The Investigation of Groundwater Using Geophysical Techniques in Baitussalam Sub-district, Aceh Besar District, Aceh Province, Indonesia

The Investigation of Groundwater Using Geophysical Techniques in Baitussalam Sub-district, Aceh Besar District, Aceh Province, Indonesia Marwan Department of Physics, Faculty of of Mathematics and Natural Sciences, Syiah Kuala University, Banda aceh Department of Geophysical Engineering, Syiah Kuala University, Banda aceh Corresponding Author: marwan.fisika@gmail.com Muzailin Affan Department of Informatics, Faculty of of Mathematics and Natural Sciences, Syiah Kuala University, Banda aceh e-mail: muzailinaffan@gmail.com Amsir Department of Geophysical Engineering, Syiah Kuala University, Banda aceh e-mail: amsir.rich@gmail.com ABSTRACT Geophysical techniques, an geo-electric method 2-D, has been general used for many year in groundwater exploration. The method is applied with drilling for determination of resistivity value and equifer depth. The result show that plain and hill was morphology characteristic in area which has relatively > 50 meter above sea level, and also the area was dominated by volcanic rock Lam Teuba. The resistivity value was 4-10 ohm.meter and aquifer layer was 2-20 meter depth under the ground surface. However, deepst equifer layer found 40-70 meter from surface in line T and line U. KEYWORDS: geo-electric method 2-D, geophysical, resistivity value, groundwater. INTRODUCTION Groundwater is explained as water situated below the ground surface in soil pore spaces and in the fractures of litho-logic formations (Anomohanran, O.2013). The groundwater occurrence in the subsurface is mainly related to the distribution of permeable layers such as sand, gravel, unconsolidated, fractured or weathered rocks, and impermeable or low-permeable layers (clay, consolidated sediments or solid rocks) (Klinmanee,P and Dürrast, H.2012). In many countries, there is not only a heavy reliance on ground water as a primary drinking supply, but also as a supply of water for both agriculture and industrial use. According a research Alabi.A.A, et al (2010), about 53% of the world population depends on groundwater as a source of drinking water. For geoscientists, In addition, groundwater is a vital natural resource which is important to be able to monitor its quality and quantity in subsurface reservoirs that called as aquifers (Carrasquilla, A.2007). - 1767 -

Vol. 20 [2015], Bund. 5 1768 Therefore, Groundwater was important in environmental geophysics, for example many of the environmental research are directly or indirectly related to groundwater, such as exploration, effects of groundwater on the soil, effects on archaeological sites and groundwater pollution. Geophysics which is particularly geo-electrical resistivity techniques has been extensively used for a wide variety of geotechnical and groundwater exploration problems (e.g. Anomohanran, O (2013), Alabi.A. A., et al (2010), Carrasquilla, A. (2007), Klinmanee,P and Dürrast, H.(2012), Ariyo,s.o (2009), Mahmoud I.I. Mohamaden et al.(2009)). This is possible by a systematic exploration program using modern scientific tools. Use of geophysical methods provides valuable information with respect to distribution, thickness, and depth of groundwater bearing formations. Actually, geophysical exploration, ground penetrating radar, seismic refraction, geo-electrical and resistivity have become practiced in engineering site characterization as being non-invasive, non-destructive, rapid and cost-effective method. In the same way, various surface geophysical techniques are available, but the most commonly used in a research for rural or urban water supply is the electrical resistivity method because of its low cost and relatively high diagnostic value. In this research, electrical resistivity used as geophysical method for localize the depth of bedrock. The system of electrical resistivity method was working base on electrical property of the earth material which called resistivity charge. The objective of the research was to study groundwater in Baitussalam Sub-district, Aceh Besar District, Aceh Province, Indonesia using geophysical method. GENERAL GEOLOGY The research has been done at Ie Sum Krueng Raya area, Aceh Besar district, Aceh Province of Indonesia. Based on Banda Aceh geological Map (S. Gafoer, et al 1981), the observation field has arranged by various formation of rock. That influenced by structural geology in a few locations. The formation that has found in location repeatly from young to old are; Alluvium (Qh), lahar (Qvtl) and volcanic rock Lam Teuba (Qtvt). GENERAL MORFOLOGY In research area, the condition of morphology has the characterised of plains and undulating hills which is relatively sloping and hilly until reach the top 50 m above sea level. In geomorphology unit, afterwards, a river valley formed U and begins to form V that characterized of horizontal erosion process dominant, and the vertical condition has sediment and erosion process founded in several locations.

Vol. 20 [2015], Bund. 5 1769 Figure 1: Geology map of the study area Figure 2: The geomorphology units of Undulating Hills, at Ie Seum-Krueng Raya, Aceh Besar, Aceh Province

Vol. 20 [2015], Bund. 5 1770 Figure 3: The river that passed the research area. STUDY AREA The research area geographically at the position of 05 33 30 05 34 10 N until 95 31 30-95 32 15 E. This research area including Ie Sum Krueng Raya area, Aceh Besar district (Figure 4).Therefore, The measurement of geo-electric takes 6 lines which is 4 lines almost parallel each other and 2 lines perpendicular. The parallel line is a choice to make it easier when collecting data was processing, and uncorrection needed. The total length of electrodes was about 330 m (3 lines), 220m (1 line), and 395 m (2 lines). Figure 4: The location of research area at Ie Sum Krueng Raya area, Aceh Besar district

Vol. 20 [2015], Bund. 5 1771 THEORY OF GEOPHYSICAL METHOD Basically, Electrical resistivity investigations are based on the principle of applying electric current to the earth through two electrodes and measuring the potential difference between two or more other electrodes. The distance between the electrodes and the measured potential difference are the data used to make interpretations of subsurface condition, the method works base on electrical property of the earth material which called resistivity charger. Therefore, Several geology parameter, such as mineral and fluid content, porosity and degree of water saturation in the rock, is related by ground resistivity (M.M Nordiana. 2012). The materials have different ability to conduct electricity. In some materials, they have at least one of the electrons in each atom which is loosely held and it requires only slight external influence to move or conduct some of the electrons from atom to atom through the material. In other materials, there are very few free electrons and they conduct electricity poorly. This type of electrical conduction is called electronic conduction. Then, types of electric conductivity are involved in electrical resistivity investigations; electronic conductivity through the soil particles and rock and electrolytic conducting in the ground water. The resistivity of a material is a fundamental property of that material in the same sense that bulk density is a fundamental property (Henbest, et al,. 1967). Figure 5: Four-point electrode configures in a two-layer model of resistivity, P1 and P2.I, current; U, voltage; C, current electrode; P, potential electrode ( Jinmin.M. et al. 2014) In general, resistivity investigation used and appropriate for scientific certification systems (SCS) work which is the Wenner electrode configuration applied with the Barner layer method of interpretation. Afterwards, in the Wenner configuration, the four electrodes are spaced equidistant. So, the distance between each electrode is equal. MEASUREMENT METHOD To determine the depth of aquifer layer/groundwater using geo-electric method 2-D, we use the Wenner configuration. This configuration is very good to detect anomalies which have vertical resistivity change value according to the depth. Slip field that will be detected using geo-electric resistivity had different rock resistivity value between top & bottom layer or had a vertically

Vol. 20 [2015], Bund. 5 1772 difference value so that the selection of the Wenger configuration is suitable for detecting the slip plane. The value of n or layers that will be used in this measurement until n=14 with total of datum point as many as 463 electrodes measuring as much as 56 electrodes. Consideration of using n = 14 is to obtain the maximum value of the total depth at the long stretch that being used at each electrode has also measured a high using Altimeter Cobra 4 Weather PHYWE. This Altimeter measurement must be done quickly to avoid a significant pressure changes between the beginning and end of the measurements. This height values are useful to correct the resistivity and 2D cross sectional results. RESULT AND DISCUSSION Data processing had been collected using Res2Dinv and Earth Imager software. They allow us to do processing geo-electric data until got 2D profile of geo-electric. This profile shows a subsurface condition that has measured. The line that had measured we know where groundwater exists based on the resistivity value of rock or soil. In location research, the measurement applied on 6 lines to processed geoelectric resistivity 2D. As shown in the figure, the line of Z,Y, W along 330 meter and X line along 220 meter and line T,U along 395 meter. Here the interpretation from 6 lines that has measured. Line Z It has a track along 330 meter and after data process using Res2Dinv software obtained the resistivity value of rock in depth 45 meter from the sub-surface.the resisitivity value (rock) that found in Z line between 5-50 ohm.meter. As shown in the figure below. Figure 6: 2-D Model of rock or soil resistivity in Line Z. The aquifer layer is a layer that consist of water that had a very low value of resistivity if we compare with other layer (e.g. rock layer) cause the characterized itself. The aquifer layer in Z line has a resistivity value between 5-10 ohm.meter. That layer found in depth of ±20 meter from the mid-surface and getting shallow to the south. The limit of aquifer layer in figure 7 show with black dashes line. In distance of 280 meter a shallowest aquifer layer was found and possibly to make a normal well.

Vol. 20 [2015], Bund. 5 1773 Line Y In this line, the Y line and Z line were parallel and have same length 330 meter, the range of the resistivity value between 7-30 ohm.meter as shown in the figure 7 below : Figure 7: 2-D Model of rock or soil resistivity in Line Y. Based on the figure 7, The aquifer layer was founded in shallower depth than Z. In Line Y, the aquifer existed in ± 8 meter with various thick (show with black dashes line). In distance 230 meter, beneath surface was founded an aquifer layer which is very thick and shallow and its possibly to make a well logging here. Line X The Line X has shorter than line Z and Y. Actually line X will processed in same lenght with line Z and Y, but according to the field the conditions that not allowed, so it take about 220 meter only. After processing data using Res2Dinv software, will show the sub-surface condition based on resistivity value until 35 meter depth as shown as in the figure 11 above. The resistivity value that founded in Line X range betwen 2-30 ohm.meter. An aquifer layer that founded in Line X has a resistivity value 2-10 ohm.meter. The aquifer layer founded in 2-15 meter depth from distance 16-180 meter (shown as black dashes line in the figure 8).The depth of water is 2-15 meter is surface water and for their extraction process you should built a normal well. In addition, it founded a shallow ground water in 30 meter depth of midle of line there is also a depth of aquifer layer.

Vol. 20 [2015], Bund. 5 1774 Figure 8: 2-D Model of rock or soil resistivity in Line X. Line W Line W Has a length of 330 meter and it can mapped sub-surface condition until approximately 45 meter depth. The resistivity value (rock or soil) that has founded in this line is about 5-25 ohm.meter. Line W has a step or following aquifer like founded in Line X or has colleration with line Line X. The resistivity value of aquifer layer in this line is 5-10 ohm.meter. The value is same as linex, liney and line Z. Based on figure 9, the aquifer layer was founded in 8-18 meter depth with various thick (shown as black dashes line). This first aquifer layer can produce a water by built a normal well. In other case, the second aquifer founded in ±30 meter depth in midle line.the water can be used by built a shallow boreholes. Figure 9: 2-D Model of rock or soil resistivity in Line W. Line T Line T has a longer length compare to line W, line X, line Y, and line Z. In this line, measurement using a multi-electrodes ARES geo-electric equipment which has a total of 80 pieces of electrodes and can to achieve a stretch of up to 400 meters with a maximum depth approximately 70 meters and also has high current compare to SuperSting R8/IP.

Vol. 20 [2015], Bund. 5 1775 The first electrode of line T was located at coordinates 5 33'4 "N, 95 o 31'45.9" E and last electrodes located at 5 33'36.5 "N, 95 o 31'55.6" E. The total path length of this lines approximately 395 meters by 5 meters spacing between the electrodes. After data processing using Res2Dinv software, 2D profile of resistivity rock or soilbenearth surface obtaines as showed in figure 10. Figure 10: 2-D profile of rock or soil resistivity in line T. The results showed that the maximum depth that can be achieved at a total length of line 395 meters was 70 meters beneath surface. Resistivity value range of rock or soilon this line about 4-50 ohm.meters. The Deepest aquifer layer on the line with resistivity values between 4-7 ohm meter was found at a depth of 25 meters and continuous down to a depth of 70 meters. Line U Line U has equal length to line T because its measurement is done using a resistivity meter 80 electrodes ARES. The first electrode in this line was put on 5 o 33'45.1 " N, 95 o 31'45.9" E and last electrode stood at 5 33'36.5 "N, 95 o 31'55.6" E with a path length of 395 meters. The results of data processing using software Res2Dinv showed that, resistivity values obtained beneath surface ranged between 4-81 ohmmeter. The total length of the line T was 395 meters with a maximum depth about 70 meters as shown in Figure 11. Figure 11: 2-D profile of rock or soil resistivity in line U.

Vol. 20 [2015], Bund. 5 1776 In this line U, the aquifer layer has resistivity values between 4-9 ohmmeters in depth from 3-15 meters and located in the middle of the line. Deepest aquifer layers are at depths of 40-70 meters and almost the same shape and connected to the aquifer line T. Perhaps, the line U and line T have connectivity because the location of the two lines was parallel, as showed in figure 11. CONCLUSION This Investigation has pointed out the result which can conclude that the morphology of the area is commonly characterized with plains and hill. Morphology relatively flat and hilly until touch the top of 50 meter above sea level and dominated by volcanic rock Lam Teuba (Qtvt). Furthermore, The resistivity value of rock to aquifer range about 4 10 ohm.meter and aquifer layer between 2 20 meter depth under the ground surface. In the region, neverthless, the second aquifer layer was at a depth of ±30 meter in X and W line. the deepest aquifer layer was found in line T and U at depth of 40 70 meter from surface. At a result, it can be infered that inverstigation of grandwater using this method has given a good result. ACKNOWLEDGMENT The author would like to extend sincere gratitude and appreciation to Geophysical Engineering, Syiah Kuala University, Banda Aceh, Indonesia for support in making the study success. REFERENCES 1. Alabi, A. A., Bello, R., Ogungbe, A. S. and Oyerinde, H. O. (2010), Determination of groundwater potential in Lagos State University, Ojo; using geoelectric methods (vertical electrical sounding and horizontal profiling), Report and Opinion, 2(5): 68-75. 2. Anomohanran,O (2013). Geo-electrical investigation of groundwater condition in Oleh, Nigeria. International Journal of Research and Reviews in Applied Sciences. 15(1):102-106 3. Ariyo s.o and Adeyemi. G.(2009). Role of electrical resistivity method for groundwater exploration in hard rock areas: a case study from fidiwo/ajebo areas of Southwestern Nigeria. The Pacific Journal of Science and Technology. 10(1): PP.483-486 4. Bennett, J. D., McC, D., Bridge, Cameron, N. R., Djunuddin, A., Ghazali, S. A., Jeffrey, D. H., Kartawa, W., Keats, W., Rock, N. M. S., Thomson, S. J. and Whandoyo, R. (1981) Geologic map of the Banda Aceh Quadrangle, Sumatra. 5. Carrasquilla, A. (2007). Evaluating the performance of different geophysical methods for groundwater prospecting In Espirito Santo Basin - Southeast Brazil. Tecnociencia. 9(2): 89-106 6. Henbest.O.J, D.C. Erinakes, D.H. Hixson. (1967). Seismic and resistivity methods of geophysical exploration. United States Department Of Agriculture Soil Conservation Service Engineering Division. Washington 7. Jinmi.M, Rosli Saad, M.Mokhtar Saidin, Y.C Kiu, and Nur Azmi Ismail. (2014). Subrurface of overburden for possible meteorite impact crater at Bukit Bunuh,

Vol. 20 [2015], Bund. 5 1777 Malaysia using 2-d electrical resistivity imaging. Electronic Journal of Geotechnical Engineering.. 19(I): pp 1957-1964 8. Klinmanee,P and Dürrast, H.(2012). Geophysical logging for groundwater investigations in southern thailand. Songklanakarin Journal of Science and Technology. 34 (4):433-444. 9. Mohamaden,M.I.I, Abuo Shagar.S, and Gamal Abd. Allh.(2009). Geoelectrical survey for groundwater exploration at the Asyuit Governorate, Nile Valley, Egypt. Journal of King Abdulaziz University : Marine Sciences.Vol. 20, pp: 91-108. 10. M.M. Nordiana, Rosli Saad, Mokhtar Saidin, M.N.M Nawawi, Nur Azwin Ismail, and Syyeh S.K.(2012). Characteristics of subsurface materials: integration of seismic refraction, 2d resistivity imaging and geotechnical borehole logs. Electronic Journal of Geotechnical Engineering. 17(B): pp 207-223 2015 ejge