Murray–Darling Basin
27.1 Off-channel water storages

The volumetric value for the line item for the 2012–13 year was 858,844 ML. The line item represents the volume of water held in constructed storages that are not connected either seasonally or perennially to rivers, filled predominantly by local catchment runoff within the Murray–Darling Basin (MDB) region. The following table presents breakdown information for the volumetric value on a surface water resource plan area basis.

 

Details of volume of water stored in off-channel water storages in the MDB region at the start and end of the 2012–13 year

Water resource plan area	Sustainable diversion limit area		State/Territory	Volume on 30 June 2013 (ML)	Volume on 30 June 2012 (ML)
	Code	Name
SW20 Warrego–Paroo–Nebine	SS29	Paroo	Qld	126,985	180,949
	SS28	Warrego	Qld
	SS27	Nebine	Qld
SW19 Condamine–Balonne	SS26	Condamine–Balonne	Qld
SW18 Moonie	SS25	Moonie	Qld
SW12 Barwon–Darling Watercourse	SS19	Barwon–Darling Watercourse	NSW
SW12 NSW Intersecting Streams	SS17	NSW Intersecting Streams	NSW
SW17 Qld Border Rivers	SS24	Qld Border Rivers	Qld	61,092	57,328
SW16 NSW Border Rivers	SS23	NSW Border Rivers	NSW
SW15 Gwydir	SS22	Gwydir	NSW	41,653	50,543
SW14 Namoi	SS21	Namoi	NSW	55,143	63,084
SW11 Macquarie–Castlereagh	SS20	Macquarie–Castlereagh	NSW	127,223	159,493
Sub-total Northern Basin				412,096	511,397
SW10 Lachlan	SS16	Lachlan	NSW	131,804	164,786
SW9 Murrumbidgee	SS15	Murrumbidgee  NSW	NSW	118,452	165,722
SW1 ACT	SS1	ACT	ACT
SW8 NSW Murray and Lower Darling	SS18	Lower Darling	NSW	68,713	87,648
	SS14	NSW Murray	NSW
SW2 Vic. Murray	SS3	Kiewa	Vic.
	SS2	Vic Murray	Vic.
SW4 Wimmera–Mallee	SS9	Wimmera–Mallee	Vic.
SW5 SA Murray Region	SS10	SA Non-prescribed areas	SA
SW6 SA River Murray	SS11	SA Murray	SA
SW3 Northern Victoria	SS4	Ovens	Vic.	24,136	32,183
	SS5	Broken	Vic.	64,194	96,968
	SS6	Goulburn	Vic.
	SS7	Campaspe	Vic.	11,516	22,101
	SS8	Loddon	Vic.	19,538	34,562
SW7 Eastern Mount Lofty Ranges	SS13	Eastern Mount Lofty Ranges	SA	8,395	11,594
	SS12	Marne Saunders	SA
Sub-total Southern Basin				446,748	615,564
Whole MDB region				858,844	1,126,961

Note: The volume reported in the 2012 Account for the 2011–12 year was 1,152,737. The volume has been recalculated as 1,126,961 for the 2013 Account.  The change was due to the choise of AWRA version 3.0 model in the 2013 Account instead of AWRA version 2.0 in the 2012 Account for the calculations.

 

(1) Bureau of Meteorology (the Bureau): National Climate Centre daily climate grids (rainfall, temperature and solar radiation); and (2) Geoscience Australia: mapping of man-made waterbodies in the MDB spatial dataset, and nine arc-second digital elevation model (DEM).

The Bureau.

A water-balance based farm dam algorithm written by the bureau was used to determine the volume of water stored in off-channel water storages. The algorithm was provided inputs in the form of climate from gridded climate datasets, runoff from the AWRA-L model version 3.0 (Van Dijk 2010), and storage details derived from spatial data.

The MDB was divided into 105 regions for the purpose of modelling the off-channel water store. The off-channel water store consisted of storages filled primarily by local catchment runoff. These were determined from waterbody mapping conducted by Geoscience Australia as those which:

• are not named storages (assuming that any storage with a name is unlikely to be a off-channel water storage); and
• are above 600 m in elevation; and/or
• are below 600 m in elevation in areas that receive greater than 400 mm per annum in precipitation and are not within 50 m of a major or perennial stream.

The above rules attempt to divide storages into those that are likely to be filled primarily by local catchment runoff and those which are filled by abstraction from surface water, groundwater or floodplain harvesting. The catchment of each individual storage was determined via analysis of the 9 arc-second digital elevation model.

The farm dam algorithm performs a water balance on each individual storage at each time step using runoff and precipitation as inflows and spills, evaporation and usage as outflows. The volume of water held in storage is an output of this water balance.

 

• The gridded climate input data are subject to approximations associated with interpolating observation point data to a national grid detailed in Jones et al. (2007).
• The estimated volume available in storage for evaporation is subject to the assumptions associated with the farm dam algorithm and the parameters used.
• The spatial extent of water bodies are subject to the assumptions and methods associated with the data provided by the Geoscience Australia.

The uncertainty estimate was not quantified.