Geochemical of Karst Water in the Western part of Gunungkidul District Area

The geological condition of the study area is included in the karst of the Panggang hydrogeological subsystem. This karst area is characterized by the presence of surface water and groundwater, which is distinctive, where the water is interesting to be studied, especially on its hydrochemistry. By knowing hydrochemistry, this research wants to know about the relationship between surface water and groundwater. The method was a hydrogeological survey and accompanied by hydrochemical testing of dolines (surface) water and groundwater. The data have been analyzed by some hydrochemical diagrams such as Schoeller, Piper, Durov, and Collins diagrams. Springs emerge from reef limestone aquifers (Gunungsewu aquifers) in several places, supported by grains, fractures, and channels porosities. Both groundwater and surface water are colorless (46 - 350 TCU) and clear (3 - 19 NTU) with a pH of 6.8 - 8.1 and TDS 76 - 308 ppm. Groundwater shows the Ca – bicarbonate and Ca, Mg - bicarbonate types, whereas dolines (surface) water has Ca, Mg - bicarbonate types. Groundwater and surface water show relatively similar hydrochemical facies. Enrichment of hydrochemical groundwater is greater in springs than in dolines. The doline water may not correlate with each other, and it means that the groundwater flows to dolines maybe not be interconnected. Thus, water in the karst area may flow in all directions, depending on the porosity of the controlling channels. Water in the study area is young, indicated by the Ca2+ and HCO3- dominant ions, supported by ion exchange and simple dissolution processes