<abstract xmlns="http://www.w3.org/1999/xhtml">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.</abstract>

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.

Hydrochemical Diversity of a Large Alluvial Aquifer in an Arid Zone (Draa River, S Morocco)

Department of Hydrometry, Faculty of Geographical and Geological Sciences

Department of Geomorphology, Faculty of Geography and Regional Studies

Department of Environmental Protection and Modelling, Faculty of Mathematics and Natural Science

Department of Analytical Chemistry, Faculty of Chemistry

Ecological Chemistry and Engineering S

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

In arid areas, with rivers functioning episodically, alluvial resources are the main source of water. Considering the intensified regulation of discharge in...

Hydrochemical Diversity of a Large Alluvial Aquifer in an Arid Zone (Draa River, S Morocco)

Publié en ligne: 15 avr. 2019

Pages: 81 - 100

DOI: https://doi.org/10.1515/eces-2019-0007

Mots clés
hydrochemistry, alluvial aquifer, salinity, arid zone, intermittent river

© 2019 Anna Szczucińska et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Hydrochemical Diversity of a Large Alluvial Aquifer in an Arid Zone (Draa River, S Morocco)

Publié en ligne: 15 avr. 2019

Pages: 81 - 100

DOI: https://doi.org/10.1515/eces-2019-0007

Mots cléshydrochemistry, alluvial aquifer, salinity, arid zone, intermittent river

© 2019 Anna Szczucińska et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Mots clés
hydrochemistry, alluvial aquifer, salinity, arid zone, intermittent river