REPUBLIC OF BOTSWANA DEPARTMENT OF WATER AFFAIRS BOTLHAPATLOU GROUNDWATER EXPLORATION AND WELLFIELD DEVELOPMENT PROJECT PR 10/ 3 /3/ 08 -2 Final Report Final April 2012 Presented by Wellfield Consulting Services Pty Ltd P.O. Box 1502 Gaborone Wellfield Consulting Services (Pty) Ltd P.O. Box 1502 Gaborone BOTLHAPATLOU GROUNDWATER EXPLORATION AND WELLFIELD DEVELOPMENT PROJECT i Final Report – April 2012 TABLE OF CONTENTS 1. INTRODUCTION ....................................................................................................................... 1 1.1 BACKGROUND .................................................................................................................................... 1 1.2 OVERVIEW OF PROJECT OBJECTIVES ................................................................................................. 2 1.3 REPORT STRUCTURE .......................................................................................................................... 3 1.4 PROJECT AREA PHYSICAL SETTING ................................................................................................... 4 1.4.1 Location and Access ........................................................................................................ 5 1.4.2 Topography ..................................................................................................................... 5 1.4.3 Geomorphology (dunes, pans, drainage) ........................................................................ 5 1.4.4 Climate ............................................................................................................................ 8 1.4.5 Vegetation ..................................................................................................................... 10 1.5 SOCIO ECONOMIC SETTING .............................................................................................................. 10 1.5.1 Population ..................................................................................................................... 10 1.5.2 Water Demand............................................................................................................... 12 2. REGIONAL GEOLOGY AND HYDROGEOLOGY ........................................................... 18 2.1 PREVIOUS STUDIES AND DATA SOURCES ......................................................................................... 18 2.2 REGIONAL GEOLOGICAL SETTING ................................................................................................... 22 2.3 PRE-KAROO GEOLOGY .................................................................................................................... 25 2.4 KAROO SUPERGROUP ....................................................................................................................... 25 2.4.1 Dwyka Group (Lower Karoo) ....................................................................................... 26 2.4.2 Ecca Group (Middle Karoo) ......................................................................................... 26 2.4.3 Beaufort Group (Middle Karoo) ................................................................................... 28 2.4.4 Lebung Group ............................................................................................................... 28 2.4.5 Stormberg Lava Group .................................................................................................. 30 2.5 POST-KAROO GEOLOGY .................................................................................................................. 31 2.5.1 Intrusives ....................................................................................................................... 31 2.5.2 Kalahari Group ............................................................................................................. 31 2.6 STRUCTURAL SETTING ..................................................................................................................... 32 2.7 KAROO DEPOSITIONAL ENVIRONMENT ............................................................................................ 33 2.8 FAULT PATTERNS AND DISPLACEMENTS .......................................................................................... 34 2.9 THE ZOETFONTEIN FAULT STRUCTURE ............................................................................................ 35 3. INCEPTION PHASE ................................................................................................................ 36 3.1 OBJECTIVES ..................................................................................................................................... 36 3.2 ACTIVITIES, TIMING AND DIFFICULTIES ENCOUNTERED .................................................................. 36 3.3 RESULTS .......................................................................................................................................... 37 3.3.1 Geology and Structure................................................................................................... 37 3.3.2 Regional Geophysical Surveys ...................................................................................... 37 3.3.3 Remote Sensing ............................................................................................................. 38 3.3.4 Geophysical Ground Surveys and Borehole Logging ................................................... 39 3.3.5 Hydrochemistry and Environmental Isotopes ............................................................... 40 3.3.6 Recharge ....................................................................................................................... 40 3.3.7 Groundwater Modelling ................................................................................................ 41 3.3.8 Hydrogeological Regime ............................................................................................... 41 3.3.9 Selection of Exploration Target Areas .......................................................................... 41 4. CONCEPTUAL MODEL ......................................................................................................... 44 4.1 AQUIFER SPATIAL DISTRIBUTION AND GEOMETRY .......................................................................... 47 4.2 TRANSMISSIVITY (T) ........................................................................................................................ 47 4.4 STORATIVITY ................................................................................................................................... 48 4.5 RECHARGE POTENTIAL .................................................................................................................... 48 5. EXPLORATION PROGRAMME........................................................................................... 50 5.1 OVERVIEW ....................................................................................................................................... 50 5.2 ACTIVITIES, TIMING AND DIFFICULTIES ENCOUNTERED .................................................................. 51 5.3 EXPLORATION BOREHOLE GROUND GEOPHYSICAL SURVEYS ......................................................... 52 Wellfield Consulting Services (Pty) Ltd P.O. Box 1502 Gaborone BOTLHAPATLOU GROUNDWATER EXPLORATION AND WELLFIELD DEVELOPMENT PROJECT ii Final Report – April 2012 5.3.1 General Survey Characteristics .................................................................................... 52 5.3.2 Survey Methodology ...................................................................................................... 52 5.3.4 Instrumentation ............................................................................................................. 52 5.3.5 Selection of Survey Targets and Traverse Alignments .................................................. 53 5.3.6 Evaluation of Geophysical Survey Results .................................................................... 57 5.3.7 Selection of Exploration Drilling Sites .......................................................................... 60 5.4 EXPLORATION DRILLING PROGRAMME ............................................................................................ 61 5.4.1 Overview ....................................................................................................................... 61 5.4.2 Drilling Results ............................................................................................................. 65 5.4.3 Comparison of Geophysical Survey and Drilling Results ............................................. 77 5.5 BOREHOLE GEOPHYSICAL LOGGING ................................................................................................ 78 5.5.1 General .......................................................................................................................... 78 5.5.2 Instrumentation ............................................................................................................. 78 5.5.3 Geophysical Logging Results ........................................................................................ 79 5.6 EXPLORATION BOREHOLE AQUIFER TESTING .................................................................................. 82 5.6.1 Ecca Boreholes - Test Pumping Results ........................................................................ 83 5.6.2 Ntane/ Lebung Boreholes - Test Pumping Results .......................................................