Poster Presentation Australasian Groundwater Conference 2017

Characterisation of terrestrial ecosystem reliance on groundwater (#83)

Garry Straughton 1 , Katie Hulmes 2 , Leighton Randell 3
  1. Eco Logical Australia Pty Ltd, Adelaide, SA, Australia
  2. Technical Services, OZ Minerals Limited, Adelaide, South Australia, Australia
  3. Prominent Hill, OZ Minerals Limited, Adelaide, South Australia, Australia

Understanding a terrestrial ecosystems’ dependence on groundwater presents a significant challenge to decision makers during the development of a Project. This challenge is particularly prevalent in arid areas of Australia, where changes to the availability of groundwater may prove detrimental to the terrestrial ecosystems that rely upon it for survival. This study assess potential sources of water used by dominant flora species (Acacia papryrocarpa, Eucalyptus camaldulensis, Meleuca xerophylla) at three locations within a proposed Project site in South Australia’s Arid Lands. Data collected in the field included groundwater levels, soil water potentials, leaf water potentials, and stable isotopes from soil water, plant xylem water and groundwater. Results suggest a degree of groundwater use by flora species, with indication of opportunistic uptake of rainfall and soil water when available. Groundwater utilised by the ecosystems is considered not to be from the regional groundwater flow system that the proposed Project will interact with, due to its high reported salinities. Groundwater utilised by flora species is considered to originate from surface water that has infiltrated during and after creek flow events, and entered shallow alluvial formations in the proposed Project area. Infiltrated surface water from creek flows are sporadic and typically seasonal in the proposed Project area, and therefore flora species are likely existing for long periods of time waiting for opportunistic uptake. This is considered to be the case for Melaleuca Xerophylla at Site 3, where highly negative leaf water potentials suggest a plant under stress, with its metabolic functions being kept at a minimum during a semi-dormant state. The conclusions drawn from this study were able to inform the Project owner and decision makers of the terrestrial ecosystem’s dependence on groundwater, and incorporate the ecosystems potential fate in Project impact assessments.

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