Understanding north Java coastal aquifer system: evidence from Kendal, Mid Java
Lukman, A.(1), Aryanto, M.D.(2), Pramudito, A.,(2), Andhika, A.(2), and Irawan, D.E.(3*)
1) Faculty of Earth Sciences and Technology, Institut Teknologi Bandung
2) PT. Supra Indodrill Indonesia
North coast of Java has been grown to be center of economic activities. Those activities must be supported by sustainable water supply, groundwater is one of the source. However the complex alluvium aquiver system has not been well-understood.
A geoelectric measurements were performed to determine which rock layer has a good potential as groundwater aquifers in the northern coast of Kaliwungu Regency, Kendal District, Central Java province. Total of 20 vertical electrical sounding (VES) points has been performed, using a Schlumberger configuration with the current electrode spacing (AB/2) varies between 200 – 300 m and the potential difference electrode spacing (MN/2) varies between 0.5 to 20 m with depths target ranging between 150 – 200 m. Geoelectrical data processing is done using Ip2win software which generates resistivity value, thickness and depth of subsurface rock layers.
Based on the correlation between resistivity value with regional geology, hydrogeology and local well data, we identify three aquifer layers. The first layer is silty clay with resistivity values vary between 0 – 10 ohm.m, then the second layer is tuffaceous claystone with resistivity value between 10 – 60 ohm.m. Both layers serve as impermeable layer. The third layer is sandy tuff with resistivity value between 60 – 100 ohm.m which serves as a confined aquifer layer located at 70 – 100 m below surface. Its thickness is vary between 70 to 110 m. The aquifer layer is a mixing of volcanic and alluvium sediment, which is a member of Damar Formation. The stratification of the aquifer system may change in short distance and depth. This natural setting prevent us to make a long continuous correlation between layers. Aquifer discharge is estimated between 5 – 71 L/s with the potential deep well locations lies in the west and southeast part of the study area.
Keywords: vertical electrical sounding (VES), Kendal, coastal aquifer system
Topic: Renewable Energies