Volcanic slopes are important sources of water. Due to altitude effects they receive significant amounts of precipitation
whereas the lower regions often receive far less (<500 mm/year). In densely populated tropical regions, like Java, Indonesia, this water source is of increasing importance both for irrigation and domestic usage. As case study, more than 100 groundwater springs are monitored and analysed on Mt. Ciremai, central Java, Indonesia. More than 15 variables have been measured. The results show radial flow patterns, a dependency on slope aspect and altitude and lithology. The aquifer system was found to be a combination of porous (several meters) and fractured rock that is built up of lava and
volcanic breccias. Cluster Analysis and Principal Component Analysis are used to trace the spring clustering and dominant variables which control spring emergence. This paper will elaborate on the relationship between physical and chemical properties of groundwater as hydrogeological tracer with local groundwater systems on volcanic slopes.