The hydrochemistry of Mt. Ciremai
Authors: Irawan Dasapta Erwin 
Published: July 2018

This project was originated from my PhD research project (2005-2009), which has been uploaded for sometime at Figshare.---The Mount Ciremai is a 3072 masl situated in the south of Cirebon. It constitutes of spring zones along its foot slopes with nearly 200 groundwater springs, discharging 10 L/s to 800 L/s of water. The spring zone is fed by volcanic aquifer system, which lie over clay-sand layers which contains large masses of intercalated evaporites. Due to these conditions, the hydrochemical composition of the volcanic springs is relatively variable. In this study a hydrogeochemical characterization of the aquifer is undertaken to identify the aquifer system and the shifting of pysico-chemical properties, based on 140 samples collected from the volcanic springs. The identification was performed by studying hydrographs, the temporal evolution of physico-chemical parameters, and by means of multivariate statistical analyses with ifteen (15) hydrochemical parameters were considered (pH, EC., TDS., Twater, Tair, elevation, lithology, aquifer medium, Ca, Mg, Na, K, HCO3, Cl, SO4). Principal Component Analysis (PCA) and Cluster Analysis (CA) were applied in order to examine the importance of each parameter, investigate correlations among them, and separate them into groups. CA recognizes two clusters. Cluster 1 consists of mesothermal and hypothermal waters which are circulating in the volcanic aquifer system. This cluster is divided in to Cluster 1a which consists of 131 springs, with Ca-HCO3 from plagioclase rocks and Cluster 2b constitutes 3 springs with Mg-HCO3 ferromagnesian rocks. These samples are closely related with meteoric water. Cluster 2 consists of two springs circulating in the volcanic rock aquifer system. Both springs are hyperthermal, with high Na-K-Cl and TDS/DHL contents from volcanic activities. PCA identifies the neutral parameters on Quadrant I and IV which consists of mesothermal and hypothermal groundwater samples located on higher altitude. Neutral parameters change to dominant pH, Mg, Ca, HCO3 in Quadrant III. The three quadrants are controlled by volcanic rock aquifer system with relatively fast circulation in fractured aquifers. The prevailing parameters alter to dominant TDS/EC, Na, K, Cl, and SO4 in Quadrant II which contains volcanic – hyperthermal groundwater samples. Along the direction of flow, hydrochemical trends are seen as the groundwater type changes from neutral type to Ca-HCO3, Mg-HCO3; then to Na-K-Cl derived from the mixture between cold waters and thermal water. Cibulan spring shows different pattern of groundwater and surface temperature graphs. It indicates closed aquifer system, un-associated with surface environment. More similar curve pattern is shown at Telaga Remis spring. It indicates that the groundwater flows in open aquifer system, associated with surface environment. Gradual curve indicates the control of porous aquifer system, while the sharp one indicates the role of fractured aquifers. The estimated time residence of groundwater is within 3-7 months period. The calculation of spring’s recharge area from the charts are 3725 km2 with 8.2x109 m3/year of recharge for Cibulan, 6188 km2 with 14.5x109 m3/year of recharge for Telaga Remis.The application of PCA and CA of hydrochemical and hydrodynamic data can be used to extract the conceptual model of hydrochemical evolution of volcanic waters. Moreover, the use of both approaches allows better establishment of volcanic aquifer characterization. Key word: volcanic aquifer system, physical and chemical properties, cluster analysis, principal component analysisTotal words: 500