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Groundwater potentiality assessment in an arid zone using a statistical approach and multi-criteria evaluation, southwestern Tunisia

Msaddek Mohamed Haythem, Souissi Dhekra, Moumni Yahya, Chenini Ismail, Bouaziz Nacira, Dlala Mahmoud

Geological Quarterly

2019

Vol. 63, No. 1

3--15

The aim of this paper is to assess the groundwater potentiality using statistical multi-criteria evaluation and AHP (analytic hierarchy process) as an additional method to the hydrogeological research in order to create a map that represents the groundwater potentiality. The extraction of this map is based on the study of multi-criteria input data, such as lineaments, land use, lithology, drainage, slope, soil, rainfall and geomorphology. Weights were assigned using the AHP method to all these multi-influencing factors according to their influence on groundwater potential. Sensitivity analysis was calculated to validate the AHP weights result. The presented methodology has been applied to the Bouhedma region in southwestern Tunisia, located in an arid climate. This technique revealed that very good, good, moderate and poor groundwater potential zones are spread over 382 km2 (26.9%), 437 km2 (30.7%), 552 km2 (38.8%) and 51 km2 (3.6%), respectively. Furthermore, the effect of each influencing factor on groundwater capacity was computed. The results provide significant information and found to be helpful in better planning and management of groundwater resources.

Hydrochemical diversity of a large alluvial aquifer in an arid zone (Draa river, S Morocco)

Szczucińska Anna, Dłużewski Maciej, Kozłowski Rafał, Niedzielski Przemysław

Ecological Chemistry and Engineering. S

2019

Vol. 26, nr 1

81--100

In arid areas, with rivers functioning episodically, alluvial resources are the main source of water. Considering the intensified regulation of discharge in montane catchments, supplying the intermittent rivers, in the nearest future alluvial aquifers will gain key importance for the functioning of people in arid zones. The research aimed to investigate the diversified chemistry of alluvial waters typical of large intermittent river valleys in hot arid zones as well as to analyse processes determining the water chemistry and affecting its diversity. The detailed study, carried out in October 2015, covered the Draa river valley (1100 km total length) in the region of the Mhamid Oasis. The examined water was sampled from all wells found in the study area. Concentrations of the main cations: Ca2+, Mg2+, K+, Na+, NH4+, and Li+, anions: Cl−, SO42−, HCO3−, and NO3−, as well as trace elements: Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, and Zn, were identified. Results were analysed with statistical, hydrochemical, and geochemical modelling methods. Alluvial waters of the eastern and western part of the oasis differed in concentrations of numerous components, what resulted from the regulation of irrigation. Specific electrical conductivity showed a 3.5-fold increase, from 3800 to 13800 μS/cm, consistent with the direction of water flow in the oasis, from east to west. Even a greater rise was observed for ions: Cl− (6x), Na+ (5.5x), Mg2+ (5.0x), Ca2+, and SO42− (3.5x). Such a composition indicated multiionic hydrochemical type of waters dominated by Na+ and Cl−. Additionally, high Pearson correlation coefficients were recorded for Na+ and Cl− (0.98) as well as Mg2+ and Cl− (0.97). The saturation index suggested that the main water components originated from dissolving of minerals such as halite, anhydrite, sylvite, and gypsum. Groundwater chemistry in the Mhamid Oasis was determined mainly by geogenic processes, such as dissolving of evaporates, precipitation of carbonate minerals, and ion exchange.

Hydrochemistry and origin of principal major elements in the groundwater of the Béchar–Kénadsa basin in arid zone, South-West of Algeria

Lachache S., Nabou M., Merzouguui T., Amroune A.

Journal of Water and Land Development

2018

no. 36

77--87

Béchar region is located in the southwest of Algeria, characterized by an arid climate with a Saharan tendency. It is subject to an increasing demand for water like all the great agglomerations due to the economic and demographic development. The groundwater of region is deteriorating because of the economic development, and the rapid growth of population. This article is devoted to the study of hydrochemistry and processes of mineralization of groundwater in this region. The results of physicochemicals analyses shows the same chemical facies of the chloride and sulphate-calcium and magnesium type, with high mineralization from North-East to South- -West to the outlet of Béchar–Kénadsa basin. The determination of the mineralization origin and the main major elements were approached by multivariate statistical treatment and geochemical. This method has identified the main chemical phenomena involved in the acquisition of mineralization of water in this aquifer. These phenomena are mainly related to the dissolution of evaporite formations, the infiltration of runoff water and direct ion exchange and mixing. However, the high mineralization anomaly is observed at the centre of Béchar–Kénadsa basin progressively by going to the outlet of this basin.

Region Béchar w południowozachodniej Algierii charakteryzuje klimat suchy z wpływami saharyjskimi. Jak wszystkie duże aglomeracje, region ten wykazuje rosnące zapotrzebowanie na wodę w związku z rozwojem ekonomicznym i demograficznym. Rozwój gospodarczy i szybki przyrost populacji jest powodem pogarszania się jakości wód gruntowych. Niniejszy artykuł jest poświęcony badaniom właściwości hydrochemicznych i procesów mineralizacji wód gruntowych w regionie. Wyniki analiz wykazują występowanie podobnych facji chemicznych typu chlorkowego i siarczanowo-wapniowych lub magnezowych o wysokim stopniu mineralizacji od północnego wschodu do południowego zachodu basenu Béchar–Kénadsa. Źródła mineralizacji i główne pierwiastki zostały oznaczone metodami geochemicznymi z zastosowaniem wieloczynnikowej analizy statystycznej. Metody te dały podstawy do identyfikacji głównych zjawisk chemicznych wpływających na mineralizację wody, takie jak rozpuszczanie formacji ewaporytowych, infiltracja spływów powierzchniowych, bezpośrednia wymiana jonowa i mieszanie. Anomalię wysokiej mineralizacji malejącą w kierunku odpływu zaobserwowano w środkowej części basenu Béchar–Kénadsa.