On the hydrology of the bauxite oases, Cape York Peninsula, Australia M. Leblanc a,b,c,⇑ , S. Tweed a,b , B.J. Lyon d , J. Bailey b , C.E. Franklin e , G. Harrington f,g , A. Suckow f,g a ANR Chair of Excellence, Research Institute for the Development (IRD), UMR G-EAU, 34000 Montpellier, France b National Centre for Groundwater Research and Training (NCGRT) and Centre for Tropical Water & Aquatic Ecosystem Research (TropWATER), James Cook University, Cairns, Australia c Laboratoire d’Hydrogéologie, UMR EMMAH, University of Avignon-INRA, Avignon, France d Australia Zoo, Steve Irwin Wildlife Reserve, Australia e School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia f CSIRO Land & Water, Gate 5 Waite Road, Urrbrae, SA 5064, Australia g National Centre for Groundwater Research and Training (NCGRT), Flinders University, School of the Environment, Adelaide, Australia article info Article history: Received 12 August 2014 Received in revised form 12 May 2015 Accepted 1 June 2015 Available online 16 June 2015 This manuscript was handled by Laurent Charlet, Editor-in-Chief, with the assistance of Renduo Zhang, Associate Editor Keywords: Bauxite Springs Ecohydrology Remote sensing Hydrogeochemistry Groundwater dating summary One of the world’s largest bauxite deposits is located in the Cape York Peninsula, North-East Australia. Little is known about the hydrology of these remote bauxite deposits. Here, we present results from a multidisciplinary study that used remote sensing, hydrochemistry, and hydrodynamics to analyse the occurrence of several large oases in connection with the bauxite plateaus. Across this vast region, other- wise dominated by savannah, these oases are sustained by permanent springs and support rich and diverse new sub-ecosystems (spring forests) of high cultural values to the local indigenous population. The spring water chemistry reveals a well-mixed system with minor inter-spring variation; TDS values of spring waters are low (27–72 mg L 1 ), major ion compositions are homogenous (Na–Si–DIC–Cl) and d 18 O and d 2 H values are reflective of rainwater origin with little evaporation prior to recharge. Dating of spring waters with anthropogenic trace gases (CFC-12 and SF 6 ) indicates mean groundwater residence times ranging from <1 to 30 years. An artificial tracing experiment highlighted the existence of a flow pathway from the bauxite land surface to the sandy aquifer that feeds the springs through discontinuities in the ferricrete layer. In addition, the soil infiltrability tests showed the bauxite land surface has very high infiltrability (15 mm min 1 ), about four times greater than other adjacent land surfaces. Across the lower part of the Wenlock Basin, satellite data indicate a total number of 57 oases consistently located on the edge of the bauxite plateaus. This super-group of permanent hillslope springs and their ecosys- tems adds another important attribute to the list of natural and cultural values of the Cape York Peninsula. Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction The early twentieth century saw the first extensive attempts by scientists to document and classify springs (Bryan, 1919; Meinzer, 1923). Many modern classification systems incorporate parts of early works and have expanded on these through the quantitative knowledge of springs (Alfaro and Wallace, 1994). There is however no widely accepted spring classification system with significance attributed to particular parameters, such as geologic origin, dis- charge, or chemical composition, and classification therefore remains subjective. In recent times the classification and descrip- tion of springs has diversified from a primary focus on physical and chemical parameters (flow regime, hydrochemistry, and geologic setting) to become increasingly interested in the microcli- mates and ecosystems they support (Fensham et al., 2004; DWLBC, 2009; Springer and Stevens, 2009). The increased recognition of surface water and groundwater interactions in general, and spring fed streams and groundwater dependent ecosystems in particular, as having significant ecological implications has increased mark- edly over the last decade with the emergence of a new field known as hydroecology or ecohydrology (e.g. Hayashi and Rosenberry, 2002; Wood et al., 2008). Management of springs and terrestrial groundwater dependent ecosystems (GDEs) requires, as a first step, the basin-scale map- ping and characterisation of permanent spring waters. The map- ping of GDEs in Australia has recently advanced though the development of The National Atlas of Groundwater Dependent Ecosystems, a comprehensive inventory of the location and charac- teristics of groundwater dependent ecosystems for Australia. It incorporates multiple lines of scientific evidence including http://dx.doi.org/10.1016/j.jhydrol.2015.06.001 0022-1694/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: Laboratoire d’Hydrogéologie, UMR EMMAH, Univer- sity of Avignon-INRA, Avignon, France. E-mail address: marc.leblanc@univ-avignon.fr (M. Leblanc). Journal of Hydrology 528 (2015) 668–682 Contents lists available at ScienceDirect Journal of Hydrology journal homepage: www.elsevier.com/locate/jhydrol