Water composition and minerals equilibria at the Syri i Kalter spring and in the Bistrica river (South Albania)

Abstract

Syri i Kalter (“Blue Eye” in english) is the name of the largest spring of Albania, situated in the south of the country, not far from the town of Sarande. The spring is located near the tectonic contact between the Mesozoic-Paleogenic Mali i Gjiere carbonate sequence and the Terziary flysch units of the “Ionian Zone” of Albania. The discharge area is characterized by the presence of Triassic evaporites, mainly constituted by gypsum and anhydrite, associated with clay, limestones, dolomite and halite. The spring consists of several discharge points, yielding as a whole an average water flow of about 11 m³/s.

Analyses of water samples from the spring show relatively high concentrations of calcium, sulphate and alkalinity, with a minor magnesium content and low concentrations of alkali-ions and chloride. Analogous composition results in samples from the Bistrica river, which is fed by the groundwater discharging from the spring. From the geological features of the area, it can be expected that minerals within the aquifer are represented mainly by calcite, dolomite and, close to the discharge point, by gypsum and anhydrite. Calculation of minerals equilibria displays that all samples are undersaturated with respect to gypsum, and oversaturated with respect to calcite. In these conditions, incongruent dissolution of dolomite (dedolomitization) is likely to occur. According to this process, the analytical Mg/Ca ratios match to the oversaturation state with respect to calcite and to the equilibrium with dolomite.