Daly
25.1 Unaccounted-for difference

In the Daly region, the unaccounted–for difference of 1,267,676 ML represents 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:

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.

The previous table shows that most of the unaccounted–for difference volume is observed in the surface water store.  Further details of the balancing item calculations is given in the Water Access and Use note.

It is likely that the volumes contained in this line item can be largely attributed to the uncertainty which is expected when modelling both groundwater and surface water flows. It is reasonable to expect a level of error associated with the modelling techniques used to derive several line items. 

The majority of uncertainty is associated with the largest surface water and groundwater increases (9.4 Runoff to surface water and 10.3 Recharge from landscape) and with the largest surface water and groundwater decreases (17.2 River outflow from the region and 18.4 Discharge to surface water).

The volume of water in the groundwater stores within the Daly region could not be quantified. The Department of Land Resource Management uses climatic data and modelling to estimate recharge volume to the aquifers to determine an allowable extraction limit each year.