26.1 Soil moisture
The volumetric value for the line item for the 2010–11 year was 175,048,227 ML. The line item represents the volume of water in the unsaturated zone in the soil profile 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||4,702,246|
|SW16 Qld Border Rivers||SS24||Qld Border Rivers||Qld||4,019,058|
|SW15 NSW Border Rivers||SS23||NSW Border Rivers||NSW||3,875,799|
|SW11 Barwon–Darling Watercourse||SS19||Barwon–Darling Watercourse||NSW||571,622|
|SW12 NSW Intersecting Streams||SS17||NSW Intersecting Streams||NSW||17,715,954|
|Sub-total Northern Basin||95,929,502|
|SW8 Murrumbidgee||SS15||Murrumbidgee NSW||NSW||14,974,708|
|SW7 NSW Murray and Lower Darling||SS18||Lower Darling||NSW||13,400,303|
|SW2 Vic Murray||SS3||Kiewa||Vic||406,750|
|SW3 Northern Victoria||SS4||Ovens||Vic||1,659,428|
|SW2 Vic Murray||SS2||Vic Murray||Vic||2,827,490|
|SW6 Eastern Mount Lofty Ranges||SS13||Eastern Mount Lofty Ranges||SA||609,657|
|SW5 SA Murray||SS11||SA Murray||SA||169,846|
|SS10||SA Non-prescribed areas||SA||8,371,083|
|SW6 Eastern Mount Lofty Ranges||SS12||Marne–Saunders||SA||137,151|
|Sub-total Southern Basin||79,118,725|
|Total for the region||175,048,227|
Soil moisture for the MDB region was estimated based on the AWRA-L version 1.0.0 (Van Dijk 2010) surface soil, shallow soil and deep soil moisture model outputs.
Using climate grid data for the MDB region (including precipitation, temperature and solar radiation data), AWRA-L was used to estimate the soil moisture for each soil layer at each grid-point within the region. Only soil moisture within the landscape was considered; therefore, the surface areas of the major storages, lakes, off-channel water storages and other waterbodies were excluded from the analysis.The total depth of water in all three layers of the soil column at each grid point was extracted. This depth was then multiplied by the surface area represented by each individual grid point to give a volumetric estimate for every grid point. The volume for each grid point was summed up to provide an estimate of soil moisture for the entire MDB landscape.
Assumptions, Limitations, Caveats and Approximations
The values provided in this note have not been compared to any real time measured data for the 2010–11 year.
The soil moisture estimates are subject to the assumptions of the AWRA-L v1.0.0 model detailed in Van Dijk (2010).
AWRA-L does not account for application of water via irrigation and lateral flow.