Sources and Fluxes of Water and Salt Below a Regional Groundwater Discharge Complex, South-Eastern Australia. submitted by Nikki Michelle Howes, B.Sc. (Hons.) as a requirement in full for the degree of Doctor of Philosophy in the School of Chemistry, Physics and Earth Sciences Flinders University of South Australia February 2003 i Table of Contents Abstract vi Declaration of Originality viii Publications Associated With This Thesis ix Acknowledgements ix CHAPTER 1 INTRODUCTION 1 1.1 SCOPE AND OBJECTIVES OF THESIS ........................................................................................ 1 1.2 METHODOLOGY ....................................................................................................................... 7 1.3 SITE DESCRIPTION ................................................................................................................... 8 1.3.1 THE MURRAY BASIN, SOUTH-EASTERN AUSTRALIA ................................................................. 8 1.3.2 THE RAAK PLAIN GROUNDWATER DISCHARGE COMPLEX ........................................................ 9 1.3.3 GEOLOGY AND HYDROGEOLOGY ............................................................................................ 14 1.3.4 PREVIOUS INVESTIGATIONS AT RAAK PLAIN ........................................................................... 16 1.3.5 CHARACTERISTICS OF THE PLAYA LAKES SELECTED FOR THIS STUDY ................................... 17 1.3.5.1 Western Salina ........................................................................................................................ 20 1.3.5.2 The Main Salina ...................................................................................................................... 20 1.3.5.3 Salt Lake ................................................................................................................................. 21 1.3.5.4 Spectacle Lake ........................................................................................................................ 22 1.3.5.5 Surface Water vs Dry Lakes ................................................................................................... 23 1.4 PRELIMINARY CONCEPTUAL MODELS OF THE PLAYA LAKES AT RAAK PLAIN.................. 25 1.5 OVERVIEW OF PREVIOUS WORK ON THE HYDROLOGY AND HYDROCHEMISTRY OF SALT LAKES AND GROUNDWATER DISCHARGE ZONES (PLAYA LAKES) ............................ 29 1.5.1 EVAPORATION RATE ESTIMATIONS ......................................................................................... 30 1.5.2 BRINE LEAKAGE ...................................................................................................................... 31 1.5.3 SALT LAKE GEOCHEMISTRY AND BRINE EVOLUTION .............................................................. 32 1.5.4 THE INFLUENCE OF LEAKAGE ON THE CHEMICAL EVOLUTION OF BRINES .............................. 33 CHAPTER 2 FIELD AND ANALYTICAL TECHNIQUES 34 2.1 FIELD METHODS .................................................................................................................... 34 2.1.1 PIEZOMETER INSTALLATION AND SEDIMENT SAMPLING ......................................................... 34 2.1.2 GROUNDWATER SAMPLING ..................................................................................................... 38 2.1.3 SHALLOW SEDIMENT PROFILE SAMPLING ............................................................................... 39 2.1.4 AQUIFER TESTING ................................................................................................................... 40 2.2 LABORATORY METHODS ....................................................................................................... 40 2.2.1 PARTICLE SIZE DISTRIBUTIONS ............................................................................................... 40 2.2.2 EXTRACTION OF PORE WATER FROM SEDIMENT SAMPLES ...................................................... 41 2.2.3 MAJOR IONS ............................................................................................................................ 41 2.2.4 STABLE ISOTOPES: OXYGEN-18 AND DEUTERIUM ................................................................... 43 2.2.4.1 Oxygen-18 .............................................................................................................................. 43 2.2.4.2 Deuterium ............................................................................................................................... 44 2.2.4.3 Isotope Activity Corrections in Concentrated Brines ............................................................. 44 2.2.5 CARBON ISOTOPES .................................................................................................................. 46 2.2.6 CHLORINE-36 .......................................................................................................................... 46 ii CHAPTER 3 CHEMICAL EVOLUTION OF THE BRINES AND GROUNDWATERS AT RAAK PLAIN 47 3.1 INTRODUCTION ...................................................................................................................... 47 3.2 PREVIOUS INVESTIGATIONS OF THE HYDROCHEMICAL EVOLUTION OF EVAPORATING BRINES .................................................................................................................................... 49 3.2.1 MODEL DEVELOPMENT ........................................................................................................... 49 3.2.2 BRINE EVOLUTION IN SURFACE WATER LAKES ...................................................................... 51 3.2.3 BRINE EVOLUTION IN DRY PLAYAS ......................................................................................... 54 3.2.4 THE INFLUENCE OF LEAKAGE ON BRINE COMPOSITIONS ......................................................... 55 3.3 THE TYRRELL GROUNDWATER DISCHARGE COMPLEX, MURRAY BASIN, AUSTRALIA ..... 56 3.4 RESULTS ................................................................................................................................. 58 3.4.1 GENERAL OVERVIEW .............................................................................................................. 58 3.4.2 BRINE CHEMISTRY .................................................................................................................. 64 3.4.3 PARILLA SAND GROUNDWATER .............................................................................................. 64 3.4.4 LOCALLY RECHARGED GROUNDWATER .................................................................................. 65 3.4.5 RAINFALL AND DRY DEPOSITION ............................................................................................ 67 3.4.6 MINERALOGY .......................................................................................................................... 68 3.4.7 ION VS DEPTH PROFILES AT SPECTACLE LAKE ........................................................................ 70 - 3.4.8 MAJOR IONS VERSUS BRINE CONCENTRATION FACTOR ([BR ]) .............................................. 72 3.4.9 MINERAL SATURATION INDICES .............................................................................................. 81 3.5 DISCUSSION ............................................................................................................................ 85 3.5.1 ORIGINS OF THE BRINES AND INTERMEDIATE TDS GROUNDWATERS ...................................... 85 3.5.2 BACK-DIFFUSION OF THE BRINES ............................................................................................ 89 3.5.3 MINERAL CONTROLS ON BRINE COMPOSITIONS ...................................................................... 91 3.5.3.1 Controls on Alkalinity ............................................................................................................ 91 3.5.3.2 Gypsum Precipitation ............................................................................................................. 92 3.5.3.3 Precipitation / Dissolution Cycles Near the Playa Surface ..................................................... 93 3.5.4 EVOLUTION OF SURFACE WATER IN THE “TYPE D” (SURFACE WATER) LAKES ...................... 95 3.5.5 TRENDS IN THE CHEMICAL COMPOSITION OF THE PARILLA SAND GROUNDWATER ................. 96 3.5.6 SPECTACLE LAKE (HARVESTED LAKE) ................................................................................... 97 3.5.7 CONSERVATION OF SOLUTES ................................................................................................. 101 3.5.8 GEOCHEMICAL MASS BALANCES .......................................................................................... 101 3.6 CONCLUSIONS ...................................................................................................................... 105 CHAPTER 4 CONCEPTUAL MODEL FOR GROUNDWATER AND SOLUTE FLUXES IN A GROUNDWATER DISCHARGE COMPLEX 107 4.1 INTRODUCTION .................................................................................................................... 107 4.1.1 SCOPE AND OBJECTIVES ........................................................................................................ 107 4.1.2 FORMATION AND LEAKAGE OF SUBSURFACE BRINES BELOW SALT LAKES .......................... 108 4.2 CONCEPTUAL MODEL DEVELOPMENT ............................................................................... 113 4.2.1 HYDROGEOLOGY ..................................................................................................................