Groundwater and surface water interaction, Wairarapa valley, New Zealand Michael Guggenmos A thesis submitted in fulfillment of the requirements for the degree of Masters of Science in Physical Geography, at the Victoria University of Wellington, New Zealand May 2010 i Abstract Physical and chemical interactions between surface and groundwater are complex and display significant spatial and temporal variability. However, relatively little is known about the chemical interaction between surface and groundwater; in particular the temporal scales at which this interaction occurs. The aim of this research was to determine if existing and/or potential water chemistry measurements could be used to investigate the interaction between surface and groundwater bodies in the Wairarapa valley, New Zealand and identify specific locations and timescales at which this interaction occurs. Analyses were undertaken at both regional and local scales. The regional scale investigation utilised Hierarchical Cluster Analysis (HCA) to categorise 268 historic surface and groundwater sites from the 3000 km² Wairarapa valley into similar hydrochemical clusters in order to infer potential interaction. Six main clusters were identified, primarily differentiated by their total dissolved solids (TDS), redox potential and major ion ratios. Shallow aquifers, located in close proximity to losing reaches of the upper Ruamahanga, Waiopoua and Waiohine Rivers, were grouped with similar Ca²⁺-HCO₃⁻ type surface waters, indicating (potential) recharge from these river systems. Likewise, rainfall-recharged groundwater sites that displayed higher Na⁺ relative to Ca²⁺ and Cl⁻ relative to HCO₃⁻ were grouped with similar surface waters such as the Mangatarere and lower Waingawa streams. This suggests the provision of this rainfall-recharged signature to river base flow. Deep anoxic aquifers, high in TDS, were grouped together, but showed no statistical link to surface water sites. Results from the regional scale investigation highlight the potential use of HCA as a rapid and cost-effective method of identifying areas of surface and groundwater interaction using existing datasets. A local scale investigation utilised existing quarterly and monthly hydrochemical data from the Mangatarere and Waiohine Rivers and nearby groundwater wells in an attempt to gain insight into temporal variability in surface and groundwater interactions. Time series analysis and HCA were employed, however, the coarse time scales at which data was available made it difficult to make reliable inferences regarding this interaction. To overcome this issue, upstream and downstream surface and groundwater gauging stations were established in the Mangatarere Stream catchment for a 92 day period. Continuous electrical conductivity, water temperature and stage measurements were obtained at three of the four stations, along with one week of hydrochemical grab sampling. The fourth gauging station provided a more limited dataset due to technical issues. The downstream Mangatarere Stream received 30-60% of base flow from neighbouring groundwaters which provided cool Na⁺-Cl⁻ type waters, high in TDS and NO₃‾ concentrations. This reach also lost water to underlying groundwaters during an extended dry period when precipitation and regional groundwater stage was low. The upstream groundwater station received recharge primarily from precipitation as indicated by a Na⁺-Cl⁻-NO₃‾ signature, the result of precipitation passage through the soil-water zone. However, it appeared 2-4 m³/s of river recharge was also provided to the upstream groundwater station by the Mangatarere stream during an extended storm event on JD021-028. Mangatarere surface waters transferred a diurnal water temperature pattern and dilute Na⁺-Ca²⁺-Mg²⁺-HCO₃⁻-Cl⁻ signature to the upstream groundwater station on JD026-028. Results obtained from the Mangatarere catchment confirm the temporal complexities of ground and surface water interaction and highlight the importance of meteorological processes in influencing this interaction. ii Acknowledgements There are a number of people and organisations that I would like to acknowledge and thank for their support and assistance in the completion of this research thesis: Firstly I would like to thank my supervisors Bethanna Jackson and Chris Daughney. You both provided an immense level of support, guidance and insight into this research and its various sub-projects. In particular I would like to thank Chris for pulling me out of the mountains and stimulating my interest in ground and surface water interactions. I would like to gratefully thank the Greater Wellington Regional Council for their financial assistance and logistical support. Without the council and its dedicated environmental team this project would not have been possible. Special thanks goes to Sheree Tidswell from the Masterton Office who provided an immense amount of her time to this project. I also wish to thank Edward Lee, Doug McAlister, Alton Perrie, Juliet Milne, Ted Taylor, and Laura Watts. Special thanks go to John Quinn and Reid‟s Piggery in the Wairarapa valley for allowing me to establish monitoring stations on their properties. In particular thanks must go to Andrew Hosken for his support and time. To GNS Science and all the team in the groundwater department for providing generous financial assistance and support. I would like to thank my office mates Conway Penne, Chris Gazley and Louise Gallard for answering all those stupid questions and putting up with my stinky gym gear. To all my friends and colleagues at Victoria University for your encouragement, proof reading and words of support. Special mention must go to Jan Thompson and Deb Maxwell – hydrology would not be nearly as sexy without you! Hamish McKoy, Gigi Woods and Andrew Rae for providing technical support and advice. Richard and the Willemsen family from the Taratahi Hotel in Carterton for hosting and entertaining me during my field work. Hill Laboratories in Hamilton for undertaking my chemical analyses. Lastly, the success of this research would not have been possible without my friends, flat mates, field assistants and family. I owe you all for your patients, support and belief. iii Table of contents Abstract …………………………………………………………. ii Acknowledgments ……………………………………………… iii Table of contents …………………………………….………... iv Table of Tables…………………………………………...……. vii Table of Figures………………………………………………… x Table of Equations……………………………………………… xi Index of Chemical Species ……………………………………. xii Chapter 1 – Introduction 1 Chapter 2 – Surface and groundwater interaction 7 2.1 Physical hydrogeology………………………..……………………...… 7 2.1.1 Groundwater movement……………………...…………..….… 9 2.1.2 Groundwater flow systems………….…….……………….…... 12 2.1.3 Topographic and Geological influences……………………….. 12 2.2 Surface and groundwater interaction…...……………………………. 15 2.2.1 Stream and aquifer interaction…………………………………. 15 2.2.2 Spatial and temporal variability of stream-aquifer interaction… 16 2.2.3 Lakes and Wetlands……………………………………………. 19 2.2.4 Hyporheic zone………………………………………………… 20 2.3 Hydrogeochemistry……………………………... ………….....……… 21 2.3.1 Chemical composition of water bodies ……………………....... 21 2.3.2 Groundwater evolution…………………….…………..……… 27 2.3.3 Chemical surface and groundwater interactions………….…… 30 2.3.4 Chemical processes: ions and molecules within solution……… 33 2.3.5 Chemical processes: surface reactions…………………………. 37 2.3.6 Mass transport processes………………………………….…… 40 2.4 Gaps in the literature and research justification…………………….. 43 Chapter 3 –The Wairarapa valley 47 3.1 Geological history…………………………………..……..…………... 47 3.2 Hydrogeology …………………………………………….…….……... 51 3.2.1 Regional groundwater flow direction …………….…………… 53 3.2.2 Groundwater recharge mechanisms……………………………. 55 3.3 Surface hydrology………………………………..……………………. 55 3.4 Climate………………………………………………………………...... 59 iv 3.5 Human history and land use………………………..………………… 61 3.5.1 Surface and groundwater abstraction…….…………………… 63 3.5.2 Current hydrological monitoring………………………………. 64 3.6 Summary……………………………………………………………...... 65 Chapter 4 – Regional scale interaction 66 4.1 Regional scale methodology………….…………………………….… 67 4.1.1 Dataset compilation…………………………….…………….. 67 4.1.2 Calculation of medians………..……..………………….…….. 68 4.1.3 Charge balance errors…..……..……………………………….. 69 4.1.4 Hierarchical Cluster Analysis………………………………….. 70 4.2 Hierarchical Cluster Analysis…………………………………............ 72 4.2.1 Nearest Neighbour Linkage method…………………………… 72 4.2.2 Outlier analysis…..……………………….……………………. 72 4.2.3 Wards Linkage method………………………….……………... 76 4.3 Cluster differentiation…………………………………………………. 78 4.3.1 One-Way ANOVA…………..……………….…….…………. 78 4.3.2 Piper diagrams……………..…………………….….…………. 80 4.3.3 Spatial distribution of clusters …..………………………...….. 81 4.4 Hydrochemical facies descriptions and discussion…………………... 83 4.5 Cluster validation……………………………………………………… 87 4.6 Regional scale limitations……………………………………………… 88 4.7 Regional scale interaction concluding remarks……………………… 91 Chapter 5 – Local scale low resolution temporal interaction 93 5.1 Local scale methodology………………………………………………. 94 5.2 Temporal cluster analysis………………………………..…………… 95 5.3 Time series analysis…………………………………………………… 102 5.4 Local scale temporal interaction concluding remarks……………… 105 Chapter 6 – Local scale high resolution interaction 106 6.1 The Mangatarere Stream……………………………………………… 107 6.2 Local scale high resolution methodology…………………………….. 113 6.2.1 Physical hydrological parameters…………………..….……… 116 6.2.2