Groundwater Contributing to Doline Hydrochemistry in Panggang and Wonosari-Baron Hydrogeological Subsystems, Indonesia

The Panggang and the Wonosari-Baron Hydrogeological Subsystems are part of the Gunungsewu karst landscape in Gunungkidul Regency, Yogyakarta, Indonesia. This landscape has many dolines as one of the epikarst of the phenomenon. These dolines usually classified as solution dolines. This study aims to determine the presence or absence of groundwater flow in doline based on hydrochemical characteristics. Hydrochemical data were collected during the dry and rainy seasons, supplemented by water doline sampling on the ten selected dolines. Data were taken from the field and laboratory, both in physical (color, taste, odor, and turbidity) and chemical (pH, EC, and ionic content) properties of water. The hydrochemical analysis was performed using Stiff and Gibbs diagrams. The doline’s water has Ca and Na-bicarbonate facies during the dry season but tends to change to Ca-bicarbonate facies in the rainy season. The water-rock interaction process and precipitation found strongly influence the hydrochemistry of dolines water. The hydrogeological system involves conduit-type groundwater flow. The groundwater is interpreted to contribute to the water doline based on its hydrochemistry, both locally and regionally.