeochemical features and evaluate the impact of anthropogenic and geological factors on groundwater chemistry. The area is characterized by the presence of ophiolitic ultramafic rock, carbonate rocks, post-Alpine sediments and hot springs with travertines, while the main anthropogenic activity is irrigation. A total of 85 groundwater samples were collected and analyzed, which were found to be enriched in Cr (3 μg/L), Ni (2.2 μg/L), Fe (4.2 μg/L), Mg (32.5 mg/L), Cl (31 mg/L), SO42- (36 mg/L) and NO3- (9.7 mg/L) compared to the median values of European and Greek streams and groundwaters. Based on the results and the statistical analysis, four main factors have been identified controlling the composition and quality of the groundwater, i.e. seawater intrusion on the groundwater aquifers in the coastal areas, intense use of fertilizers in cultivated areas, the influence of the carbonate and the ophiolitic ultramafic rocks. The hydrothermal system and its depositions, which exist in the study area, seem to have not played any major role in the controlling of the chemical composition of the cold groundwater aquifers. The statistical assessment of hydrogeochemical data alongside the classical hydrogeochemical approach is recommended in future studies, combined with efforts to develop new tools that help a deeper understanding of groundwater characteristics.

Hydrogeochemical approach in the assessment of coastal aquifer for domestic, industrial, and agricultural utilities in Port Harcourt urban, Southern Nigeria

Hydrogeochemical approach in the assessment of coastal aquifer for domestic, industrial, and agricultural utilities in Port Harcourt urban, Southern Nigeria

A hydrogeochemical approach to evaluate groundwater quality in the vicinity of three tributaries of the Beas River, North-West India

The present study focused on the seasonal investigation of hydro-geochemical characteristics of groundwater samples collected from the vicinity of three tributaries of the Beas River, Punjab, India. Total 45 samples were analyzed during the pre- and post-monsoon season for physico-chemical parameters and heavy metals along with health risk assessment. Results revealed that the majority of samples were below the permissible limits set by the BIS and WHO. The relative abundance of major cations was Ca2+ > Mg2+ > Na+ > K+ and Ca2+ > Na+ > Mg2+ > K+, while that of the major anions was HCO3− > SO42− > Cl− > CO32− in the pre- and post-monsoon season, respectively. Groundwater was alkaline and hard in nature at most of the sites. Bicarbonate content exceeded the desirable limit having an average concentration of 337.26 mg/L and 391.48 mg/L, respectively, during the pre- and post-monsoon season. Tukey’s multiple comparison test was applied for finding significant differences among samples at p < 0.05. The dominant hydrochemical face of water was Ca–Mg–HCO3 type. US salinity (USSL) diagram indicated that during the pre-monsoon, 48.9% samples were C2S1 type and remaining 51.1% were C3S1 type while during the post-monsoon all samples were C3S1 type. It indicates that groundwater of the study area is at risk of salinity hazards in future and is not to be ignored. Such monitoring studies are recommended to design future safety plans to combat soil and human health risks.

A hydrogeochemical approach to the characterization of low-enthalpy geothermal systems: the Scordia – Lentini graben (Sicily, Italy)

We describe the geochemical characteristics of groundwater samples collected in 23 water wells located on the northern margin of the Hyblean plateau (East Sicily). This area, mostly made of highly permeable carbonate rocks, is rich in low temperature (T &lt; 50° C) hydrothermal groundwaters, distributed in an active sismogenetic zone, with several ENE-WSW-directed tectonic structures that drove magma to the surface during Upper Pliocene and Pleistocene. The chemical features suggest complex mixing between rainwater, CO2-rich groundwater, steam-heated groundwater and geothermal brines, as highlighted by Principal Component Analysis (PCA). Some parameters, however, indicate widespread pollution of the aquifers from human activities. Stable isotopes analysis confirms the meteoric origin of groundwater and supports the origin of dissolved CO2 mostly from mantle degassing through deep tectonic faults. Geothermometric estimates, mostly based on quartz and Saturation Indexes geothermometers, suggest minimum reservoir temperature between 100 and 120° C.

Assessment of groundwater quality and the controlling factors in coastal aquifers of Ghana: An integrated statistical, geostatistical and hydrogeochemical approach

Coastal aquifers are complex groundwater bearing zones with multiple ways of interacting with seawater. Understanding of the main controls and evolution of such aquifers is essential for effective management of the groundwater. In this paper, a comprehensive study was conducted to characterize and identify the main factors and processes controlling the groundwater quality in some coastal aquifers through an integrated approach of Principal Component Analysis (PCA), Cluster Analysis (CA), geostatistical analysis and information entropy-based groundwater quality index coupled with detailed hydrogeochemical assessments. The PCA and CA yielded four clusters with distinct hydrogeochemical signatures (Cluster 1 and 2: freshwater influenced by rain, Cluster 3 transition zone and Cluster 4 marine influence/seawater intrusion or aerosol spray). Geostatistical analysis showed a wide variation in salinity from the coast to the inland while piper diagram revealed the evolution of the aquifers from Ca–HCO 3 , Ca–Cl which correspond to natural recharge zone in the north, to mixed Ca–Na–Mg–Cl–HCO 3 representing transition and Na–Cl towards the coast. The water suitability assessment for drinking using entropy-based groundwater quality index showed that about 59.4%, 20.3%, 7.8%, 2.6%, and 9.9% of the groundwater sample were estimated to be excellent, good, average/medium, poor, and extremely poor water quality. Ion exchange mechanism, dissolution of minerals from the rocks and marine influence are the dominant processes controlling the groundwater chemistry in the area. Recommendations for groundwater resource management and future research needs have also been discussed. • We examined the factors controlling the quality in a sparsely studied coastal aquifer. • Some areas of the aquifer have elevated levels of chloride, sulphate and sodium. • IEBGQI reveals areas that are not suitable for drinking. • Ca–HCO 3 , Ca–Cl, Ca–Na–Mg–Cl–HCO 3 and Na–Cl were delineated. • Water rock interaction, anthropogenic activities and marine influence control the groundwater chemistry.

Integrated statistical and hydro-geochemical approach to identify the origin and process of saline contamination of Remila plain groundwater (Khenchela, Algeria)

ABSTRACTGroundwater is widely used in the semi-arid region of Remila plain (Khenchela, Algeria) for urban and agricultural supplies. An integrated statistical and hydro-geochemical approach was performed with 70 water samples in order to identify the main processes and the origin of water salinisation. The results have suggested the dominance of three chemical facies: Sulphato cloruro calcic (SO4–Cl–Ca) in the northeastern part, Sulphato cloruro calci magnisian (SO–4Cl–Ca–Mg) in most of the waters andalkali-earth bicarbonate (HCO3–Ca–Mg) in the southeastern part. Although based on principal component analysis and hierarchical clustering analysis, the statistical approach identified three water groups: (1) saline water (17 %; total dissolved solids &gt;1000 mg l−1 with the dominance of Sulphate (SO42−)); (2) moderately saline water (17 %) with a dominance of bicarbonate (HCO3−); and (3) moderately saline water (66 %) with mixed facies. The binary diagrams confirmed the predominance of three processes: evaporite dissolution and/or precipitation, combined by ionic exchange. In the northeastern part of the area, however, another process was detected – the saline intrusion of Sabkha water, favoured by extensive groundwater use.

Groundwater quality in semi-arid environments (Essaouira Basin, Morocco)

Hydrochemical, isotopy, and geostatistical approaches have been used to highlight the processes that control groundwater salinization in the detrital aquifer of Essaouira (Morocco). The hydrogeochemical approach shows that: (i) The dissolution of halite, gypsum, and/or anhydrite would contribute to the salinization of groundwater, (ii) the basic-exchange and marine intrusion phenomena are generally responsible for the wide variation in cation concentrations in groundwater. The use of this water for drinking purpose requires treatment before its use. For irrigation purpose, groundwater of the studied aquifer remains suitable for plants supporting high salinity. The nitrate contamination study shows that highest concentrations could be explained by: (i) the high concentration of tourism activity (Sidi Kaouki zone), (ii) the absence of sanitation network and wastewater treatment plant, and (iii) waste from livestock during watering. The stable isotope contents show that (i) Plio-Quaternary aquifer recharge is provided by the direct infiltration of Atlantic precipitation and (ii) the groundwater of the study area has undergone evaporation phenomena and marine intrusion. While the Geostatistics technique confirmed the results obtained by the hydrogeochemical and isotopic approach, highlighting the processes controlling the groundwater mineralization of the study area. However, the results of this paper can be used for better and realistic management of the water resource.

Assessment of groundwater quality from semi-arid area for drinking purpose using statistical, water quality index (WQI) and GIS technique

This study aims to assess the groundwater status of a basin in a semi-arid climate, based on the hydrogeochemical, piezometric, statistical and geographic information system (GIS) approach. The region held as an example is the upstream part of the Essaouira basin (Morocco). Analysis of the evolution of the rainfall series by applying the Pettitt and Mann–Kendall tests shows a rainfall deficit of around 14% for the study period (1940–2015). For temperatures and with the application of both tests, an upward trend was observed with a warming of about 2.3 °C for the period 1987–2014. The same trend was observed for ETP, with an increase of around 5 mm for the period 1987–2014. The piezometric study shows a general decrease in the piezometric level over the last 24 years, as a result of the rainfall deficit. The hydrogeochemical approach shows (1) the dominance of the mixed Ca–Mg–Cl and Ca–Cl facies and that by passing from one campaign to another, groundwater generally keeps the same facies; (2) groundwater mineralization is controlled by the phenomenon of dissolution of evaporite and carbonate minerals and by the phenomenon of reverse ion exchange; (3) water quality index (WQI) values show that groundwater quality is becoming increasingly poor from each year to the next. However, the results obtained could be a reference to decision makers to protect this vital resource.