25.1 Unaccounted–for difference

Supporting information

The volume recognised in the water accounting statements (2,799,023 ML) represents the total unaccounted-for difference for the Ord region for the 2011–12 year.

The unaccounted–for difference is the volume necessary to reconcile the opening water storage and closing water storage with the total water inflows and total water outflows reported in the water accounting statements. It is calculated according to the following table:

Calculation of unaccounted–for difference for the 2011–12 year

Account Volume (ML)

Opening water storage (30 June 2011) 15,148,491
add Total water inflows 7,565,330
less Total  water outflows 9,139,017
less Closing water storage (30 June 2012) 10,775,781

Unaccounted–for difference 2,799,023

The unaccounted–for difference can also be calculated by summing the volumes necessary to reconcile (balance) the opening and closing storage with the water inflows and outflows of each of the separate water stores of the region, as shown in the following table.

Balancing volumes of the water stores of the Ord region for the 2011–12 year

Balancing item

Volume (ML)

Balancing item—surface water store


Balancing item—groundwater store


Unaccounted–for difference


The unaccounted–for difference volume is entirely attributed to the balancing item of the surface water store. Detail of the balancing item's calculation is given in Table 4 of the Surface water note.

The volume of water in the groundwater stores within the Ord region could not be quantified. The Department of Water, in managing groundwater in the region, estimate that the volume of recharge to groundwater was equivalent to the volume of extraction. Therefore the volume of the balancing item for the groundwater store was quantified as 0 ML.