View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Federation ResearchOnline Beyond hydrogeologic evidence: challenging the current assumptions about salinity processes in the Corangamite region, Australia P. G. Dahlhaus & J. W. Cox & C. T. Simmons & C. M. Smitt Abstract In keeping with the standard scientific methods, evidence found which supports significant rises in ground- investigations of salinity processes focus on the collec- water following widespread land-use change. In many tion and interpretation of contemporary scientific data. areas, salinity is an inherent component of the region’s However, using multiple lines of evidence from non- landscapes, and sustains world-class environmental assets hydrogeologic sources such as geomorphic, archaeologi- that require appropriate salinity levels for their ecological cal and historical records can substantially add value to health. Managing salinity requires understanding the the scientific investigations. By using such evidence, the specific salinity processes in each landscape. validity of the assumptions about salinity processes in Australian landscapes is challenged, especially the Résumé En se conformant aux méthodes scientifiques assumption that the clearing of native vegetation has standard, les études de l’acquisition de la salinité se resulted in rising saline groundwater in all landscapes. concentrent sur la collecte et l’interprétation de données In the Corangamite region of south-west Victoria, scientifiques contemporaines. Toutefois, l’utilisation de salinity has been an episodic feature of the landscapes filières multiples de données provenant de sources non throughout the Quaternary and was present at the time hydrogéologiques telles que des compilations géomorpho- of the Aboriginal inhabitants and the first pastoral logiques, archéologiques et historiques peut ajouter de settlement by Europeans. Although surface-water salinity façon substantielle de la valeur aux études scientifiques. has increased in some waterways and the area of salinised En utilisant de telles données, la validité des hypothèses land has expanded in some landscapes, there is no recorded concernant l’acquisition de la salinité dans les espaces naturels Australiens est mise en question, en particulier l’hypothèse que le défrichement de la végétation indigène a entraîné une remontée d’eau souterraine saline dans Received: 11 July 2007 /Accepted: 16 April 2008 toutes les espaces naturels. Dans la région de Corangamite du Sud Ouest du Victoria la salinité a été une caractéris- tique épisodique des espaces naturels pendant tout le Quaternaire et était présente du temps des habitants ) Aborigènes et des premiers peuplements pastoraux par P. G. Dahlhaus ( ) ’ School of Science and Engineering, les Européens. Bien que la salinité de l eau de surface ait University of Ballarat, P.O. Box 663, Ballarat 3353, Australia augmentée dans quelques cours d’eau et que la superficie e-mail: [email protected] de terres devenues salines se soit développée dans Tel.: +61-3-53413994 certaines régions, aucune preuve documentée n’aété J. W. Cox trouvée qui confirme des remontées d’eau souterraine CSIRO Land and Water, Private Bag 2, Glen Osmond 5064, significatives à la suite de modifications extensives de Australia l’utilisation du sol. Dans de nombreuses régions la salinité e-mail: [email protected] est une composante inhérente aux espaces naturels de la C. T. Simmons région, et entretiennent une richesse environnementale de School of Chemistry, Physics and Earth Sciences, niveau mondial qui exige des niveaux de salinité Flinders University of South Australia, GPO Box 2100, Adelaide 5001, Australia convenant à leur santé écologique. La gestion de la e-mail: craig.simmons@flinders.edu.au salinité exige la compréhension du développement spéc- ifique de la salinité dans chaque espace naturel. C. M. Smitt Hyder Consulting Pty Ltd, 16/31 Queen Street, Melbourne 3000, Australia Resumen De acuerdo con los métodos científicos, las e-mail: [email protected] investigaciones de procesos de salinización se centran en la recolección e interpretación de datos científicos mod- habitats for migratory birds subject to international treaties. ernos. Sin embargo, el uso de líneas múltiples de In the 1.3 million ha of the Corangamite region, over evidencia de fuentes no hidrogeológicas –tales como 17,000 ha of salt-affected land have been mapped and the registros geomórficos, arqueológicos e históricos-pueden area continues to expand (Nicholson et al. 2006). agregar un valor sustancial a las investigaciones científ- The Corangamite regional population is approximately icas. Mediante el uso de tales evidencias, se cuestiona la 400,000 persons and is growing at 5.2% per year, with validez de las hipótesis sobre procesos de salinización en manufacturing, tourism, agriculture and forestry as major ambientes australianos, especialmente la noción que la industries. The climate is generally warm temperate, with eliminación de la vegetación nativa ha resultado en en la winter/spring dominant rainfall that varies from 400 to elevación de agua subterránea salina en los ambientes. En 2,000 mm annually across the region. Four drainage la región de Corangamite, al sudoeste de Victoria, la basins—the Barwon, Moorabool, Lake Corangamite and salinidad ha sido una característica episódica del paisaje Otway Coast—cover the region, and the major drainage durante el Cuarternario y estaba presente en tiempo de los systems are those of the Barwon, Woady Yaloak, Moor- habitantes aborígenes y de los primeros asentamientos abool, Leigh, Gellibrand and Curdies rivers. Over 1,500 pastoriles europeos. Aunque la salinidad de cuerpos de lakes and wetlands are a feature of the region, including the agua superficiales se ha incrementado y las tierras internationally significant Lake Corangamite, Lake Colac, alinizadas se han expandidos en algunos ambientes, no Lake Murdeduke and Lake Connewarre (Fig. 1). se encontraron registros que sustenten que la elevación del In 2001, the National Land and Water Resources Audit agua subterránea fue la consecuencia de la generalización released the “Australian Dryland Salinity Assessment de cambios en el uso de la tierra. En muchas áreas, la 2000” (NLWRA 2001). The predictions for the Coranga- salinidad es un componente inherente a la región, que mite region were dire; with the worst-case scenario posee “activos“ambientales que requieren de niveles suggesting that 48.5% of agricultural land is at risk from apropiados de salinidad para su sanidad ecológica. La shallow water tables by 2050, costing the region AUD$ 29 gestión de la salinidad supone una comprensión de los million per year and with over 40% of the region’s procesos de salidad en cada ambiente. wetlands threatened by 2050. Based on the predictions of increasing salinity, the Corangamite region is nominated as Keywords Salinisation . Saline wetlands . Conceptual one of the priority regions in Australia, under the National models . Corangamite . Australia Action Plan for Salinity and Water Quality (CoAG 2000). The main cause of the salinity is assumed to be rising saline groundwater following widespread clearing of Introduction native vegetation in the mid to late nineteenth century for pastoral settlement, agriculture and mining (NLWRA The common conception for the salinisation of land and 2001). Since the first regional salinity strategy in 1992, water resources in Australian dryland agricultural regions is approximately AUD$ 50 million of government funding that of evaporative concentration of salts from shallow has been provided to the region for salinity management, water tables that have risen following the clearing of native and many millions of dollars in landholder, industry and vegetation for agriculture (Peck and Williamson 1987; community contributions. This funding has been provided George et al. 1997; Salama et al. 1999). This paper argues a to establish over 5,000 ha of trees, treat around 1,500 ha major shift away from that notion, by linking evidence of salt-affected land, establish over 500 groundwater from the fields of geomorphology, archaeology and monitoring bores and support several major research environmental history. Using data sources beyond the usual programs (Nicholson et al. 2006). hydrogeologic evidence (such as groundwater hydraulics, This paper reviews the evidence for salinity in the hydrochemistry, isotopes, modelling etc.) has developed Corangamite region during the Quaternary Period and more empirically accurate conceptualisations for salinity time since first European settlement. The validity of the processes that are occurring in the Corangamite region of current assumption that the clearing of native vegetation south-eastern Australia. Examining the salinity processes has resulted in rising saline groundwater in all landscapes over an extended timeline can provide a context for the throughout the region is challenged. Although the cause current day observations and lead to a different conclusion (land clearing) and effect (salinisation) has been well than that based on short-term monitoring and prediction. It established in other areas of Australia (Ghassemi et al. is contended that supplementing hydrogeological research 1995), it is not universally applicable in this region. The with multiple lines of evidence from non-scientific sources implications for the current salinity management actions can substantially add value to such scientific investigations. are discussed. Dryland salinity