When do ecosystems become dependent on groundwater? (9 m deep and rising)


Ecosystems dependent on groundwater can suffer from changes in groundwater availability, for example due to pumping. However, groundwater can be found at some depth below most ecosystems, which makes it challenging to determine which ecosystems should be regarded to be dependent on groundwater and which are not.

A new study by Professor Derek Eamus and colleagues from the University of Technology Sydney presents the results of a detailed analysis of multiple vegetation traits across a gradient of depth-to-groundwater. From this, the ecohydrology team at UTS were able to identify a robust ecosystem-scale integrated response function for eucalypt woodlands in SE Australia to differences in depth-to-groundwater.

Eucalypt woodlands in SE Australia that have access to groundwater water within seven to nine metres below the surface develop different structure and properties than those that do not, the study finds, and therefore can be considered groundwater dependent ecosystems (GDEs).

“GDEs are at risk globally because of unsustainable rates of groundwater extraction, especially in arid and semi-arid regions where recharge is low and extraction rates large. Three major questions facing land and water managers in the context of GDEs are: (1) how do we locate GDEs; (2) how much water is being transpired by GDEs; (3) what might be the response of GDEs to excessive extraction from the underlying aquifer? “ says Professor Eamus.

According to the authors of the work “the review offers a critical synthesis of answers to these questions based upon both field and remote sensing methods/analyses, including use of stable isotopes, the GRACE satellites, dendrochronology and the integration of eddy covariance with remote sensing to estimate rates of groundwater-use.”

The paper also discusses results of two long-term field studies of the interaction of GW with terrestrial vegetation in the USA and Australia.

Eamus, D., Zolfaghar, S., Villalobos-Vega, R., Cleverly, J. and Huete, A. 2015, Groundwater-dependent ecosystems: recent insights from satellite and field-based studies, Hydrology and Earth System Sciences, Volume 19, Pages 4229–4256.  doi:10.5194/hess-19-4229-2015

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