17.6 Diversions - other statutory rights
The volume reported (2,728 ML) represents non-licensed surface water diversions from across the Adelaide region. Surface water diversions reported here do not require a licence to divert and use water; instead the right to divert surface water is provided for by sections 124(4), 124(6), 128, 132 and 164N of the Natural Resources Management Act 2004 (South Australia), (the Act).
For further information on these water rights see line item 32.1 Other statutory surface water rights.
The volume reported included diversions from watercourses within the Western Mount Lofty Ranges (WMLR) Prescribed Water Resources Area (PWRA). The water allocation plan (WAP) for this area is currently in draft format. When the WAP is adopted it will cover the following prescribed watercourses: Gawler River, Little Para River, River Torrens/Karrawirra Parri River and Onkaparinga River.
The volume reported did not include surface water diversions for stock and domestic purposes, and mining purposes described in sections 124(4) and 124(6) of the Act. These types of surface water diversions are not metered and therefore could not be quantified in a way that was complete, neutral and free from material error.
Domestic water demand in the Adelaide region is predominantly serviced by the urban water system. Therefore the volume of surface water diverted for domestic purposes is probably small and its omission is not likely to have a material impact on the surface water balance or influence the decisions made by users of the National Water Account.
Stock water demand in the Adelaide region is supplied form several sources: surface water diversion, groundwater extractions and runoff capture from local farm dams. Stock water use from all these water sources is estimated to be 1,016 ML (this estimate was calculated based on a method similar to the equation underlying the software package Damcat (Luke 1987; Farmer 2004)). Given that this volume is split across a range of sources, the volume of surface water diversions for stock purposes is expected to be reasonably small. While its omission is relevant to the users of the National Water Account, the omission of this volume is not expected to have a material impact on the surface water store.
Water taken in mining and quarrying operations that was not used for water supply is exempt from requiring a water licence in the Adelaide region. While this type of surface water diversion is important, insufficient information was available to estimate the magnitude of the impact to the surface water balance.
The maximum potential watercourse diversion demands were derived from a survey of existing users. An adjacent area to the Western Mount Lofty Ranges PWRA within the Adelaide Region is the Barossa PWRA, which is managed under a WAP. Watercourse diversions in the Barossa area in the 2010–11 year were expressed as a percentage of allocations (45%).
This adjustment was applied to the total potential demand for the WMLR area to derive an estimated demand for the 2010–11 year of 2,728 ML.
Assumptions, Limitations, Caveats and Approximations
The Barossa climate, management practices, mix of available water sources and water intensive industries are quite different to the WMLR PWRA. Extrapolation of changes observed in the Barossa PWRA to the WMLR should only be considered as a rough indication of annual surface water diversions.
The uncertainty estimate was in the range of +/– 30–50%.
This corresponds to the line item 14.5 Surface water diversion under other statutory right. In the 2011 Account this item was unquantified. In the 2011 Account, reclassification of this line item caused the values of the 2009–10 year to be restated. An improved understanding of the nature of surface water rights in the Adelaide region identified that the volume reported at line item 14.6 Entitled diversion of unregulated surface water flows in the 2010 Account was not licensed. Therefore this volume should be reported at line item 17.6 Diversions – other statutory rights.
Restatement of the value published in the 2010 Account was made as the change was material and increased the accuracy and comparability of the information provided to the users of the National Water Account. The changes and their respective values are detailed in the following table. The restated comparative year volume is 3,500 ML.
|2010 Account line item name||Management area||Purpose||Volume at 30 June 2010 reported in 2010 Account (ML)||Value difference to volume reported due to improved data availability (ML)||Volume at 30 June 2010 reported in 2011 Account (ML)|
|14.6 Entitled diversion of unregulated surface water flows||Barossa Prescribed Water Resources Area||Irrigation||1,028||(1,028)|
|Industrial and commercial||39||(39)|
|Western Mount Lofty Ranges Prescribed Water Resources Area||Irrigation||3,500||3,500|