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Title: The canary or the coalmine? Isotopic evidence of drying climate versus groundwater outflow as the cause for recent losses from Thirlmere Lakes, NSW
Authors: Peterson, MA
Cendón, DI
Hughes, CE
Crawford, J
Hankin, SI
Krogh, M
Cowley, KL
Cohen, TJ
Andersen, MS
Anibas, C
Glamore, W
Chen, SY
Timms, W
McMillan, T
Keywords: Lakes
New South Wales
Underground mining
Geologic fractures
Climatic change
Stable isotopes
Rain water
Issue Date: 24-Nov-2019
Publisher: National Centre for Groundwater Research And Training, & Australian Chapter International Association Of Hydrogeologists
Citation: Peterson, M. A., Cendón, D. Hughes, C., Crawford, J., Hankin, S., Krogh, M., Cowley, K. L., Cohen, T., Andersen, S., Anibas, C., Glamore, W., Shenyang, C., Timms, W., & McMillan, T. (2019). The canary or the coalmine? Isotopic evidence of drying climate versus groundwater outflow as the cause for recent losses from Thirlmere Lakes, NSW. Paper presented to the Australasian Groundwater Conference, "Groundwater in a Changing World", 24 - 27 November 2019, Brisbane Convention and Exhibition Centre, Queensland. Retrieved from:
Abstract: The Thirlmere Lakes Research Program (TLRP) is a collaboration investigating water loss mechanisms in recent drying of five adjacent lakes, located 75 km south-west of Sydney. Some stakeholders and previous studies have perceived a correlation with local longwall coal mining history and suspect deep fracture outflow. Others suggest the lakes are simply responding to a drier climate, serving as the canary in the broader climate-change ‘coal mine’. ANSTO has applied recurrent isotopic and chemical monitoring of the lakes and adjacent groundwater over two years to unravel some of the mystery of their recent water losses. Each lake behaved uniquely, but they shared some common trends. Steady enrichment of stable water isotopes, 2H and 18O, indicates the dominance of evaporation, with minimal losses to groundwater or through transpiration. Lake Cl/Br ratios were very low and clustered in three groups, two trending away from initial ratios indicative of groundwater input. 3H and 14C show recent rainfall and/or runoff as the main contributors to lake waters, with apparent ages in the adjacent shallow groundwater up to several decades. High levels of 222Rn from shallow bores suggest a close association between the peats enclosing the lakes and 238 U from ancient erosion, or proximity of an underlying shale lens. The only deep piezometer (72-84 m) near the lakes showed negligible contributions from the lakes or recent surface water. The trends in isotopic and chemical parameters infer that evaporation is sufficient to explain recent water losses from most of these perched lakes. Trends in some lakes hint that these had previous inputs from groundwater. While the historical variability of groundwater input to the lakes remains unknown, there is no current evidence of major losses to groundwater. Thirlmere Lakes will exist only intermittently under dry climate conditions. © The Authors
ISBN: 978-1-925562-35-4
Appears in Collections:Conference Publications

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