28.1 Precipitation on landscape
The volumetric value for the line item for the 2010–11 year was 819,237,686 ML. The line item represents the volume of all forms (rain, sleet, snow, hail, or drizzle) of water falling on the landscape within the Murray–Darling Basin (MDB) region. The following table presents breakdown information for the volumetric value on sustainable diversion limit (SDL) area basis.
|Water resource plan area||
|SW19 Warrego – Paroo – Nebine||SS29||Paroo||Qld||19,065,188|
|SW16 Qld Border Rivers||SS24||Qld Border Rivers||Qld||21,146,789|
|SW15 NSW Border Rivers||SS23||NSW Border Rivers||NSW||20,002,724|
|SW11 Barwon–Darling Watercourse||SS19||Barwon–Darling Watercourse||NSW||2,172,260|
|SW12 NSW Intersecting Streams||SS17||NSW Intersecting Streams||NSW||71,458,914|
|Sub-total Northern Basin||433,331,315|
|SW8 Murrumbidgee||SS15||Murrumbidgee NSW||NSW||72,805,800|
|SW7 NSW Murray and Lower Darling||SS18||Lower Darling||NSW||67,482,184|
|SW2 Vic Murray||SS3||Kiewa||Vic||3,370,891|
|SW3 Northern Victoria||SS4||Ovens||Vic||12,174,382|
|SW2 Vic Murray||SS2||Vic Murray||Vic||20,346,078|
|SW6 Eastern Mount Lofty Ranges||SS13||Eastern Mount Lofty Ranges||SA||2,018,812|
|SW5 SA Murray||SS11||SA Murray||SA||725,488|
|SS10||SA Non-prescribed areas||SA||35,134,029|
|SW6 Eastern Mount Lofty Ranges||SS12||Marne–Saunders||SA||490,307|
|Sub-total Southern Basin||385,906,371|
|Total for the region||819,237,686|
Monthly precipitation data was produced by the Bureau of Meteorology. It was 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 average precipitation depth across the MDB landscape was determined as the weighted mean of precipitation occurring onto 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 was not wholly within the MDB region) and the effect of changing area represented with changing latitude. The depth of precipitation was converted to a volumetric estimate by multiplying by the total area of the MDB landscape.Only precipitation falling onto the landscape was considered in the line item. Precipitation falling onto storages, lakes, off-channel water storages and other water bodies was not included.
Assumptions, Limitations, Caveats and Approximations
The precipitation estimates were subject to approximations associated with interpolating observation point data to a national grid detailed in Jones et al. (2007).