Faculty of Natural Sciences Degree Course Geosciences Institute of Soil Science

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia

Report based on Diploma Thesis

Stephan Bödecker Examiners of Diploma Thesis: PD Dr. Thomas Himmelsbach BGR Hannover Prof. Dr. Jürgen Böttcher December 2008, Hannover Leibniz University of Hannover

Declaration / Erklärung

This report is based on the Diploma thesis with the topic “Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia”. I hereby certify that the Diploma thesis as well as this report have been composed by me and that no other than the cited sources and utilities have been used. Literal and analogous citations are characterized accordingly.

To match the international character the chosen language is American English.

Note: Due to copyright restrictions, three satellite images taken from the Google Earth™ map service and used for explanation in the Diploma thesis cannot be shown in this report.

Dieser Bericht basiert auf der Diplomarbeit mit dem Thema „Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia“. Hiermit versichere ich, die Diplomarbeit sowie diesen Bericht selbstständig verfasst und keine anderen als die angegebenen Quellen und Hilfsmittel benutzt sowie wörtliche und sinngemäße Zitate als solche gekennzeichnet zu haben.

Um der Internationalität des Themas zu entsprechen wurde als Sprache amerikanisches Englisch gewählt.

Anmerkung: Drei Satellitenbilder vom Google Earth™ Kartenservice, die in der Diplomarbeit verwendet wurden, können in diesem Bericht aus Copyright Gründen nicht gezeigt werden.

December 23rd, 2008, Hannover ______Stephan Bödecker

I Acknowledgement

I would like to express my special gratitude to PD Dr. Thomas Himmelsbach of the Federal Institute for Geosciences and Natural Resources (BGR) and to Prof. Dr. Jürgen Böttcher of the Leibniz University of Hannover for the supervision of my diploma thesis and for the support during my work.

Furthermore, I would like to thank all members of section B1.17 (BGR) for the friendly acceptance in their team and for their assistance concerning data processing, creation of figures, and in every other respect.

I am indebted to Dr. Dieter Plöthner (BGR) for his support with literature, data, and contact addresses and for worthwhile conversations and descriptions about his personal experiences in the study area.

For the preparation and explanation of the lineament mapping, explanations regarding remote sensing data and his personal experiences in the study area, and for valuable conversations I would like to thank Dr. Uwe Schäffer (BGR).

Furthermore, I would like to thank Ing. Herwig Paulus (Hall AG, Hall in Tirol) for his guidance through the “drinking water gallery Halltal” in October 2008 as well as for much useful information.

For organizing the visit of the “gallery system Mühlau” in October 2008 I am obliged to Dr. Dietrich Feil of the University of Innsbruck and to Mr. Eichelbacher of the IKB (Innsbrucker Kommunalbetriebe) for being our guide.

Further on, I thank all other staff members of waterworks, geological surveys, consultants, and university members I contacted especially during the literature research and who provided me with data or forwarded me to other contact persons.

I would like to thank my whole family for their continuous support during my academic study.

Finally, I would like to give my special thanks to my girlfriend for her infinite patience and support in every way.

II Abstract

English Karst water galleries can be described as effective man-made water capture constructions in hard rock formations (mostly limestone or dolomite) draining water from the rock mass. In particular, examples from Austria impressively demonstrate the function of these partly several kilometer long tunnels. They are mostly located in mountainous areas built up by slightly karstified limestones where high precipitation and high infiltration result in increased groundwater potential often accompanied by the retention of groundwater due to an aquitard. Characteristically, most discharge in otherwise low-permeable limestone and dolomite occurs along large faults and fractures, and hence, the highest water inrushes into karst water galleries generally appear where the galleries penetrate these fault or fracture zones. When trying to find a potential target area for a karst water gallery in a tropical region like in the case study Banda Aceh it can generally be said that the overall climatic conditions are suitable for potentially high discharges. High annual precipitation in combination with high infiltration in karstified limestones leads to high groundwater potential. These areas of high groundwater potential have to be detected by different approaches all aiming at the understanding of the prevailing hydrogeological drainage pattern. A first key to the overall distribution of areas with high groundwater potential is the classification of the geological formations to hydrostratigraphical units that mirror the hydrogeological properties of the formations. Furthermore, known spring locations are analyzed especially regarding their discharge characteristics, the prevailing physical and chemical water properties, and the altitude maybe suggesting different karst levels. The structural pattern also has strong influence on the prevailing drainage pattern since especially neotectonically active faults and fractures can be characterized as weakness zones that are subject to higher karstification and therefore can be seen as major groundwater flow paths that can drain huge interconnected areas. To distinguish an overall structural pattern the analysis of lineaments via remote sensing is a suitable tool. Additionally, it can be said that karstification in tropical regions is often extremely increased compared to more moderate climates due to higher precipitation and higher partial pressure of CO2 resulting from different soil characteristics. Highly active to maturely developed karstification can complicate the interpretation of a hydrogeological drainage pattern especially when only few basic data are available. Nevertheless, it is tried to figure out the basic hydrogeological conditions in the investigated area and to determine if a karst water gallery could be a suitable option for the future water supply of Banda Aceh.

III German

Karstwasserlösestollen sind leistungsfähige Bauwerke, die der Fassung von Wasser aus Festgestein (meistens Kalkstein oder Dolomit) dienen. Eindrucksvolle Beispiele, an denen das Funktionsprinzip dieser teilweise mehrere Kilometer langen Stollen erkennbar ist, gibt es besonders in Österreich. Sie befinden sich meist in gebirgigen Regionen mit vorwiegend leicht verkarsteten Kalksteinen. Dort führt in den meisten Fällen hoher Niederschlag kombiniert mit hoher Infiltration zu einem erhöhten Grundwasser-Potential. Charakteristisch für die ansonsten eher gering permeablen Kalksteine und Dolomite ist ein hoher Grundwasser-Abfluss entlang von großen Störungen und Bruchflächen. Daher strömt der größte Teil des Wassers dort in die Karstwasserlösestollen, wo sie Störungs- oder Bruchzonen durchstoßen. Bei dem Versuch ein potentielles Zielgebiet für einen Karstwasserlösestollen in einem tropischen Gebiet wie im Fallbeispiel Banda Aceh zu finden kann generell davon ausgegangen werden, dass die allgemeinen klimatischen Bedingungen potentiell hohe Abflussmengen liefern. Hoher Jahresniederschlag verbunden mit hohem Infiltrationsvermögen in verkarsteten Kalksteinen führt zu hohem Grundwasser-Potential. Diese Bereiche mit erhöhtem Grundwasser-Potential sollen mithilfe von mehreren Untersuchungsansätzen gefunden werden und damit zum Verständnis des vorherrschenden hydrogeologischen Abflussregimes beitragen. Ein erster Ansatz zum Verständnis der Verteilung von Gebieten mit hohem Grundwasser- Potential ist die Einteilung der geologischen Formationen in hydrostratigraphische Einheiten, die die hydrogeologischen Eigenschaften der Formationen widerspiegeln. Desweiteren wird das Schüttungsverhalten von bekannten Quellen analysiert. Dabei werden auch die vorherrschenden physikalischen und chemischen Eigenschaften des Wassers betrachtet, sowie die Höhenlagen der Quellen, die mögliche Karstniveaus anzeigen könnten. Das strukturgeologische Modell hat ebenfalls starken Einfluss auf das vorherrschende Abflussregime, da vor allem neotektonisch aktive Störungen und Bruchflächen Schwächezonen darstellen, die höherer Verkarstung ausgesetzt sind und daher als präferentielle Grundwasserfließwege gesehen werden können. Diese können große verknüpfte Gebiete entwässern. Die Analyse von Lineamenten mithilfe der Fernerkundung ist ein gebräuchliches Vorgehen, um das allgemeine strukturgeologische Modell zu bestimmen. Weiterhin kann erwähnt werden, dass Verkarstung in tropischen Regionen verglichen mit moderaten Klimazonen oft extrem verstärkt stattfinden kann. Dies ist auf den erhöhten

Niederschlag und den höheren CO2-Partialdruck, der von anderen Bodeneigenschaften herrührt, zurück zu führen. Hoch aktive bis maturierte Verkarstung kann die Interpretation

IV des Grundwasser-Abflussregimes verkomplizieren, besonders wenn nur wenige Daten zur Verfügung stehen. Es wird versucht, die hydrogeologischen Grundbedingungen im Untersuchungsgebiet herauszustellen und herauszufinden, ob ein Karstwasserlösestollen für die zukünftige Wasserversorgung von Banda Aceh geeignet wäre.

V Table of Contents

Declaration / Erklärung ...... I Acknowledgement...... II Abstract ...... III English ...... III German ...... IV Table of Contents ...... VI List of Figures ...... VIII List of Tables ...... XI List of Appendices ...... XII List of Abbreviations ...... XIII 1 Introduction ...... 1 1.1 Background ...... 1 1.2 Aims of this thesis ...... 3 2 Karst water galleries ...... 5 2.1 Definition and function ...... 5 2.2 Examples ...... 6 2.2.1 “Förolach gallery” ...... 7 2.2.1.1 Location and construction ...... 7 2.2.1.2 Geological situation ...... 8 2.2.1.3 Discharge and water quality ...... 9 2.2.2 “Gallery system Mühlau” ...... 10 2.2.2.1 Location and construction ...... 11 2.2.2.2 Geological situation ...... 12 2.2.2.3 Discharge and water quality ...... 14 2.2.2.4 Water supply and energy generation ...... 15 2.2.3 “Drinking water gallery Halltal” ...... 16 2.2.3.1 Location and construction ...... 16 2.2.3.2 Geological situation ...... 17 2.2.3.3 Discharge and water quality ...... 19 2.2.3.4 Water supply and energy generation ...... 20 2.3 Hydroelectric power plants ...... 20 2.4 Conclusions ...... 23 3 Case study Banda Aceh ...... 25 3.1 Physical Geography of the study area ...... 25 3.1.1 Location ...... 25 3.1.2 Population ...... 26 3.1.3 Physiography ...... 27 3.1.4 Climate ...... 28 3.1.5 Vegetation ...... 29 3.1.6 Land use ...... 30 3.1.7 Pedology ...... 31 3.2 Geology ...... 32 3.2.1 General setting ...... 32 3.2.1.1 Sumatra ...... 32 3.2.1.2 The Banda Aceh Quadrangle ...... 35 3.2.2 Lithology and geological evolution ...... 38 3.2.2.1 Late Jurassic to Early Cretaceous ...... 38 3.2.2.1.1 Woyla Group ...... 38 3.2.2.2 Late Cretaceous ...... 42 3.2.2.3 Tertiary...... 42 3.2.2.3.1 Meureudu Group ...... 42 3.2.2.3.2 Hulumasen Group ...... 43 3.2.2.3.3 Late-Tertiary volcanics and intrusives ...... 44

VI 3.2.2.3.4 Tiro Group ...... 45 3.2.2.4 Quaternary ...... 45 3.2.3 Structure and neotectonics ...... 46 4 Basic data and methodology ...... 51 4.1 Basic data ...... 51 4.2 Generation and application of digital data in ESRI® ArcGIS® ...... 52 4.2.1 Classification of hydrostratigraphical units ...... 53 4.3 Digital elevation model ...... 53 4.4 Lineament mapping ...... 54 4.4.1 Mapping procedure ...... 54 4.4.2 Segmentation of lineaments ...... 55 4.4.3 Analysis of lineament distribution ...... 57 4.5 Detection of springs via remote sensing ...... 57 4.6 Detection of submarine discharge using thermal imagery ...... 58 4.7 Calculation of long-term effective groundwater recharge rate ...... 60 5 Hydrogeology of a potential target area for a karst water gallery ...... 61 5.1 Hydrostratigraphical units...... 61 5.1.1 Hydrostratigraphical unit 1 ...... 61 5.1.2 Hydrostratigraphical unit 2 ...... 62 5.1.3 Hydrostratigraphical unit 3 and 4 ...... 63 5.1.4 Hydrostratigraphical unit 5 ...... 64 5.2 Springs and karst levels ...... 64 5.2.1 Spring locations ...... 64 5.2.2 Discharge and water quality ...... 67 5.2.2.1 Discharge characteristics of spring ID 1 (spring of Krueng Raba)...... 69 5.2.3 Karst levels ...... 70 5.3 Submarine discharge ...... 73 5.4 Lineaments ...... 75 5.4.1 Analysis of lineament distribution ...... 76 5.4.1.1 All lineaments...... 77 5.4.1.2 Lineaments in Reef Member of the Raba Limestone Formation (g29) ...... 79 5.4.1.3 Lineament intersections ...... 81 5.5 Closer look at the structural geology of the Reef Member of the Raba Limestone Formation (g29) ...... 83 5.5.1 Published interpretation ...... 84 5.5.2 New interpretation ...... 84 5.5.2.1 Interpretation of satellite imagery ...... 84 5.5.2.2 Hypothetic structural model ...... 84 5.6 Combined hydrogeological model ...... 86 6 Discussion ...... 91 7 Summary ...... 93 8 Outlook and further investigations ...... 97 9 References ...... 99 9.1 Literature ...... 99 9.2 Online sources ...... 103 10 Appendix ...... 105

VII List of Figures

Figure 2-1: General map of Austria showing the locations of the three karst water galleries described as examples (map modified after SCHUBERT 2000) ...... 7 Figure 2-2: Simplified geological top view section of “Förolach gallery“ showing geological units and major faults (modified after RAMSPACHER, RIEPLER et al. 1991) ...... 8 Figure 2-3: Simplified geological cross section of the “Förolach gallery“ (modified after RAMSPACHER, RIEPLER et al. 1991) ...... 9 Figure 2-4: Construction principle of the “gallery system Mühlau” and the connected hydroelectric power plant; distance from surge chamber to power plant is truncated (modified after STADTWERKE INNSBRUCK 1954) ...... 12 Figure 2-5: Geological cross section of the “Rum gallery“ which is part of the “gallery system Mühlau” (modified after SCHUBERT 2000 and FLEISCHHACKER, HEISSEL et al. 1996) ...... 13 Figure 2-6: Water inflow into “Rum gallery” from Alpine Muschelkalk in an uncased section at 260 m from interconnection with collector gallery; water flows on the gallery floor below the walkway into the viewers direction (photograph taken on October 23rd, 2008) ...... 14 Figure 2-7: Construction principle of the “drinking water gallery Halltal“; lengths of uncased gallery sections and distance between main gallery and hydroelectric turbine are truncated (schematic image after ground plan shown during the visit of the gallery) ...... 17 Figure 2-8: Simplified geological cross section of the “drinking water gallery Halltal” (modified after Dr. Gert Gasser GmbH, original image by courtesy of Hall AG) ...... 18 Figure 2-9: Water inflows into the right side gallery of the “drinking water water gallery Halltal”; water flows on the gallery floor into the viewers direction (photograph taken on October 21st, 2008)...... 18 Figure 2-10: Scheme of combined water exploitation and energy generation (references: top left: photograph taken on October 21st, 2008; top right: photograph taken on October 23rd, 2008; bottom left: modified after ENERGIE SCHWEIZ 2003; bottom right: taken from RITZ-ATRO GMBH) ...... 21 Figure 2-11: Different types of pressure pipes; 1: coated sheet steel type “gallery system Mühlau” to hydroelectric power plant under construction, view direction is to the south (modified after STADTWERKE INNSBRUCK 1954); 2: modern coated sheet steel type inside “drinking water gallery Halltal”, view direction is to the southwest (also notice the sampling outlet near the bend of the pipe and concrete blooming on the roof ridge) (photograph taken on October 21st, 2008); 3 & 4: wood type as used near Yogyakarta (after BLAß, FELLMOSER 2006) ...... 22 Figure 2-12: Hydroelectric turbines; 1: one of two turbines of the hydroelectric power plant in Mühlau near Innsbruck, connected to the “gallery system Mühlau”, runner diameter ~ 1,500 mm (photograph taken on October 23rd, 2008); 2: small hydroelectric turbine at the gallery mouth of the “drinking water gallery Halltal”, runner diameter ~ 600 mm (photograph taken on October 21st, 2008) ...... 23 Figure 3-1: General map of the northwestern Aceh Province comprising the districts Aceh Besar, Aceh Jaya, Pidie, and the provincial capital Banda Aceh (locations derived from JANTOP TNI 1978) ...... 26 Figure 3-2: Annual precipitation in the whole Aceh Province; climate diagrams show annual precipitation and potential evapotranspiration (ETpot) from forest cover (data for Lamno and Meulaboh taken from BINNIE &PARTNERS 1986b, data for Banda Aceh taken from centennial series (BINNIE &PARTNERS 1986b) and precipitation rates from 2000 – 2005 measured at Blang Bintang Airport; image of precipitation distribution modified after IWACO 1993) ...... 29 Figure 3-3: General structural setting of Sumatra and the adjacent subduction zone; top view: red arrows show moving directions of the obliquely subducted Indian Ocean Plate together with mean movement rates; cross section: the two symbols (cross and dot) on the sides of the Sumatran Fault System indicate dextral strike-slip movement at the fault; dextral strike-slip movement also occurs at the Mentawai fault (modified after BARBER, CROW et al. 2005; subduction rates and directions derived from SIEH, NATAWIDJAJA 2000) ...... 34

VIII Figure 3-4: Geological map of the Banda Aceh Quadrangle (geological formations and faults were digitized from BENNET, BRIDGE et al. 1981) (for larger image see Appendix 8) ...... 36 Figure 3-5: Geological map only focused on the study area (geological formations and faults were digitized from BENNET, BRIDGE et al. 1981) ...... 39 Figure 3-6: Geological cross section A-B; for location see figure 3-4 or figure 3-5 (modified after BENNET, BRIDGE et al. 1981); cross section C-D and E-F will be described later (also see Appendix 13 and figure 5-16, respectively) ...... 40 Figure 3-7: Schematic interpretation of the structural pattern at a dextral strike-slip fault zone; A: simplified movement at a strike-slip fault; B: schematic interpretation of the overall structural pattern at a dextral strike-slip fault zone; C: combination of A and B (modified after PARK 1989) ...... 48 Figure 4-1: Lineaments (red lines) on a false-colored satellite image of the Banda Aceh Quadrangle (Landsat TM™ scene 08/15/2008, Path 131, Row 56; RGB-channels 7(R) 4(G) 1(B)) (image provided by Dr. Uwe Schäffer (BGR)) (for larger image see Appendix 7) ...... 55 Figure 4-2: Example of the segmentation of bended and angled lineaments into straight features with distinct orientations (manually done using ESRI® ArcMap®) ...... 56 Figure 4-3: Lineament mapping results for the study area (segmented lineaments) ...... 56 Figure 4-4: Flight-strips along the west coast where thermal images were taken ...... 59 Figure 4-5: Example of a thermal image taken on the flight-strips along the west coast (see figure 4-4); scale on the right shows the min. and max. temperature recorded in the image section; spot means temperature in the reticle; temperatures are only approximated due to no reference temperature measured on the ground but the general trend can be distinguished ...... 59 Figure 5-1: Hydrostratigraphical units in the study area; black labels mark geological formations ...... 63 Figure 5-2: Spring locations in the study area; black labels mark geological formations ...... 65 Figure 5-3: Spring locations in the area around the Reef Member of the Raba Limestone Formation (g29); black labels mark geological formations, white labels show spring ID’s ..... 67 Figure 5-4: Discharge characteristic of spring ID 1 (spring of Krueng Raba) after two precipitation events measured by the rise of the water level above the ground of the dammed reservoir; dots represent hourly measurements (modified after original image provided by Jens Böhme (BGR)) ...... 69 Figure 5-5: Elevation distribution of all springs in Reef Member of Raba Limestone Formation (g29); number of bins 160, bin size 7 m ...... 71 Figure 5-6: Elevation distribution of springs in Reef Member of Raba Limestone Formation (g29) with possible karst levels, focused on elevations from 0 to 350 m; dashed ellipse marks uncertain single spring; number of bins 160, bin size 7 m, x-axis truncated at 350 m ...... 72 Figure 5-7: Thermal image, example 1; circle marks a point inflow of groundwater into the Indian Ocean; section width 830 m, section height 625 m ...... 74 Figure 5-8: Thermal image, example 2; ellipses mark extensive plume-like inflows of groundwater into the Indian Ocean; section width 830 m, section height 625 m ...... 75 Figure 5-9: Lineaments on hydrostratigraphical units; towns, rivers, and labels are not shown for a clear view on the lineaments ...... 76 Figure 5-10: Length distribution of all lineaments; histogram class width: 738 m = two times shortest lineament ...... 78 Figure 5-11: Orientation of all lineaments; class width: 10 °...... 79 Figure 5-12: Lineament length distribution in Reef Member of Raba Limestone Formation (g29); histogram class width: 763 m = two times shortest lineament ...... 80 Figure 5-13: Orientation of lineaments in Reef Member of Raba Limestone Formation (g29); class width: 10 ° ...... 80 Figure 5-14: Lineaments and lineament intersections; purple circles show manually distinguished intersection accumulations ...... 81 Figure 5-15: Lineaments and lineament intersections overlain by a simple automated density statistics of the lineament intersections; conducted with Density tool of Spatial Analyst in ESRI® ArcGIS®, search radius 1738 m, output cell size 369 m; densities were calculated in the overlying square section ...... 83

IX Figure 5-16: Simplified geological cross section E-F; elevation is two times exaggerated ... 86 Figure 5-17: Lineaments, lineament intersections, and spring locations highlighting the structure-controlled drainage pattern ...... 87 Figure 5-18: Simple hydrogeological discharge model showing preferential groundwater flow paths especially in the key target area of the eastern ridge; long key lineament sub- orthogonal to the SFS is marked pink, long key lineaments sub-parallel to the SFS are marked green; catchment area (yellow dotted line) is roughly estimated for the junction point of pink marked lineament with first green marked lineament ...... 88

X List of Tables

Table 2-1: Karst water galleries encountered during the literature research (for further details see Appendix 1) ...... 5 Table 3-1: Geological formations in the study area (for more details see Appendix 2) ...... 37 Table 4-1: Map sheets of the Topographical Map (1:50,000) (JANTOP TNI 1978) included in the study area ...... 51 Table 5-1: Hydrostratigraphical units ...... 62 Table 5-2: GPS measured springs with discharge rates and chemical water analysis (for further details see Appendix 4) ...... 68 Table 5-3: Karst levels and according spring ID’s ...... 72

XI List of Appendices

Appendix 1: Karst water galleries encountered during the literature research (detailed table) ...... 106 Appendix 2: Geological formations in the study area (detailed table) ...... 107 Appendix 3: All springs in the study area (continued on the following two pages) ...... 108 Appendix 4: Springs around Reef Member of Raba Limestone Formation (g29) ...... 111 Appendix 5: Typical cockpit karst landforms near the town Lho’nga, especially behind the cement factory in the center of the figure (collage of photographs derived from Dr. Dieter Plöthner (BGR)) ...... 112 Appendix 6: Spring ID 1 (spring of Krueng Raba); view from northwest (collage of photographs derived from Dr. Dieter Plöthner (BGR)) ...... 113 Appendix 7: Lineaments (red lines) on a false-colored satellite image of the Banda Aceh Quadrangle (Landsat TM™ scene 08/15/2008, Path 131, Row 56; RGB-channels 7(R) 4(G) 1(B)) (image provided by Dr. Uwe Schäffer (BGR)) ...... 114 Appendix 8: Geological map of the Banda Aceh Quadrangle (1:250,000) (geological formations and faults were digitized from BENNET, BRIDGE et al. 1981) ...... 115 Appendix 9: Land use / land cover map of Banda Aceh and region (SCHMITZ,LOHMANN et al. 2007) ...... 116 Appendix 10: Geologic Map of the Bandaaceh Quadrangle, Sumatra (1:250,000) (BENNET, BRIDGE et al. 1981) (in this thesis called Geological Map (1:250,000)) ...... 117 Appendix 11: Hydrogeological Map of Indonesia (1:250,000), sheet 0421 Banda Aceh (Sumatera) (SOETRISNO 1993) (in this thesis called Hydrogeological Map (1:250,000)) ..... 118 Appendix 12: Hydrogeological Map of Indonesia (1:1,000,000), sheet i Dan Sebagian (part of) II (SETIADI 2004) (in this thesis called Hydrogeological Map (1:1,000,000)) ...... 119 Appendix 13: Cross section C-D ...... 120

XII List of Abbreviations

2-D two-dimensional 3-D three-dimensional a annum, year agl above ground level asl above sea level BGR Federal Institute for Geosciences and Natural Resources, Bundesanstalt für Geowissenschaften und Rohstoffe BGS British Geological Survey d day DEM digital elevation model °d H degrees German hardness (water hardness) DMR former Directorate of Mineral Resources E. coli Escherichia coli EC electrical conductivity ET evapotranspiration G. Gunung, mountain GIS Geographic Information System GPS Global Positioning System GTZ German Development Cooperation Agency (Deutsche Gesellschaft für Technische Zusammenarbeit mbH) ha hectar ID identification IGS former Institute of Geological Sciences and Overseas Development Administration (today part of BGS) IKB Innsbrucker Kommunalbetriebe (public utility of Innsbruck) IT information technology Kr. Krueng, river kW kilowatt kWh kilowatt hour Landsat TM™ Landsat Thematic Mapper™ l liter Ma million years m meter min minute min. minimum

XIII MANGEONAD Management of Georisks in Nanggroe Aceh Darussalam max. maximum NASA National Aeronautics and Space Administration no. number NSP North Sumatra Project (geological survey by former DMR and BGS from 1975 to 1980) pot potential RGB color scheme (red / green / blue) S siemens s second SDC Swiss Agency for Development and Cooperation SFS Sumatran Fault System SFZ Sumatran Fault Zone SRK Swiss Red Cross (Schweizerisches Rotes Kreuz) SRTM Shuttle Radar Topography Mission THW German Federal Agency for Technical Relief (Technisches Hilfswerk) UNICEF United Nations International Children’s Emergency Fund USAID United States Agency for International Development UTC Coordinated Universal Time UTM Universal Transverse Mercator (coordinate system) (system used in this thesis: UTM-zone 46N, WGS-84) WGS-84 World Geodetic System 1984 .xz-file file format including distance and elevation values ° degree ® registered trademark ™ trademark

XIV Chapter 1 Introduction

1 Introduction

1.1 Background

On December 26th, 2004, at 0:58 UTC (7:58 AM local time) the province of Nanggroe Aceh Darussalam (in the following called Aceh Province) was hit by one of the largest and deadliest tsunamis recorded in human history. The tsunami was set off by up to 5 m vertical seafloor displacement caused by a submarine earthquake 100 km to the east of the Sunda Trench. The so called Sumatra-Andaman earthquake had a magnitude of 9.1 to 9.3 on the

Richter scale (MCCLOSKEY, ANTONIOLI et al. 2007; SIEH, NATAWIDJAJA 2000). Three main waves up to 30 m high approached the coast and runups reached up to 50 m asl, at some places up to 6 km inland, inundating huge areas of urbanized and cultivated land (PARIS,

LAVIGNE et al. 2007). A second earthquake, the Simeulue-Nias earthquake, followed on March 28th, 2005, with a lower magnitude of 8.7 on the Richter scale, still effectual to release another tsunami causing again major damage especially to the islands Simeulue and Nias located 100 km off the west coast of Sumatra (MCCLOSKEY, ANTONIOLI et al. 2007; JAMA 2006). Besides many other countries that have a shoreline to the Indian Ocean, Indonesia was most affected by the tsunamis. More than 120,000 people lost their lives in the Aceh Province, about 30,000 died in the provincial capital Banda Aceh and 40,000 in Meulaboh on the west coast, respectively. More than 110,000 people are still missing. Nearly 80 % of the private houses, basic infrastructure and public facilities were destroyed (PLOETHNER, SIEMON 2005; online source 07). Large amounts of soil were eroded or covered by up to 50 cm thick layers of tsunami sediments (MONECKE, FINGER et al. 2008).

It is assumed that supply with clean water was a problem throughout the Aceh Province in the past. As an example, in 1985 only 30 % of the inhabitants of the capital Banda Aceh had access to clean water, in 2002 this figure had increased to 52 % (ACEH 2007; KEITEL 1985). Nevertheless, this situation is supposed to have dramatically worsened after the tsunami, especially in the coastal regions. The inhabitants of towns on the coasts of the Aceh Province captured their drinking water and domestic water mainly from dug wells. Due to the tsunami many of the dug wells became unusable because salt water intruded into the uppermost aquifers near the coast. Furthermore, most of the wells were extremely polluted or were even totally destroyed

(SIEMON, PLOETHNER et al. 2005).

Together with many international organizations like German Development Cooperation Agency (GTZ), Swiss Agency for Development and Cooperation (SDC), German Federal

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 1 Chapter 1 Introduction

Agency for Technical Relief (THW), United Nations International Children’s Emergency Fund (UNICEF) or United States Agency for International Development (USAID), to name only a few, the Federal Institute for Geosciences and Natural Resources (BGR) supported the local authorities after the tsunami. This proceeded within the framework of two projects. HELP Aceh (Helicopter-Borne Geophysical Investigation in the Province Nanggroe Aceh Darussalam) was a BGR project during which geophysical data were recorded by aerial surveys on flight-strips along the west coast from Calang to Meulaboh, in the Banda Aceh Embayment and alongside the Krueng Aceh valley, and on the east coast around Sigli. It was mostly conducted using electromagnetics measuring the electrical conductivity in the ground. Later on maps were produced to show regions where saltwater intruded the uppermost aquifers (SIEMON, PLOETHNER et al. 2005). MANGEONAD (Management of Georisks in Nanggroe Aceh Darussalam) is the other still ongoing project between the German and Indonesian governments that is dedicated to restore the public life and to secure future health and wealth of the inhabitants who suffered from the consequences of the catastrophe. The main aim of the project is to assist the local counterpart facilities in their efforts to rebuild a sustainable community infrastructure by providing geophysical, hydrogeological, geological, and topographical data that can serve as a basis for future planning. Obtaining a sustainably operating freshwater supply is a major task in this respect (PLOETHNER, SIEMON 2005). The MANGEONAD project will end by July 2009. As a result of the project surveys BGR gave recommendations for siting well drillings to abstract groundwater from deeper aquifers of multi-layer aquifer systems that were not polluted.

Another possibility for drinking water supply than dug wells or bore wells are water treatment plants, e.g. the river water treatment plant Lambaro which supplies parts of Banda Aceh. This plant was rehabilitated with support, for instance, of SDC after being run down e.g. due to insufficient maintenance for years. Raw water from Krueng Aceh is cleaned here using, for instance, rapid sand filters. The current capacity of the water treatment plant ranges around 430 l/s. At the moment this amount is just about able to cover the demand of Banda Aceh and its near surroundings. But the water demand of Banda Aceh will presumably increase in the future because of rehabilitation of the district and because of future economic growth due to high investments after the catastrophe. There is also a general trend for people to live and work in the city. Hence, it is believed that the water treatment plant will not be able to cover the increasing demand anymore in the near future. Furthermore, the raw water treatment causes high expenditures on energy and chemicals and the vulnerability of the river is high due to the large number of settlements and

2 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 1 Introduction agricultural activities as well as intensive mining of river gravel and sand alongside the river course. In addition to that, the plant will also become uneconomical presumably in less than

20 years (KELLER, NICOLE 2006; online source 10). These facts clearly demonstrate the need for other sustainable supply solutions that could provide a major part of the required freshwater, in particular for the capital Banda Aceh.

Besides ideas to capture drinking water from other rivers than Krueng Aceh, especially from smaller rivers emerging from karstified limestone areas, or by well constructions in limestone areas with high groundwater potential (KELLER, NICOLE 2006; PLOETHNER, SIEMON 2005), a very interesting solution could be the construction of a karst water gallery or karst tunnel. Examples from Austria, Switzerland, and Germany show that this method of capturing karst water directly in the rock mass can result in high capacities and very good water quality delivered by a system that needs almost no maintenance and is able to operate for a very long period of time at low running costs. By this, even energy can be generated at low costs.

1.2 Aims of this thesis Trying to capture water from a karstified rock may at first sound like a “hit or miss” attempt since karst aquifers seem unpredictable with no constant flow conditions. But in fact, there are criteria that can be chosen to depict preferential water flow paths in karst areas

(LATTMAN, PARIZEK 1964). The aim of this thesis was to show if a possible target area for a karst water gallery could be found in the mountain range to the southwest of Banda Aceh. The motivation was that this kind of gallery could be a future option to support the drinking water supply of Banda Aceh or other towns in the investigated area on a sustainable level. To collect examples of existing karst water galleries and to understand their function an intensive literature was carried out as first elemental part of this thesis. Within this scope a literature database was compiled to allow faster access to the most interesting publications for further investigations in the future. Concerning the function of a karst water gallery special attention was turned on geological, hydrogeological, and structural conditions. Moreover, factors like possible water yield, water quality, maintenance, costs, and possible energy generation by using the difference in elevation were attended to (see chapter 2). In a second step the study area in West-Sumatra located to the southwest of Banda Aceh was surveyed using the available geological and non-geological data. It was attempted to apply the knowledge achieved by the literature research onto the study area and to find a location where the conditions seem suitable for the construction of a karst water gallery

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 3 Chapter 1 Introduction concerning geological, hydrogeological, structural, topographical, and further criteria that will be discussed in chapter 3 and the following.

The enclosed CD-ROM contains all figures used in this thesis saved as high-resolution files as well as all text chapters saved as individual pdf-documents and photographs taken during the visit of two karst water galleries in Austria (by courtesy of the respective public utilities).

4 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 2 Karst water galleries

2 Karst water galleries

As the first elemental part of this thesis an intensive literature research was carried out to find existing examples of karst water galleries. Since there was no database available concerning this topic the aim was to compile all data that could be found and to establish a literature database. Soon it became obvious that available publications about karst water galleries were very few. Web research provided some more examples of karst water galleries and further information was obtained by personal contacts to staff members of public utilities, geological surveys, consultants, and university members all around the world. High expenditure of time and work was invested in this task and the result is a database that comprises the information that could be found within the scope of this thesis. Although more data exist about karst water galleries especially regarding construction details not all of them could be made available, for instance due to legal restrictions.

Table 2-1: Karst water galleries encountered during the literature research (for further details see Appendix 1)

Gallery name / project Country Length [m] Discharge [l/s]

"Förolach gallery" (Förolacher ~ 700 (50 % from two major Austria 3,228 Stollen) faults) "gallery system Mühlau" 1,663 (side galleries 1,159, min. 500, max. > 2,000, mean Austria (Stollensystem Mühlau) collector gallery 564) 1,370 "drinking water gallery Halltal" 1,130 (main gallery 950, right (Trinkwasserstollen Halltal; Austria side gallery 100, left side gallery min. 360, max. 660, mean 400 Margarethe-Stollen) 80) ~ 1,200 (Zeller-Berg-gallery 700, 3 galleries of the public utility min.120, max. 250, mean 200 Germany Schulhaus- + Norbertusheim- Zell (mostly through small faults) gallery ~ 500) Neubrunnen (spring capturing Germany 24 min. 49, max. 260, mean 107 by short gallery) Biel Vody (spring capturing by Czechoslovakia 100.5 mean ~ 90 gallery) Montenegro (former gallery in Mokrine karst region 1,200 min.~ 100, max. ~ 300 - 400 Yugoslavia)

Galerie des Moyats Switzerland 660 ~ 30 - 85

project Gua Bribin (not real karst > 1,000 even during "dry" water gallery but dammed karst Indonesia (Java) - season cave)

2.1 Definition and function

Karst water galleries are man-made tunnels in hard rock formations (mostly limestone) that capture water from the rock mass. They can extend from a few meters to some kilometers in length and their courses are often angled. In some cases there is only one main gallery in use, in others a whole system of galleries (e.g. fan-shaped with one collector

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 5 Chapter 2 Karst water galleries gallery) exists. In part they are newly-built for the purpose of drinking water supply, in part they were formerly used for mining or they are old drainage galleries that were used for drainage of other mining galleries. The old German mining term “Wasserlösestollen” can be traced back to the latter (FESTSCHRIFT 1989). It has to be pointed out that connection tunnels through karstified rock formations, e.g. for leading river courses from one valley into another, are not understood as karst water galleries in this thesis since they are mostly cased or built in the form of pressure pipes so that no groundwater inflow occurs or cannot be quantified.

Karst water galleries capture groundwater from major water pathways in mostly moderately karstified hard rock formations (RAMSPACHER, RIEPLER et al. 1991; STADTWERKE

INNSBRUCK 1954; SCHUBERT 2000). The major flow pathways in hard rock formations are fault zones, fractures, and fissures and it is tried to drain these pathways by a tunnel. The water intruding into the gallery is collected on the sometimes cased gallery floor or by pressure pipes and flows to the gallery mouth due to the slope and the water pressure. Near or outside the gallery mouth the water stream is in some cases either pumped directly into water reservoirs or it is directed into pressure pipes which lead the water under pressure to an adjacent hydroelectric power plant (see chapter 2.3). The following examples show that the main water inflow into karst water galleries occurs where large fault zones are penetrated. Inflow through fissures and corrosion holes is also present but not with discharge rates comparable to those of large fault zones (RAMSPACHER,

RIEPLER et al. 1991; STADTWERKE INNSBRUCK 1954).

2.2 Examples Some examples of karst water galleries exhibit useful geological, hydrogeological, and other technical information that can be taken into account when trying to understand their function (see Table 2-1). The most important examples found during the literature research are located in the Limestone Alps in Austria (see figure 2-1). Delivering the most data are the “Förolach gallery” (German: Förolacher Stollen) in Förolach, the “gallery system Mühlau” (German: Stollensystem Mühlau) near Innsbruck, and the “drinking water gallery Halltal” (German: Trinkwasserstollen Halltal) in Hall in Tirol. It is expected that there are more karst water galleries in use but were not found, e.g. due to the age of the galleries, or inaccessible data, e.g. at an engineering office or in archives under restriction. The three galleries mentioned above are described in more detail in the following. Especially the gallery systems “Mühlau” and “Halltal” have to be highlighted, since the author

6 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 2 Karst water galleries had the chance to visit these impressive constructions in the framework of this thesis in October 2008.

Figure 2-1: General map of Austria showing the locations of the three karst water galleries described as examples (map modified after SCHUBERT 2000)

2.2.1 “Förolach gallery” From 1981 to 1988 the Austrian research institution Joanneum Research accomplished a hydrogeological investigation program in the central Gailtal Alps. Within the scope of this program the “Förolach gallery” was also investigated. Besides the denoted references all information concerning this gallery was obtained from the hydrogeological survey report by

RAMSPACHER, RIEPLER et al. 1991.

2.2.1.1 Location and construction

The “Förolach gallery” is located near the village Förolach in Kärnten, Austria. It was built for the purpose of lead prospection and drainage of a mine east of it. This gallery has a total length of 3,228 m and was constructed in a north-northeastern direction (see figure 2-2) orthogonal to the strike of the Gailtal Alps which are part of the Southern Limestone Alps (online source 11). It shows a mean slope of about 10 ‰, the total elevation difference is around 30 m. The gallery was constructed roughly straight with little variations in direction and some side galleries only in the first section. Due to mining problems during too heavy water inrushes and at badly penetratable lithologies the driving direction had to be changed a

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 7 Chapter 2 Karst water galleries few times and at the end the gallery construction was totally stopped because of too hard mining conditions.

Figure 2-2: Simplified geological top view section of “Förolach gallery“ showing geological units and major faults (modified after RAMSPACHER, RIEPLER et al. 1991)

2.2.1.2 Geological situation The formations penetrated by the gallery are mainly composed of carbonate rocks. The moderately karstified Wetterstein-Dolomite and Wetterstein-Limestone (both of Mid-Triassic age) make up the major part of the encountered formations. In the first 1,200 m (see figure 2-3) from the gallery mouth and in the last section from 2,630 to 3,228 m argillaceous schists and marls are interbedded with the limestones. All formations were vertically and laterally displaced by tectonic activity and exhibit a dipping angle subvertically to the south- southwest. Associated faults show an approximate strike from west to east (see figure 2-3). The most intensive water inrushes into the gallery during the tunnel driving occurred at faults and RAMSPACHER, RIEPLER et al. 1991 found out that the most productive water inflows are still located where two main faults are penetrated (Zuchen- and KAK-fault) (see

8 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 2 Karst water galleries figure 2-3). The main discharge rates occur in the rear of the gallery between 1,700 and 2,500 m where alternating sequences of Wetterstein-Dolomite and Wetterstein- Limestone prevail. About half of the total discharge of the gallery intrudes through the two main faults, the rest mainly through fissures and many corrosion holes which are also believed to be related to smaller faults. The argillaceous schists and marls from 700 to 1,200 m and 2,630 to 3,228 m are supposed to act as aquitards retaining the groundwater to the north-northeast. This explains the main water inrushes in the rear sections of the gallery and also the very heavy inflow after penetrating the schists and marls near the end of the gallery (see figure 2-3).

Figure 2-3: Simplified geological cross section of the “Förolach gallery“ (modified after RAMSPACHER, RIEPLER et al. 1991)

2.2.1.3 Discharge and water quality

Total discharge can be summed up to 637 l/s but it has to be noted that the measurements by RAMSPACHER, RIEPLER et al. 1991 were conducted during a phase of low flow so that somewhat higher rates can be assumed averaged over a longer period of time to about 700 l/s. Maximum discharge occurs during the summer when the delayed effect of snow melting appears. Mean precipitation rates are about 1,400 mm/a. Mean evapotranspiration (ET) rates were only estimated to be about 500 mm/a. An exact orographic catchment could not exactly be figured out due to water by some creeks that adds

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 9 Chapter 2 Karst water galleries up to the infiltrated precipitation. Nevertheless, a precipitation-discharge analysis was conducted by RAMSPACHER, RIEPLER et al. 1991 leading to the assumption that around 47 % of the water infiltrated in a 50 km² catchment area discharges over the “Förolach gallery”. The rest of 53 % infiltrates into the nearby Gailtal valley. Hence, a catchment area of around 23.5 km² (47 % of 50 km²) can be assumed for the “Förolach gallery” if the discharge conditions are supposed to be identical in the whole area. Concerning these data the long- term effective groundwater recharge rate can be calculated to be around 29,8 l/(s·km²) which equals 940 mm/a. At mean precipitation rates of 1400 mm/a the uncertain ET rates must in fact be lower than the estimated 500 mm/a or the precipitation rates were measured too low. Otherwise the 940 mm/a long-term effective groundwater recharge rate are not explainable (for calculation details see chapter 4.7). The temperature of the inflowing water shows almost no seasonal changes and decreases towards the rear of the gallery from 9 °C to 5.5 °C. The lower water temperature towards the rear is explained by higher rock coverage, and hence, longer retention times in the rock mass. 18O-measurements also allude to longer retention times in sections with higher rock coverage which reach up to five years in the schists and marls but also occur in the less karstified parts of the Wetterstein-Dolomite. Near the gallery mouth shorter retention times of about two years were calculated caused by lower rock coverage. The shortest water passage was measured by tracer tests around the two large faults where tracers could be detected after one month. Furthermore, measurements on electrical conductivity (EC) showed values in the range of 200 - 400 μS/cm corrected to 20 °C. After HÖLTING 1996 one can calculate 223 - 446 μS/cm corrected to 25 °C. Lower EC values are correlated to lower mineralization and occur where water intrudes through large faults or where higher karstification especially of the Wetterstein-Dolomite prevails. Lower mineralization is assumed to be aroused by shorter retention times implicating lower dissolution rates. The water from the “Förolach gallery” is in part used for drinking water supply. A small hydroelectric power plant is also installed (also see chapter 2.3) but exact data concerning power production as well as figures on supplied inhabitants could not be found.

2.2.2 “Gallery system Mühlau”

Details concerning this gallery system that are not denoted in the text were either obtained from Mr. Eichelbacher (IKB (Innsbrucker Kommunalbetriebe; public utility of Innsbruck)) who guided the author in October 2008 or are based on own notices made during the short visit. Photographs made during the visit can be found on the enclosed CD-ROM.

10 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 2 Karst water galleries

2.2.2.1 Location and construction The Tyrolean capital Innsbruck and its surroundings could always rely on an adequate supply with drinking water in the past centuries due to several large springs in the adjacent Nordkette which is the southern chain of the Karwendel, a large carbonate massif in the Northern Limestone Alps comprising mostly Triassic rock formations. Especially the springs in the so called “Mühlauer Graben” exhibited high water yields and were used as the main drinking water source until the early 20th century (SCHUBERT 2000; online source 12; online source 18). Nevertheless, during the first decades of the 20th century Innsbruck was subject to a huge population growth because the city developed to a major traffic junction and tourism arose. The number of inhabitants soon approached 100,000. Therefore, difficulties with water supply emerged and plans about the construction of a new and larger system of karst water galleries including some parts of still existing enlarged spring tappings were made (STADTWERKE INNSBRUCK 1954; AMPFERER 1949). From 1942 to 1953 the “gallery system Mühlau” (today operated by the municipal utility IKB) was built featuring one collector gallery and three side galleries (“Wurmbach gallery”, “Klammbach gallery”, and “Rum gallery” (German: “Wurmbachstollen”, “Klammbachstollen”, and “Rumerstollen”)) with a total length of 1,663 m (see figure 2-4). It was placed about 100 m above the actual spring locations in the “Mühlauer Graben” at an altitude of 1,140 m. The first section of the collector gallery and the longest side gallery (“Rum gallery”) extend almost orthogonal to the strike of the Nordkette and the whole Karwendel massif which exhibits a general west-east trend (STADTWERKE INNSBRUCK 1954; RAMSPACHER, ZOJER et al. 1992). Concrete casings are constructed where the galleries cut formations that brought up mining problems due to rockfall, for instance. Only the stable sections and those where the most water intrudes are left uncased. Nevertheless, a drainage system is installed behind the casings leading the water through smaller pipes into the collector gallery. Mining conditions in the relatively small gallery were very rough due to the high amounts of cold water intruding and the nonexistence of hi-tech mining machinery in the 1950’s (STADTWERKE

INNSBRUCK 1954).

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 11 Chapter 2 Karst water galleries

Figure 2-4: Construction principle of the “gallery system Mühlau” and the connected hydroelectric power plant; distance from surge chamber to power plant is truncated (modified after STADTWERKE INNSBRUCK 1954)

2.2.2.2 Geological situation

The Karwendel is a huge carbonate massif extending 40 km from west to east and 20 km from north to south. It is mainly composed of Wetterstein-Limestone formations which can exceed thicknesses of 1,500 m in the Nordkette and were intensively folded during the orogenesis of the Alps building a complex nappe structure (RAMSPACHER, ZOJER et al. 1992) (see figure 2-5). These limestones exhibit intensive fracturing as a result of the strong tectonic deformation. Karstification is only slightly to moderately developed which is assumed to be caused by the chemical composition of the partly dolomitizated limestones and by the steep dip of the bedding planes (STADTWERKE INNSBRUCK 1954). Sparse vegetation and little soil development in most areas of the Karwendel massif, and hence, lower partial pressure of

CO2 also lead to lower carbonate dissolution rates (for further explanation see chapter 3.1.7). The galleries are placed where a large normal fault dipping to the north separates the Nordkette into a northern and southern part. The northern part is built up by the Inntal Nappe which unconformably overlies the southern part built up by the Thaur Unit (see figure 2-5). The springs of the “Mühlauer Graben” are also related to this fault. The bottom formation of the Inntal Nappe (Alpine Bunter (alternation of sandstones and shales)) and the uppermost formations of the Thaur Unit (Hauptdolomit (compact dolomite) and Raibl Formation (alternation of shales, marls, and limestones)) act as aquitards retaining the water in the limestones of the Inntal Nappe (SCHUBERT 2000; STADTWERKE INNSBRUCK 1954). Figure 2-5 shows the geological situation at the “Rum gallery” which delivers the highest discharge ranging around 70 % of the total discharge of the system (SCHUBERT 2000). The operational principle is the same in all galleries. Main water inrushes occur where the Alpine Muschelkalk (mostly dark and thin bedded limestones) is penetrated which underlies the

12 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 2 Karst water galleries highly water-bearing Wetterstein-Limestone. The water intrudes here from all sides into the gallery (see figure 2-6), even from the floor.

Figure 2-5: Geological cross section of the “Rum gallery“ which is part of the “gallery system Mühlau” (modified after SCHUBERT 2000 and FLEISCHHACKER, HEISSEL et al. 1996)

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 13 Chapter 2 Karst water galleries

Figure 2-6: Water inflow into “Rum gallery” from Alpine Muschelkalk in an uncased section at 260 m from interconnection with collector gallery; water flows on the gallery floor below the walkway into the viewers direction (photograph taken on October 23rd, 2008)

2.2.2.3 Discharge and water quality The total discharge of the “gallery system Mühlau” ranges from minimum values of 500 l/s during the winter to maximum values exceeding 2,000 l/s during the summer caused by the delayed effect of snow melting. During the visit of the galleries in October 2008 the discharge rate was 1,550 l/s which is slightly higher than the long-term mean value of 1,370 l/s

(SCHUBERT 2000; RAMSPACHER, ZOJER et al. 1992) Mean precipitation rates are around

2,000 mm/a and ET rates are about 500 mm/a (SCHUBERT 2000). The catchment area is estimated to span over 30 – 36 km2 which is much larger than the southern flank of the adjacent part of the Nordkette and it is believed that large areas of the broad and nearly planar Karwendel massif to the north act as additional catchment area (RAMSPACHER, ZOJER et al. 1992). Assuming an average catchment area of 33 km² the long-term effective groundwater recharge rate (HÖLTING 1996) can be calculated to be around 41.5 l/(s·km²) which equals 1310 mm/a. These figures show that at ET rates of 500 mm/a in the catchment area, about 87.3 % of the remaining precipitation of 1500 mm/a infiltrate into the ground and

14 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 2 Karst water galleries are captured by the gallery. Only 12.7 % (190 mm/a) remain as surface runoff (for calculation details see chapter 4.7). The mean retention time of the water is estimated to be about 12 years calculated from

18O- and 3H-measurements (RAMSPACHER, ZOJER et al. 1992) and caused by slow groundwater passage through small fissures and fractures and missing of larger karst forms that would allow faster flow (SCHUBERT 2000). Mean water temperatures range around 4 - 5 °C in the “Rum gallery” and about 5 - 5.6 °C in the other galleries. Hardness values are relatively low ranging around 5 – 6 °dH in the “Rum gallery” and approximately 7 – 9 °dH in the other sections (STADTWERKE INNSBRUCK 1954). Accordingly, the measured EC is relatively low compared for example with values from the “Förolach gallery” (see chapter 2.2.1.3). Mean EC values from the “Rum gallery” are around 170 μS/cm (corrected to

25 °C) exhibiting slightly lower values during periods of higher discharge (RAMSPACHER,

ZOJER et al. 1992). Except one incident of higher turbidity in the past caused by a major precipitation event with water passing quickly through the Quaternary Hötting Breccia in the section with lower rock coverage (see figure 2-5) the mean turbidity of the gallery water is very low. Since the incident a turbidity analyzer is installed in the surge chamber to prevent the water supply network and the turbines of the installed hydroelectric power plant from possible high turbidity water. Overall, the water captured by this gallery system can be considered to be very suitable as drinking water having a very good chemical and physical quality (SCHUBERT 2000). Therefore, the water that flows out of the gallery on the gallery floor can be directly headed into pressure pipes that lead to the hydroelectric power plant, afterwards into freshwater reservoirs (26,400 m3 total storage capacity (STADTWERKE INNSBRUCK 1954)), and then into the water supply network.

2.2.2.4 Water supply and energy generation Due to the high discharge rates almost 85 % of the inhabitants of Innsbruck (total population approximately 120,000 in 2008) can be supplied with drinking water directly from the “gallery system Mühlau”. No water treatment is necessary except leading the water through a slurry tank in the surge chamber to remove the few suspended solids. The gallery system itself needs almost no maintenance except for the removal of concrete blooming and sinter precipitations which is conducted every few years. The drop height from the surge chamber to the hydroelectric power plant amounts to 445 m and the pipelines follow a steep slope down to the Inntal valley. The plant is constructed for discharge rates of 1,150 l/s and delivers a maximum power output of

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 15 Chapter 2 Karst water galleries

6,000 kW. Average power outputs are around 4,000 kW (STADTWERKE INNSBRUCK 1954) which sum up to about 34 million kWh/a (online source 14 ) (also see chapter 2.3).

2.2.3 “Drinking water gallery Halltal”

Details concerning this gallery system that are not denoted in the text were either obtained from Ing. Herwig Paulus (Hall AG, public utility of Hall in Tirol) who also guided the author in October 2008 or are based on own notices made during the short visit. Photographs made during the visit can be found on the enclosed CD-ROM.

2.2.3.1 Location and construction

The “drinking water gallery Halltal” (also called “Margarethe-Stollen”) is located about 8 km east of the “gallery system Mühlau” at an altitude of 1,000 m in the Halltal valley which divides the Nordkette mountain chain from the Bettelwurf massif. It is run by the Hall AG (a municipal utility supplying the city Hall in Tirol which lies about 5 km east of Innsbruck) and the adjacent community Absam. This modern construction was built between 1995 and 2002 and cost about 9.5 million Euros (online source 16). This time span included long periods of clarifying legal formalities. The actual gallery driving only took about three years using modern tunnel driving machinery including winter periods when the work had to be discontinued due to danger of avalanches at the gallery portal. At the end the gallery driving had to be totally stopped when a huge water-bearing fault zone was opened up by drilling and immensely high water pressure forced back the drilling rod. One almost straight main gallery and two side galleries build up the gallery system (see figure 2-7) all exhibiting an approximate cross section surface of 9 m2. The 950 m long main gallery is stabilized by shotcrete over almost the whole length and only the last section (approximately 100 m long) is left uncased. Two uncased side galleries of 100 m (right side gallery) and 80 m length (left side gallery) diverge from the main gallery at about 850 m measured from the gallery mouth. The main gallery is driven in a northeastern direction into the Bettelwurf massif quasi perpendicular to the general west-northwest to east-southeast strike of the mountains. Water is only captured in the uncased sections of the three galleries and is lead on the gallery floor to the merging point with the main gallery. There it is directed over an overflow edge where the few solids are removed by sedimentation. Afterwards, a pressure pipe leads the water through the main gallery to the gallery mouth.

16 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 2 Karst water galleries

Figure 2-7: Construction principle of the “drinking water gallery Halltal“; lengths of uncased gallery sections and distance between main gallery and hydroelectric turbine are truncated (schematic image after ground plan shown during the visit of the gallery)

2.2.3.2 Geological situation The simplified geological situation can be seen in figure 2-8. Mainly three formations are penetrated by the main gallery. Measured from the gallery mouth the first formation (Hauptdolomit) extends over 730 m, almost over the whole length of the main. These rocks are compact dolomites that show no larger fracturing or karstification phenomena and do not act as productive aquifers. The second formation from 730 to 760 m is called Kössen Layers and comprises an alternation of marls and limestones. To the northeast of the Kössen Layers from 760 to 950 m the unconformably attached Wetterstein-Limestone occurs which is separated to the latter formations by a large thrust fault dipping to the northeast. It has to be stated that according to HEISSEL 1978 the main parts of the uncased sections in the rear should at least in part penetrate the Alpine Muschelkalk which actually underlies the highly water-bearing Wetterstein-Limestone but this is not clearly expressed by the actual rock facies. The lighter colored and rather thicker bedded limestones here differ from the dark colored thin bedded Alpine Muschelkalk encountered in the “gallery system Mühlau”, for instance. Anyhow, the fault-related Kössing Layers act as aquitard and retain the water in the Wetterstein-Limestone. Being driven directly into this retained groundwater body the gallery receives the main water inflow through fractures and faults from all sides especially in the rear of the right side gallery (see figure 2-9).

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 17 Chapter 2 Karst water galleries

Figure 2-8: Simplified geological cross section of the “drinking water gallery Halltal” (modified after Dr. Gert Gasser GmbH, original image by courtesy of Hall AG)

Figure 2-9: Water inflows into the right side gallery of the “drinking water water gallery Halltal”; water flows on the gallery floor into the viewers direction (photograph taken on October 21st, 2008)

18 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 2 Karst water galleries

2.2.3.3 Discharge and water quality In October 2008, the mean discharge rate was about 400 l/s which equals the long-term mean discharge. Minimum rates of 360 l/s and maximum rates of up to 660 l/s can occur (online source 16). Discharge rates are measured separately in each of the three galleries and the biggest portion is contributed by the right side gallery. The captured water features a slightly alkaline pH, temperatures around 5 °C (5.3 °C on October 21st, 2008), and a mean hardness of 5 °dH which classifies it as soft water. The mean EC values range around 165 μS/cm (162 μS/cm on October 21st, 2008) and mean retention times in the rock mass are estimated to be 8 – 13 years (online source 16). Mean precipitation rates around

2,000 mm/a and mean ET rates of about 500 mm/a (SCHUBERT 2000) can be assumed to be the same as in the catchment area of the nearby “gallery system Mühlau” (see chapter 2.2.2.3). The actual size of the catchment area here is not known in detail but is supposed to be larger than 25 km2 extending to the north of the gallery and spanning over large parts of the Bettelwurf massif. Supposing an average catchment area of 25 km² the long-term effective groundwater recharge rate can be calculated to be around 16 l/(s·km²) which equals 505 mm/a. These figures show that at ET rates of 500 mm/a in the catchment area, only about 33.7 % of the remaining precipitation of 1,500 mm/a infiltrate into the ground and are captured by the gallery. The rest of 66.3 % (995 mm/a) remains as surface runoff (for calculation details see chapter 4.7). Thus, surface runoff here is much higher than in the catchment area of the “gallery system Mühlau” with only 10.5 % at otherwise similar climatic and geological conditions. Assuming that the size of the catchment area is correct, it is supposed that steep slopes at both sides of the penetrated mountain chain in the Bettelwurf massif cause higher amounts of surface runoff. In contrast to that, the catchment area of the “gallery system Mühlau” extends nearly planar to the north in the Karwendel massif with very few surface runoff especially during snow melting. Overall, it can be said that the water from the “drinking water gallery Halltal” approximately shows the same properties like the water from the “gallery system Mühlau”. Long retention times in the high rock coverage above the gallery (> 450 m) and flow passage through fractures and fissures of the only slightly karstified Wetterstein-Limestones lead to this high quality drinking water. The low amounts of dissolved solids indicated by the relatively low EC are interpreted as a result of lower dissolution rates maybe supported by the sparse vegetation and soil coverage in the catchment area (for further explanation see chapter 3.1.7) and the relatively low chemical solubility of the Wetterstein-Limestones.

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 19 Chapter 2 Karst water galleries

2.2.3.4 Water supply and energy generation The operating communities Hall in Tirol and Absam together have approximately 19,000 inhabitants (online source 19; online source 20). Their mean water demand is around 140 l/s (online source 16) which can be totally covered by the discharge of the gallery. Besides water supply, hydroelectric energy is generated using two small turbines. The first is installed directly at the gallery mouth only utilizing the water pressure in the pressure pipe that follows the slope of the gallery. A second turbine is installed in the valley near the town Hall in Tirol which utilizes the altitude difference of 400 m. The maximum power production is 150 kW and the average 850,000 kWh/a are enough to supply 210 households with electrical energy (online source 16). Nevertheless, only a part of the whole discharge is directed in pressure pipes down to the power plant in the valley. Excess water is lead into the Halltal creek near the gallery mouth. Regarding this excess water it is planned to connect further surrounding communities to the supply network in the future. Weekly maintenance is needed for the hydroelectric turbines but the gallery itself is believed to exceed operating times of some centuries without any maintenance. Anyhow, sinter and concrete blooming in the gallery are removed once a year.

2.3 Hydroelectric power plants The working principle of hydroelectric power plants is to generate electrical energy from water that exhibits potential and kinetic energy. In the case of karst water galleries the natural slope from the surge chamber to the plant can be used to pipe the water by gravity over long distances or to use its kinetic energy to run turbines. The amount of energy produced or the distance that can be covered depends on the altitude difference and the slope besides other technical parameters like friction losses in pipes and so on. Figure 2-10 shows an abstracted scheme of the components of a water capturing and energy generating system in a mountainous area. To calculate the approximate energy yield that would be generated by a hydroelectric power plant the stated empirical formula has proven to fit in most cases (ENERGIE SCHWEIZ 2003).

The first component of the system is the water capture operated by a water gallery or a spring tapping. After being captured the water has to be directed into pressure pipes which lead down to the hydroelectric power plant. These pressure pipes can be made of different materials like coated sheet steel as in the case of the “gallery system Mühlau” (STADTWERKE

INNSBRUCK 1954) and the “drinking water gallery Halltal” or they can be made of wood as near Yogyakarta within the scope of the Gunung Sewu project (BLAß, FELLMOSER 2006) (see figure 2-11). The latter is particularly interesting when thinking about low-cost alternatives

20 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 2 Karst water galleries and quickly available materials. Of course, pipe diameters have to match the anticipated discharge rates.

Figure 2-10: Scheme of combined water exploitation and energy generation (references: top left: photograph taken on October 21st, 2008; top right: photograph taken on October 23rd, 2008; bottom left: modified after ENERGIE SCHWEIZ 2003; bottom right: taken from RITZ-ATRO GMBH)

The next component is the hydroelectric power plant where the pressure pipes are connected to hydroelectric turbines. These are often impulse type turbines (e.g. Pelton turbines as in the case of the “gallery system Mühlau” (STADTWERKE INNSBRUCK 1954) and the “drinking water gallery Halltal”) (see figure 2-12) which show high efficiency gradients of up to 90 % and are suitable for a wide range of flow rates (online source 13). Certainly, the dimension of the turbine has to fit the occuring flow rates and the water has to be screened before getting into the turbines since suspended solids could damage the blades. Whereas turbines are generally applicable for greater drop heights of more than 50 m, hydrodynamic screws are an alternative for lower drop heights up to 10 m. Nevertheless, they are more

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 21 Chapter 2 Karst water galleries likely to be used within naturally running streams and can be operated without having to filter out solids (RITZ-ATRO GMBH). The generated electrical energy is fed in the power supply network. Excess energy from the high velocity water flow has to be diminished by an energy dissipater since the water reservoirs and distribution networks are not designed for very high water pressures. In Mühlau this is done by letting the water rush through a widening tube into a concrete funnel

(STADTWERKE INNSBRUCK 1954). This device is especially necessary when the turbines have to be maintained or show malfunctions. After reducing the energy of the water the low velocity flow is directed into reservoirs. Reservoirs are more than essential to support public water supply during periods of high demands and to be able to maintain the technical components of the system (turbines, pipes etc.) without having to reduce the delivered water amount for at least a short period of time. They should be dimensioned to fit the supply situation and the predictable maintenance scenarios. Finally, the water can be distributed to the consumers through the public water supply network.

Figure 2-11: Different types of pressure pipes; 1: coated sheet steel type “gallery system Mühlau” to hydroelectric power plant under construction, view direction is to the south (modified after STADTWERKE INNSBRUCK 1954); 2: modern coated sheet steel type inside “drinking water gallery Halltal”, view direction is to the southwest (also notice the sampling outlet near the bend of the pipe and concrete blooming on the roof ridge) (photograph taken on October 21st, 2008); 3 & 4: wood type as used near Yogyakarta (after BLAß, FELLMOSER 2006)

22 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 2 Karst water galleries

Figure 2-12: Hydroelectric turbines; 1: one of two turbines of the hydroelectric power plant in Mühlau near Innsbruck, connected to the “gallery system Mühlau”, runner diameter ~ 1,500 mm (photograph taken on October 23rd, 2008); 2: small hydroelectric turbine at the gallery mouth of the “drinking water gallery Halltal”, runner diameter ~ 600 mm (photograph taken on October 21st, 2008)

2.4 Conclusions Summarizing the results of the literature research on the topic of karst water galleries one can say that these constructions are appropriate to deliver huge amounts of drinking water and can serve as main sources for a sustainable water supply if the geological, hydrogeological, and technical conditions are suitable. All of the examples described above are located in mountainous areas with high precipitation rates and assumed high groundwater recharge. The groundwater systems in the mostly slightly to moderately karstified limestones are predominantly structure-controlled with the strongest water inflows occurring at large fault zones and through fractures and fissures.

Nevertheless, inflow through large karst cavities can also result in high discharge (MIJATOVIC 1984) Anyhow, it has to be stated that the latter is likely to be related to fast water passage after high precipitation events and does not necessarily contribute to high long-term mean discharge. In almost all cases the retention of groundwater to the rear of the gallery by an aquitard combined with high rock coverage and large catchment areas is essential for high and steady discharge rates throughout the year without extreme peaks. When dealing with drinking water, aquifer vulnerability should not be forgotten especially in karst areas. It should be stated that galleries in populated areas with lower rock coverage or intensively karstified formations (MIJATOVIC 1984) are of course more prone to pollution due to shorter retention times of water discharging through karst cavities. But if the catchment areas are known and water protection areas are defined like in the described examples, no great danger of pollution exists especially in lower populated mountainous areas with nonexistent agriculture.

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 23 Chapter 2 Karst water galleries

Bacteriological water pollution is also unlikely due to few vegetation and soil coverage in the catchment areas, high retention times in the rock mass, and low water temperatures. If all these conditions are met and if the galleries are driven perpendicular to major fault zones in highly water-bearing hard rock formations huge amounts of high quality drinking water can be obtained. The water may vary in terms of mineralization and hardness depending on the dissolubility of the rock formations it flows through but in most cases it can be consumed almost directly without need of major treatment. The high initial investments for the galleries are compensated by very long operating times and almost no maintenance costs. The “gallery system Mühlau”, for example, is running for over 50 years yet and it is still able to cover nearly the whole drinking water demand of the Tyrolean capital Innsbruck. In case of an adequate downward slope from the surge chamber at the gallery mouth to the supply network a hydroelectric power plant can be interconnected to produce electrical energy by utilizing the high velocity water flow. This is already possible with altitude differences starting at 50 m and flow rates of 500 l/min

(ENERGIE SCHWEIZ 2003; SCHMID 2003). Hydroelectric power plants assure simple and durable operation with established and reliable technics and can shorten the amortization time of the whole supply system by recouping some of the investment costs.

24 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 3 Case study Banda Aceh

3 Case study Banda Aceh

In this chapter the study area and its properties are described in detail whereas the hydrogeology of a potential target area is dealt with in chapter 5. It has to be noted that proper names of towns, mountains, rivers, springs etc. are subject to change in different publications and on Indonesian maps. Therefore, the most contemporary names are used in this thesis and some prior or secondary denominations of the most important localities are stated additionally. Nevertheless, it has to be pointed out that definite locations should generally be checked via coordinates especially when relating to older maps.

3.1 Physical Geography of the study area

3.1.1 Location

The Aceh Province is located on the northwestern tip of Sumatra (see figure 3-1). Sumatra (Indonesian: Sumatera) is part of the Indonesian archipelago and is the sixth largest island in the world. In the west the Aceh Province is surrounded by the Indian Ocean and in the north and east by the Andaman Sea. In the southeast between Sumatra and Malaysia the Andaman Sea turns into the Malacca Strait (see figure 3-2). 23 districts build up the Aceh Province, more precisely 18 regencies (Indonesian: kabupaten) and 5 municipalities (Indonesian: kota, kodya, kotya) (online source 17). The area investigated in this thesis partially lies within the districts Aceh Besar and Aceh Jaya and expands over 2,066 km² (see figure 3-1) (corner coordinates: UTM, zone 46N: 735372 / 607869, 750234 / 614990, 808718 / 561880, 756080 / 554991; geographical (WGS-84): 5.50 °N / 95.12 °E , 5.56 °N / 95.26 °E, 5.08 °N / 95.78 °E, 5.02 °N / 95.31 °E). These districts are located in the northwestern part of the Aceh Province. The city district of the provincial capital Banda Aceh (also spelled Bandaaceh; in former times named Kota Raja or Kutaraja) lies on the north coast near the northeastern corner of the study area but is not incorporated itself. Focusing on the western mountain range in this thesis the study area spans in a not rectangular way over the west coast mountains (see figure 3-1).

Eight sheets of the Topographical Map of Indonesia (1:50,000) (JANTOP TNI 1978) (in the following called Topographical Map (1:50,000)) are at least partly incorporated by the investigated area (also see table 4 1).

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 25 Chapter 3 Case study Banda Aceh

Figure 3-1: General map of the northwestern Aceh Province comprising the districts Aceh Besar, Aceh Jaya, Pidie, and the provincial capital Banda Aceh (locations derived from JANTOP TNI 1978)

3.1.2 Population

The inhabitants of the Aceh Province are predominantly Muslim (97 %) with only a few Christians and Animists (online source 02). In 1980 the total population was 2,550,726

(BINNIE &PARTNERS 1986a). Until 2008 it has almost doubled with now 4,211,000 inhabitants (online source 02). Populated areas are mainly concentrated along the coastal plains and alongside rivers and main roads being most dense in the north and east (also see Appendix 9). In the remaining forested areas and in the higher mountains population density was and still is very low. (BINNIE &PARTNERS 1986a; BINNIE &PARTNERS 1986b). The population of Banda Aceh has also nearly doubled from 142,818 in 1980 to about 260,000 in

26 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 3 Case study Banda Aceh

2008 (BINNIE &PARTNERS 1986b; online source 03). In 2005 the population growth rate was 0.5 % and is estimated to be 1.5 % or even more in the near future (2010) (USAID 2006) due to the rehabilitation of the area after the tsunami and a general trend to live and work in the city (KELLER, NICOLE 2006) (see chapter 1).

3.1.3 Physiography

The study area mainly includes the northwestern tail of the Barisan Mountains (Indonesian: Bukit Barisan) (see figure 3-1). This mountain range draws close to the west coast over 1,700 km through the entire island of Sumatra from Banda Aceh in the north to

Banda Lampung in the south (BARBER, CROW 2005b; online source 01] (also see figure 3-3). The mountains in the study area mainly reach altitudes of 1,000 – 2,000 m. In most cases the hillsides show steep slopes and are often densely forested (ACEH 2007). Gunung Batemeucica (gunung = mountain) constitutes the highest peak with an altitude of 2,125 m located near the district border of Aceh Besar and Aceh Jaya in the eastern part of the study area. To the east the Barisan Mountains are adjoined by foothills that reach up to 500 m altitude. The Barisan Mountain Range acts as a main water divide. Surface streams drain the mountains to the west into the Indian Ocean and to the east into Krueng Aceh that meanders in a northwestern direction through a wide coastal plain and discharges into the Andaman Sea (see figure 3-1). The city of Banda Aceh is located directly around the estuary of Krueng Aceh. Outside the study area dry and mostly grass covered highlands border the Krueng Aceh river valley to the east. These mostly 500 – 800 m high hills are part of a young volcano field (see figure 3-4, labels g18, g42), the most outstanding volcano is Gunung Seulawah Agam with an altitude of 1,810 m. Two main routes connect the capital Banda Aceh to the next bigger cities, the intact north- coast highway alongside Krueng Aceh to Sigli and the main west coast road to Calang via Lamno. The latter has been massively destroyed by the tsunami and is being rebuilt at the moment. The limestone formations in the study area are in most parts highly karstified. In the northwestern part of the study area they form typical tropical karst forms like cockpit karst and huge karst caves especially in the maturely karstified limestones around Lho’nga (compare Appendix 5). The limestones located to the east show less karstification phenomena than those on the west coast (information by field observations and photographs of BGR staff members). On satellite images and aerial photographs no other surface karst phenomena than the mentioned cockpit karst could be detected. It is supposed that they are camouflaged by the dense vegetation.

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 27 Chapter 3 Case study Banda Aceh

3.1.4 Climate The climate of the Aceh Province can be described as tropical with a high relative humidity of 80 – 90 % and mean daily temperatures of 25 – 27 °C with only little variations throughout the year (PLOETHNER, SIEMON 2005). Temperature decreases by approximately 0.5 °C per

100 m altitude (ACEH 2007). The Barisan Mountain Range acts as a barrier to the predominating monsoons which results in sharp regional variations in rainfall. With a mean annual precipitation of 3,500 mm the west coast receives high rainfall. In the mountain range values of even up to 4,500 - 5,000 mm can occur (see figure 3-2). Although precipitation is high all over the year, the west monsoon generally delivers the highest rates raining down in the mountains and causing warm and dry foehn winds in the areas to the east (VERSTAPPEN 1973). Mean annual rainfall in Banda Aceh is around 1,600 mm (see figure 3-2). Here the rainy season occurs from September through February caused by the east monsoon making December the wettest month with rainfall of nearly 200 mm. The driest months in the “dry” season from March through August are June and July with approximately 90 mm of rainfall when the west monsoon prevails (PLOETHNER, SIEMON 2005). Banda Aceh then lies in the precipitation shadow of the mountain range. On the west coast around Lamno the circumstances are contrary and the west monsoon causes the highest rainfall in August with 380 mm. Here the “dry” season starts when the east monsoon prevails and the mountains act as barrier to the west.

The potential evapotranspiration (ETpot) defined as the maximum height of evapotranspiration possible is in the range of 1,600 – 1,900 mm/a. For areas under forest cover ETpot (after Penman equation, albedo: 0.15) ranges from 1,500 mm on the west coast (e.g. Lamno and Meulaboh) to 1,600 mm/a in Banda Aceh (BINNIE &PARTNERS 1986b; online source 08) (see figure 3-2). Although there might be only few forest cover in the city of

Banda Aceh the values of ETpot for forest cover are stated. This is done due to reasons of comparability with the west coast and the mountainous regions which are indeed mostly covered by forest. Wind speeds are generally low at about 1.5 - 2.5 m/sec. In coastal areas higher wind speeds of about 4 – 8 m/sec can be observed. Wind directions are generally from west to east or from east to west due to the seasonal monsoons (ACEH 2007; PT SEMEN

ANDALAS INDONESIA 2006)

28 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 3 Case study Banda Aceh

Figure 3-2: Annual precipitation in the whole Aceh Province; climate diagrams show annual precipitation and potential evapotranspiration (ETpot) from forest cover (data for Lamno and Meulaboh taken from BINNIE &PARTNERS 1986b, data for Banda Aceh taken from centennial series (BINNIE & PARTNERS 1986b) and precipitation rates from 2000 – 2005 measured at Blang Bintang Airport; image of precipitation distribution modified after IWACO 1993)

3.1.5 Vegetation

The Aceh Province contains the largest contiguous area of tropical forest left in Sumatra. This forest mostly covers the Barisan Mountains and stretches from the north near the capital

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 29 Chapter 3 Case study Banda Aceh

Banda Aceh to the southeastern border of the province. It spreads over an area of about 3.3 million ha. Although no detailed floral surveys were carried out in the so called Ulu Masen ecosystem until today it can be said that there exists a high diversity of forest sub-types

(UNEP 2007; ACEH 2007). Due to the variety of geological formations, climate regimes, and elevation gradients many different species of plants can be forecasted like in the adjoining Leuser ecosystem further to the southeast. In the Leuser ecosystem lowland broadleaf forest, pine forest, sub-montane broadleaf forest, montane broadleaf forest, and peat swamp were recorded (ACEH 2007). Most of the rich lowland forests are today converted into agricultural land or deforested for other purposes (see chapter 3.1.6) but there are still substantial areas of tropical forest left above 500 m altitude. On the coastlines mangroves, swamps, and swampy forests occur (ACEH 2007).

3.1.6 Land use

While the highland areas above 500 m altitude are almost everywhere covered with contiguous tropical forest many lowland areas are used as agricultural land (see chapter 3.1.5). Wetlands surrounding main rivers are often used as paddy fields for rice cultivation, in dry periods soybeans and green beans are grown. In the 1980’s more than one million tons of rice per year were harvested from approximately 250,000 ha of paddy fields. These figures are assumed to have increased until today (2008). Rice cultivation forms approximately one third of the total cultivated area in the Aceh Province. Besides rice, other (acre-) crops are cultivated like cassava (manioc), sugar cane, tobacco, maize, and different vegetables (ACEH

2007); BINNIE &PARTNERS 1986b). Another big and growing part plays the production of the so called estate crops like coconut, coffee, and rubber (BINNIE &PARTNERS 1986b). In the time of renewable energy sources and bio-fuel the production of palm oil also shows a significant upturn. In many areas oil palms are cultivated yet. A concept was brought forward in 2007 to build an oil palm plantation in the Aceh Province of 20,000 ha in size (SCHAD, SCHINDLER et al. 2007; JAEGGI 2006). Furthermore, the problem of illegal deforestation broadens throughout the whole Aceh province and also becomes a major issue in the northern districts since there is a huge demand on wood for the reconstruction of houses (JAEGGI 2006). In 2005, BGR conducted a remote sensing land use mapping of the area around Banda

Aceh based on satellite data within the framework of a diploma thesis (SCHMITZ, LOHMANN et al. 2007). In Appendix 9 the final map of this land use mapping is shown. The main conclusion that can be drawn from the map for this thesis is that no housing or other anthropogenic influence can be encountered in the higher mountainous areas. Instead,

30 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 3 Case study Banda Aceh dense rainforest occurs while lower elevated areas tend to show a more sparse vegetation cover. Main settlements are located along the coast in the coastal plains and alongside Krueng Aceh.

3.1.7 Pedology

The pedology of the study area is not well known. Detailed studies regarding soils have been carried out in areas in central and southern Sumatra. Mainly Acrisols, Alisols, and

Plinthosols (FAO-88 classification) can generally occur in northern Sumatra (FAO 1993). As far as the reef-like limestone bodies are concerned (see chapter 3.2.2.1.1), a Ferallic Cambisol could be presumed by the comparison to a reference profile mapped on the Indonesian island Ambon to the east of Sumatra. This soil developed on a reef-like limestone lithology and exhibits well drainage (CSAR-ISRIC 1994). Almost all soils in the humid tropical monsoon climate show intense weathering and dominance of clay minerals (FAO 1993). Anyhow, exact spatial assignments to the geological formations cannot be made. Acrisols are described as highly weathered soils in an advanced formation stage on old land surfaces with hilly or undulating topography. They appear under closed or open woodland and show a predominance of kaolinitic clays and a general depletion of nutrients.

Acrisols show poor chemical and physical properties and are easily erodible (FAO 1993). Alisols were found to be in a weathering stage where smectitic or illitic clays are being degraded. The clay fraction is still of a mixed mineralogy. The very acid Alisols generally show a high exchangeable aluminium content and due to clay migration a dense accumulation of clay is located in the subsoil. This accumulation together with low structural stability of the surface horizon results in reduced permeability and lower internal drainage

(FAO 1993). In contrast to Acrisols and Alisols, Plinthosols exhibit a dominant presence of Plinthite, an iron-rich mixture of clay and silica which develop to hardened ironstone concretions on exposure. This effectively reduces rooting depths and the water holding capacity. High concentration of Kaolinite, a low activity clay, results in poor nutrient content and a low natural fertility (FAO 1993).

Besides much higher precipitation rates compared to moderate climates, a soil characteristic in humid tropical climates intensifies karstification processes. Higher dissolution rates of CaCO3 can be assigned to higher partial pressure of CO2 in the circulating water. Especially microbial activity leads to a much higher partial pressure of CO2 in the soil compared to the partial pressure of CO2 in the atmosphere (online source 05, online source 06). Generally, high temperatures in tropical climates strongly increase microbial activity, and hence, cause higher partial pressures of CO2 in the tropical soils

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 31 Chapter 3 Case study Banda Aceh besides intensified deep weathering with large soil thicknesses. Waters circulating in limestones of tropical climates with high soil coverage cause increased dissolution of CaCO3, and hence, karstification phenomena compared to limestones in moderate climates with low or absent soil coverage.

3.2 Geology

Geological surveys around Banda Aceh and in the whole Aceh Province are still in the phase of reconnaissance. In the Quaternary embayment around Banda Aceh and in the northern parts of the Aceh Besar district studies have been carried out especially regarding groundwater quality in the upper aquifers after the 2004 tsunami. BGR was and still is involved in these studies (see chapter 1). The west coast areas and especially the Barisan Mountain Range have not been subject to many geological surveys. Nevertheless, data from the North Sumatra Project (NSP) undertaken from 1975 – 1980 and resulting in the publication of the Geologic Map of the

Bandaaceh Quadrangle, Sumatra (1:250,000) (BENNET, BRIDGE et al. 1981, (see Appendix 10) (in the following called Geological Map (1:250,000)) deliver basic geological data for the study area as well as some further publications. The existence of more detailed unpublished geological subarea reports and maps (1:100,000) for the study area was claimed which were also prepared within the scope of the NSP (BENNET, BRIDGE et al. 1981). It was stated that these were either available at the former Directorate of Mineral Resources (DMR) in Bandung (Java, Indonesia) or at the former Institute of Geological Sciences and Overseas Development Administration (IGS) in Keyworth (Nottingham, UK) (today part of the British Geological Survey (BGS)). Several contact persons and library staff members in Bandung and at the BGS were contacted but the conclusion was that these unpublished reports and maps were lost.

3.2.1 General setting

3.2.1.1 Sumatra

Sumatra forms the active southwestern margin of the Sundaland Continental Plate (Sunda Craton). About 200 km southwest of the Sumatran west coast the Indian Ocean Plate is subducted under the Sundaland Continental Plate which is part of the Eurasian Plate. Sumatra and its proximity make up a typical volcanic arc and marginal basin environment

(BARBER, CROW et al. 2005; BENNET, BRIDGE et al. 1981) (see figure 3-3). At the so called Sunda Trench in the southwest, where water depths of more than 5,000 m occur, oblique subduction with angles up to 45° takes place. The dipping angle and rate of the subducting plate also vary along the Sunda Trench. Mean movement rates of the Indian

32 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 3 Case study Banda Aceh

Ocean Plate are assumed to be around 55 mm/a (VITA-FINZI 2008) but subduction rates vary around 52 – 60 mm/a at different locations along the trench (see figure 3-3). In contrast,

BARBER, CROW 2005b assume much higher subduction rates of mean 70 mm/a. Overall, the oblique subduction with varying subduction rates results in major scale compression faults and strike-slip faults with dextral movements in the overriding plate (SIEH, NATAWIDJAJA 2000). Stress that is built up during irregular subduction of the Indian Ocean Plate causes major earthquakes when released abruptly, like in December 2004 (see chapter 1). The most outstanding structure showing dextral movement is the so called Sumatran Fault System (SFS; also called Sumatran Fault Zone (SFZ)) extending through the whole island of Sumatra near the west coast from the Andaman Sea in the north to the Sunda Strait in the south (MILSOM 2005). To the northeast of the Sunda Trench the present accretionary prism is followed by ridges forming the western islands (e.g. Simeulue, Nias, and Siberut) (see figure 3-3) and the forearc basin with material from earlier accretionary complexes that were tied up to the

Sunda Craton (BARBER, CROW et al. 2005; BARBER 2000). Here another dextral strike-slipe fault, the Mentawai Fault, is located extending parallel to the SFS along the ridge islands to the west of Sumatra decoupling the forearc region from the Sundaland Continental Plate and building a disconnected “sliver” plate (MILSOM 2005). The adjoining Sumatran west coast constitutes the volcanic arc with many Quaternary volcanoes like Pulau Weh and Seulawah Agam (see figure 3-1) on the northwestern tip of Sumatra and Marapi, Talang, Kerinci, and Dempo further to the southeast, to name only a few (online source 04). The volcanic belt is developed along the tectonically weak SFS and this tectonic weakness is supposed to have triggered volcanism. Most of the volcanoes are quiet but some are still active (GASPARON 2005). Toba, the huge caldera in the upper center of Sumatra is one of the largest Quaternary caldera complexes known (see figure 3-3). It is located in an oval-shaped topographic depression on the trace of the SFS (MASTURYONO, MCCAFFREY et al. 2001). Almost all of these volcanoes are located within the Barisan Mountain Range which extends along the whole Sumatran west coast (see figure 3-1) (MILSOM 2005; online source 04). Further to the northeast the hinterland of the Barisan Mountains represents former backarc basins followed by the present backarc basin, the Malacca Strait (BARBER, CROW et al. 2005).

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 33 Chapter 3 Case study Banda Aceh

Figure 3-3: General structural setting of Sumatra and the adjacent subduction zone; top view: red arrows show moving directions of the obliquely subducted Indian Ocean Plate together with mean movement rates; cross section: the two symbols (cross and dot) on the sides of the Sumatran Fault System indicate dextral strike-slip movement at the fault; dextral strike-slip movement also occurs at the Mentawai fault (modified after BARBER, CROW et al. 2005; subduction rates and directions derived from SIEH, NATAWIDJAJA 2000)

34 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 3 Case study Banda Aceh

The stratigraphical basement is built up by Pre-Tertiary formations mostly exposed in the Barisan Mountains (see figure 3-3). The oldest rocks in Sumatra that could be dated on a reliable basis are sediments of Carboniferous to Permian age (~ 300 Ma) although some gneisses that could not be dated may represent a Pre-Carboniferous continental crystalline basement. Igneous rocks of Permian to Late Cretaceous age cut the Pre-Tertiary basement together with some Tertiary intrusions. To the northeast of the SFS most of the older rocks show at least some degree of metamorphism, younger Permo-Triassic sediments and volcanics are less metamorphosed. Variably metamorphosed rocks of Jurassic to Cretaceous age appear mostly to the southwest of the SFS. During the Tertiary the basement was overlain by volcanoclastic and siliciclastic sediments. Today the older rocks of the Barisan Mountains are almost everywhere overlain by lavas and tuffs from young volcanic eruptions of Quaternary age, except on the northwestern tip of Sumatra. Recent alluvial sediments can be found in depressions in the mountain range where they are of fluvial origin and in the northeastern and southwestern part of Sumatra as swamps, lacustrines, and coastal deposits (BARBER, CROW 2005a; BENNET,

BRIDGE et al. 1981).

3.2.1.2 The Banda Aceh Quadrangle

The Banda Aceh Quadrangle as described by BENNET, BRIDGE et al. 1981 is the northwestern tip of Sumatra where the study area of this thesis is also located (see figure 3-4). Here the SFS splits into two major northwest-southeast running strike-slip faults with dextral movements, the Seulimeum Fault and the Aceh Fault (formerly known as Lam-

Teuba-Baro Fault and Banda Aceh-Anu Fault (BENNET, BRIDGE et al. 1981) or East Semanko

Fault and West Semanko Fault, respectively (PLOETHNER, SIEMON 2005). To the northeast of the Aceh Fault extensive Plio-Pleistocene volcanism formed the area around the volcano Seulawah Agam. In the north the Aceh Fault is adjoined by a large coastal plain in which Krueng Aceh meanders towards the northern coast. To the southwest the Aceh Fault builds the direct border to the highly structurally deformed Pre-Tertiary formations of the Barisan

Mountains (BENNET, BRIDGE et al. 1981). In chapter 3.2.2 the lithological units and the geological history of the geological formations in the study area mainly to the southwest of the Aceh Fault (see figure 3-4) will be described in detail.

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 35 Chapter 3 Case study Banda Aceh

Figure 3-4: Geological map of the Banda Aceh Quadrangle (geological formations and faults were digitized from BENNET, BRIDGE et al. 1981) (for larger image see Appendix 8)

36 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 3 Case study Banda Aceh

Table 3-1: Geological formations in the study area (for more details see Appendix 2)

Period Group Formation Labels Lithological description

(undifferentiated) gravels, sands, and Alluvium g1 muds Quaternary Meulaboh g24 semi-consolidated sands and gravels older terrace deposits, partly volcanic Indrapuri g11 gravels and sands tuffaceous and calcareous sandstones, Seulimeum g32 conglomerates, minor mudstones Tiro Kotabakti (Padangtiji calcareous sandstones, conglomerates, g14 Member) siltstones, minor limestones tectonic melange of serpentinites, Indrapuri Complex g10 serpentinized ultramafic, undifferentiated igneous, and sedimentary rocks porphyritic, epidotized, intermediate Calang Volcanic g5 volcanic, subvolcanic intrusives Geunteut Granodiorite g8 Granodiorite and subsidiary diorite micaceous sandstones, conglomerates, Tertiary Peunasu g26 shales, mudstones, reef limestones volcanogenic sandstone, conglomerates, Tangla g36 quartzose arenites Hulumasen Tangla (Keubang argillaceous limestone, minor calcareous g37 Member) sandstones and siltstones, thin coals Tangla (Ligan Quartz sandstones, micaceous g38 Member) sandstones, siltstones micaceous sandstones, polymictic conglomerates, conglomeratic Meureudu Meucampli g23 sandstones, siltstones, limestones, amygdaloidal mafic volcanics Miscellaneous miscellaneous granodiorite to diorite g25 intrusives intrusives Late Cretaceous Sikuleh Batholith g34 Dioritoids (older complex) Phyllites, slates, volcanic and turbiditic Lho'nga g21 sediments, thin limestones dark, thin bedded argillaceous and Raba Limestone g28 siliceous limestones Raba Limestone (Reef g29 massive gray reef-like facies Member) Lamno Limestone g19 dark limestones with volcanic debris Lamno Limestone g20 massive gray reef-like facies (Reef Member) Late Jurassic – Woyla volcanic wackes, subordinate Early Cretaceous Lhoong g22 sandstones and siltstones, mafic volcanics and limestones

Basalts, agglomerates, mafic dykes, Bentaro Volcanic g3 basaltic vents

variably altered and metamorphosed intermediate to mafic volcanics and Geumpang g6 pyroclastic, minor phyllites, greenschists and metalimestones

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 37 Chapter 3 Case study Banda Aceh

3.2.2 Lithology and geological evolution Due to the proximity of the Sunda subduction zone and many phases of deformation the geology in the study area is immensely complex with a lot of varying lithologies and intricate structures due to many overthrust events. In the following, the geological formations in the study area and their geological and structural evolution are described (see table 3-1). Lithological properties are important for the delineation of hydrostratigraphical units shown in chapter 5.1. The distribution of the geological formations is shown in figure 3-5. The geological cross section A-B is shown in figure 3-6 and the other cross sections will be addressed to in the following chapters.

Most information on the geological formations was obtained from BENNET, BRIDGE et al.

1981. Additional descriptions were derived from (BARBER, CROW 2005a; COBBING 2005;

CROW 2005; BARBER 2000; PLOETHNER, SIEMON 2005).

3.2.2.1 Late Jurassic to Early Cretaceous

3.2.2.1.1 Woyla Group The rocks of the Woyla Group are extensively exposed in the Aceh Province and especially in the Banda Aceh Quadrangle. The Woyla Group consists of formations of Late Jurassic to Early Cretaceous age. It is separated into two successions with different lithologies and structural complexity divided by a large scale east-dipping thrust, the Geumpang Line (see figure 3-5), that is attributed to movements on the SFS and was later subject to displacement. In the study area mainly the formations of the West Woyla Group crop out which are located to the west of the Geumpang Line. Only the Geumpang Formation (g6) is a member of the East Woyla Group located to the east of the Geumpang Line. The West Woyla Group represents a partially subaerial volcanic arc-fringing reef environment with three different assemblages, an oceanic assemblage, a basaltic-andesitic arc assemblage, and a limestone assemblage.

Oceanic assemblage The oceanic assemblage generally shows a mixture of different ocean floor materials. The rocks are variously internally deformed, separated by faults (mostly thrusts), and almost randomly distributed. The geological environment in which these characteristics occur is an accretionary complex at a subduction zone. • Geumpang Formation (g6) The only member of the oceanic assemblage is the Geumpang Formation (g6) that crops out near the eastern corner of the study area. It comprises mafic volcanics like

38 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 3 Case study Banda Aceh

pillow basalts and pyroclatics like volcaniclastic sandstones and tuffs that were variously altered and metamorphosed commonly to greenschists or phyllites. Furthermore, thin gray or black limestones occur which were also partly metamorphosed.

Figure 3-5: Geological map only focused on the study area (geological formations and faults were digitized from BENNET, BRIDGE et al. 1981)

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 39 Chapter 3 Case study Banda Aceh

Figure 3-6: Geological cross section A-B; for location see figure 3-4 or figure 3-5 (modified after BENNET, BRIDGE et al. 1981); cross section C-D and E-F will be described later (also see Appendix 13 and figure 5-16, respectively)

Arc assemblage The main units of the arc assemblage are built up by basaltic-andesitic volcanics and intrusive dykes as well as agglomerates, volcaniclastic sandstones, and shales. In the study area the Bentaro Volcanic Formation (g3) is the typical member of the arc assemblage followed by the Lho’nga (g21) and Lhoong Formations (g22). These formations represent the remains of a Late Jurassic to Early Cretaceous volcanic arc. It is supposed that this volcanic arc rose above the sea level leading to its erosion and deposition of breccias and volcaniclastic sediments at the sides of the arc.

• Bentaro Volcanic Formation (g3) The Bentaro Volcanic Formation (g3) is the most representative unit of the arc assemblage. It comprises porphyritic and andesitic basalts, basaltic vents as well as agglomerates in which intrusions of mafic dykes occur. It crops out in the western part of the study area close to the coastline and can be seen as the typical remnant of volcanic islands. • Lhoong Formation (g22) The Lhoong Formation (g22) comprises mafic volcanics as well as conglomeratic volcanic wackes and subordinate sandstones and siltstones. Also occurring is a limestone unit that could rather be assigned to the limestone assemblage (see below). Outcrops of the Lhoong Formation (g22) can be found in the southern central and eastern part of the study area. Thicknesses of up to 2,000 m are estimated. • Lho’nga Formation (g21) In the northernmost part of the study area, to the west of the Banda Aceh district near the town of Lho’nga, the Lho’nga Formation (g21) crops out. It comprises gray and colored slates and phyllites as well as a high proportion of volcaniclastical material like volcanic and turbiditic sediments and thin limestones. Thicknesses are estimated

40 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 3 Case study Banda Aceh

to be around or under 500 m. This formation is supposed to be underlain by the Raba Limestone Formation (g28).

Limestone assemblage The volcanic islands of the arc assemblage are believed to have been adjoined by fringing carbonate reefs that were connected to the islands. In the field this limestone assemblage is also linked very closely to the arc assemblage, especially to the Bentaro Volcanic Formation (g3). It comprises often recrystallized layered limestones as well as more massive thick- layered limestones forming reef-like bodies and is divided into the Raba Limestone Formation (g28, g29) and the Lamno Limestone Formation (g19, g20). The limestones are highly karstified especially near the west coast.

• Raba Limestone Formation with Reef Member (g28, g29) The Raba Limestone Formation (g28, g29) comprises often recrystallized dark thin bedded argillaceous and siliceous limestones as well as massive gray calcarenites and calcilutites. The karstified calcarenites and calcilutites are named the Reef Member of the formation since they tend to form reef-like bodies. They are believed to be thick-layered and it is supposed that they formed directly around the volcanic islands represented by the Bentaro Volcanic Formation (g3). A subdivision of the calcarenites and calcilutites in the field is not known. The Raba Limestone Formation (g28, g29) crops out across the whole central part of the study area. In the central to northern part one major complex of the Reef Member constitutes the main part of the Barisan Mountain Range to the southwest of Banda Aceh. Thicknesses are estimated to be around 1,000 to 1,500 m. These rocks are supposed to be extensively underlain by the Lhoong Formation (g22) sometimes building overthrusted nappe structures (see figure 3-6). • Lamno Limestone Formation with Reef Member (g19, g20) Like the Raba Limestone Formation (g28, g29) the Lamno Limestone Formation (g19, g20) is also linked to the Bentaro Volcanic Formation (g3). It comprises dark fossiliferous limestones with volcanic debris near the base which shows the proximity to the former volcanic islands. The fossils contained in the limestones, mostly corals, algae, and foraminiferae, point out the Late Jurassic to Early Cretaceous age. As well as the Raba Limestone Formation (g28, g29) the Lamno Limestone Formation (g19, g20) also includes a Reef Member with a massive gray reef-like facies that is assumed to be thick-layered. The outcrops of the formation are located at the west coast directly connected to a major outcrop of the Bentaro Volcanic Formation (g3).

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 41 Chapter 3 Case study Banda Aceh

Thicknesses are estimated to be around 750 m. These rocks are supposed to be conformably underlain by the Bentaro Volcanic Formation (g3).

3.2.2.2 Late Cretaceous

During the Late Cretaceous a phase of intrusive activity proceeded. At the time the Pre- Tertiary deposits of the Woyla Group were intruded by the Sikuleh Batholith and other miscellaneous intrusives.

• Sikuleh Batholith (older complex) (g34) In the study area the older complex of the Sikuleh Batholith occurs. Only the northernmost extension of this huge batholith is part of the investigated region located on the southern edge of the study area. This intrusive complex consists of sheared and in part weakly foliated inhomogeneous dioritoids. Intruding mainly the arc assemblage of the Woyla Group it is suggested that the intrusive material was derived from the underlying continental crust. • Miscellaneous intrusives (g25) Further diorite and granodiorite intrusions of Late Cretaceous age are combined in the unit of miscellaneous intrusives. These are often smaller intrusions located in the southeastern part of the study area. Mainly the Lhoong Formation (g22) was intruded by these rocks and it is suggested that they have a connection to the more southern Sikuleh Batholith.

3.2.2.3 Tertiary

3.2.2.3.1 Meureudu Group The Meureudu Group comprises different formations accumulating in a depositional basin in the Early Tertiary approximately during the Eocene to Early Oligocene. This depositional basin is supposed to have gradually deepened, probably behind another periodically active volcanic arc. The lower beds represent fluviatile to restricted marine conditions while the upper beds were deposited in an open marine environment. This alludes to the gradually deepening conditions of the basin. The Meucampli Formation (g23) is the only unit of the Meureudu Group occurring in the study area.

• Meucampli Formation (g23) The Meucampli formation (g23) crops out near the border of the study area in the central eastern part, where it overlies the Pre-Tertiary deposits of the Woyla Group

42 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 3 Case study Banda Aceh

with major unconformity. It contains micaceous and conglomeratic sandstones, polymictic conglomerates, siltstones, limestones, and amygdaloidal mafic volcanics.

3.2.2.3.2 Hulumasen Group

After the first Cenozoic phase of deformation in the Late Oligocene that was accompanied by tectonic uplift and the resulting development of the Barisan Mountain Range depositional basins emerged at the sides of the mountains. These basins are called the West Aceh Basin and the Northwest Aceh Basin. Almost immediately after the uplift phase sedimentation began in the West Aceh Basin in the Late Oligocene with the deposition of fluviatile to paralic and partly shallow to open marine sediments, the latter deposited during short sea level rises. The remains of the West Aceh Basin are represented by the Hulumasen Group consisting of the Tangla Formation (g36) and the Peunasu Formation (g26) both of which are of Late Oligocene to Early Miocene age. Since younger formations are missing in the onshore succession it is believed that it was uplifted shortly after its deposition. It is also suggested that the sedimentation took place further to the southeast and that subsequent movement along the Geumpang Line emplaced the formations in their present positions.

• Tangla Formation with Keubang and Ligan Member (g36, g37, g38) The Tangla Formation (g36, g37, g38) comprises partially cross-bedded volcanogenic sandstones, conglomerates, and quartzose arenites showing fluviatile to paralic depositional conditions. It generally caps higher summits in the south of the study area and partially shows evidence of limited volcanism during its deposition due to the existence of volcanic clasts. The Keubang Member contains argillaceous limestones, subordinate calcareous sandstones and partly pyritic siltstones, and thin impure coals. To the west of the Keubang member the Ligan member crops out over a greater area. It comprises quartzose and micaceous sandstones, siltstones, and intermediate volcanics. This formation is supposed to be unconformably underlain by the Raba Limestone Formation (g28). • Peunasu Formation (g26) Aside from fluviatile and paralic sediments like micaceous sandstones and conglomerates the Peunasu Formation (g26) contains shallow to open marine deposits like lagoonal mudstones, shales, and reef limestones. The Peunasu Formation (g26) only crops out on the northern border of the study area to the west of

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 43 Chapter 3 Case study Banda Aceh

Banda Aceh. The Peunasu Formation (g26) is supposed to be unconformably underlain by the Lho’nga Formation (g21).

3.2.2.3.3 Late-Tertiary volcanics and intrusives

During the Late Tertiary low extrusive and intrusive activity occurred in the regions that are today located at the west coast of the study area. Transcurrent movements along the Geumpang Line occurred at the same time representing the second Cenozoic phase of deformation that could be connected to the opening of the Andaman Sea around 11 – 12 Ma ago (BENNET, BRIDGE et al. 1981). The remains of these activities are represented by the Geunteut Granodiorite, the Calang Volcanic Formation (g5), and the Indrapuri Complex (g10).

• Geunteut Granodiorite (g8) The Geunteut Granodiorite is an intrusive complex of Miocene age, dated by K-Ar

and biotite methods to 14.3 ± 0.5 Ma (BENNET, BRIDGE et al. 1981). It is composed of granodiorite and subsidiary diorite and crops out over an area of 6 km² in the east of the study area where it intruded the Lamno Limestone Formation (g19). Granodiorite dykes and veins found up to 6 km from the margin of the outcrop are supposed to be evidence of a larger complex in greater depths. • Calang Volcanic Formation (g5) During the Middle to Late Miocene the Calang Volcanic Formation (g5) emerged consisting of porphyritic epidotised intermediate volcanics and subvolcanic intrusives. In the study area two outcrops are located in the southwest at the side of the Tangla Formation (g36) and inside the Ligan Member of the Tangla Formation (g38). • Indrapuri Complex (g10) Along the Aceh Fault in the eastern part of the study area and directly linked to the Geumpang Line the rocks of the Indrapuri Complex crop out. The formation comprises a tectonic mélange of remobilized ophiolites containing mainly serpentinites and serpentinized ultramafic and undifferentiated igneous and sedimentary rocks. This mélange was developed around the Miocene to Pliocene boundary under conditions related to overthrusting. On a northwest-southeast directed fault-line associated with the Geumpang Line these rocks were extensively overriding the eastern margin of the Barisan Mountain Range. The ophiolite material may well be derived from the Late Jurassic to Early Cretaceous oceanic assemblage of the Woyla Group (see chapter 3.2.2.1.1).

44 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 3 Case study Banda Aceh

3.2.2.3.4 Tiro Group In the Early to Middle Miocene the northeastern sector of the Banda Aceh Quadrangle was subject to a transgression-phase that reached its climax during the Middle Miocene and turned back into a phase of regression in the Late Miocene. In the Late Miocene shallowing and sedimentation of clastics occurred which continued until the Pliocene when the Lam Teuba volcano began to rise in the northeast of the Banda Aceh Quadrangle (today the volcano Seulawah Agam lies in the former Lam Teuba caldera (see figure 3-4). During that period the Tiro Group containing the Kotabakti Formation (g14) and the Seulimeum Formation (g32) was deposited.

• Kotabakti Formation (Padangtiji Member) (g14) In the study area only the Padangtiji Member of the Kotabakti Formation (g14) occurs at the eastern border directly beneath the Aceh Fault. It consists of calcareous sandstones, conglomerates, siltstones, and minor limestones representing an open marine sublittoral depositional environment. This formation is supposed to be unconformably underlain by the Meucampli Formation (g23) (see figure 3-6). • Seulimeum Formation (g32) On the Pliocene to Pleistocene boundary the Seulimeum Formation (g32) was deposited. It comprises tuffaceous and calcareous sometimes cross-bedded sandstones, conglomerates, and minor mudstones and is located beneath the Kotabakti Formation (Padangtiji Member, g14) directly at the Aceh Fault. The tuffaceous constituents can be attributed to the rise of the Lam Teuba volcano. Overall, the Seulimeum Formation (g32) represents a sublittoral depositional environment. Thicknesses are estimated to be around 500 m. This formation is supposed to be unconformably underlain by the Padangtiji Member of the Kotabakti Formation (g14) (see figure 3-6).

3.2.2.4 Quaternary

The third Cenozoic phase of deformation set in during the Early Pleistocene with folding and uplift of all younger Tertiary sediments followed by fast growth of Quaternary volcanoes like Lam Teuba or Pulau Weh and fissure eruptions. Against the eastern edge of the Barisan Mountain Range the deformation was most extensive. Vertical and transcurrent movements prevailed and emplaced the Barisan Mountains in their present position. During this phase of deformation the prominent arms of the SFS, the Aceh Fault and the Seulimeum Fault, were formed by reactivation of former structures. Short marine transgressions and regressions lead to the extensive coverage with sediments of Pleistocene and Holocene age. In the study area the Quaternary successions

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 45 Chapter 3 Case study Banda Aceh are represented by the Indrapuri Formation (g11), the Meulaboh Formation (g24) and the Alluvium (g1).

• Indrapuri Formation (g11) The Indrapuri Formation (g11) represents terrace deposits containing coarse and partly volcanic gravels and sands of Pleistocene age. The depositional environment can be described as fluviatile to paralic. Outcrops are located at the sides Krueng Aceh especially in its southeastern part. Some of these outcrops are located at the eastern border of the study area along the Aceh Fault. Thicknesses of the Indrapuri Formation (g11) are estimated to be around 75 m. This formation is unconformably underlain by the Seulimeum Formation (g32) (see figure 3-6). • Meulaboh Formation (g24) The Meulaboh Formation (g24) was also deposited during the Pleistocene and contains semi-consolidated sands and gravels and partly occurring clays. It also represents fluviatile to paralic depositional conditions and is located near Lamno at the southwestern edge of the study area to the sides of a smaller coastal plain. This formation is supposed to be unconformably underlain by the Tangla Formation (g36). • Alluvium (g1) The youngest deposits in the study area are represented by the Alluvium. This Holocene formation is built up by undifferentiated gravels, sands, and muds and covers large areas of the Banda Aceh Quadrangle. It mainly constitutes the top layer on the wide coastal plain around Krueng Aceh as well as on plains along the west coast. • Recent activities Recently most of the volcanism in the Banda Aceh Quadrangle is quiet but thermal activity is still present.

3.2.3 Structure and neotectonics

The overall seismic situation in Sumatra can be described as very active (compare chapter 3.2.1). This does not astonish at a highly active and complex continental margin

(BARBER, CROW et al. 2005) and was demonstrated not least by the major earthquakes in 2004 and 2005 ahead of the Sumatran west coast (see chapter 1). Slip partitioning of the Indian Ocean Plate and subduction induce high levels of seismicity in the Barisan Mountains as well as in the forearc areas (see figure 3-3) (MILSOM 2005). Very interesting surveys concerning the understanding of the highly complex subduction environment especially

46 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 3 Case study Banda Aceh regarding the obliquely subducting slabs of the Indian Ocean Plate are currently made by BGR in section 3.22. As a result of the north-northeast directed compression forces (see figure 3-3) uplift and coastline progradation are still proceeding which can be observed on terrace sets along the main rivers and on the prograding coastline (VERSTAPPEN 1973; BENNET, BRIDGE et al. 1981). Accordingly, almost all geologic formations in the study area were subject to major deformation phases and were vertically and laterally displaced. This was sometimes accompanied by metamorphism (BARBER, CROW 2005a; BENNET, BRIDGE et al. 1981).

The most obvious neotectonically active faults in the Banda Aceh Quadrangle are the Aceh Fault and the Seulimeum Fault (see figure 3-4) which are the northernmost arms of the SFS extending in a northwest-southeast direction (see chapter 3.2.1.2). At these faults dextral strike-slip movement can be observed (see figure 3-7 A) accompanied by sometimes huge displacements in the adjoining successions (BENNET, BRIDGE et al. 1981; SIEH,

NATAWIDJAJA 2000). Only the Aceh Fault is in part incorporated in the study area and is supposed to highly affect the structure of the surrounding rock formations. Besides the large and dominant strike-slip faults other faults and structures can be observed that formed as a result of the compression and strike-slip movements (BENNET,

BRIDGE et al. 1981). These faults are still large-scale faults and are often several kilometers long (see Appendix 10). They generally extend in two major directions either sub-orthogonal or sub-parallel to the Aceh Fault and likewise to the Sunda Trench. It seems that they are strongly bound to the mechanisms of the strike-slip movements along the SFS. Being interpreted as subsidiary faults to a major strike-slip system they are supposed to result from forces occurring sub-orthogonal and sub-parallel to the SFS (MILSOM 2005). Small- and large-scale folding and overthrusting are supposed to occur in many formations throughout the whole study area as a result of compression. Overthrusting appears predominantly sub-orthogonal to the SFS resulting in thrust faults with a dipping angle to the northeast (see figure 3-6). Formations formerly lying to the east were thrusted over western formations sometimes building up nappe structures, e.g. represented by the limestones of the Raba Limestone Formation (g28 & g29) (see figure 3-6). Large-scale folding structures in the study area are only published in the limestones of the

Woyla Group developed as anticlines or overturned anticlines after BENNET, BRIDGE et al. 1981. As for the northern part of the study area this topic will be addressed to in more detail in chapter 5.5.

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 47 Chapter 3 Case study Banda Aceh

Figure 3-7: Schematic interpretation of the structural pattern at a dextral strike-slip fault zone; A: simplified movement at a strike-slip fault; B: schematic interpretation of the overall structural pattern at a dextral strike-slip fault zone; C: combination of A and B (modified after PARK 1989)

Figures 3-7 B and C show a schematic interpretation of the overall structural pattern at a dextral strike-slip fault zone. Dextral strike-slip movement can be subdivided into a compressional and extensional component resulting in transpression (red arrows) and transtension (green arrows). Resulting subsidiary fault directions (blue lines) are either sub- orthogonal to the main strike-slip extension axis (black arrows) showing sinistral relative movement or sub-parallel to the main extension axis exhibiting dextral relative movement

(PARK 1989). This matches the main fault directions given on the Geological Map (1:250,000) (see Appendix 10). Moreover, faults extending sub-parallel to the SFS mostly show compression features like overthrusting in a southwestern direction as described above (see figure 3-6). Subsidiary faults directed sub-orthogonal to the SFS are supposed to exhibit no

48 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 3 Case study Banda Aceh large-scale compression features since any signs of compression like overthrust phenomena or topographical ridges can be clearly associated with them. They are furthermore interpreted as being subject to at least small-scale extension directed sub-parallel to the extension axis of the SFS. Anyhow, this should be additionally checked by future field observations of the mapped faults (see chapter 7).

In chapter 5.4 the distribution of faults and fractures will be investigated in more detail by an analysis of lineaments which were derived via remote sensing. There it will also be responded to the hydrogeological characteristics of faults and fractures.

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 49

Chapter 4 Basic data and methodology

4 Basic data and methodology

4.1 Basic data Generally, the basis for this thesis is provided by literature data, thematic maps, satellite images, aerial photographs, a pre-processed lineament mapping, survey reports, and personal information by contact persons. Furthermore, two karst water galleries were visited in Austria. The personal impressions improved the understanding of these constructions. Analysis of the available data was conducted using the software products ESRI® ArcGIS® version 9.2 (contains ESRI® ArcMap®), Global Mapper® version 9.03, Google Earth™ map service version 4.2, Grapher® version 7.0, and Origin® version 7.5G SR6. For the purpose of image editing and creation of figures the software products Adobe® Photoshop® CS version 8.0.1 and the CorelDRAW® Graphics Suite versions 12 and 13 were used.

The following thematic maps were available for the investigated area and used in this thesis:

• Geologic Map of the Bandaaceh Quadrangle, Sumatra (1:250,000) (BENNET,

BRIDGE et al. 1981) (see Appendix 10) (in this thesis called Geological Map (1:250,000)) • Hydrogeological Map of Indonesia (1:250,000), sheet 0421 Banda Aceh

(Sumatera) (SOETRISNO 1993) (see Appendix 11) (in this thesis called Hydrogeological Map (1:250,000)) • Hydrogeological Map of Indonesia (1:1,000,000), sheet i Dan Sebagian (part of) II

(SETIADI 2004) (see Appendix 12) (in this thesis called Hydrogeological Map (1:1,000,000))

• Topographical Map of Indonesia (1:50,000) (JANTOP TNI 1978), 8 sheets (see table 4-1) (in this thesis called Topographical Map (1:50,000))

Table 4-1: Map sheets of the Topographical Map (1:50,000) (JANTOP TNI 1978) included in the study area

Map sheet No. Name 0421-22 Lamno 0421-23 Lho'nga 0421-24 Indrapuri 0421-31 Cotabuset 0421-32 Keumala 0421-33 Seulimeum 0421-51 Lampuyang 0421-52 Banda Aceh

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 51 Chapter 4 Basic data and methodology

4.2 Generation and application of digital data in ESRI® ArcGIS® The main work of this thesis was supposed to be accomplished on the basis of digital data. Therefore, the available analog thematic maps and other data from literature and surveys reports had to be digitized, processed, and displayed with the Geographical Information System software ESRI® ArcGIS®. Scans of the Geological Map (1:250,000) (see Appendix 10), the Hydrogeological Map (1:250,000) (see Appendix 11), and sheets of the Topographical Map (1:50,000) were first cut to the actual map section using Adobe® Photoshop® CS to minimize the data volume. Afterwards, the cut maps were georeferenced with ESRI® ArcMap®. Especially the topographical maps had to be cut since they were later on put together as a mosaic and the overlapping edges would have caused unclean transitions. Nevertheless, little overlap effects could not be avoided due to the nature of the projection used to plot the topographical maps exhibiting non-parallel outlines. In a further step, all geological formations, major fault structures, hydrogeological features, important rivers, relevant mountains, major settlements, and main roads were digitized separately in the map section shown in the Geological Map (1:250,000) (the so called Banda Aceh Quadrangle (see chapter 3.2.1.2)). A digital river network was available but due to its inconvenient fit with the maps and satellite images and its poor quality it was digitized again especially for the study area southwest of Krueng Aceh. For the area northeast of Krueng Aceh the main rivers were plotted to show the major drainage directions (see e.g. figure 3-1). Additional information on single features like, for instance, geological descriptions was added to the respective attribute tables in ESRI® ArcMap®. These data are now available as “shapefiles” which can be used with many GIS and mapping software. The symbology of the geological formations was taken from the original map legend and digitized as good as possible (see figure 3-4). Anyhow, the short names of the geological formations were replaced by labels consecutively numbered in alphabetical order of the formation names (e.g. Murlr replaced by g29 representing the Reef Member of the Raba Limestone Formation) (see table 3-1). For comparison the original short names are also listed in a detailed table (see Appendix 2). In the following chapters the formation names will always be stated together with their respective labels since the labels will be displayed in all geological maps. All digitized features were later on clipped to the dimensions of the study area located only in the mountainous western part of the Banda Aceh Quadrangle (see chapter 3.1.1).

52 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 4 Basic data and methodology

4.2.1 Classification of hydrostratigraphical units According to their lithological and hydrogeological properties, the geological formations in the study area were combined to five hydrostratigraphical units (unit 1 – unit 5) with different hydrogeological properties (see chapter 5.1). Information on the lithology (see chapter 3.2.2) and data from the Hydrogeological Map (1:250,000) (see Appendix 11) and the Hydrogeological Map (1:1,000,000) (see Appendix 12) was used to determine the different units. Several geological formations combined to the same hydrostratigraphical unit were given the same symbology according to the color code (see table 5-1). They were saved as individual “shapefiles” to be able to display them and to conduct further analysis in ESRI® ArcMap® (see figure 5-1).

4.3 Digital elevation model

A digital elevation model (DEM) was needed to determine altitudes of point features such as not GPS-measured spring locations as well as for the generation of topographical profiles that would later be used as the basis for geological profiles. Furthermore, the elevation data can be used to generate shading effects in ESRI® ArcMap® to visualize the 3-D topography on 2-D top view maps. SRTM™ data were used to generate the DEM. These satellite data were recorded during the Shuttle Radar Topography Mission (SRTM™, operated by NASA in 2000) and exhibit information about surface altitudes. They show a resolution of 90 m/pixel and are available for the whole world (online source 21). The raw data had to be transformed and processed using Global Mapper® to be displayable in ESRI® ArcMap®. During this step voids that existed in the raw data (e.g. where clouds disguise the surface) were automatically interpolated by the surrounding raster values. Besides determining altitudes of selected point features and the generation of shading effects (hillshade function) in ESRI® ArcMap® the obtained raster data were used to generate contour lines interpolated at intervals of 25 m, e.g. to be able to determine mountain peaks visually. To create the topographical basis for a geological profile the SRTM™ raw data of a certain line section were exported as “.xz-files” (distance/elevation files) using Global Mapper® and afterwards exported as raster graphics using Grapher®.

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 53 Chapter 4 Basic data and methodology

4.4 Lineament mapping

4.4.1 Mapping procedure

Major geological fault-zones and fractures were detected by a lineament mapping via remote sensing. In the following the technique of the mapping will be explained whereas the results and the further investigations on the occurring lineaments are described in chapter 5.4. The lineament mapping was conducted optically via remote sensing using Landsat TM™ and Aster™ satellite images as well as aerial photographs provided by the MANGEONAD project. Satellite images are available for the whole Banda Aceh Quadrangle while aerial photographs are only available for the coastal areas. Nevertheless, the Aster™ images exhibited too heavy cloud cover to be analyzed. Radar data derived from the Envisat™ and Radarsat™ satellites were not suitable for an analysis due to shadow effects. Automated detection of linear structures aided by so called “edge detection techniques” was supposed to be impracticable since anthropogenic structures would predominantly be detected and geological features would be cushioned by the strong relief, dense vegetation, and illumination and shadow effects leading to misinterpretations. Mainly a false-colored Landsat TM™ scene (scene 08/15/2008, Path 131, Row 56) (see figure 4-1) was used to detect the lineaments representing structural features on the surface while the aerial photographs were partly used for verification. The RGB-channels (color space Red-Green-Blue) of the scene were set to 7(R) 4(G) 1(B) using the GIS-imagery software ERDAS® Imagine®. This approach proved to display the surface structures very well. On the basis of the false-colored images linear structures were detected optically and mapped by plotting them as digital features. The mapped lineaments were checked afterwards and compared to true colored images to identify and delete features of anthropogenic origin. In fact, in the study area and especially in the higher mountain range no anthropogenic elements were found due to any existing settlements or infrastructure in these areas (also see chapter 3.1.6). Natural but geologically unimportant lineaments were also deleted to receive a map only comprising elements reflecting structural features such as faults, fractures or large fissures (see figure 4-1). Locations of the mapped lineaments were compared to those published on the Geological Map (1:250,000) (see Appendix 10) showing well correlations and were also ground checked in the field when accessible (most highland areas could not be checked since they were difficult to access). Up to this point the lineament mapping and ground check were accomplished by Dr. Uwe Schäffer (BGR). The respective BGR project report is still in processing.

54 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 4 Basic data and methodology

Figure 4-1: Lineaments (red lines) on a false-colored satellite image of the Banda Aceh Quadrangle (Landsat TM™ scene 08/15/2008, Path 131, Row 56; RGB-channels 7(R) 4(G) 1(B)) (image provided by Dr. Uwe Schäffer (BGR)) (for larger image see Appendix 7)

4.4.2 Segmentation of lineaments

The mapped lineaments were not strictly straight but were slightly bended and angled following the more or less large-scale linear structures. Nevertheless, differences in lineament directions show different tectonic encroachments and even small variances can have different origins (WENCAI 1990; STADLER, SACCON et al. 2003). Not strictly straight lineaments were manually segmented into several straight vectors having distinct orientations (see figure 4-2) (compare TAM, DE SMEDT et al. 2004). This was done to restrict interpolation effects during software-based statistical analysis aroused by too many small segments the bended lineaments would be cut to by the software. The segmentation was done manually with ESRI® ArcMap®. Afterwards the lineaments that were first drawn over the whole Banda Aceh Quadrangle were limited to the study area. This was done to avoid effects by lineaments outside the study area on the later analysis. Lineaments that reached over the border of the study area were not truncated to keep their original length (see figure 4-3).

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 55 Chapter 4 Basic data and methodology

Figure 4-2: Example of the segmentation of bended and angled lineaments into straight features with distinct orientations (manually done using ESRI® ArcMap®)

Figure 4-3: Lineament mapping results for the study area (segmented lineaments)

56 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 4 Basic data and methodology

4.4.3 Analysis of lineament distribution The lineament distribution was analyzed using diagrams generated with Grapher® and Origin®. Statistical analysis of important features like lineament intersections was accomplished using the statistics tools provided by ESRI® ArcGIS®. Especially the “Density” function of the “Spatial Analyst Extension” was used in this respect. The results are described and interpreted in chapter 5.4.1.

4.5 Detection of springs via remote sensing In addition to the spring locations obtained in the field or derived from the Hydrogeological Map (1:250,000) (see Appendix 11) further springs were mapped via remote sensing. High- resolution satellite images were used to detect springs throughout the whole study area. The main tool was the Google Earth™ map service providing QuickBird™ and Landsat TM™ images for the study area. Additional Landsat TM™ data, other BGR-internal satellite data, and aerial photographs were provided by the remote sensing section of BGR. Besides obvious large springs with high discharge rates smaller springs were assumed by backtracking water-bearing river courses to their source. Certainly, springs that discharge into creeks or rivers along the water-bearing river course can hardly be detected using this technique. Nevertheless, it became clear that this method of detecting spring locations using satellite data even works in tropical regions with high plant and forest cover. The other spring locations (measured or taken from map locations) were partly not known or were not taken into account during the mapping on satellite images. This approach showed that most of the measured springs were also detected via remote sensing which proved the operational benefit of the technique. In most cases water-bearing river courses were followed upstream until the edge of the mountain range. There, the rivers or creeks can be followed further upstream up the respective valleys to their assumed spring. Naturally, the assumed spring locations in chapter 5.2.1 detected by this method have a certain confidence region in the way that they cannot be clearly projected to a single point with definite coordinates. The confidence region is supposed to be in the range of some tens of meters. Nevertheless, the assumed springs are displayed as point features like the other springs in the analysis with ESRI® ArcMap®. Assumed spring locations were deleted when coinciding with GPS-measured locations or with locations derived from the Hydrogeological Map (1:250,000) (see Appendix 11). Altitudes of assumed spring locations where furthermore derived from the DEM (see chapter 4.3) and justified with adjacent GPS-measured spring locations (if available) and with interpolated elevation data provided by the Google Earth™ map service. In this regard, GPS- measured altitudes are supposed to be most assured. In case of strong variations between

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 57 Chapter 4 Basic data and methodology altitudes derived from the DEM and provided by the Google Earth™ map service an average altitude was calculated especially when no adjacent GPS-measurements were available. The satellite image example taken from the Google Earth™ map service and used for explanation in the according Diploma thesis cannot be shown in this report due to copyright restrictions.

4.6 Detection of submarine discharge using thermal imagery

To determine submarine freshwater discharges into the Indian Ocean from the karst formation on the west coast (Reef Member of the Raba Limestone Formation, g29 (see chapter 3.2.2.1.1)) an aerial survey was conducted by BGR and Indonesian counterparts during which thermal imagery was recorded using a thermal camera. Thermal imagery provides information on surface temperatures and can therefore be used as a tool to detect colder groundwater inflows into warmer ocean water (information by Dr. Uwe Schäffer (BGR)). On the coastline near Lho’nga and Leupung thermal images were recorded along four parallel flight-strips (see figure 4-4) and GPS data were supposed to be taken simultaneously for later spatial correlation. After receiving the data it became obvious that the survey was not conducted according to plan by the Indonesian counterparts. Partly wrong aircraft altitudes as well as partly not documented correlations between GPS-measurements and respective thermal images inhibit a complete analysis of the data. Nevertheless, some data can be analyzed but the analysis is still in processing at BGR. Therefore, a spatial correlation on a map is not yet possible and only two thermal images (see figures 4-5, 5-7, and 5-8) are shown as examples and are explained in chapter 5.3. The images were taken by a FLIR® P640 camera 90 min before sunrise to avoid side-effects by light reflections. Flight altitude was around 1,000 m at 110 knots cruise. At a 640 x 480 resolution the images show a section of 830 m width and 625 m height. The respective BGR project report is still in processing.

58 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 4 Basic data and methodology

Figure 4-4: Flight-strips along the west coast where thermal images were taken

Figure 4-5: Example of a thermal image taken on the flight-strips along the west coast (see figure 4-4); scale on the right shows the min. and max. temperature recorded in the image section; spot means temperature in the reticle; temperatures are only approximated due to no reference temperature measured on the ground but the general trend can be distinguished

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 59 Chapter 4 Basic data and methodology

4.7 Calculation of long-term effective groundwater recharge rate Concerning karst water galleries with known catchment areas, the long-term effective groundwater recharge rate can be calculated from long-term discharge rates (after HÖLTING

1996). This is done using the following formulas. Equation 1 (after HÖLTING 1996) gives the long-term effective groundwater recharge rate as [l/(s·km²)] while equation 2 shows the conversion to [l/(m²·a)] which equals [mm/a]. To figure out what percentage of the actual long-term mean precipitation discharges into the ground, and hence, through the gallery, equation 3 is used.

parameters:

Gr: long-term effective groundwater recharge rate

Qm: long-term mean discharge from the gallery [l/s]

Au: groundwater catchment area [km²] P: long-term mean precipitation [mm/a] ET: long-term mean evapotranspiration [mm/a] 60·60·24·365.25: conversion factor from second to year including leap years

Q []l / s Equation 1: G []l /(s ⋅ km²) = m r [] Au km²

G []l /(s ⋅km²) ⋅()60⋅60⋅24⋅365.25 Equation 2: G []mm/ a = r r 1⋅106

G []mm / a Equation 3: G []% = r ⋅100 r ()P − ET []mm / a

In the following a model calculation is shown for the “gallery system Mühlau” in Austria (also see chapter 2.2.3.3):

given parameters: Qm: 1370 l/s, Au: 33 km², P: 2000 mm/a, ET: 500 mm/a

1370 []l / s Equation 1: G []l /(s ⋅km²) = = 41.5 l /(s ⋅km²) r 33 []km²

41.5 []l /(s ⋅km²) ⋅()60⋅60⋅24⋅365.25 Equation 2: G []mm/ a = = 1310 mm/ a r 1⋅106

1310 []mm / a Equation 3: G []% = ⋅100 = 87.3 % r ()2000 − 500 []mm / a

60 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 5 Hydrogeology of a potential target area for a karst water gallery

5 Hydrogeology of a potential target area for a karst water gallery

In this chapter the hydrogeology of the study area is investigated. It is tried to figure out the general hydrogeological properties by different approaches. In particular, the limestones of the study area as potential host formations for a karst water gallery are analyzed. This is done to understand the overall hydrogeological drainage pattern which is important for a comparison with the situation at the example locations shown in chapter 2. A combined hydrogeological model will be given in chapter 5.6 summarizing the results of the different investigations.

5.1 Hydrostratigraphical units

Groundwater recharge and especially groundwater flow are massively dependent on the lithology of the considered area. Lithological properties eminently affect parameters like permeability or storage coefficients of rock formations (GOLDSCHEIDER, DREW et al. 2007;

HÖLTING 1996). To determine which carbonate formations in the study area exhibit productive aquifers and which formations could act as aquitards retaining the groundwater in adjacent carbonate formations a classification of hydrostratigraphical units was conducted. Therefore, the geological formations derived from chapter 3.2.2 were combined to five units which are subdivided after the potential occurrence and productivity of groundwater aquifers from extensive productive to not productive (see table 5-1 and figure 5-1). For a more exact classification a further subdivision of the geological formations given by BENNET, BRIDGE et al. 1981 would have been necessary especially delineating outcrops of different materials combined in the same formation (see table 3-1). A more detailed field mapping would be an important future task in this respect (also see chapter 7).

5.1.1 Hydrostratigraphical unit 1 Only three hard rock formations in the study area could be classified as productive in the sense of potentially comprising productive aquifers that could be exploited for water supply. Besides the Lamno Limestone Formation (g19) consisting of layered limestones, the Reef Members of the Raba Limestone Formation (g29) and the Lamno Limestone Formation (g20) are supposed to conduct high amounts of water. Both formations comprise massive karstified limestones which form reef-like bodies and are supposed to be thick-layered. The matrix permeability of the pure limestone is low (HÖLTING 1996). Nevertheless, the total rock-mass permeability of these rocks can be assumed as high since groundwater flow occurs through fissures, fractures, and solution cavities or along bedding planes enlarged by dissolution of

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 61 Chapter 5 Hydrogeology of a potential target area for a karst water gallery the circulating water (SOETRISNO 1993; HÖLTING 1996). Dissolution phenomena are caused by karstification and the mentioned formations show highly active karstification. Especially the Raba Limestone Formation and its Reef Member (g28, g29) are widely underlain by the Lhoong Formation (g22) (see figure 3-6) which potentially acts as aquitard and could retain the water in the overlying rocks.

Table 5-1: Hydrostratigraphical units

Color Formation Label Hydrostratigraphical unit code Lamno Limestone Formation (Reef Member) g20 Raba Limestone Formation (Reef Member) g29 unit 1: productive Lamno Limestone Formation g19 Indrapuri Complex g10 Kotabakti Formation (Padangtiji Member) g14 Lho'nga Formation g21 Lhoong Formation g22 Meucampli Formation g23 Peunasu Formation g26 unit 2: poorly productive Raba Limestone Formation g28 Seulimeum Formation g32 Tangla Formation g36 Tangla Formation (Keubang Member) g37 Tangla Formation (Ligan Member) g38 Bentaro Volcanic Formation g3 Calang Volcanic Formation g5 unit 3: not productive; volcanics Geumpang Formation g6 Geunteut Granodiorite g8 Miscellaneous intrusives g25 unit 4: not productive; intrusives Sikuleh Batholith (older complex) g34 Alluvium g1 unit 5: locally to extensive Indrapuri Formation g11 productive Meulaboh Formation g24

5.1.2 Hydrostratigraphical unit 2 The consolidated sediments in this unit are classified as poorly productive. They mainly consist of highly deformed sandstones, argillaceous or siliceous limestones, and conglomerates with fine grained matrix which are mostly thin-bedded and interlayered by siltstones or mudstones. Hydrostratigraphical unit 2 mainly comprises the Tertiary sediments of the Indrapuri Complex (g10), the Padangtiji Member of the Kotabakti Formation (g14), the Meucampli Formation (g23), the Peunasu Formation (g26), the Seulimeum Formation (g32), and the Tangla Formation (g36) with its Keubang (g37) and Ligan Members (g38). Other than the adjacent massive limestone formations, the Pre-Tertiary Lhoong Formation (g22), Lho’nga Formation (g21), and Raba Limestone Formation (g28) are also supposed to exhibit poorly productive aquifers. These rocks are also thin-bedded, highly deformed, and interlayered by siltstones which are supposed to act as aquitards. It cannot be excluded that groundwater potential is higher in the limestone layers between the interlayered materials.

62 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 5 Hydrogeology of a potential target area for a karst water gallery

But due to the presumably high deformation of these rocks no drainage pattern can be forecasted especially because of the unknown occurence of materials acting as aquitards.

Figure 5-1: Hydrostratigraphical units in the study area; black labels mark geological formations

5.1.3 Hydrostratigraphical unit 3 and 4 Partly metamorphosed volcanics comprising the Bentaro Volcanic Formation (g3), the Calang Volcanic Formation (g5), and the Geumpang Formation (g6) as well as the intrusive complexes consisting of the Geunteut Granodiorite (g8), the Sikuleh Batholith (g34), and the Miscellaneous intrusives (g25) are classified as not productive and also act as aquitards. Generally low permeabilities limit the potential groundwater flow to weathered zones

(SOETRISNO 1993). It cannot be excluded that major fissures and faults could drain these rock formations besides surface drainage, but, as will be described in the following (chapters 5.2 and 5.4), accumulations of fault zones and appearance of springs could not be observed in this unit on the major scale.

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5.1.4 Hydrostratigraphical unit 5 The Quaternary successions represented by the Alluvium (g1), the Indrapuri Formation (g11), and the Meulaboh Formation (g24) are classified as locally to extensive productive. They are mainly composed of unconsolidated sediments, mostly sands and gravels, and are mostly spread over the coastal plains (compare figures 3-5 and 5-1). In the western part of the study area these unconsolidated sediments are likely to form extensive multi-layer aquifers with high to moderate permeabilities (SOETRISNO 1993; PLOETHNER, SIEMON 2005). These aquifers can be exploited by wells, e.g. by dug wells that constituted the main possibility for drinking water supply around Banda Aceh before the 2004 tsunami (see chapter 1). Regions with mostly incoherent aquifers of low thickness are located in the smaller coastal plains on the west coast maybe due to the regionally changing sedimentation milieu caused by the fast uplift of the western mountain range (SOETRISNO 1993) (see chapter 3.2.3).

5.2 Springs and karst levels

To determine the drainage pattern in the study area spring locations were detected using many different basic data (see Appendix 3). For most springs no names are available and those which are available are subject to change in different reports and on maps. Therefore, the springs were given ID’s and one should rather refer to the respective coordinates than to uncertain names. Generally single springs or lines of springs discharging hard rock formations mark locations where preferential groundwater flow paths reach the surface. This can be the case where groundwater is dammed by underlying or unconformably attached aquitards or where layers of rock formations crop out at the surface (HÖLTING 1996). Lines of springs can often be observed in karstified rock formations where they mark active karst levels (STRAHLER,

STRAHLER 2002). These karst levels are mostly located along the perimeter of the erosion base, i.e. at river valleys and at the sea level (MILANOVIC 2000).

5.2.1 Spring locations

GPS measured locations of karst springs were provided by survey reports (PLOETHNER,

SIEMON 2005; KELLER, NICOLE 2006) and unpublished data recorded by staff members of BGR during field observations to the southwest of Banda Aceh within the scope of BGR projects. Additional data like chemical analysis or discharge characteristics are also available for some springs. It has to be stated that the activities of BGR in the study area, and hence the recorded spring locations are limited to the northern part of the study area where the Reef Member of the Raba Limestone Formation (g29) prevails (see figure 3-5).

64 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 5 Hydrogeology of a potential target area for a karst water gallery

Further spring locations are published on the Hydrogeological Map (1:250,000) (see Appendix 11) with estimated discharge rates. Besides GPS measured springs and those taken from the Hydrogeological Map (1:250,000), more spring locations were assumed via remote sensing using satellite images and aerial photographs (see chapter 4.5). All spring locations are shown with their according rivers in figure 5-2. It has to be noted that not all creeks or rivers have to be running at all time due to non-perennial discharge of some springs (also see Appendix 3). Moreover, some springs are also known to be captured and piped for drinking water supply which leads to lower or no runoff in the according river beds.

Figure 5-2: Spring locations in the study area; black labels mark geological formations

In chapter 5.1 it was shown that only the Reef Members of the Raba Limestone Formation (g29) and of the Lamno Limestone Formation (g20) and the Lamno Limestone Formation

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(g19) itself can be supposed to act as potentially productive aquifers. This assumption can be substantiated by the distribution of springs in the study area. It is obvious that most springs are located within formations classified as productive (hydrostratigraphical unit 1) (see figure 5-2) especially around the Reef Member of the Raba Limestone Formation (g29) in the northern part of the study area and within the Lamno Limestone Formation (g19) including its Reef Member (g29) to the north and northeast of Lamno. Within poorly productive formations (hydrostratigraphical unit 2) only detached spring locations can be observed. These are mostly assumed springs with only a set of published and GPS measured springs to the south of Leupung within the Raba Limestone Formation (g28). In formations classified as not productive (hydrostratigraphical unit 3 and 4) almost any springs appear. Only a few springs emerge at the west coast mostly in volcanic formations (hydrostratigraphical unit 3) but these seem to have a strong relationship to neighboring productive formations since they all occur near boundaries to hydrostratigraphical unit 1. Especially the springs within hydrostratigraphical unit 2 seem randomly positioned at first sight. In fact, these locations are far from being random but are strictly bound to a network of fault-structures. This will be explained in chapter 5-6. Springs which are located in the unconsolidated sediments classified as hydrostratigraphical unit 5 only occur very close to outcrops of hard rock formations. Therefore, they are always assigned to the according hard rock formations since there exists no evidence arguing for the emergence of springs from the unconsolidated formations near hard rock outcrops.

Regarding the data available within the framework of this thesis, it is obvious that the highest density of spring locations exists around the Reef Member of the Raba Limestone Formation (g29) especially near the northeastern corner of the study area (see figure 5-3). It is supposed that some more springs must exist in the other parts of the large study area than those delineated in this thesis but were not published or otherwise available. Detection via remote sensing proofed to be a suitable tool for the locating of larger springs (see chapter 4.5) but the low number of springs especially in hydrostratigraphical unit 2 shows that certainly there must have been springs left undetected.

66 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 5 Hydrogeology of a potential target area for a karst water gallery

Figure 5-3: Spring locations in the area around the Reef Member of the Raba Limestone Formation (g29); black labels mark geological formations, white labels show spring ID’s

5.2.2 Discharge and water quality The GPS measured springs deliver the most valuable information on the karst water properties within the scope of this thesis. Due to the fact that measured discharges and chemical analysis are only available for some of these springs (see table 5-2), the following chapters mostly focus on the area around the karstified reef-like limestone body (g29, hydrostratigraphical unit 1) where the GPS measured springs are located. All springs in the limestone body or those that have a relationship with this formation, e.g. occurring near the formation boundary, are shown in Appendix 4.

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 67 Chapter 5 Hydrogeology of a potential target area for a karst water gallery

Table 5-2: GPS measured springs with discharge rates and chemical water analysis (for further details see Appendix 4)

EC [μS/cm] Spring Discharge Discharge Temperature Hardness Water- Name (uncertain) Description (corrected to pH ID [l/s] characteristics [°C] [°dH] type 25°C) 273 (800 Spring of Krueng Raba huge dammed karst spring; min. 10; reported after Ca2+- 1 perennial - 7.4 8.0 - (ID: MW-006) start of Krueng Raba max. > 300 longer dry HCO3 period) Mata Gle Taron (also completed in 1904/05; Ca2+- 2 < 50 non-perennial 25.7 350 7.5 - - Gue Gajah) captured and piped HCO3 Leu Ue (Mata Ie, piped; completed in year 100 (min. 25; Ca2+- 8 perennial 21.8 270 7.5 - - Mosque) 1904/05 max. 240) HCO3 piped; completed in year Ca2+- 9 Leu Ue (Mata Ie, Bath) - - 21.8 290 7.3 - - 1904/05 HCO3 Ca2+- 10 Payaroh (Biluy Spring) at top of waterfall - perennial 23.9 320 7.8 - - HCO3 Ca2+- 11 Payaroh (Biluy Spring) at bottom of waterfall 15 (min. 5) perennial 25.0 320 7.9 - - HCO3 Ca2+- 17 Karst-01 - - non-perennial 25.7 287 7.3 - - HCO3 supposedly non- Ca2+- 18 Karst-02 - - 24.3 319 7.5 9.4 - perennial HCO3

The springs show different discharge rates from 0 l/s estimated for non-perennial springs during dry periods to more than 300 l/s after precipitation events. This conspicuously shows the temporally highly diverse discharge regimes in the karst area. However, the springs generally show similar parameters concerning water quality. Water temperatures are around 25 °C with slightly lower temperatures at spring ID 8 and 9 with 21.8 °C. The waters are only slightly colder than the mean daily air temperatures of 25 – 27 °C (see chapter 3.1.4). EC values range around 300 μS/cm but they are expected to be dependent on the time of the measurement, e.g. before or after a precipitation event (see chapter 5.2.2.1). All springs show slightly basic pH values around 7.5. Water hardness was only measured for two springs with 8 °dH at spring ID 1 and 9.4 °dH at spring ID 18. Analog hardness values are estimated for the otherwise relatively similar karst spring waters. 2+ - Overall the quality of the measured karst waters (Ca -HCO3 -type) can be described as very good concerning the given parameters. Nevertheless, high water temperatures combined with fast flow through the rock-mass after high precipitation events could contribute to bacteriological contamination (STÜBEN, NEUMANN 2006). Turbidity is also assumed to increase after high rainfall (MILANOVIC 2002).

Further discharge rates are provided by the Hydrogeological Map (1:250,000) (see Appendix 11) for springs all over the study area but these only represent estimations. Concerning the area around the Reef Member of the Raba Limestone Formation (g29) all discharge rates of springs taken from this data source are classified as less than 10 l/s except for spring ID 31 with a discharge rate of 50 – 100 l/s. The latter is located close to the spring ID’s 8 and 9 (both part of the location sometimes called Mata Ie) which also exhibit high discharge rates and it is possible that spring ID 31 represents the same spring location. Nevertheless, this is uncertain especially since another huge spring taken from the

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Hydrogeological Map (1:250,000) was deleted yet in favor of the more exact GPS measured location. Therefore, spring ID 31 is seen as independent spring and is not deleted.

Except for spring ID 1 (see chapter 5.2.2.1) no long-term discharge measurements exist for any of the karst springs but these would be necessary to determine mean discharges.

Karst spring discharges mostly show a direct dependence on precipitation (MILANOVIC 2000), especially in highly karstified tropical regions (SWEETING 1995). Against this background the available discharge rates and water quality measurements have to be considered as single point measurements in time of rather qualitative significance.

Figure 5-4: Discharge characteristic of spring ID 1 (spring of Krueng Raba) after two precipitation events measured by the rise of the water level above the ground of the dammed reservoir; dots represent hourly measurements (modified after original image provided by Jens Böhme (BGR))

5.2.2.1 Discharge characteristics of spring ID 1 (spring of Krueng Raba)

The spring of Krueng Raba (spring ID 1) is the largest spring in the study area. It is located at the northern edge of the Reef Member of the Raba Limestone Formation (g29) (see figure 5-3) near the town Lho’nga and it is captured by a dammed pond (see Appendix 6). Discharge is perennial and rates of 10 l/s during dry periods and of more than 300 l/s shortly after precipitation events can occur. This discharge characteristic was also surveyed by Jens Böhme (BGR) within the scope of the MANGEONAD project. A data logger was installed to measure the water level above the ground of the dammed pond. Figure 5-4

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 69 Chapter 5 Hydrogeology of a potential target area for a karst water gallery shows that the spring reacts very quickly to precipitation events. After a precipitation event on July 14th, 2008, the water level rose from 4 to 4.7 m agl and sank again after only one day to 4 m agl. After a second heavier precipitation event on July 16th, 2008, the water level rose even faster from 4 to 6.6 m agl and began to sink again after about a week. The electrical conductivity of the water was reported to be around 800 μS/cm after a longer dry period before the precipitation events and decreased to about 220 μS/cm shortly after the second event during high discharge (information by Jens Böhme (BGR)). The quick reaction to the precipitation event can be attributed to the mature karstification in the area around Lho’nga (see chapter 3.1.3 and Appendix 5) causing vast water flows through presumably huge karst cavities.

5.2.3 Karst levels

Information on possible karst levels in the Reef Member of the Raba Limestone Formation (g29) are derived from elevations of karst spring locations and from information about their discharge characteristics (see Appendix 4 and chapter 5.2.2). Information on whether a spring discharge is perennial or non-perennial can be very important since perennial springs are supposed to mark active karst levels. On the other hand, non-perennial springs can represent outlets of palaeo karst levels which become active when the groundwater table rises after high precipitation events (STRAHLER, STRAHLER 2002; GOLDSCHEIDER, ANDREO 2007).

The elevation distribution of the karst springs is shown in figure 5-5. Due to the relatively low number of 40 springs and the elevation range from 11 to 1,108 m asl the class width (bin size) in this histogram was adjusted to only 7 m. This was done to display all elevations in one diagram and to avoid unintentional merge of elevations probably representing different karst levels. Nevertheless, spring ID’s 52, 53, and 54 were left out of the further investigation since they are relatively high elevated and the distance between them is fairly big so that they cannot be interpreted as a single karst level. Furthermore, they are located in the south of the focused limestone formation (g29) with no adjacent reference springs (see figure 5-3).

70 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 5 Hydrogeology of a potential target area for a karst water gallery

Figure 5-5: Elevation distribution of all springs in Reef Member of Raba Limestone Formation (g29); number of bins 160, bin size 7 m

To focus on the remaining spring elevations from 0 to 350 m asl figure 5-6 shows only this part of the histogram. It can be seen that spring elevations in this range form several accumulations which can be interpreted as possible karst levels. Due to the fact that assumed springs also contribute to the analysis, the karst levels described in the following have to be seen as approximated. Spring ID’s related to the delineated possible karst levels are shown in table 5-3.

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 71 Chapter 5 Hydrogeology of a potential target area for a karst water gallery

Figure 5-6: Elevation distribution of springs in Reef Member of Raba Limestone Formation (g29) with possible karst levels, focused on elevations from 0 to 350 m; dashed ellipse marks uncertain single spring; number of bins 160, bin size 7 m, x-axis truncated at 350 m

Table 5-3: Karst levels and according spring ID’s

Elevation Mean elevation Karst level Spring ID range [m asl] [m asl] 1, 2, 4, 5, 6, 8, 9, 12, 13, 14, 16, 1 10 - 70 40 17, 18, 19, 20, 31, 45, 47, 49, 50, 51, 67, 68, 69 2 80 - 140 110 10, 11, 21, 44, 46, 48, 71, 74, 75 3 280 - 320 300 15, 66, 70

The first accumulation occurs from about 10 to 70 m asl (see figure 5-6). It is interpreted as karst level 1 located near the erosion base, i.e. the sea level. The accumulation may be subdivided at about 25 m asl into two karst levels from 10 to 25 m asl and from 25 to about 70 m asl but this is fairly uncertain. Karst level 2 is assumed at about 80 to 140 m asl. The two springs from 126 to 140 m asl are located slightly aside from the

72 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 5 Hydrogeology of a potential target area for a karst water gallery major accumulation of the possible karst level 2 but are incorporated as well. Karst level 3 is assumed from about 280 to 320 m asl. The single spring at about 200 m asl is left out since no adjacent springs appear which could contribute to the delineation of another karst level. Karst level 1 (mean elevation 40 m) is supposed to be the most active karst level. It consists of many springs discharging near the sea level comprising the largest perennial springs with the highest discharges (spring ID’s 1, 2, 8, 9, 31) (see Appendix 4). Nevertheless, all known non-perennial springs (spring ID’s 2, 16, 17, 18) are also included in this karst level but they are located in the higher range from 25 to about 70 m asl. Due to this fact, the most active karst level could well be expressed by the mentioned lower range of karst level 1 from 10 to 25 m asl and the range from 25 to about 70 m asl could also be a higher elevated separate karst level which is activated when the groundwater table rises, e.g. after high precipitation events. Karst level 2 (mean elevation 110 m) comprises two known perennial springs (spring ID’s 10, 11) which shows that this level also seems to be active throughout the year. Nevertheless, the overall discharge rates are much lower than those exhibited at large springs in karst level 1. Karst level 3 (mean elevation 300 m) is comprised by a line of one GPS-measured and two assumed springs (spring ID’s 15, 66, 70). It is not known if these springs are perennial or non-perennial so no conclusion can be made if karst level 3 is active or not. Considering only the high altitude it could be a palaeo karst level which only becomes active during heavy precipitation events. However, possible aquitards located near these springs (hydrostratigraphical unit 2, especially Raba Limestone Formation (g28)) (see figure 5-3) could retain the groundwater leading to possible perennial spring discharges.

5.3 Submarine discharge Submarine groundwater discharge is assumed to appear at the west coast into the Indian Ocean emerging from the Reef Member of the Raba Limestone Formation (g29) (compare figure 4-4). Although the thermal images which should be used to distinguish the freshwater inflows into the sea were not analyzable or are still in processing by BGR (see chapter 4.6), it is assumed that high amounts of groundwater discharge into the ocean along the west coast. Generally, it was hoped that submarine discharges could be detected where important lineaments would extend into the ocean (see figure 5-9). SESÖREN 1986 and ELKHATIB,

GÜNAY 1993 described this phenomenon for lineaments extending into the Mediterranean Sea from two large karst areas in southern Turkey. In both cases large fault structures are supposed to reach into the sea represented by lineaments encountered on Landsat TM™

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 73 Chapter 5 Hydrogeology of a potential target area for a karst water gallery satellite images. These faults may provide high discharges of freshwater especially after heavy rainfall (SESÖREN 1986; ELKHATIB, GÜNAY 1993).

Considering the study area it can generally be said that groundwater inflow from the karstified limestones on the west coast exists. This qualitative conclusion can be substantiated by two examples of the thermal images. Sadly, these images could not yet be spatially correlated (see chapter 4.6) so that no comparison between the inflow locations and the encountered lineaments (see chapter 5.4) could be made. Example 1 (see figure 5-7) shows a point inflow of colder water from the coast (dark colored limb-like feature) into the warmer ocean water. Since no river or other surface inflow can be encountered on the coastline this feature can be seen as groundwater discharge from the coastal rock formation. Due to its elongate inflow the water may well be discharging through a linear fault structure. Example 2 (see figure 5-8) shows more extensive inflows of colder water (dark colored plume-like features) into the ocean. These may be interpreted as groundwater inflows through a submarine level of karst cavities. In both examples the groundwater inflows are only visible near the coastline. It is believed that quick mixture of cold freshwater and warm ocean water takes place due to high swell near the coast.

Figure 5-7: Thermal image, example 1; circle marks a point inflow of groundwater into the Indian Ocean; section width 830 m, section height 625 m

74 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 5 Hydrogeology of a potential target area for a karst water gallery

Figure 5-8: Thermal image, example 2; ellipses mark extensive plume-like inflows of groundwater into the Indian Ocean; section width 830 m, section height 625 m

5.4 Lineaments Lineaments are defined as more or less straight mappable lines on the earth’s surface that can be attributed to discontinuities of different kind. They can either be of anthropogenic or natural origin. Anthropogenic origins are in most cases related to land use, e.g. boundaries of agricultural fields, other typical straight lines can be aroused by roads, trails or power lines (STADLER, SACCON et al. 2003). Natural elements reflected by lineaments can be trenches, mountain ridges, rock walls, erosion channels and especially faults, fractures, and large fissures representing strain patterns and traces of crust deformations. (WENCAI 1990; STADLER, SACCON et al. 2003). The latter structural elements have to be filtered out from features that are obviously of anthropogenic or topographic origin. This is done by verification and expertise during the lineament mapping (see chapter 4.4).

The common assumption in lineament mapping for groundwater exploration is that linear structural elements reflect vertically extending zones of fracture concentration. These are assumed to be preferential flow paths for groundwater due to increased permeability, weathering, and dissolution (KRESIC, BUSBEY et al. 1994; PAVLOVIC, KRESIC 1990) and are therefore factors controlling e.g. karstification and groundwater potential (LATTMAN, PARIZEK 1964). The method of lineament mapping for the delineation of faults and fractures is well established and has been an integral part of many groundwater exploration programs in hard

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 75 Chapter 5 Hydrogeology of a potential target area for a karst water gallery rock terrains (TAM, DE SMEDT et al. 2004 LATTMAN, PARIZEK 1964). It can be seen as a useful and inexpensive tool to develop a regional hydrogeological concept model and to find the most promising areas of potential groundwater occurrence where further investigations could be concentrated (WENCAI 1990; KRESIC, BUSBEY et al. 1994). Moreover, it is seen as a mandatory procedure when dealing with karst hydrogeology. (GOLDSCHEIDER, ANDREO 2007).

Figure 5-9: Lineaments on hydrostratigraphical units; towns, rivers, and labels are not shown for a clear view on the lineaments

5.4.1 Analysis of lineament distribution

At first sight the lineaments may seem randomly distributed throughout the study area (see figure 5-9) with an accumulation in the northern part and are limited to the Barisan Mountain Range. The accumulation in the northern part derives from the more detailed mapping in this area. In the Quaternary deposits of the coastal plains lineaments cannot be

76 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 5 Hydrogeology of a potential target area for a karst water gallery anticipated. Even if they exist in underlying formations they do not trace through unconsolidated lowland sediments (TAM, DE SMEDT et al. 2004). Nevertheless, in the mountain range which can be seen as the groundwater recharge area lineaments representing faults, fractures, and larger fissures were detected. In the following it will be exhibited that the lineament features are not randomly distributed but reflect tectonic structures which can be considered as the most important condition governing the hydrogeological situation in hard rock formations (OBYEDKOV 1990).

5.4.1.1 All lineaments

At first the distribution of lineament lengths for all lineaments is investigated. Concerning the whole study area lineament lengths from 369 to 11,636 m occur. The length distribution of all lineaments can be described as log-normal (see figure 5-10 A) exhibiting mean lengths of 2,165 m and a median at 1,738 m (see figure 5-10 B). Extremely long lineaments of more than 7000 m length can mostly be assigned to the zone around the Aceh Fault as part of the SFS (see figure 5-9). In the south of the study area long lineaments also extend sub- orthogonal to the strike of the SFS. Long fracture traces are believed to be important since they are able to discharge huge areas even over formation boundaries. This will be further addressed to in chapter 5.6. It has to be stated that histogram class widths were not calculated by predetermined equations like e.g. given by SCHÖNWIESE 2000. These equations should be used e.g. when displaying large numbers of samples to avoid empty classes. In this case it was more important not to distort the distribution in the histogram especially because of the low number of lineaments. Therefore, empty classes were accepted. A class width of two times the shortest lineament proved to display the distributions satisfactorily.

Bidirectional rose diagrams were chosen to display the lineament orientations. Therefore, azimuth orientations of segmented lineaments were calculated with ESRI® ArcGIS®. These orientations represent vector orientations depending on the direction in which they were digitized. Later on, all of these vector orientations exceeding 180° were standardized for azimuths between 0° and 180° by a shift factor of 180°. A lineament showing a vector direction of 270°, for example, would be given a direction of 90° in the diagram. This was done to be able to plot the strike orientations of lineaments as bidirectional rose diagram instead of showing unidirectional vector orientations. The lineament orientations for all lineaments are shown in figure 5-11. Major orientations can be observed from north-northwest to south-southeast and from northeast to southwest. These directions generally match the presumed orientations of neotectonically active subsidiary faults to the major strike-slip system of the SFS which extends from northwest to

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 77 Chapter 5 Hydrogeology of a potential target area for a karst water gallery southeast (see chapter 3.2.3). The lineaments orientated from north-northwest to south- southeast and extending sub-parallel to the SFS may therefore be interpreted as faults resulting from transpressional forces (compare figure 3-7). Lineaments orientated sub- orthogonal to the SFS from northeast to southwest can be interpreted as resulting from transtensional forces. Lineaments not showing these two distinct directions may be interpreted as further subsidiary faults or fractures of other tectonic origin.

Figure 5-10: Length distribution of all lineaments; histogram class width: 738 m = two times shortest lineament

78 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 5 Hydrogeology of a potential target area for a karst water gallery

Figure 5-11: Orientation of all lineaments; class width: 10 °

5.4.1.2 Lineaments in Reef Member of the Raba Limestone Formation (g29)

In the northern part of the study area at the outcrops of the Reef Member of the Raba Limestone Formation (g29) (see figure 5-9) a dense network of lineaments was mapped. Since all known springs are also located there it will be focused on this accumulation of lineaments in the following. Therefore, only the lineaments lying in or extending into the limestone formation (g29) are taken into account. The overall lineament distribution in this area is similar to the distribution of all lineaments shown in chapter 5.4.1.1. The length distribution is also log-normal (see figure 5-12) and lineament lengths range from 381 m to 6,399 m showing a mean length of 1,803 m and a median at 1,553 m. Extremely long lineaments over 7,000 m do not exist here (compare chapter 5.4.1.1). The longest lineaments extend both sub-orthogonal and sub-parallel to the strike of the SFS (see figure 5-9).

Lineament orientations show that the main directions of subsidiary faults to the SFS are also predominantly represented in this area (see figure 5-13). Faults directed from north- northwest to south-southeast prevail but the second main direction from northeast to southwest is also clearly distinguishable.

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 79 Chapter 5 Hydrogeology of a potential target area for a karst water gallery

Figure 5-12: Lineament length distribution in Reef Member of Raba Limestone Formation (g29); histogram class width: 763 m = two times shortest lineament

Figure 5-13: Orientation of lineaments in Reef Member of Raba Limestone Formation (g29); class width: 10 °

80 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 5 Hydrogeology of a potential target area for a karst water gallery

5.4.1.3 Lineament intersections Some workers in hydrogeology are convinced that areas where lineaments intersect are even more important than single lineament traces (LATTMAN, PARIZEK 1964). It is believed that higher fracture densities with many intersections correlate positively with higher groundwater potential in hard rock formations (MAGOWE, CARR 1999). Therefore, intersections of lineaments in the study area were analyzed. They were plotted manually onto the lineament map (see figure 5-14).

Figure 5-14: Lineaments and lineament intersections; purple circles show manually distinguished intersection accumulations

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 81 Chapter 5 Hydrogeology of a potential target area for a karst water gallery

The most obvious accumulations are again located in the Reef Member of the Raba Limestone Formation (g29). Highest intersection densities can be observed to the south of the town Lho’nga and to the west of the town Leupung. This manual analysis is substantiated by an automated statistical analysis conducted with the Density tool of the Spatial Analyst provided by ESRI® ArcGIS® (see figure 5-15). A simple density statistics was calculated by the software. Setting the search radius to 1738 m (median of all lineaments) and the output cell size to 369 m (shortest lineament length) proofed to be quite suitable to display intersection density. Around intersection accumulations the highest density of fractures is supposed. Regarding the lithology of the formation a large network of karst cavities can be assumed at these locations which presumably act as preferential groundwater flow paths. Interestingly, the spring showing the highest discharge in the whole study area (spring ID 1, spring of Krueng Raba, see figure 5-15 and table 5-2) is located very close to the area showing the highest lineament intersection density. It is supposed that the proximity to this highly fractured area causes the observed high discharge rates after heavy precipitation events (see chapter 5.2.2.1). Presumably, a dense network of fractures provides preferential groundwater flow to the spring location with flow direction to the north. The highly mature karstification at the spring can be seen by huge karst cavities around the spring location (see Appendix 6).

82 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 5 Hydrogeology of a potential target area for a karst water gallery

Figure 5-15: Lineaments and lineament intersections overlain by a simple automated density statistics of the lineament intersections; conducted with Density tool of Spatial Analyst in ESRI® ArcGIS®, search radius 1738 m, output cell size 369 m; densities were calculated in the overlying square section

5.5 Closer look at the structural geology of the Reef Member of the Raba Limestone Formation (g29)

Satellite imagery provided by the Google Earth™ map service can be considered the crucial factor for a closer look at the published structural geology of the Reef Member of the Raba Limestone Formation (g29). This can be fundamental for the development of a hydrogeological discharge model in this area.

Topographically, two ridges are separated here by a dry valley which is characterized by the absence of springs and surface drainage. In contrast to the surrounding mountains, the dry valley is deeply incised and exhibits relatively low elevations ranging around 30 – 100 m in the northern part and not exceeding 140 m in the southern part. To the east the limestone

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 83 Chapter 5 Hydrogeology of a potential target area for a karst water gallery formation builds up the highly elevated eastern ridge with altitudes around 900 m directly to the side of the dry valley and up to 1,660 m to the southeast. The western ridge shows lower elevations around 200 – 300 m in the northern part and up to 960 m to the south.

5.5.1 Published interpretation

BENNET, BRIDGE et al. 1981 published two anticlines in this area on the Geological Map (1:250,000) (see Appendix 10), a normal anticline in the higher elevated east and an overturned anticline in the lower elevated west of the formation near the coast. Since there are no greater quarries in these areas, except one near the Lho’nga cement factory, this explanation of the structural geology seems to be only based on the topography and a few smaller outcrops at the sides of the formation that may not be supposed to represent the large-scale structural properties.

5.5.2 New interpretation

5.5.2.1 Interpretation of satellite imagery On satellite imagery of this area one can distinguish several lines of lighter color that clearly stand out from the rest of the mostly forested area. These lines strictly follow smaller ridge-like structures on the limestones to the east of the dry valley, especially in higher altitudes. They are interpreted as heads of layers outcropping at the surface and dipping with a certain angle to the east (compare the German word “Schichtköpfe”). Due to tectonic activity, for instance, material from these outcrops may be eroded and may build up small debris accumulations tracing the strike of the layers through the otherwise forested surface. The satellite image examples taken from the Google Earth™ map service and used for explanation in the according Diploma thesis cannot be shown in this report due to copyright restrictions.

5.5.2.2 Hypothetic structural model

BENNET, BRIDGE et al. 1981 assume that the western limb of the supposed anticline forms the eastern hillside of the dry valley. In contrast to that, the analysis of the satellite imagery indicates that on the eastern hillside of the dry valley layers of the limestone formation crop out with a dipping angle to the northeast, not to the southwest. This assumption would also better correlate with the drainage pattern displayed by the appearance of karst spring locations around this formation (see chapter 5.2.1). At the eastern hillside of the eastern ridge karst springs emerge from the limestone formation and karst levels are expected to be developed near the sea-level and around 110 m and 300 m altitude (see figure 5-6).

84 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 5 Hydrogeology of a potential target area for a karst water gallery

Except one small spring at the northern end (spring ID 16) the dry valley comprises no springs at all although the valley floor widely lies far below the karst levels. Preferential groundwater flow directions are therefore assumed to be almost exclusively to the northeast at the eastern ridge (compare concept of inception horizons by FILIPPONI,JEANNIN 2006)

To clarify the overall structural and hydrogeological situation a structural model was drawn to combine the new hypothetic structural geology and the drainage pattern of the area. The eastern ridge is assumed to show layers dipping to the northeast with a dipping angle of 26°. This angle is calculated from altitude differences on the eastern hillside of the eastern ridge. The western ridge is assumed to exhibit layers also dipping to the northeast and the dipping angle is estimated to be about the same as at the eastern ridge. This is substantiated by photographs taken at spring ID 1 (spring of Krueng Raba, see Appendix 6). There, the general large-scale layering can be seen presumably dipping to the northeast. Nevertheless, this could also be a cutting phenomenon only pretending a general dip to the northeast. The general dip of the layers should be checked three-dimensionally in the field to establish a clear interpretation. In this thesis it is assumed that the layers of the western ridge also dip to the northeast. The idea of a former large anticline spanning over both ridges with the eastern ridge as eastern limb and the western ridge as western limb was discarded. Formation thicknesses would have been too big and near the active subduction zone a more complex structural pattern than a simple huge anticline could be expected. Therefore, both ridges may well be interpreted as two successively overthrusted parts of the same formation (see figure 5-16). Furthermore, it is assumed that the dry valley constitutes an overthrust fault. Overthrusting in a southwestern direction would fit the general structural pattern with main compression forces in northeastern direction resulting in overthrust faults dipping to the northeast (compare chapter 3.2.3 and figure 3-6). Possibly, due to exposition to higher precipitation rates from west monsoon rainfalls (see chapter 3.1.4) the western ridge shows higher erosion. This assumption is substantiated by the fact that the limestones to the west of the dry valley show stronger karstification (compare chapter 5.4.1.3) as can be seen by the typical tropical cockpit karst phenomena developed here, for instance, in the area around the Lho’nga cement factory (see Appendix 5 and Appendix 6). Considering thicknesses one can say that the overall formation thickness can be estimated to be at least 1,500 m. This value is higher than the published thickness of 1,000 m. Anyhow, the published value seems to be a rough estimation as well when looking at figure 3-6. Calculated from horizontal distances between outcrops of layer heads and a dipping angle of 26 ° layer thicknesses are estimated to be around 200 - 300 m. At least,

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 85 Chapter 5 Hydrogeology of a potential target area for a karst water gallery these are maximum values and a subdivision into several layers of lower thickness is possible but not distinguishable by the visible outcrops.

Figure 5-16: Simplified geological cross section E-F; elevation is two times exaggerated

5.6 Combined hydrogeological model Summarizing the overall hydrogeology of the study area it can be said that the classification of the hydrostratigraphical units is substantiated by the different investigations, at least, given the available data. Especially the northern part of the large reef-like complex in the north of the study area stands out in this respect. This Reef Member of the Raba Limestone Formation (g29), classified as hydrostratigraphical unit 1, shows the highest density of lineaments representing potentially water-bearing faults and fractures in an otherwise low-permeable compact limestone. Lineament traces as well as the most spring locations in this area constitute the best known drainage pattern in the whole study area. Other smaller areas classified as hydrostratigraphical unit 1 cannot be interpreted on the basis of the few given data.

Combining the results of the lineament mapping with the encountered spring locations (see figure 5-17) it becomes clear that the overall drainage pattern in the study area can be described as structure-controlled. Almost all springs are located on or near structural elements represented by the lineaments. Exceptions can only be found along the west coast near the towns Gleburk, Glebruk, and Lamno. It cannot be excluded that lineaments were not detected there due to dense vegetation or other effects disguising the structural features. Around the limestone formation in the north (g29) it can also be seen that accumulations of lineament intersections seem to correlate with accumulations of spring locations further downhill connected by a network of lineaments (compare figure 5-15).

86 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 5 Hydrogeology of a potential target area for a karst water gallery

Figure 5-17: Lineaments, lineament intersections, and spring locations highlighting the structure- controlled drainage pattern

In particular, long neotectonically active faults and fractures are supposed to be very important. Recent tectonic activity leads to zones of mechanically weakened rock and increased dissolution at these weakness zones leads to increased karstification (KRESIC,

BUSBEY 1994). Hence, these zones are favorable for groundwater flow (PAVLOVIC,KRESIC 1990). These neotectonically active zones are represented by lineaments showing the major subsidiary fault directions described in chapters 3.2.3 and 5.4.1. Long lineaments that show these characteristics and emerge from areas of high intersection density (compare figure 5-15) are assumed to drain huge highland areas presumably leading high amounts of water through fractures enlarged by highly active karstification.

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 87 Chapter 5 Hydrogeology of a potential target area for a karst water gallery

Figure 5-18: Simple hydrogeological discharge model showing preferential groundwater flow paths especially in the key target area of the eastern ridge; long key lineament sub-orthogonal to the SFS is marked pink, long key lineaments sub-parallel to the SFS are marked green; catchment area (yellow dotted line) is roughly estimated for the junction point of pink marked lineament with first green marked lineament

Figure 5-18 shows a discharge model for the target area derived from the investigations in this chapter. The northern part of the Reef Member of the Raba Limestone Formation (g29) can be subdivided into a western ridge and an eastern ridge. These ridges are divided by a dry valley and exhibit quite different hydrogeological patterns. The western ridge seems to be maturely karstified. Highest lineament intersection densities represent an extremely dense network of supposedly highly enlarged neotectonically active faults and fractures. This

88 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 5 Hydrogeology of a potential target area for a karst water gallery results in extremely quick groundwater passage through large cavities especially after high precipitation events (see chapter 5.2.2.1). Karst conduits seem not to be linked to the prevailing dip of the formation layers (see chapter 5.5.2.2). Submarine discharge from the karstified limestones can also be qualitatively observed on the west coast (see chapter 5.3).It is supposed that discharge rates into the sea are high due to the direct contact of the highly karstified limestone complex to the ocean. As far as the western ridge is concerned, spring characteristics were only observed at spring ID 1. In fact, the extremely fluctuant discharge characteristics and chemical and physical properties (especially EC, see table 5-2) of this spring are perfect representatives of a maturely karstified carbonate aquifer system. In contrast to that, the eastern ridge (see figure 5-18) constitutes less surface phenomena formed by karstification like, for instance, the cockpit karst near the town Lho’nga (see Appendix 5). This is also confirmed by field observations of BGR staff members. Topographically, the eastern ridge shows much higher elevations than the western ridge reaching up to 1,089 m asl at Gunung Rajah in the south descending to an average ridge altitude of 800 m asl to the northwest. Lineament intersection density is not as high as at the western ridge. By this, the system of faults and fractures is believed to be not as densely developed compared to the western ridge. The drainage pattern seems to be directed, at least in part, along the general dip of the formation layers to the northeast. It seems that especially the springs at the eastern margin of the limestone complex with the spring ID’s 19, 12, 13, 20, 14 and perhaps even 10, 11, 15, 68, and 67 have a close relationship to a central long lineament (see figure 5-18, marked pink) emerging from a zone of higher intersection density (compare figure 5-15). This structural feature could well be supposed to drain huge amounts of water from the higher elevated area of higher intersection density and to direct the groundwater in its northeastern orientation sub-orthogonal to the SFS (compare chapter 5.4.1.2). At intersections with two long lineaments orientated sub-parallel to the SFS (see figure 5-18, marked green) the groundwater flow could be at least in part redirected flowing along the northwest headed fracture zones, e.g. to prominent spring locations like spring ID’s 31 and 8 / 9 (Mata Ie spring) or to spring ID’s 17 and 18. Together with the fact that some springs especially at the western edge of the limestone complex are perennial (information by field surveys of BGR staff members) the above mentioned aspects could argue for a slower and directed discharge regime contrasting to the highly fluctuant discharge characteristics at the western ridge. Slightly higher water hardness at spring ID 18 (9.4 °dH) (see table 5-2) compared to spring ID 1 (8.0 °dH) could suggest higher water mineralization which could also argue for longer retention times of the water in the rock- mass. Certainly, the difference between the two values is marginal and due to missing long- term measurements the validity is low. Furthermore, it shall not be left unaccented that the main karst level at the eastern ridge is developed at a low altitude near the erosion base, i.e.

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 89 Chapter 5 Hydrogeology of a potential target area for a karst water gallery the sea level (see chapter 5.2.3). It can be concluded that also at the eastern ridge groundwater flow is accelerated through a system of enlarged fractures and faults discharging quickly through the high rock coverage of partly more than 1,000 m to the base level.

90 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 6 Discussion

6 Discussion

The combined hydrogeological model developed in chapter 5 shows where preferential groundwater flow paths are supposed to be located in the study area (see figure 5-18). The key target area found for the possible construction of a karst water gallery is the eastern ridge of the Reef Member of the Raba Limestone Formation (g29) in the northeastern part of the study area. Hydrogeological conditions concerning presumed groundwater potential, discharge rates, and retention time of water in the rock mass can only be interpreted by the available data in this key target area. As a result it can be said that the eastern ridge offers at least some data allowing a fairly rough interpretation of the potential groundwater flow. Further on, the available data are able to delimit the drainage pattern of the eastern ridge from the pattern at the supposedly maturely karstified western ridge (see figure 5-18). At the western ridge groundwater flow seems to be extremely fluctuant and only vaguely directed along predictable flow paths. However, when focusing on the assumed groundwater flow directions at the eastern ridge as shown in figure 5-18, a possible water capturing could be located at the long presumably neotectonically active and extended lineament (marked pink in the figure). A roughly estimated catchment area relating to a location on this zone of increased fracturing is given in figure 5-18, assuming that large higher elevated areas are drained by a network of faults and fractures. This catchment area could reach up to the highest elevation of the eastern ridge at Gunung Rajah with an altitude of 1,630 m spanning over an area of possibly more than 17 km². The climatic conditions in the humid tropical zone deliver high amounts of precipitation ranging around 3,000 mm/a in the target area (see chapter 3.1.4 and figure 3-2). ETpot ranges around 1,500 – 1,600 mm/a which would result in 1,450 mm/a contributing to groundwater recharge or surface runoff. Surface runoff is presumably low in the highly karstified catchment area. Soil permeability could also contribute to high groundwater recharge rates, at least for those soils in the study area developed on the reef-like limestone complex (see chapter 3.1.7) but this is rather uncertain. Surface streams cannot be detected in higher altitudes, neither on satellite images nor on topographical, hydrogeological, and geological maps (compare stream network shown in figure 5-18). Therefore, high amounts of precipitation are assumed to infiltrate into the limestone complex and to contribute to groundwater recharge. PLOETHNER, SIEMON 2005 assume groundwater recharge in the Reef Member of the Raba Limestone Formation (g29) to range around 30 % of the mean annual precipitation of 3,000 mm/a which equals about 900 mm/a. When considering the broad and sub-horizontally extending top of the eastern ridge (compare figure 5-16) maybe even higher

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 91 Chapter 6 Discussion groundwater recharge could be expected, like, for instance, in the catchment area of the “gallery system Mühlau” (see chapter 2.2.2.3). There, the broad and extensively flat Karwendel massif including the catchment area seems to be the governing factor for extremely high groundwater recharge rates. Anyhow, assuming that the figure of 900 mm/a groundwater recharge withstands future investigations on actual recharge rates (see chapter 8) the groundwater potential can be calculated to be about 485 l/s for the defined location on the long lineament (calculated by the principle shown in chapter 4.7). PLOETHNER,

SIEMON 2005 had assumed about 688 l/s for a larger catchment area of 25 km² which was roughly estimated. Nevertheless, it shall again be accentuated that groundwater flow is presumably quick through the highly karstified limestone and not retained for years in the rock-mass like at the examples described in chapter 2. Granted that the high discharge rates could be captured one would need huge reservoirs to store the presumably intermittent discharge maxima. Otherwise no sustainable supply could be guaranteed. Additionally to the possible supply with freshwater, electrical energy could be generated by installing a hydroelectric power plant. Therefore, a certain altitude difference of at least 50 m would be necessary between the surge chamber and the power plant. Just to give a rough outline on the amount of electrical energy that could be produced the above mentioned 485 l/s discharge would result in about 10 million kWh/a at an altitude difference of about 350 m (approximate altitude of the catchment area benchmark) (compare figure 2-10).

A further aspect that should not be left unevaluated is the vulnerability of the karst aquifer. Increased flow velocities and decreased physical and chemical filter effects contribute to the overall high potential vulnerability of karst aquifers (GOLDSCHEIDER, DREW et al. 2007). In this regard, potential contaminant sources in the respective catchment areas have to be figured out to delineate vulnerability. As far as the catchment area analyzed in this thesis is concerned, vulnerability can be considered as low. The catchment area spans over the higher elevated part of the eastern ridge which is exclusively covered by dense tropical forest (see chapter 3.1.6 and Appendix 9) and is difficult to access. No settlements, agricultural use or other anthropogenic influences occur except maybe for some illegal deforestation which is anyway conducted without technical machinery (JAEGGI 2006). In general, a karst water gallery would be most vulnerable near the gallery mouth due to lower rock coverage, and hence, even shorter retention times of the groundwater in the rock- mass. This should be particularly considered when defining water protection areas. At the same time, investigations regarding possible bacteriological contamination should be accomplished. Potentially harmful bacteria like E. coli can be present in warm karst water

(STÜBEN,NEUMANN 2006) in contrast to the cold karst water at the galleries in Austria, for instance.

92 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 7 Summary

7 Summary

Within the scope of this diploma thesis the function of karst water galleries was investigated especially regarding the basic geological and hydrogeological conditions. During a literature research examples of karst water galleries were found and their function was analyzed in detail. Summarizing this first elemental part of the thesis, it can be said that if the almost perfect conditions for a karst water gallery are met like in the “gallery system Mühlau” near Innsbruck, Austria, they can be seen as effective water capture constructions showing high discharge rates of high-quality drinking water at low running costs. Especially in the Limestone Alps very good conditions are present for these galleries. Certainly, faults and fractures in the nappe structures of the Limestone Alps are supposed to be the main preferential flow paths for circulating water in otherwise low-permeable only slightly karstified limestones. Besides that, many other factors contribute to high and steady discharges through these galleries, e.g. high precipitation in elevated uninhabited regions sometimes comprising broad and sub-horizontal catchment areas with low soil coverage and no danger of contamination. Of course, high investment costs have to be faced at the beginning but these costs are compensated by very long operation times at low running costs, e.g. for maintenance, and by possible energy generation by a hydroelectric power plant when the surge chamber and the power plant exhibit enough elevation difference. In a further step the knowledge achieved from the literature research was applied to the case study Banda Aceh. Banda Aceh was heavily affected by the 2004 Tsunami and is supposed to experience a freshwater problem in the foreseeable future due to an insufficient water supply infrastructure. Therefore, different options were compiled that could contribute to drinking water supply on a more sustainable level. The idea of a karst water gallery for Banda Aceh came up and it was believed that this kind of water capturing working excellently in the Limestone Alps of Austria, for instance, could possibly be constructed in the nearby limestone areas of the adjacent Barisan Mountain Range. Since the hydrogeological conditions of the limestone formations to the southwest of Banda Aceh were in most parts unknown, the aim of this thesis was to investigate the hydrogeology of potential host formations for a karst water gallery and to highlight their governing hydrogeological conditions. Besides investigations according the general geological properties of the study area that is located at the highly active Sunda subduction zone, hydrogeologically important features were analyzed in more detail. Since basic data were very limited to the area around the northern part of the study area (Reef Member of the Raba Limestone Formation (g29)) it was

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 93 Chapter 7 Summary possible to determine at least major scale hydrogeological conditions around this reef-like limestone body. The highly complex geological formations of the study area were combined to hydrostratigraphical units exhibiting first assumptions where high groundwater potentials could be assumed. Further on, spring locations were investigated especially considering their discharge characteristics as well as their physical and chemical water qualities. Elevations of springs were investigated to find potentially active karst levels which presumably seem to be developed near the base level, i.e. the sea level, showing that the karst groundwater drains fairly quick through the large limestone body. To gain some more data concerning springs the detection of spring locations via remote sensing with high resolution satellite data proved to be a useful tool. Investigations on possible submarine groundwater discharges were believed to show that major inflows into the Indian Ocean appear over large lineaments representing water-bearing faults and fractures. Sadly, the thermal images that were supposed to be analyzed in this respect could not be spatially correlated or are still in processing at BGR. Nevertheless, it could be found out that submarine discharge qualitatively exists by analyzing two example images. The distribution and orientation of lineaments was supposed to show preferential groundwater flow paths like neotectonically active faults. It could be figured out that the lineaments mapped on satellite imagery mainly followed subsidiary fault directions to the major fault system around the study area, the SFS, and therefore were believed to be neotectonically active constituting weakness zones where preferential karstification, and hence, enhanced water flow can be presumed. Especially high densities of lineament intersections seem to display areas of highly active fracturing, and hence, highly active karstification in the humid tropical climate. The first attempt was that high lineament intersection densities would constitute a target area for a karst water gallery but it soon became obvious that karstification at the most dense fracture accumulations seemed to be maturely developed. This was specifically the case for the area around spring ID 1 on the western ridge of the limestone complex investigated as target area. This spring shows highly fluctuant discharge characteristics and the whole western ridge can be considered maturely karstified with unpredictable groundwater flow. In contrast to the western ridge, the eastern ridge seems to exhibit more directed groundwater flow which is substantiated by the appearance of springs only to the east. In this respect, a hypothetical structural model was developed that argues against the published structural model. The published anticline structure at the eastern ridge is interpreted as overthrusted parts of the same formation in this thesis which show a general dipping angle to the northeast.

94 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 7 Summary

This hypothesis is substantiated by the development of a simple hydrogeological model of the eastern ridge. There, the general groundwater flow directions can be roughly estimated as well as a potential target area for a karst water gallery. High groundwater potential can be calculated for the eastern ridge but discharges are supposed to be very quick due to the high karstification, and hence, fast water flow through enlarged cavities.

As an overall summary, it can be said that much more information and data are necessary to be able to make further statements on more exact locations and orientations of preferential groundwater flow paths. An exact location for the construction or even a construction principle of a karst water gallery cannot be ascertained by the analysis of the given data. Nevertheless, a key target area for the possible location of a karst water gallery can be delineated at the eastern hillside of the eastern ridge (see figure 5-18). Further investigations have to be accomplished in the future to understand the hydrogeological pattern in more detail (see chapter 7).

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 95

Chapter 8 Outlook and further investigations

8 Outlook and further investigations

The demand on freshwater will increase in Banda Aceh in the future, there is no doubt. Different scenarios at different population growth rates can be calculated which lead to the conclusion that the water demand will rapidly increase in the near future. The need for a sustainable water supply solution for the future is therefore highly visible.

This thesis can only be seen as a first step to a possible exploitation of karst waters from the limestones of the study area in the future. More detailed investigations have to follow up to better understand the hydrogeological conditions of the limestones especially in the northern reef-like complex (g29).

Field observations should be carried out in the future to verify the mapped lineament traces and to understand their hydrogeological significance. This could possibly be aided by geophysical surveys (compare BECHTEL,BOSCH et al. 2007). In this respect, the thermal images should be further interpreted when processed to find possible connections of water-bearing fault zones represented by lineaments and submarine discharge as it is indicated in figure 5-7.

Furthermore, more long-term discharge measurements at spring locations should be conducted to be able to develop discharge models that are not only based on single point measurements in time. Further on, not only discharge rates but also long-term measurements on conductivities, water hardness, temperature etc. could deliver much useful data especially to understand how springs react to high precipitation events, for instance (compare chapter 5.2.2.1). To be able to interpret possibly long-term measured discharge rates correctly, the main climatic parameters like precipitation and ET should also be long-term measured in the respective investigated area.

The application of tracer techniques is believed to be a powerful tool to visualize groundwater flow directions and to assume groundwater flow velocities. They are often the only method that is able to clearly demonstrate the connections in karst groundwater flow systems (GOLDSCHEIDER,DREW et al. 2007). Tracer tests could for example be conducted at the roughly assumed catchment area described in chapter 5.6 to find out if the presumed groundwater flow directions can be substantiated or if other flow directions prevail.

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 97 Chapter 8 Outlook and further investigations

Additionally, the hypothetic structural model described in chapter 5.5.2.2 should be ground checked by surveying the hypothetically outcropping layer heads on top of the eastern ridge of the Reef Member of the Raba Limestone Formation (g29). This could also be supported by paleontological investigations on fossils at both sides of the presumed monoclinal structure.

When some of these initial methods have led to a better understanding of the overall drainage pattern, a feasibility study could be conducted especially with test drillings. It has to be stated that major mining problems could occur when trying to penetrate a highly karstified and weathered fault or fracture (information by Dr. Jürgen Vasters (BGR)). Large karst cavities filled with weathered material could also be a major problem in this respect (compare PÖTTLER 2004; DEMEL,SCHULZ 1976). Further problems could occur due to the highly active seismicity caused by the proximity to the subduction zone and not least demonstrated by the 2004 tsunami. Seismic activity could cause rockfall in the gallery or could even lead to the total collapse (compare the rockfall event at the Gua Bribin karst cave project near Yogyakarta, Java (online source 09)).

It cannot be excluded that well drillings or maybe a damming of a karst cave like at the Gua Bribin (online source 09) could be more appropriate for the exploitation of karst water from the apparently highly karstified limestone complex. Against the background of the few available data for the study area, at least the key target area could be located where further investigations should be concentrated.

98 Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia Chapter 9 References

9 References

9.1 Literature

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SCHAD, J.; SCHINDLER,T. & SCHWEISSHELM, E. (2007): Biotreibstoff aus Palmöl - Klimaschutz oder ökologischer Bumerang? Der Fall Indonesien.-- Kurzberichte aus der internationalen Entwicklungszusammenarbeit, Asien und Pazifik (Friedrich-Ebert- Stiftung, Internationale Entwicklungszusammenarbeit, Referat Asien und Pazifik): 4 p. SCHAER,J.-P.;STETTLER,R.;ARAGNO,P.-O.;BURKHARD,M.&MEIA, J. (1998): Géologie du Creux du Van et des Gorges de l'Areuse. (In: DUMONT, M. et al.: Nature au Creux du Van).--, Vol. 2: 143 - 220. SCHMID, F. (2003): Ökostrom aus Trinkwasser.-- tec21, Sonderdruck aus Heft 10/2003: 14 - 16. SCHMITZ, M.; LOHMANN, P.; SÖRGEL, U.; KÜHN,F. & SCHÄFFER, U. (2007): Land use / land cover map of Banda Aceh and region (1:50,000).--, unpublished map, BGR; Hannover. SCHÖNWIESE, C.-D. (2000): Praktische Statistik für Meteorologen und Geowissenschaftler.--: 298 p.; Berlin (Borntraeger). SCHUBERT, G. (2000): Water Resources - Drinking Water.-- Mitteilungen der Österreichischen Geologischen Gesellschaft, 92 (1999): 295 - 311; Wien. SESÖREN, A. (1986): Potential of remote sensing use in a karstic area, Antalya region in the south of Turkey.-- IAHS, 1986: Karst Water Resources (Proceedings of the Ankara - Antalya Symposium, July 1985): 271 - 277; Wallingford. SETIADI, H. (2004): Peta Hidrogeologi Indonesia (1:1,000,000). Hydrogeological Map of Indonesia.--, lembar (sheet) i Dan Sebagian (part of) II; Bandung. SIEH,K. & NATAWIDJAJA, D. (2000): Neotectonics of the Sumatran fault, Indonesia.-- Journal of Geophysical Research, Vol. 105, No. B12: 28,295 - 28,326. SIEMON, B.; PLOETHNER,D. & PIELAWA, J. (2005): Helicopter-Borne Geophysical Investigation in the Province Nanggroe Aceh Darussalam, Northern Sumatra, Indonesia. Survey Area: Banda Aceh / Aceh Besar 2005, Interpretation of Electromagnetic Data.-- Technical report, BGR, Vol. B-1. SOETRISNO, S. (1993): Peta Hidrogeologi Indonesia (1:250,000). Hydrogeological Map of Indonesia.--, lembar (sheet) 0421 Banda Aceh (Sumatera); Bandung. STADLER, H.; SACCON,P. & STROBL, E. (2003): Lineamentauswertung im Gebiet Schneeberg/Rax.-- project report by Joanneum Research Forschungsgesellschaft mbH, Institut für Hydrogeologie und Geothermie: 35 p.; Graz. STADTWERKE INNSBRUCK. (1954): Das neue Trinkwasserwerk und Kraftwerk Mühlau.-- Festschrift: 63 p. STRAHLER,A.H. & STRAHLER, A. N. (2002): Physical geography: science and systems of the human environment.--: 748 p.; New York (Wiley). STÜBEN,D. & NEUMANN, T. (2006): Wasser/Gestein-Wechselwirkungen in den Karstgebieten von Wonosari: Verwitterungsresistenz der Kalkgesteine, Wasserwegsamkeiten im Gesteinsverbund und Verbesserung der Wasserqualität. BMBF-Verbundprojekt Erschließung und Bewirtschaftung unterirdischer Karstfließgewässer in Mitteljava, Indonesien, Teilprojekt 2, Abschlussbericht.--: 76 p.; Karlsruhe. SWEETING, M. M. (1995): Karst in China. Its Geomorphology and Environment.--: 265 p.; Berlin (Springer). TAM,V.T.; DE SMEDT, F.; BATELAAN,O. & DASSARGUES, A. (2004): Study on the relationship between lineaments and borehole specific capacity in a fractured and karstified limestone area in Vietnam.-- Hydrogeology Journal, 12: 662 - 673; (Springer). UNEP (2007): Environment and reconstruction in Aceh. Two years after the tsunami.--: 72 p. USAID (2006): Infrastructure Outline Concept Plan: Kabupaten Aceh Besar. Water, Sanitation, Solid Waste, Drainage.--: 96 p. VERSTAPPEN, H. T. (1973): A geomorphological reconnaissance of Sumatra and adjacent islands (Indonesia).--: 182 p.; Groningen (Wolters-Noordhoff Publishing). VILLINGER, E. (1969): Dissertation: Karsthydrologische Untersuchungen auf der Reutlinger Alb (Schwäbischer Jura).-- Jh. geol. Landesamt Baden-Württemberg, No. 11: 201 - 277; Freiburg.

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VILLINGER, E. (1994): Hydrogeologie. (In: OHMERT, W. (Ed.): Erläuterungen zu Blatt 7521 Reutlingen, Geologische Karte 1:25000 von Baden-Württemberg).--: 148 - 181; Freiburg. VITA-FINZI, C. (2008): Neotectonics and the 2004 and 2005 earthquake sequences at Sumatra.-- Marine Geology, 248 (2008): 47 - 52; (Elsevier). WENCAI, D. (1990): The comprehensive analysis method of the lineaments for groundwater survey. STANFORD,J.A. & VALETT, H. M. (Eds.).-- International Symposium: Remote sensing and water resources: proceedings, org. by: The International Association of Hydrogeologists; The Netherlands Society for Remote Sensing: 539 - 548; Enschede.

9.2 Online sources online source 01: http://en.wikipedia.org/wiki/Barisan_Mountains as at September 23rd, 2008 online source 02: http://de.wikipedia.org/wiki/Aceh as at November 30th, 2008 online source 03: http://de.wikipedia.org/wiki/Banda_Aceh as at October 16th, 2008 online source 04: http://www.volcanodiscovery.com/volcano-tours/indonesia/sumatra.html as at December 1st, 2008 online source 05: http://www.geo.unizh.ch/bodenkunde/kapitel/kap1.html as at December 1st, 2008 online source 06: http://www.hydroskript.de/html/hykp1104.html#hykp110404 as at August 25th, 2008 online source 07: http://de.wikipedia.org/wiki/Seebeben_im_Indischen_Ozean_2004 as at April 25th, 2008 online source 08: http://www.fao.org/tsunami/environment/idn/bnd/index.html as at December 1st, 2008 online source 09: http://www.hoehlenbewirtschaftung.de/ as at December 14th, 2008 online source 10: http://www.deza.admin.ch/ressources/resource_en_151364.pdf as at December 1st, 2008 online source 11: http://en.wikipedia.org/wiki/Southern_Limestone_Alps as at September 24th, 2008 online source 12: http://www.wasserwerk.at/gesinnsb2.htm as at December 1st, 2008 online source 13: http://en.wikipedia.org/wiki/Water_turbine as at November 27th, 2008 online source 14: http://www2.ikb.at/geschaeftsbereich/strom/stromerzeugung/kraftwerke/trinkwasserkw_m uehlau/index.php as at December 1st, 2008 online source 15: http://www.wasserwerk.at/geschichhal.htm as at December 1st, 2008 online source 16: http://www.stadtwerke-hall.at/press/show.php3?id=7 with downloadable press info; as at December 13th, 2007; not accessible anymore in December 2008 online source 17: http://en.wikipedia.org/wiki/Aceh as at December 1st, 2008 online source 18: http://homepage.uibk.ac.at/~c61404/ARZL/Natur/Geologie/Wasser.html as at December 1st, 2008 online source 19: http://de.wikipedia.org/wiki/Hall_in_Tirol as at November 11th, 2008 online source 20: http://de.wikipedia.org/wiki/Absam as at November 5th, 2008 online source 21: http://en.wikipedia.org/wiki/SRTM as at November 26th, 2008

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 103

Chapter 10 Appendix

10 Appendix

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 105 Chapter 10 Appendix

Appendix 1: Karst water galleries encountered during the literature research (detailed table)

Hydroelectic power Gallery name / project Country Length [m] Discharge [l/s] Water-bearing formations Literature production

slightly karstified and fractured Wetterstein- "Förolach gallery" (Förolacher Stollen) Austria 3,228 ~ 700 (50 % from two major faults) - RAMSPACHER,RIEPLER et al. 1991 Dolomite and Wetterstein-Limestone

GRAZIADEI,ZÖTL 1984; RAMSPACHER, slightly karstified and fractured Alpine ZOJER et al. 1992; STADTWERKE "gallery system Mühlau" (Stollensystem 1,663 (side galleries 1,159, collector 6,000 kW max., 34,000,000 Austria min. 500, max. > 2,000, mean 1,370 Muschelkalk overlain by slightly karstified INNSBRUCK 1954; SCHUBERT 2000; Mühlau) gallery 564) kWh/a Wetterstein-Limestone AMPFERER 1949; FLEISCHHACKER, HEISSEL et al. 1996

"drinking water gallery Halltal" 1,130 (main gallery 950, right side gallery slightly karstified and fractured Wetterstein- (Trinkwasserstollen Halltal; Margarethe- Austria min. 360, max. 660, mean 400 150 kW max., 850,000 kWh/a online source 15; online source 16 100, left side gallery 80) Limestone Stollen) ~ 1,200 (Zeller-Berg-gallery 700, min.120, max. 250, mean 200 (mostly fractured and karstified upper and lower 3 galleries of the public utility Zell Germany Schulhaus- + Norbertusheim-gallery ~ not enough slope Public utility Zell am Main through small faults) Muschelkalk 500) Neubrunnen (spring capturing by short karstified Oxford-Limestones overlain by BAUER,SELG et al. 2002; VILLINGER Germany 24 min. 49, max. 260, mean 107 - gallery) Kimmeridge-Marl und -Limestones 1994, VILLINGER 1969 Biel Vody (spring capturing by gallery) Czechoslovakia 100.5 mean ~ 90 karstified and fractured dolomites of Triassic age - KULLMANN 1984 Montenegro (former gallery in Mokrine karst region 1,200 min.~ 100, max. ~ 300 - 400 Mokrine-Limestone and -Dolomite - MIJATOVIC 1984 Yugoslavia) energy generation only in the Galerie des Moyats Switzerland 660 ~ 30 - 85 karstified limestones of Jurassic age SCHAER,STETTLER, et al. 1998 adjacent gorge project Gua Bribin (not real karst water karstified porous and cavernous reef limestones energy generated to pump online source 09; STÜBEN,NEUMANN Indonesia (Java) - > 1,000 even during "dry" season gallery but dammed karst cave) overlain by compact limestones water up to the surface 2006

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 106 Chapter 10 Appendix

Appendix 2: Geological formations in the study area (detailed table)

Code on Geological Map (1:250,000) Eon Era Period Epoch Group Formation Labels Lithological group Lithological description (BENNET,BRIDGE et al. 1981)

Holocene Alluvium g1 Qh Sediments (undifferentiated) gravels, sands, and muds

Quaternary Meulaboh g24 Qpm Sediments semi-consolidated sands and gravels Pleistocene Indrapuri g11 Qpin Sediments older terrace deposits, partly volcanic gravels, and sands

Sediments and Pliocene - Pleistocene Seulimeum g32 QTps tuffaceous and calcareous sandstones, conglomerates, minor mudstones Metasediments Tiro Kotabakti (Padangtiji Sediments and g14 Tuktp calcareous sandstones, conglomerates, siltstones, minor limestones Member) Metasediments Miocene - Pliocene tectonic melange of serpentinites, serpentinized ultramafic, undifferentiated igneous, Indrapuri Complex g10 Tuic Intrusives and sedimentary rocks

Middle – Late Miocene Calang Volcanic g5 Tmvc Volcanics porphyritic, epidotized, intermediate volcanics, subvolcanic intrusives

Miocene Geunteut Granodiorite g8 Tmig Intrusives granodiorite and subsidiary diorite

Cenozoic Tertiary Sediments and Peunasu g26 Tlp micaceous sandstones, conglomerates, shales, mudstones, reef limestones Metasediments

Sediments and Tangla g36 Tlt volcanogenic sandstone, conglomerates, quartzose arenites Metasediments Late Oligocene – Hulumasen Early Miocene Sediments and Tangla (Keubang Member) g37 Tltk argillaceous limestone, minor calcareous sandstones and siltstones, thin coals Metasediments

Sediments and Tangla (Ligan Member) g38 Tltl quartz sandstones, micaceous sandstones, siltstones Metasediments

Sediments and micaceous sandstones, polymictic conglomerates, conglomeratic sandstones, Eocene – Early Oligocene Meureudu Meucampli g23 Tlm Metasediments siltstones, limestones, amygdaloidal mafic volcanics Phanerozoic

Miscellaneous intrusives g25 TMi Intrusives miscellaneous granodiorite to diorite intrusives Late Cretaceous Sikuleh Batholith (older g34 Miski Intrusives dioritoids complex)

Sediments and Lho'nga g21 Mul phyllites, slates, volcanic and turbiditic sediments, thin limestones Metasediments

Sediments and Raba Limestone g28 Murl dark, thin bedded argillaceous and siliceous limestones Metasediments

Raba Limestone (Reef Sediments and g29 Murlr calcarenites and calcilutites, massive, gray, tends to form reef-like bodies Member) Metasediments

Sediments and Lamno Limestone g19 Mull dark limestones with volcanic debris Metasediments Late Jurassic –

Mesozoic Mesozoic Woyla Early Cretaceous Lamno Limestone (Reef Sediments and g20 Mullr massive gray reef-like facies Member) Metasediments

Sediments and volcanic wackes, subordinate sandstones and siltstones, mafic volcanics and Lhoong g22 Mulh Metasediments limestones

Bentaro Volcanic g3 Muvb Volcanics basalts, agglomerates, mafic dykes, basaltic vents

variably altered and metamorphosed intermediate to mafic volcanics and pyroclastics, Geumpang g6 Mug Volcanics minor phyllites, greenschists, and metalimestones

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 107 Chapter 10 Appendix

Appendix 3: All springs in the study area (continued on the following two pages)

UTM Spring ID Name (uncertain) Type Description UTM northing Elevation [m] Location source References / field observation by Discharge [l/s] Discharge characteristics Temperature [°C] EC [μS/cm] pH Hardness [°dH] Water-type easting

karst min. 10; max. > 273 (800 reported after 2+ - 1 Spring of Krueng Raba (ID: MW-006) huge dammed karst spring; start of Krueng Raba 750586 604058 41 GPS measured THW; Jens Böhme (BGR); Dr. Uwe Schäffer (BGR); chemical analysis by BGR laboratory perennial - 7.4 8.0 Ca -HCO spring 300 longer dry period) 3

karst completed in 1904/05; captured and piped; organizations: Swiss Red 2+ - 2 Mata Gle Taron (also Gue Gajah) 753116 606855 51 GPS measured PLOETHNER, SIEMON 2005; Jens Böhme (BGR); Dr. Uwe Schäffer (BGR) < 50 perennial 25.7 350 7.5 - Ca -HCO spring Cross (SRK) and THW 3

karst 3 - captured 749441 592532 33 GPS measured Dr. Uwe Schäffer (BGR) < 10 ------spring

karst 4 - captured 749870 598466 17 GPS measured Dr. Uwe Schäffer (BGR) < 10 ------spring

karst 5 - incompletely dammed; nearly inaccessible 748809 612979 41 GPS measured Dr. Uwe Schäffer (BGR) < 10 ------spring

karst 6 - captured; usage unknown 749849 612725 26 GPS measured Dr. Uwe Schäffer (BGR) ------spring

karst 7 - at waterfall 750508 584708 18 GPS measured Dr. Uwe Schäffer (BGR) < 10 ------spring

karst 100 (min. 25; max. 2+ - 8 Leu Ue (Mata Ie, Mosque) piped; completed in year 1904/05 754323 608117 20 GPS measured PLOETHNER, SIEMON 2005 perennial 21.8 270 7.5 - Ca -HCO spring 240) 3

karst 2+ - 9 Leu Ue (Mata Ie, Bath) piped; completed in year 1904/05 754349 608192 20 GPS measured PLOETHNER, SIEMON 2005 - - 21.8 290 7.3 - Ca -HCO spring 3

karst 2+ - 10 Payaroh (Biluy Spring) at top of waterfall 757507 603994 110 GPS measured PLOETHNER, SIEMON 2005 - perennial 23.9 320 7.8 - Ca -HCO spring 3

karst 2+ - 11 Payaroh (Biluy Spring) at bottom of waterfall 757809 604060 94 GPS measured PLOETHNER, SIEMON 2005; Dr. Uwe Schäffer (BGR) 15 (min. 5) perennial 25.0 320 7.9 - Ca -HCO spring 3

karst 12 - - 759131 603917 68 GPS measured Jens Böhme (BGR) ------spring

karst 13 - - 759500 603576 60 GPS measured Jens Böhme (BGR) ------spring

karst 14 - - 760497 603083 32 GPS measured Jens Böhme (BGR) ------spring

karst 15 - - 759149 601643 275 GPS measured Jens Böhme (BGR) ------spring

karst 16 Lemjot - 751958 602886 49 GPS measured KELLER, NICOLE 2006; Jens Böhme (BGR) - non-perennial - - - - - spring

karst 2+ - 17 Karst-01 - 755981 606952 31 GPS measured Jens Böhme (BGR) - non-perennial 25.7 287 7.3 - Ca -HCO spring 3

karst 2+ - 18 Karst-02 - 756773 606337 38 GPS measured Jens Böhme (BGR); chemical analysis by BGR laboratory - supposedly non-perennial 24.3 319 7.5 9.4 Ca -HCO spring 3

karst 19 - - 758865 604742 19 Hydrogeological Map (1:250:000) SOETRISNO 1993 < 10 ------spring

karst 20 - - 759974 603281 52 Hydrogeological Map (1:250:000) SOETRISNO 1993 < 10 ------spring

karst 21 - - 751947 596532 130 Hydrogeological Map (1:250:000) SOETRISNO 1993 < 10 ------spring

karst 22 - - 752475 595648 209 Hydrogeological Map (1:250:000) SOETRISNO 1993 < 10 ------spring

karst 23 - - 750099 591357 277 Hydrogeological Map (1:250:000) SOETRISNO 1993 < 10 ------spring

karst 24 - - 750389 591066 220 Hydrogeological Map (1:250:000) SOETRISNO 1993 < 10 ------spring

karst 25 - - 750772 590882 341 Hydrogeological Map (1:250:000) SOETRISNO 1993 < 10 ------spring

karst 26 - - 750772 591449 304 Hydrogeological Map (1:250:000) SOETRISNO 1993 < 10 ------spring

karst 27 - - 750416 591687 207 Hydrogeological Map (1:250:000) SOETRISNO 1993 < 10 ------spring

karst 28 - - 753822 576029 3 Hydrogeological Map (1:250:000) SOETRISNO 1993 < 10 ------spring

karst 29 - - 754205 575897 9 Hydrogeological Map (1:250:000) SOETRISNO 1993 < 10 ------spring

karst 30 - - 755472 573732 332 Hydrogeological Map (1:250:000) SOETRISNO 1993 < 10 ------spring

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 108 Chapter 10 Appendix continued from Appendix 3 All springs in the study area

Spring UTM UTM Discharge Name (uncertain) Type Description Elevation [m] Location source References / field observation by Discharge [l/s] Temperature [°C] EC [μS/cm] pH Hardness [°dH] Water-type ID easting northing characteristics

karst Hydrogeological Map supposedly 31 - - 754614 607426 18 SOETRISNO 1993 10-50 - - - - - spring (1:250:000) perennial

karst Hydrogeological Map 32 - - 765895 569190 49 SOETRISNO 1993 50-100 ------spring (1:250:000)

karst Hydrogeological Map 33 - - 768123 567804 112 SOETRISNO 1993 50-100 ------spring (1:250:000)

Hydrogeological Map 34 - spring - 749871 588699 237 SOETRISNO 1993 < 10 ------(1:250:000)

Hydrogeological Map 35 - spring - 752525 580590 186 SOETRISNO 1993 < 10 ------(1:250:000)

Hydrogeological Map 36 - spring - 755525 575173 30 SOETRISNO 1993 < 10 ------(1:250:000)

Hydrogeological Map 37 - spring - 757911 564955 80 SOETRISNO 1993 < 10 ------(1:250:000)

Hydrogeological Map 38 - spring - 762337 564896 324 SOETRISNO 1993 < 10 ------(1:250:000)

Hydrogeological Map 39 - spring - 762991 564658 104 SOETRISNO 1993 < 10 ------(1:250:000)

Hydrogeological Map 40 - spring - 759842 562648 134 SOETRISNO 1993 < 10 ------(1:250:000)

Hydrogeological Map 41 - spring - 759575 561876 64 SOETRISNO 1993 < 10 ------(1:250:000)

Hydrogeological Map 42 - spring - 759080 561519 28 SOETRISNO 1993 < 10 ------(1:250:000)

Hydrogeological Map 43 - spring - 758626 559443 26 SOETRISNO 1993 < 10 ------(1:250:000)

karst Hydrogeological Map 44 - - 749955 612223 84 SOETRISNO 1993 < 10 ------spring (1:250:000)

karst Hydrogeological Map 45 - - 749462 611653 46 SOETRISNO 1993 < 10 ------spring (1:250:000)

karst Hydrogeological Map 46 - - 748782 611160 85 SOETRISNO 1993 < 10 ------spring (1:250:000)

karst Hydrogeological Map 47 - - 748376 609898 20 SOETRISNO 1993 < 10 ------spring (1:250:000)

karst Hydrogeological Map 48 - - 752302 610206 103 SOETRISNO 1993 < 10 ------spring (1:250:000)

karst Hydrogeological Map 49 - - 752247 609701 37 SOETRISNO 1993 < 10 ------spring (1:250:000)

karst Hydrogeological Map 50 - - 753366 610063 11 SOETRISNO 1993 < 10 ------spring (1:250:000)

karst Hydrogeological Map 51 - - 753815 609460 12 SOETRISNO 1993 < 10 ------spring (1:250:000)

52 - spring - 762548 588178 704 assumed via remote sensing ------

53 - spring - 760384 587051 878 assumed via remote sensing ------

54 - spring - 762290 585260 1108 assumed via remote sensing ------

55 - spring - 770712 581859 289 assumed via remote sensing ------

56 - spring - 779514 579563 762 assumed via remote sensing ------

57 - spring - 784534 575265 992 assumed via remote sensing ------

58 - spring - 751235 589358 101 assumed via remote sensing ------

59 - spring - 758034 580602 231 assumed via remote sensing ------

60 - spring - 756658 576499 389 assumed via remote sensing ------

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 109 Chapter 10 Appendix continued from Appendix 3 All springs in the study area

Spring UTM UTM Discharge Discharge Name (uncertain) Type Description Elevation [m] Location source References / field observation by Temperature [°C] EC [μS/cm] pH Hardness [°dH] Water-type ID easting northing [l/s] characteristics

61 - spring - 759749 568386 11 assumed via remote sensing ------

62 - spring - 760784 568442 17 assumed via remote sensing ------

63 - spring - 761591 574413 221 assumed via remote sensing ------

64 - spring - 771211 572158 240 assumed via remote sensing ------

65 - spring - 780110 561579 579 assumed via remote sensing ------

66 - spring - 760529 599527 310 assumed via remote sensing ------

67 - spring - 761190 601826 61 assumed via remote sensing ------

68 - spring - 760999 602725 30 assumed via remote sensing ------

69 - spring - 749821 604207 14 assumed via remote sensing ------

70 - spring - 762568 596501 296 assumed via remote sensing ------

71 - spring - 761943 599784 108 assumed via remote sensing ------

72 - spring - 757279 588414 229 assumed via remote sensing ------

73 - spring - 767438 579773 724 assumed via remote sensing ------

karst 74 - start of Krueng Belee 749582 602272 136 GPS measured Jens Böhme (BGR) ------spring

karst 75 - start of Krueng Mon 749183 601786 81 GPS measured Jens Böhme (BGR) ------spring

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 110 Chapter 10 Appendix

Appendix 4: Springs around Reef Member of Raba Limestone Formation (g29)

Discharge EC [μS/cm] (corrected to Hardness Spring ID Name (uncertain) Type Description UTM easting UTM northing Elevation [m] Location source References / field observation by Discharge [l/s] Temperature [°C] pH Water-type characteristics 25°C) [°dH] huge dammed karst spring; start of Krueng THW; Jens Böhme (BGR); Dr. Uwe Schäffer (BGR); min. 10; max. > 273 (800 reported after longer 1 Spring of Krueng Raba (ID: MW-006) karst spring 750586 604058 41 GPS measured perennial - 7.4 8.0 Ca2+-HCO - Raba chemical analysis by BGR laboratory 300 dry period) 3 completed in 1904/05; captured and piped; PLOETHNER, SIEMON 2005; Jens Böhme (BGR); 2+ - 2 Mata Gle Taron (also Gue Gajah) karst spring organizations: Swiss Red Cross (SRK) and 753116 606855 51 GPS measured < 50 non-perennial 25.7 350 7.5 - Ca -HCO Dr. Uwe Schäffer (BGR) 3 THW 4 - karst spring captured 749870 598466 17 GPS measured Dr. Uwe Schäffer (BGR) < 10 ------5 - karst spring incompletely dammed; nearly inaccessible 748809 612979 41 GPS measured Dr. Uwe Schäffer (BGR) < 10 ------6 - karst spring captured; usage unknown 749849 612725 26 GPS measured Dr. Uwe Schäffer (BGR) ------100 (min. 25; 8 Leu Ue (Mata Ie, Mosque) karst spring piped; completed in year 1904/05 754323 608117 20 GPS measured PLOETHNER, SIEMON 2005 perennial 21.8 270 7.5 - Ca2+-HCO - max. 240) 3 2+ - 9 Leu Ue (Mata Ie, Bath) karst spring piped; completed in year 1904/05 754349 608192 20 GPS measured PLOETHNER, SIEMON 2005 - - 21.8 290 7.3 - Ca -HCO3 2+ - 10 Payaroh (Biluy Spring) karst spring at top of waterfall 757507 603994 110 GPS measured PLOETHNER, SIEMON 2005 - perennial 23.9 320 7.8 - Ca -HCO3 PLOETHNER, SIEMON 2005; Dr. Uwe Schäffer 11 Payaroh (Biluy Spring) karst spring at bottom of waterfall 757809 604060 94 GPS measured 15 (min. 5) perennial 25.0 320 7.9 - Ca2+-HCO - (BGR) 3 12 - karst spring - 759131 603917 68 GPS measured Jens Böhme (BGR) ------13 - karst spring - 759500 603576 60 GPS measured Jens Böhme (BGR) ------14 - karst spring - 760497 603083 32 GPS measured Jens Böhme (BGR) ------15 - karst spring - 759149 601643 275 GPS measured Jens Böhme (BGR) ------16 Lemjot karst spring - 751958 602886 49 GPS measured KELLER, NICOLE 2006; Jens Böhme (BGR) - non-perennial - - - - - 2+ - 17 Karst-01 karst spring - 755981 606952 31 GPS measured Jens Böhme (BGR) - non-perennial 25.7 287 7.3 - Ca -HCO3

Jens Böhme (BGR); chemical analysis by BGR supposedly non- 2+ - 18 Karst-02 karst spring - 756773 606337 38 GPS measured - 24.3 319 7.5 9.4 Ca -HCO laboratory perennial 3 Hydrogeological Map 19 - karst spring - 758865 604742 19 SOETRISNO 1993 < 10 ------(1:250:000) Hydrogeological Map 20 - karst spring - 759974 603281 52 SOETRISNO 1993 < 10 ------(1:250:000) Hydrogeological Map 21 - karst spring - 751947 596532 130 SOETRISNO 1993 < 10 ------(1:250:000) Hydrogeological Map 22 - karst spring - 752475 595648 209 SOETRISNO 1993 < 10 ------(1:250:000) Hydrogeological Map 31 - karst spring - 754614 607426 18 SOETRISNO 1993 10-50 supposedly perennial - - - - - (1:250:000) Hydrogeological Map 44 - karst spring - 749955 612223 84 SOETRISNO 1993 < 10 ------(1:250:000) Hydrogeological Map 45 - karst spring - 749462 611653 46 SOETRISNO 1993 < 10 ------(1:250:000) Hydrogeological Map 46 - karst spring - 748782 611160 85 SOETRISNO 1993 < 10 ------(1:250:000) Hydrogeological Map 47 - karst spring - 748376 609898 20 SOETRISNO 1993 < 10 ------(1:250:000) Hydrogeological Map 48 - karst spring - 752302 610206 103 SOETRISNO 1993 < 10 ------(1:250:000) Hydrogeological Map 49 - karst spring - 752247 609701 37 SOETRISNO 1993 < 10 ------(1:250:000) Hydrogeological Map 50 - karst spring - 753366 610063 11 SOETRISNO 1993 < 10 ------(1:250:000) Hydrogeological Map 51 - karst spring - 753815 609460 12 SOETRISNO 1993 < 10 ------(1:250:000) assumed via remote 52 - spring - 762548 588178 704 ------sensing assumed via remote 53 - spring - 760384 587051 878 ------sensing assumed via remote 54 - spring - 762290 585260 1108 ------sensing assumed via remote 66 - spring - 760529 599527 310 ------sensing assumed via remote 67 - spring - 761190 601826 61 ------sensing assumed via remote 68 - spring - 760999 602725 30 ------sensing assumed via remote 69 - spring - 749821 604207 14 ------sensing assumed via remote 70 - spring - 762568 596501 296 ------sensing assumed via remote 71 - spring - 761943 599784 108 ------sensing 74 - karst spring start of Krueng Belee 749582 602272 136 GPS measured Jens Böhme (BGR) ------75 - karst spring start of Krueng Mon 749183 601786 81 GPS measured Jens Böhme (BGR) ------

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 111 Chapter 10 Appendix

Appendix 5: Typical cockpit karst landforms near the town Lho’nga, especially behind the cement factory in the center of the figure (collage of photographs derived from Dr. Dieter Plöthner (BGR))

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 112 Chapter 10 Appendix

Appendix 6: Spring ID 1 (spring of Krueng Raba); view from northwest (collage of photographs derived from Dr. Dieter Plöthner (BGR))

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 113 Chapter 10 Appendix

Appendix 7: Lineaments (red lines) on a false-colored satellite image of the Banda Aceh Quadrangle (Landsat TM™ scene 08/15/2008, Path 131, Row 56; RGB-channels 7(R) 4(G) 1(B)) (image provided by Dr. Uwe Schäffer (BGR))

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 114 Chapter 10 Appendix

Appendix 8: Geological map of the Banda Aceh Quadrangle (1:250,000) (geological formations and faults were digitized from BENNET, BRIDGE et al. 1981)

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 115 Chapter 10 Appendix

Appendix 9: Land use / land cover map of Banda Aceh and region (SCHMITZ,LOHMANN et al. 2007)

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 116 Chapter 10 Appendix

Appendix 10: Geologic Map of the Bandaaceh Quadrangle, Sumatra (1:250,000) (BENNET, BRIDGE et al. 1981) (in this thesis called Geological Map (1:250,000))

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 117 Chapter 10 Appendix

Appendix 11: Hydrogeological Map of Indonesia (1:250,000), sheet 0421 Banda Aceh (Sumatera) (SOETRISNO 1993) (in this thesis called Hydrogeological Map (1:250,000))

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 118 Chapter 10 Appendix

Appendix 12: Hydrogeological Map of Indonesia (1:1,000,000), sheet i Dan Sebagian (part of) II (SETIADI 2004) (in this thesis called Hydrogeological Map (1:1,000,000))

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Appendix 13: Cross section C-D

Karst water galleries in hard rock formations for drinking water supply in West-Sumatra, Indonesia 120