Irawan, DE., Puradimaja, DJ., Notosiswoyo, S., Sumintadireja, P.

1. Characterization of Tropical Volcanic Hydrogeology based on Temperature and Electrical Conductivity Analysis: Mount Ciremai, West Java Province, Indonesia Irawan, DE., Puradimaja, DJ., Notosiswoyo, S., Sumintadireja, P. Presented in 2011 European Geosciences Union General Assembly, Vienna Austria, 3-8 April 2011

2. For more discussions, today I will be at:Hall A Board #A27217.30-19.00

3. Introduction (Where’s Mount Ciremai) Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

4. Just to give you an idea in term of size • 13,000 of islands • Nearly 350 Million of population • 130 of volcanoes • 81.000 km of coastline • ( 400.000.000 Coca Cola cans in line) Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

5. Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

6. Why Mount Ciremai, among other 129 volcanoes in Indonesia ?

7. 5 seconds of your time = nearly 40,000 L/sec of fresh high quality groundwater 1 2 3 4 5 Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

8. Introduction (Mount Ciremai’s Profile) Large number of springs, with no systematic catchment monitoring and management. Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

9. The Hydrogeological Features(Geology, from Situmorang, 1995) • Consists of old and young volcanic products of pyroclastics flow and intruded lava underlied by Oligocene-Miocene clastics sediment. • Main geological structure: • NW-SE fault at south from the peak • E-W fault at easter slope, resulting Sangkanhurip and Pejambon geothermal prospect. Map and sections are on the poster location Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

10. Why are we doing this ? • To measure groundwater response: with relatively efficient and cheap method. • To explain groundwater infiltration processes: with the thickness variation of the soil and complex condition of the strato volcanic deposits. Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

11. Why are the problems ? • Thick weathered soil and fractured rock • Complex volcanic geology • Outcrops of rock is hard to find • Unpredictable subsurface condition (buried faults, buried valley, etc from geophysical method) Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

12. How do we approach the conditions ? • What if we can extract something (by any chance) from: • The hydrochemistry parameters • The hydrodynamic parameters Lack of long continuous time series data Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

13. Methods (Field measurements) • 24 hours measurements of: • Environmental temperature (measured at the surface) • Groundwater temperature (measure at spring site) • Daily measurements in 2006-2007 time frame of: • Rainfall: using standard rain gauge, obtained at the nearest station: • The Susukan Station (309 masl) • The Mandirancan Station (293 masl) • Groundwater discharge at spring site: using channel measurement technique • Groundwater EC and TDS: using standard portable equipments. • 24 hours measurements of: • Environmental temperature (measured at the surface) • Groundwater temperature (measure at spring site) Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

14. What do we know so far ? • Irawan (2009, doi:10.1016/j.jhydrol.2009.07.033): There are 3 groundwater systems (based on the hydrochemistry) • Herdianita et al (2010): Isotopes confirm that the recharge area is at around 1250-2500 masl (in regional scale of the volcano). • Sumintadireja et al (2011): confirm buried structures in the volcanic layers (MT and geoelectric) Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

15. The Hydrogeological Features Extracted from 140 spring site Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

16. Result (Cibulan Spring) Temperature profile Thick permeable soil (5-10 m) 350-400 L/sec Lava (unknown thickness) Proportionally sketch (no scale) • Air temp fluctuates • AND • Water temp fluctuates • Open aquifersystem • Interaction with surface Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

17. Results (Cibulan Spring) Spring discharge hydrograph • Response: • Highest discharge: three to four months from the peak of rainy season. • Lowering discharge: two months since the dry season begins. • Lowest discharge: six months since the dry season begins. Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

18. Results (Cibulan Spring) TDS-EC hydrograph Dissolution Dilution Dissolution Recovery Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

19. Results (Telaga Remis Spring) Temperature profile Thin-permeable soil (5-10m) 200-400 L/sec Water lake (1-5 m depth) Thick-fractured lava (unknown??) Proportionally sketch (no scale) • Water temp relatively constant • VS • Air/surface temp fluctuates • Closed/deeper aquifer system • No interaction with surface Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

20. Results (Telaga Remis Spring) • Response: • Highest discharge: three to five months from the peak of rainy season. • Lowering discharge: four months since the dry season begins. • Lowest discharge: seven months since the dry season begins. Spring discharge hydrograph Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

21. Results (Telaga Remis Spring) TDS-EC hydrograph • TDS dry = 2 x TDS rainy • EC dry = 1.7 x EC rainy • Dissolution 1st cycle • Dilution • Recovery • Recovery • Dissolution • Dilution 2nd cycle Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

22. Conclusion • With this methode, in my point of view we can interpret the subsurface condition. • We have to have enough geology observation and geophysical data to support that. • This convey our prediction that the aquifer is a combination of porous medium aquifer from weathered soil and fracture medium from fractured lava and breccias. • In volcanic system, the boundary is beyond the topographical catchment area. It’s controlled by the lobes of lava or volcanic breccias. Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

23. Conclusion (Proposed type curve) Model A Model B Slower period in the base flow recession curve. More vulnerable to dry season. Relatively short storage period. Combination porous-fractured medium. • Quick rising period in the baseflow recession curve. • Relatively have better compliance to the dry season. • Relatively long storage period. • Combination porous-fractured medium. Applied Geology Research Division, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung

24. The authors would like to thank: Chevron Pacific Indonesia for funding the participation to EGU 2011 Mr. Wouter Buytaert (Convener) for contacting myself to fill in the free oral session Ministry of National Education of Indonesia for funding the PhD research Department of Water Supply Kuningan Regency for data and permission to visit spring site Dr. Thom Bogaard (TU Delft) for the discussions Contact information Email: erwin@fitb.itb.ac.id or d.erwin.irawan@gmail.com Website: blog.fitb.itb.ac.id/derwinirawan Tel: +62222514990, Fax: +62222514837 Address: Faculty of Earth Sciences and Technology JalanGanesa No. 10, Bandung-40132 West Java, Indonesia