Murray–Darling Basin
30.1 Precipitation on off-channel water store

The volumetric value for the line item for the 2012–13 year was 802,372 ML. The line item includes the volume of all forms (rain, sleet, snow, hail, or drizzle) of water falls on off-channel water storages within the Murray–Darling Basin (MDB) region. The following table presents breakdown information for the line item on a surface water resource plan area basis.

 

Precipitation on off-channel water storages in the MDB region for the 2012–13 year

Water resource plan area	Sustainable diversion limit area		State/Territory	Volume (ML) for the 2012–13 year
	Code	Name
SW20 Warrego–Paroo–Nebine	SS29	Paroo	Qld	151,357
	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
SW13 NSW Intersecting Streams	SS17	NSW Intersecting Streams	NSW
SW17 Qld Border Rivers	SS24	Qld Border Rivers	Qld	118,996
SW16 NSW Border Rivers	SS23	NSW Border Rivers	NSW
SW15 Gwydir	SS22	Gwydir	NSW	103,647
SW14 Namoi	SS21	Namoi	NSW	65,435
SW11 Macquarie–Castlereagh	SS20	Macquarie–Castlereagh	NSW	92,062
Sub-total Northern Basin				531,497
SW10 Lachlan	SS16	Lachlan	NSW	64,433
SW9 Murrumbidgee	SS15	Murrumbidgee  NSW	NSW	67,293
SW1 ACT	SS1	ACT	ACT
SW8 NSW Murray and Lower Darling	SS18	Lower Darling	NSW	49,154
	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.	16,614
	SS5	Broken	Vic.	42,637
	SS6	Goulburn	Vic.
	SS7	Campaspe	Vic.	9,707
	SS8	Loddon	Vic.	14,888
SW7 Eastern Mount Lofty Ranges	SS13	Eastern Mount Lofty Ranges	SA	6,149
	SS12	Marne Saunders	SA
Sub-total Southern Basin				270,875
Whole MDB region				802,372

(1) Bureau of Meteorology (the Bureau): National Climate Centre daily climate grids (rainfall, temperature and solar radiation); and (2) Geoscience Australia: MDB human-made waterbody feature class and built-up area feature class.

The Bureau.

Monthly precipitation data were based on daily data from approximately 6,500 rain gauge stations and interpolated to a 0.05 degree (approximately 5 km) national grid (Jones et al. 2007).

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 that:

• 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 average precipitation depth across the MDB subregions was determined as the weighted mean of precipitation occurring from the relevant grid points within the region boundary. Points were weighted upon the area they represented within the MDB landscape to remove edge effects (where the area represented is not wholly within the MDB region) and the effect of changing area represented with changing latitude. The farm dam algorithm written by the bureau for the calculations used the average precipitation depth as an input for estimating storage impacts. The algorithm converted the depth of precipitation to a volume using the surface area of off-channel water storages within the region.

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 spatial extent of water bodies subject to the assumptions and methods associated with the data provided by Geoscience Australia.

The uncertainty estimate was not quantified.