Adelaide

30.2 Unaccounted-for difference—connected surface water 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 is 220,348 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 connected surface water store is calculated according to the table below.

Calculation	Line Item	Volume (ML)
	Opening balance (as at 1 July 2009) Connected surface water store	109,491
add	TOTAL 13 Connected surface water inflows	254,424
minus	TOTAL 15 Connected surface water outflows	291,734
minus	Closing balance (as at 30 June 2010) Connected surface water store	110,546
	Unaccounted-for difference	(38,365)

The connected surface water has a relatively small unaccounted-for difference (38,365 ML or 35%). The difference is due to exclusion of some important flows and water assets (e.g. river channel storage and river leakage) and underestimation of runoff.