Tracing water quality changes in water level manipulated lakes in central Tasmania using high resolution core scanning and isotopic dating techniques
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Date
2017-09-24
Journal Title
Journal ISSN
Volume Title
Publisher
Australian Society for Limnology
Abstract
Great Lake and Woods Lake, located on the Central Plateau of Tasmania, are shallow lakes that are water level manipulated by Hydro Tasmania for power generation and irrigation supply. This has led to concerns regarding the ecological stability of these lakes under varying water levels. Hydro Tasmania has been maintaining and recording lake levels since their damming in the early and mid 1900s: Water level measurements for Great Lake exist since 1916, and for Woods Lake since 1968. These unique long-term water level records show that both lakes underwent significant water level fluctuations over the past few decades.
In this project we reconstructed the history of sedimentation during the past 150 years to investigate changes in nutrient fluxes since and prior to damming of the lakes in the early 1900s, using 210Pb dating techniques and high resolution X-ray Fluorescence core scanning (ITRAX). Most lakes in Tasmania are not suitable to investigate recent (<150 years) changes in environmental conditions due to extremely low sedimentation rates. However, the damming of Woods Lake and Great Lake has caused significant increases in sedimentation rates, making them also suitable for investigating changes in atmospheric deposition of anthropogenic pollutants.
Our results suggest that water level changes due to water level manipulation since the damming of the lakes have not significantly affected the ecological functioning of the lakes, but the damming itself increased sedimentation rates and burial rates of nutrients (nitrogen, phosphorus). 210Pb dating has also revealed that sediment resuspension does not occur to a depth >1 cm, even at times of low lake levels. Comparison of sediment core proxies (e.g. for water temperature) with 3 decades of water column data demonstrates the limitations of such proxies for paleoclimatology.
Description
Keywords
Geochemistry, Water quality, Lakes, Sedimentation, Drill cores, Tasmania
Citation
Proemse, B., Gadd, P., Zawadzki, A., Maxwell, C., & Barmuta, L. (2017). Tracing water quality changes in water level manipulated lakes in central Tasmania using high resolution core scanning and isotopic dating techniques. Paper presented at the Australian Society for Limnology Conference 2017, "New Science for a Changing World", University of Technology, Sydney, 24 to 28 September 2017. Retrieved from: https://static1.squarespace.com/static/5ebb667d8b14426c39e8dad4/t/5ec20819ddb38d4ce0e2e8c3/1589774368706/AFSS-2017.pdf