Adelaide

30.5 Unaccounted-for difference—water distribution system store

Supporting information

The unaccounted-for difference is the difference between the directly measured closing water asset and the closing water asset calculated from the statement of physical flows. The total unaccounted-for difference in the Adelaide water accounting statement is220,348 ML or about 150% of the total water assets. In general, this large difference is due to:

uncertainty in the line items arising from the quantification approaches
extent to which assets and flows in the water accounting statements represent the physical system.

The unaccounted-for difference for the individual stores in the Adelaide Region is presented in the table below.

Store	Measured/estimated (ML)	Calculated from physical flows (ML)	Difference (ML)	Difference (%)
Connected surface water	110,546	72,369	(38,365)	(35)
Groundwater	39,268	308,620	269,352	686
Water distribution system	1,676	(9,709)	(10,639)	(635)
Total water assets	151,490	372,412	220,348	146

The unaccounted-for difference for the water distribution store is calculated according to the table below.

Calculation	Line item	Volume (ML)
	Opening balance (as at 1 July 2009) Water distribution system store	1,670
add	TOTAL 19 Water distribution system inflows	153,313
minus	TOTAL 20 Water distribution system outflows	163,946
minus	Closing balance (as at 30 June 2010) Water distribution system store	1,676
	Unaccounted-for difference	(10,639)

The absolute unaccounted-for difference is relatively small for the water distribution store (10,639 ML). The percentage difference (635%), however, is very large because only the small volume held in pipes and tanks has been recognised as the asset for the water distribution system. The percentage difference is only 7% when calculated as a percentage of the inflows to the water distribution system (rather than as a percentage of the asset).