Abstract:
The Zagros Range of south-central Iran is characterized by long and regular anticlinal and synclinal folds. Most highlands are karstified limestone and dolomite aquifers, which are sandwiched between thick non-karstic marl, marlstone, manly limestone, gypsum and anhydrite formations. Hydrochemical data from 195 karst springs, emerging from five different karstic formations, were used to determine the factors controlling spring water quality. The size and boundaries of catchment area of each spring were determined using water balance and geological methods. The springs were classified based on water type and specific conductance; and discrimination analysis was performed on the major anions, cations, and the specific conductance of all the springs to confirm the proposed classification. The Piper diagram reveals bicarbonate, bicarbonate-dominant, sulphate-dominant, or chloride water type with specific conductances ranging from 190 to 13500µS/cm. The lithology of the neighbouring formations and its extent of outcrop into the catchment area of the karst springs have a major effect on water quality. Large exposures of marl, marlstone, and manly limestone on the catchment area of the karst springs can change bicarbonate water to bicarbonate-sulphate, whereas gypsum and anhydrite produce sulphate-type waters. Salt domes, and saline water from adjacent lakes or alluvial aquifers are the main sources for chloride-type water.