Water diversions and extractions
As part of AWR 2005 the management of water resources and relationship with
environmentally sustainable levels of extraction has been investigated by considering:
- identified sustainable yields within water management plans
- caps on water diversions and extractions
- diversions and extractions during 200405
It is in this context that information around water diversions and extractions
has been collated and analysed.
The level of diversions and extractions from water resources varies greatly
across Australia because of the variation in available surface and groundwater
resources, the uneven distribution of population, and variation in the area
of land that is suitable for agriculture, mining or other development. Water
diversions and extractions for irrigation also vary according to seasonal requirements
for crops.
Climatic variability is also a major factor in the level of diversions and
extractions. Changes in rainfall leads to changes in:
- irrigation requirements
- availability of water for flood harvesting
- filling of major water storages for distributed water supply
systems
- the level of water restrictions placed on urban and rural
water users during times of drought
Periods of low rainfall reduce groundwater recharge disproportionately due
to the reduction in deep drainage and reduced flow of water beyond the plant
root zones and into the groundwater systems. Groundwater extractions also increase
dramatically in times of low rainfall due to the lack of available surface
water and the transfer of demand to groundwater. For further information on
the climatic conditions from July 2004 to June 2005, refer to the Climatic
Contextual Data section [Link to Appendix E Climatic Contextual Data].
Groundwater bore being used for irrigation
Image by Arthur Mostead, sourced from the Murray-Darling Basin Commission
The Level 1 assessment of the states and territories included collating available
information relating to surface water diversions and groundwater extractions.
Key datasets requested included:
- total surface water diversion and groundwater extraction in the
surface water management area or groundwater management unit for 200405
(megalitres from July 2004 to June 2005)
- percentage of surface water diversion and groundwater extraction
in the surface water management area or groundwater management unit as
determined from metered data
- information on how the surface water diversion and groundwater
extraction was determined for the period 200405 for supplies that were NOT metered
The volume of surface water extractions or groundwater diversions are critical
to understanding the priorities for water resource management across the country.
Knowing the volumes of diversions and extractions allows usage volumes to be
compared with cap volumes and sustainable yield estimates. By doing so, it
enables the identification of areas that are highly developed or overallocated
and thus are a priority for further action under the National Water Initiative
(NWI).
Key areas of water diversion and use that are generally excluded from accounting of water resources are:
- forestry
- mining and oil industry
- stock and domestic licences.
Irrigation is the dominant user of water in Australia
Image by Arthur Mostead, sourced from the Murray-Darling Basin Commission
Forestry
Reafforestation of catchments has the potential to reduce catchment runoff, to reduce recharge to groundwater, and to extract water directly from groundwater. Many of the states and territories are aware of this impact, but none has considered increased forestry development in their water resource planning frameworks.
South Australia has introduced a system of “water effecting permits” to account for the impact of plantation forestry on groundwater recharge in the south east of the state (Lower Limestone Coast Prescribed Wells Area). The policy also requires that larger plantations (above a certain threshold area) must comply with licensed water allocations. Only then can the water transfer market offset the recharge impact. There is also some potential for plantations to directly extract groundwater from shallow watertables, for which policy is being developed to manage.
Mining and oil industry
Mine dewatering, extraction for minerals processing, or co-extraction with oil and gas production do not generally require a licence for water extraction and they are not recognised in water resource caps.
Stock and domestic licences
Stock and domestic water use is mostly not licensed; it is generally seen as a riparian right in state and territory legislation. There is some licensing in some areas that are at or near overallocation of water resources, but this is only where a problem has occurred due to the high number of farm dams or groundwater bores, most of which provide water to stock and domestic users. Some states, including Victoria and South Australia, have implemented changes to require farm dams to be registered or to hold an entitlement.
Related links
Water diversions and extractions are discussed in more detail in the following
sections:
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