Oral Presentation Australasian Groundwater Conference 2017

Ecohydrologic functioning of ephemeral streams (#130)

Shawan Dogramaci 1 2 , Craig Simmons 3 , Pauline Grierson 2 , Peter Cook 3 , Greg Skrzypek 2
  1. Rio Tinto Iron Ore, Perth, WA
  2. West Australian Biogeochemistry Centre School of Biological Sciences, The University of Western Australia, Perth, WA
  3. National Centre for Groundwater Research and Training, School of Environment, Flinders University, Adelaide, SA, Australia

While arid and semiarid environments encompass 70% of Australia's land mass and one third globally, information on the hydrology and ecologic functioning of dryland regions is limited. Accelerating human demand for water resources as well as changing climate are driving significant changes in surface and subsurface flows of ephemeral streams, which pose enormous challenges to their sustainable management (Safeeq & Fares 2016).

Best practice in the management of rivers and streams requires predictive data on the relationships among flow regimes, surface-ground water interactions, and the key ecological water requirements of the biota. However, disentangling these interactions and the pressures on them can be particularly difficult in arid regions because of extreme natural variability in rainfall and recharge (Dogramaci et al. 2015; O'Donnell et al. 2015).

Mining poses one of the main pressures on water resources in dryland regions; many of the world’s largest mines operate in arid environments, including the major iron ore operations of Rio Tinto and others in the Pilbara region of northwest Australia. These mines increasingly abstract large volumes of fresh groundwater to access ore below water table. Water that is surplus to mining needs may be re-injected to aquifers, discharged back to the environment, or diverted offsite to develop regional agricultural programs (GHD 2015). Thus, one of the most pressing issues for managers in the mining sector (both in Australia and worldwide) is devising best practices for managing water for the life of the mine through to closure, including minimising impacts on key rivers and streams.

The University of Western Australia (UWA), NCGRT and Flinders University in collaboration with Rio Tinto, are investigating how surface and ground waters interact in ephemeral streams, and how riparian and floodplain vegetation both respond to and influence these interactions on daily, seasonal, and decadal scales. The study  will address the worldwide paucity of integrated ecohydrologic studies of arid environments. The approach will utilise a suite of innovative as well as well-tested and robust isotopic and environmental tracer techniques, coupled with measurement of water flux and integrative modelling, in order to resolve the relative importance of shallow alluvial water, deeper groundwater and soil water in sustaining riparian and floodplain ecosystems.

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