GIS-based evaluation of groundwater quality and estimation of soil salinization and land degradation risks in an arid Mediterranean site (SW Tunisia)

In southern Tunisia, the lack of permanent surface water, associated with drought conditions, leads to an endless abstraction from the limited low renewable multi-layered aquifer system of Système Aquifère du Sahara Septentrional containing two principal aquifers, the complex terminal and the Continental Intercalaire (CI) multi-layered systems. The deepest aquifer embodies the low-enthalpy thermal resources of Southern Tunisia. The thermo-mineral surface manifestations of the conductively heated waters reveal the complexity of the geotectonic history of the region and create oases systems in net contrast to the desertic landscape of the Chotts region. As agriculture constitutes the principal economic activity in the studied area and as it is currently threatened by thermal water quality degradation, the present hydrogeological investigation aims for a characterization of the CI thermal resources on the basis of a critical quality evaluation. Thus, different geothermometry approaches have been applied to characterize the low-enthalpy thermal field showing a temperature ranging from 27 to 72 °C. The application of cations geothermometers owns to different temperature estimations ranging from 28 to 202 °C. Based on Na + -Mg 2+ -K + , K + -Mg 2+ -Ca 2+ and HCO 3 − -Cl − -SO 4 2− geoindicators, the CI thermal resources refer to immature waters characterized by MI varying from − 0.5 to 0.19. The assessment of groundwater chemical composition based on a Durov diagram proves that CI thermal water is governed by mixing between different water bodies with relative abundance of Na + , Cl − , and SO 4 2− elements. According to D'Amore genetic diagram and meteoric genesis indices, the analyzed groundwater derived from deep circulation in sandy formations. The water quality can change along fluid migration pathways expressed by scattered isotopic and chemical data and a number of mixing ratios. Most changes in the background CI composition result from continuous pumping that modifies natural flows and increase quality degradation.

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“…Agriculture activities in Chotts Basin are currently threatened by soil fertility loss and crops quality reduction (Besser et al 2017). …”

Section: Hydrogeological Settingmentioning

confidence: 99%

Groundwater mixing and geochemical assessment of low-enthalpy resources in the geothermal field of southwestern Tunisia

Besser

Mokadem

Redhaounia

et al. 2018

Euro-Mediterr J Environ Integr

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“…However, classification based on EC showed 55% of groundwater samples from Gwandu aquifer fall into Doubtful-Unsuitable Class. In contrast, 95% of groundwater samples from the Illo aquifer fall into Excellent-Good Class [23]. Aquifers having the total hardness in the range of 0-75 mg/l are classified as soft [93].…”

Section: Classification Of Groundwatermentioning

confidence: 99%

Hydrogeochemical evaluation and mechanisms controlling groundwater in different geologic environments, Western Sokoto Basin, Northwestern Nigeria

2020

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The hydrogeochemistry of aquifers in the western Sokoto basin was assessed. The objective of this study is to identify the impact of geological variability on groundwater hydrochemistry and the mechanisms controlling the hydrochemistry of aquifers. Univariate statistics (several samples ANOVA), Pearson's (r), and multivariate statistics-hierarchical cluster analysis (HCA) and Factor analysis (FA) were used to interpret the hydrochemistry of aquifers. Subsequently, geochemical modeling was applied to assess the saturation index (SI) of rock minerals. Forty groundwater samples were collected from Gwandu (n = 20) and Illo (n = 20) formations. ANOVA results indicated that geological variability exerted a considerable impact on groundwater in Gwandu and Illo aquifers. It is characterized by a substantial amount of Ca 2+ , Mg 2+ , SO 4 2− , HCO 3 − , Na + , and K +. The hydrogeochemical facies indicated mixing conditions. FA and correlations analysis further revealed that groundwater received the noticeable influence of silicate weathering and dissolution of carbonates. There were significant differences in SI values for chrysotile, goethite, gypsum, H 2 (g), H 2 O(g), H 2 S(g), illite, and sepiolite minerals between the two geologic environments. Positive SI values for gibbsite were noticed in eleven sampling locations, indicative of potential recharge zones. Likewise, all the sampling locations have positive values for K-feldspar and are supersaturated with mica, suggesting both discharge and transition zones. The HCA classified aquifers into three clusters based on their hydrogeochemical characteristics. Geochemical modeling, univariate, and multivariate analyses are user-friendly tools for hydrochemical analysis.

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“…For example, the applied water in the Faouar area shows a surplus of more than 7,000 to 10,000 m 3 /ha for a water salinity of 2.4 and 3.6 g/L. With regard to the poor water quality of the used water for irrigation and the insufficient drainage system (Marlet et al, 2009), numerous infiltration and land degradation issues may be observed, namely water logging problems (Ben Hassine et al, 2016) and creation of gypsum crust (Besser et al, 2017) due to the evaporation of the surplus of irrigation water (Bouajila et al, 2016). Consequently, more than 20,000 kg of salt per m 3 may be F I G U R E 1 4 Distribution of water irrigation quantities for a number of water wells [Colour figure can be viewed at wileyonlinelibrary.com] deposited taking in account the likely consequences on soil fertility, structure, and aeration.…”

Section: Water Quality Degradationmentioning

confidence: 99%

“…In this context, in southern Tunisia, as a large part of the Mediterranean basin, fresh water deficiency constitutes an important challenge that leads to continuous exploitation of deep low renewable groundwater of deep Système aquifer du Sahara Septentrional (SASS) aquifers (Edmunds et al, 2003;Hamed et al, 2013Hamed et al, , 2014Hamed et al, , 2018Hamed, 2015;Mokadem et al, 2016;Besser et al, 2017Besser et al, , 2018. The continuous overdraft of the highly productive deep aquifers of the multi-layered SASS aquifers and the long dry periods lead to increased utilization of these chemically evolved waters (Continental Intercalaire, CI, and Complex Terminal, CT), which will have undoubtedly numerous ecological impacts namely the continuous decline in land productivity (Zammouri et al, 2007;Ben Hassine et al, 2013, Ben Hassine et al, 2016Besser et al, 2017;Dahoua et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Agriculture sustainability in arid lands of southern Tunisia: Ecological impacts of irrigation water quality and human practices*

Dhaouadi¹,

Besser

Wassar

et al. 2020

Irrigation and Drainage

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Groundwater resources in southwestern Tunisia are facing serious quantity and quality degradation. Given that they are the only source used for oasis irrigation, serious impacts on the soil of the region are expected. Accordingly, the main objective of this study is to evaluate the suitability of the sampled water from the Complex Terminal aquifer for irrigation purposes and to determine the potential impacts of their long-term use within the present agricultural practices on soil properties. The calculated ionic ratios indicate different classes ranging from permissible to unsuitable waters with respect to alkalinity standards (sodium adsorption ratio from 3.68 to 9.34, %Na from 36.7 to 61.2, and rill erodibility from 0.48 to 1.43). Water samples present high values of electrical conductivity, total dissolved solids, and potential salinity, about 54.5, 29.4, and 32.2%, respectively, which indicates serious salinity hazard. All the sampled waters may induce corrosion and clogging problems as deduced from the calculated light dynamic penetrometer and total hardness indices. The weighted water quality indices results (Canadian Water Quality Index and the irrigation water quality index) confirm the poor quality of the used irrigation water. The results of this study coupled with field investigations indicate that the cumulative impacts of low water quality and poor agricultural practices have damaged the total oasean ecosystem. K E Y W O R D S agricultural development, Complex Terminal, groundwater quality, land degradation, southern Tunisia oasis Résumé Les ressources en eau souterraine du sud-ouest de la Tunisie sont confrontées à une grave dégradation de la quantité et de la qualité. Étant donné qu'ils sont la seule source utilisée pour l'irrigation des oasis, de graves impacts sur le sol * Durabilité de l'agriculture dans les terres arides du sud de la Tunisie: impacts écologiques de la qualité de l'eau d'irrigation et des pratiques humaines

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GIS-based evaluation of groundwater quality and estimation of soil salinization and land degradation risks in an arid Mediterranean site (SW Tunisia)

Cited by 58 publications

References 41 publications

Groundwater mixing and geochemical assessment of low-enthalpy resources in the geothermal field of southwestern Tunisia

Groundwater mixing and geochemical assessment of low-enthalpy resources in the geothermal field of southwestern Tunisia

Hydrogeochemical evaluation and mechanisms controlling groundwater in different geologic environments, Western Sokoto Basin, Northwestern Nigeria

Agriculture sustainability in arid lands of southern Tunisia: Ecological impacts of irrigation water quality and human practices*

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