Hydrochemical characterization of geothermal and non-geothermal waters from Wadi Fatima, western Saudi Arabia

Abstract

The present study was conducted in the Wadi Fatima catchment in western Saudi Arabia with the primary objective of finding the major hydrochemical differences among geothermal and non-geothermal groundwater samples. Based on the dissolved-silica content of 124 groundwater samples, the chalcedony geothermometer with no steam loss was used to classify them as geothermal or non-geothermal. The mean total dissolved solids (TDS) of the non-geothermal and geothermal samples were 1254 mg/L and 4389 mg/L, respectively. The high TDS of the geothermal samples can be attributed to the higher temperature of circulation leading to a greater degree of mineral dissolution, as well as the mixing of fresh, shallow groundwater with deeper saline water, as can be seen on Piper and Durov plots. Silicate weathering is the primary hydrochemical process active in the area. Based on the saturation indices of commonly dissolved mineral phases, the geothermal water samples showed higher saturation. Using chalcedony geothermometer can be an effective tool for classifying groundwater from low-temperature reservoirs as geothermal and non-geothermal. Further groundwater facies analysis, ionic relationships, and saturation indices can be employed to determine hydrochemical characteristics of these two different types of waters.