Hydrographic and hydrochemical characteristics of selected groundwater outflows in desert and semi-desert areas
2024
Tadeusz Molenda
The presence of natural groundwater outflows depends on many factors, such as lithology, geological structure, and climate. Areas with particularly poor crenological recognition are arid and semi-arid regions, primarily due to rarity of groundwater outflows in these locations. The article presents the hydrographic and hydrochemical characteristics of selected groundwater outflows in arid and semi-arid areas. In addition to hydrographic mapping, basic physical parameters of water were measured in selected springs, such as temperature (T, °C), electrolytic conductivity (EC, μS∙cm–1), and reaction (pH, –). Laboratory analyses determined the major cations and anions in water: Ca2+, Mg2+, Na+, K+, NH4+, SO42−, Cl−, NO3−, Br−, PO43−,. The analyses were performed using an ion chromatograph Metrohm 850 Professional IC. Twenty-four natural groundwater outflows in South America, Africa, and Asia were selected for research. It was found that the vast majority of outflows are transit sources. Their supply area may be far from discharge points. The supply source is rainwater or meltwater from high mountain massifs. Other types of outflow are springs of alluvial fans and braided rivers. They are fed by waters from glacial rivers, which infiltrate alluvial deposits and flow back to the surface. Hydrochemical analysis has shown that the physicochemical properties of water in dry areas vary significantly. Still in the hydrochemical type, there is a predominance of sulphate, chloride, and sodium ions. This distinguishes the spring waters from these areas in temperate latitudes, which are dominated by bicarbonate and calcium ions.
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