Poster Presentation NCGRT/IAH Australasian Groundwater Conference 2019

Spatial and temporal stable isotope variability within Alpine Streams of the Snowy Mountains (367)

Reuben Parige 1 , Sharon Gray 1 , Cath Hughes 2 , Bradley Opdyke 1 , Leah Moore 1 3
  1. Research School of Earth Science, Australian National University, Canberra, ACT, Australia
  2. Australian Nuclear Science and Technology Organisation, Sydney, NSW, Australia
  3. Institute for Applied Ecology, University of Canberra, Canberra, ACT, Australia

As an alpine region, the Snowy Mountains are identified as susceptible to the impacts of climate change. This is projected to influence annual variability in rainfall and snowfall amounts which will change availability of runoff water. The Snowy Mountains Hydro-electric Scheme has also altered natural flows in the area since the 1970s, changing behaviours of water resources in the Murrumbidgee and Snowy River catchments. Understanding processes that affect and have affected these surface waters can therefore improve the scientific basis for future water resource management decisions of the region.

Historical physiochemical data of streams in the Snowy Mountains region has been monitored by NSW government and Snowy Hydro over the past half century. However, little stable water isotope data in alpine streams and rivers currently exists. As stable water isotopes (δ2H and δ18O) are excellent tracers of water through the hydrologic cycle, their use can better current understanding of the regions surface waters.

Rapid stream surveys in 2019 have collected stable isotope and physiochemical data of streams within the Snowy Mountains, as well as Murray and Murrumbidgee systems downstream. Analyses of both these and archived samples from 2004-2017 were undertaken for this project. The data was then used with precipitation isotope data from parallel ANSTO studies, and historical records on regional streams for interpretation.

Results showed that stable isotopes in streams varied spatially amongst sites with elevation, temperature difference, and location in the reservoir network, with distinct variance over smaller distances with steeper elevation. Temporal affects were seen with the appearance of seasonal snowmelt contributions into streams and climate. Physiochemical data saw trends similar to historical reports, with significant climate and geographic influence.

This data will specifically contribute to further research into groundwater sustainability, isotope forensics and agricultural water use led by ANSTO and ANU for future betterment of the catchment.