Groundwater Quality Analysis to Determine Groundwater Facies in Pati-Rembang Groundwater Basin

Abstract

Pati-Rembang Groundwater Basin is located in Pati Regency, Rembang Regency, and Jepara Regency. Industrial growth and groundwater utilisation increase every year in line with increasing population. Hence, it is necessary to evaluate the quality of groundwater both in unconfined aquifer and confined aquifer as drinking water and irrigation as well as to define groundwater facies as the goals of the research. The methods of groundwater quality evaluation are hydrogeological mapping to determine the geological surface condition, measuring water table of unconfined aquifer and confined aquifer, conducting a hydrogeochemistry analysis of 50 groundwater samples. The results showed that Pati-Rembang groundwater basin consists of 5 lithology units, i.e. Sandy tuff, Andesite Porfiri Lava, Tuff, Volcanic Andesite, and Alluvial Deposit. Groundwater in the unconfined aquifer flows from the west to the north, to the east, and the south. The confined aquifer flows from the west to the centre, and the north. There are five groundwater facies in the unconfined aquifer while in the confined aquifer consist of three facies. Magnesium bicarbonate dominates both of the unconfined aquifer and confined aquifer. Calculation of water quality index both unconfined aquifer and confined aquifer showed that groundwater is still suitable for drinking water.