The interconnection of the Volcanic Aquifer Layers Influences the Interaction of Hydrogeological and Hydrology Systems on Cisadane River

Abstract The high groundwater potential on the eastern slopes of Mount Salak and the western slopes of Mount Pangrango, there are approximately 12 aquifer layers, in the form of confined aquifers and unconfined aquifers. More than 120 springs spread from slopes to valleys, discharge between 1 - 150 lt/second, and easy accessibility have implications for the rapid growth of the drinking water industry which utilizes groundwater springs, and river water. This large increase in utilization will certainly affect the condition of groundwater in CAT Bogor. It is feared that groundwater extraction with excessive withdrawal discharge will affect the condition of the groundwater level from dug wells and surface water and the influence of climate change will also affect the potential of water resources. Research on the interconnection of hydrogeological systems and river hydrology is carried out by mapping surface and subsurface geology to determine the aquifer system using 1D and 2D geoelectric methods as well as hydrochemical analysis, as well as measurements, of 18O, 2H isotopes, in springs, dug wells and deep wells, to find out how interconnection of groundwater flow with surface water and vice versa. This research aims to identify the interconnection of groundwater and surface water systems to understand risks such as drought, flooding, or a decrease in the quantity of water quality due to excessive use. The research results show that the genesis of groundwater in dug wells, springs, and drilled wells originating from unconfined aquifers, the genesis is the same as the genesis of surface water in the Cisadane River. Knowing the relationship between hydrogeological systems and river hydrology is necessary to build a hydrogeological system on the eastern slopes of Mount Salak and the western slopes of Mount Pangrango, for sustainable water resource management.