The benefits of a multidisciplinary team model for groundwater-surface water investigations, Thirlmere Lakes, NSW.

The Thirlmere Lakes Research Program (TLRP) is a four-year collaborative multidisciplinary program designed to gain a whole-of-system understanding of the hydro-dynamics of a complex lake environment. The program was established from concerns that proximal aquifer interference activities were factors in recent lake level declines. Five research teams were established to investigate five adjacent lakes set within an entrenched meander bend located south-west of Sydney. The project involved lithological, geochemical and geochronological analysis from lake beds and surrounding slopes to understand lake evolution and determine potential past lake-drying events. Further geological understanding of the lake area was obtained from resistivity imaging (RI), ground penetrating radar (GPR), and analysis of rock cores that were drilled from two deep bores adjacent the lakes. Development of water balance budgets involved fine-scale on-site meteorological measurements including on-site evapotranspiration monitoring, combined with high-resolution bathymetry from RTK GPS, LiDAR surveying and drone photogrammetry. Groundwater-surface water interactions were measured using lake-bed multilevel temperature and pressure arrays, hydraulic head measurements and fine-scale isotope, major ion and environmental tracer time-series analysis. Preliminary findings indicate that the five lakes have been separated for over ~100,000 years and that the lakes themselves contain sediment that is possibly up to 250,000 years old. Assessing the modern dynamics we show that current lake level declines during a period of low rainfall are largely evaporation dominated. One lake however appears to have greater water storage in adjacent sediments providing compensatory inflows. In a second lake, there are indications of localised connectivity with shallow (≤18m) groundwater, but no evidence of connectivity with deeper aquifers. Geological surveys indicate a clay layer 6-8 m below the lakes and spatial variations in both sediment and rock geology. The influence of these geological features, including structures projecting towards the lakes, on groundwater storage and flow is the focus of ongoing research as is temporal variability and lake interactions at different lake levels. The benefits of the multidisciplinary team model include refining the research targeting areas of uncertainty and to enhance and calibrate each team’s results. This approach will provide a comprehensive whole-of-system model of the evolution and hydro-dynamics of a complex lake system. © The Authors

Keywords

Lakes, New South Wales, Australia, Aquifers, Geochemical surveys, Radar, Evaporation, Geologic surveys, Ground water, Tracer techniques

Citation

Cowley, K., Cohen, T., Forbes, M., Barber, E., Allenby, J., Andersen, M. S., Anibas, C., Glamore, W., Chen, S., Johnson, F., Timms, W., David, K., McMillan, T., S., Cendon, D., , Peterson, M. A., Hughes, C. E., & Krogh, M. (2019). The benefits of a multidisciplinary team model for groundwater-surface water investigations, 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: http://www.groundwater.com.au/documents/agc2019-book-of-abstracts-updated.pdf

URI

http://www.groundwater.com.au/documents/agc2019-book-of-abstracts-updated.pdf
https://apo.ansto.gov.au/dspace/handle/10238/11557

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