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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.