SETTINGS AND GROUNDWATER LINKS COX, M.E., JAMES, A., HAWKE, A., SPECHT, A., RAIBER, M. & TAULIS, M. North Stradbroke Island is a large sand mass of ecological and economic value and is a unique geological and hydrological feature. The island has evolved through a variety of marine- and wind-driven processes involving movement and deposition of sands. These processes have resulted in characteristic geomorphology and physical properties. An essential part of the development and function of the island is the regional groundwater body and in particular its relation to environmentally significant wetlands and lakes. Many of these surface features are perched above the regional watertable, but others can be connected. Here we utilise 3D visualisation of the island morphology to display these features. We use a scheme where surface water bodies or features, are categorised as Type A (high elevation discharge features), Type B (low elevation discharge features) and Type C (coastal seepage discharge features) and discuss the relationship to the groundwater system. Malcolm Cox, Allan James, Amy Hawke, Matthias Raiber & Mauricio Taulis, Institute for Sustainable Resources and Faculty of Science & Technology, Queensland University of Technology, Brisbane, OLD 4001, Australia. Alison Specht, Australian Centre for Ecological Analysis and Synthesis, The University of Queensland, St. Lucia, OLD 4067, Australia. Malcolm Cox and Matthias Raber, National 47 NORTH STRADBROKE ISLAND 3D HYDROLOGY: SURFACE WATER FEATURES, Centre for Groundwater Research & Training. Received: 28 April 2011; Revised: 18 July 2011; Accepted: 22 August 2011 INTRODUCTION North Stradbroke Island is a large sand mass and forms the southeastern boundary of Moreton Bay (Figure1).Theislandisofimportanceforitssupplies of good quality groundwater but also its unique ecosystems; economically the island is of value for tourism,andcurrentlysandminingoperations.The island (Minjerriba) also has high indigenous value and a permanent population of around 3,500, located in Dunwich (42%), Amity Point (16%) and Point Lookout(35%),andseveralothersmallsettlements (7%). In addition, well over 200,000 people visit the island annually, notably over the summer vacation period. There is no bridge connection from the mainlandandaccess is bylargelybyboat. There are a numerous morphological features on North Stradbroke Island, which have been produced by a wide range of natural processes. Water is fundamental to this sand island both in its formation and as a critical resource, in particular the different forms of groundwater. Of prime significance are the numerous lakes (or lagoons) that mostly represent surface runoff, or seepage, in localised catchments. These lakes andassociatedwetlandsarecommonlyperchedon low permeability material on valley floors and local depressions. Also of note are a number of flowing streams on the low-lying fringes of the island. All these surface water features reflect the intimate relationship between groundwater and surface water, however, this is highly variable spatially and temporally. The island has a regional groundwater body, thesurfaceof whichoccursat different depths, andcanvarysubstantiallyinresponsetorainfall. The main natural recharge mechanism to this aquifer is by infiltrationofrainfallthroughthepermeablesands. From an environmental perspective the links between groundwater and the ground surface are very important in the maintenance of different ecosystems. In an attempt to better understand these variably connected systems and their processes we use a visualisation approach in both two- and three-dimensions to display the relationships. PHYSICAL SETTING CLIMATE The Moreton Bay region experiences a subtropical climatewithmeandailytemperaturesintheorderof 15°—29°C in summer, and 9°—20°C in winter. Average annual rainfall varies within the region depending on location. On North Stradbroke Island mean annual rainfall is estimated as 1677 mm at Point Lookout (1947-1999), with mean annual pan evaporation of 1,498mm.Themeanrainfallalsovarieswithlocation ontheisland,butamedianvalueis1645mm;rainfall on the island is significantly higher than that for