Formulation of the relationship between temperature and groundwater conductivity in varying geological conditions

Abstract

The Yogyakarta and Central Java regions of Indonesia have diverse geological conditions. This geological diversity has encouraged researchers to conduct hydrogeological research, particularly on the parameters of temperature (T) and electrical conductivity (EC) of groundwater. This research was carried out using hydrogeological mapping methods and T/EC measurement experiments both in the studio and in the laboratory. This study aims to formulate the relationship between T and EC of groundwater under various geological conditions. Geological variations, particularly lithology and geothermal processes, can influence the thermal dynamics and electrical properties of groundwater. The selected locations represent a range of geological conditions, including geothermal, karst, alluvial, and volcanic areas. Temperature and conductivity data were measured directly in the field at 10 wells and 33 springs, with support from laboratory tests. Additionally, experiments were conducted to determine the EC at various temperatures. The results showed that the relationship between T and EC in all samples is exponential in nature. This study developed a general formula based on a second-order polynomial graph, with varying coefficients A, B, and C. A wide range of coefficient values is shown by geothermal springs, while less variable values are shown by water in karst and volcanic areas. The formula obtained helps validate the EC value (σ) to be a valid field EC value (σFV), which is in accordance with local geological characteristics.