Canberra
25.1 Unaccounted-for difference
Supporting information
In the Canberra region, 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. The unaccounted-for difference is 155,204 ML for the 2012–13 year as shown in the following table:
Account |
Volume (ML) |
Opening water storage at 1 July 2012 |
241,667 |
Total water inflows |
711,431 |
Total water outflows |
(581,018) |
Closing water storage at 30 June 2013 |
(216,876) |
Unaccounted-for difference |
155,204 |
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 item | Volume (ML) |
| Balancing item—surface water store | 153,459 |
| Balancing item—groundwater store | 1,783 |
| Balancing item—urban water system store | (38) |
| Unaccounted–for difference | 155,204 |
Detail of the balancing items calculation is given in the following Water resources and systems note:
- surface water note (Table 4)
- groundwater note (Table 8)
- urban system note (Table12)
The second table above shows that the unaccounted-for difference volume is primarily explained by the balancing item of the surface water store. The surface water balancing item is attributed to the fact that river and floodplain losses cannot be quantified, as well as uncertainty associated with runoff and river outflow (see Surface water note).