Fact sheet 3: Groundwater Dependent Ecosystems
Groundwater Dependent Ecosystems (GDEs) are groups of plants and animals that depend on
groundwater to live, grow and reproduce. GDEs are likely to occur wherever groundwater emerges at the
ground surface or is shallow enough to be reached by tree roots, see Figure 1. The National Atlas of
GDEs recognizes three broad types of GDE:
 Ecosystems dependent on the surface expression of groundwater. This includes rivers, springs, lakes
and other wetlands.
 Ecosystems dependent on the presence of groundwater below the surface. These are terrestrial
vegetation communities.
 Ecosystems in aquifers and caves.
The best known GDEs in the Great Artesian Basin (GAB) are the GAB Springs. Hundreds of springs
occur across the GAB supporting a diverse and unique collection of flora and fauna. They have been
categorized into two main types: recharge springs and discharge springs. Recharge springs occur mostly
along the eastern and northern edges of the Basin where GAB aquifers outcrop at the surface and may
overflow after local rainfall. Discharge springs occur where water emerges naturally under artesian
pressure from the Basin. This occurs mostly along the western and southern margins and in association
with faulting and fracturing.
The GAB Water Resource Assessment completed in 2013 revealed the potential for other types of GDE
to occur in the GAB. The Assessment found that some rivers in the GAB area may receive discharge
from the GAB, and that GAB water may flow upwards along faults and discharge into shallow
groundwater tables. This means that the terrestrial vegetation in the vicinity of these faults may be
groundwater dependent. The extent of this GAB discharge into rivers and shallow groundwater tables is
poorly understood.
Some aquifers and caves are habitat for stygofauna, aquatic fauna living in groundwater. Some
stygofauna have adapted to a subterranean existence and have lost their eyes and pigment. There is no
particular aquifer type or depth below the ground’s surface which can be used to predict where
stygofauna may occur; suitable habitat can be found at a range of aquifer environments and depths. The
most important factors are living space, oxygen and a food supply of dissolved and particulate organic
matter. This means that stygofauna are most likely to be found in unconfined aquifers with good
connections to surface water, or in semi-confined aquifers with strong connectivity with riverine
sediments above. They are unlikely to be found in deep confined GAB aquifers but may be present
where the GAB aquifers outcrop and are fractured and associated with rivers.
What are the water requirements of GDEs?
Sound groundwater resource management principles require that water allocation processes for
agricultural, mining, urban and commercial developments should consider the environmental needs of
GDEs. In the GAB, water allocation decisions must take into account the potential impacts on the
artesian pressure that supplies water to springs. There are rules governing the issue of water extraction
licenses to protect the flow of water to springs.
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Figure 1 Conceptual Model Case Study Series: Eulo-springs super group, Queensland 2011
What are the pressures on GDEs?
Artesian pressure loss due to free-flowing bores is a major threat to GAB springs and other GDEs. The
GAB Sustainability Initiative, a program to cap bores and replace wasteful open bore drains with piping,
has been in place for some years and is restoring artesian pressure in some areas. A recovery plan for
the on-going protection and management of GAB springs is now in place. Other threats to GAB springs
include excavation, invasion by weeds, disturbance by stock and feral animals, and trampling and
pollution resulting from poor visitor management. There are many on-ground projects to control the
weeds and feral animals that have degraded springs. Some of these projects are benefiting from
partnerships with the traditional owners.
What knowledge is needed for effective management of GDEs?
The first step in understanding, conserving and managing GDEs is to systematically map the location
and type of known and potential GDEs. Hydrogeological conceptualization, groundwater pressure levels
and wetlands and vegetation mapping all help to identify and map GDEs. Research to better understand
the values and needs of GAB springs is underway, supported by an extensive GAB bibliography,
database and mapping of thousands of spring vents. More information is needed to better understand
the locations and water requirements of other types of GDEs. Much remains to be learned about the
distribution, composition and biodiversity value of Australian stygofauna.
More information
Great Artesian Basin Coordinating Committee Secretariat
Water Division, Department of Agriculture and Water Resources
GPO Box 858
Canberra ACT 2601
Phone 1800 900 090
Email [email protected]
Web gabcc.gov.au
July 2016
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