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Ord

                                                                                                   

Significant Water Accounting Policy (SWAP) Notes

                             

Significant Water Accounting Policies   

The information presented in the Ord region water accounting report is based on agreements between the Western Australian Department of Water and the Bureau of Meteorology.

The report has been prepared using an accrual basis of water accounting, with the exception of the physical water flow information. The water attribute being quantified is volume and the unit of account is megalitres (ML). Where a reported volume is negative, it is shown in brackets.

 

Recognition of water assets and water liabilities

Only water that is held or managed by the state licensing authority or the urban utility and that is part of the entitlement system is defined as a water asset. Provided its volume can be adequately quantified, the asset is recognised in the Statement of Water Assets and Water Liabilities.

Where a water asset or water liability does not meet the recognition criteria, it is reported in the Statement of Water Assets and Water Liabilities with a dash (–). Water held in storages that has already been abstracted from the entitlement system is deemed not to be part of the region (irrespective of their size or connection to the system). This is because the attendant water right has already been exercised.

The regulated channel of the lower Ord River is recognised as a water asset when the electrical conductivity is below 1,500 μs/cm. Water in the regulated channel above this salinity level is not deemed fit for purpose and as such does not provide a future benefit to the Ord water report entity.

 

Recognition of changes in water assets and water liabilities

Increases and decreases to the water assets and water liabilities consist only of changes that can be adequately quantified. Where a change to a water asset or water liability does not meet the recognition criteria, it is reported in the Statement of Water Assets and Water Liabilities with a dash (–). These increases and decreases form part of the unaccounted-for difference, and are explained in the notes.

Precipitation and evaporation are only recognised in relation to major storage surfaces. These figures do not represent all precipitation and evaporation within the physical region of the water report entity.

Runoff is quantified and recognised for water that flows into the connected surface water storages. The runoff includes precipitation captured on the landscape in the catchment minus the water lost via landscape evapotranspiration and seepage.

Regulated or unregulated: The definition of 'regulated' or 'unregulated' for the purpose of the National Water Account (2010) (the 2010 Account) may be different from the meaning applied by the jurisdiction. For the purpose of the 2010 Account, if water can be ordered from a water supply scheme and has a resource operation licence it is defined as regulated; if not it is deemed to be unregulated.

 

Assets that failed to meet the recognition critera

Where a water asset or water liability does not meet the recognition criteria, it is reported in the Statement of Water Assets and Water Liabilities with a dash (–). The following assets failed to meet the recognition criteria:

Line item 1.2 Unregulated channel: Unregulated channel storage was not recognised as a water asset, because it could not be quantified adequately.

Unregulated channels in the Ord region have negligible flows during the middle of the dry season (May to September), unlike the regulated lower Ord River, which receives releases from Lake Argyle to maintain flows in the lower Ord River. The dry season coincides with the start and end of the reporting period; therefore, the amount of water stored in unregulated channels as at 30 June 2010 does not have a material impact on this water accounting report.

An expansion of the monitoring gauge network, and improved understanding of water levels and channel parameters, is required to calculate the storage volume of river channels.

Line item 1.4 Lakes and wetlands connected: The volume of water within lakes and wetlands, such as floodplain wetlands, that are associated with the connected surface water store was not recognised as a water asset, because it could not be quantified adequately.

Wetlands in the Ord region receive flows and fill up during the wet season (October to April) and then proceed to evaporate during dry season (May to September). The dry season coincides with the start and end of the reporting period; therefore, the amount of water stored in connected lakes and wetlands as at 30 June 2010 does not have a material impact on this water accounting report.

An expansion of the monitoring gauge network, and improved understanding of river water levels and volumes, is required to calculate the storage volume of wetlands in the region.

Line item 2.1 Water table aquifer: The volume of water stored in water table aquifers was not recognised as a water asset, because it could not be quantified adequately.

The Western Australian Department of Water maintains a limited number of monitoring bores across the Ord region, including the sedimentary water table aquifer beneath the Ord River Irrigation Area, and the sedimentary water table aquifer adjacent to Lake Kununurra.

The aquifer underlying the Ord River Irrigation Area results from the drainage of irrigation water applied at the land surface. Some of the water stored in the aquifer has an electrical conductivity greater than 1,500 μs/cm and is not fit for purpose. Improved understanding of aquifer extent, aquifer properties, groundwater processes, and water quality is required to adequately quantify the volume of the aquifer.

The volume of the aquifer adjacent to Lake Kununurra has a relationship with the reservoir, and is used for urban water supply to the town of Kununurra. Improved understanding of aquifer extent, aquifer properties, groundwater processes, and relationships between the aquifer and the reservoir is required to adequately quantify the volume of the aquifer.

Line item 2.2 Underlying aquifer: The volume of water stored in underlying aquifers was not recognised as a water asset, because it could not be quantified adequately.

The Western Australian Department of Water maintains a limited number of monitoring bores across the Ord region. Groundwater is extracted under license from localised underlying fractured rock aquifers in the upper Ord River Basin. An expansion of the monitoring bore network, and improved understanding of aquifer extent, aquifer properties, and groundwater processes, is required to adequately quantify the volume of the aquifers across the region.

Line item 5.1 Urban potable water supply system: The volume of water stored in the urban water supply systems for Wyndham, Kununurra and Halls Creek was not recognised as a water asset, because it could not be quantified adequately.

The volume of water held in the water supply systems is estimated to be less than 20 ML, and does not have a material impact on this water accounting report.

Line item 5.2 Urban wastewater system: The volume of water stored in wastewater treatment plants at Wyndham and Kununurra was not recognised as a water asset, because it could not be quantified adequately.

The volume of water held in the treatment plants at any one time is negligible, and does not have a material impact on this water accounting report.

Line item 5.4 Irrigation water supply system: The volume of water stored in the Ord River Irrigation Area network was not recognised as a water asset, because it could not be quantified adequately.

The irrigation network is used to deliver water to irrigators in the Ord River Irrigation Area, and is not used to store water. The volume of water in the network fluctuates according to demand for water from Lake Kununurra. The volume of water held in the channel at any one time is negligible, and does not have a material impact on this water accounting report.