Perth
17.4 Leakage to landscape

This line item refers to leakage from surface water storages within the Perth region that supply water to the urban water system.

The total annual seepage at each storage, where seepage data are collected, during the 2010–11 year is given in the following table.

Instantaneous seepage data (L/s) are measured at surface water storages within the Perth region on an approximately daily basis. These data were inputted to Hydstra and converted to daily volume data (ML) to determine the total annual seepage (in ML) at each storage.

Seepage data are only collected at approximately half of the storages within the Perth region. It is assumed that no seepage has occurred at the remaining unmetered storages. Consequently, the reported leakage volume of 90 ML is likely to be an underestimate.

It is assumed that the dam seepage measuring points reflect the total seepage from the storages.

These data were not quality coded. Significant spikes in the data (i.e. where daily data were orders of magnitude different to daily data collected before and after the spike) were removed from the datasets for the calculation of total seepage volume.

The following table presents substantive changes in the line item reported in this 2011 Account with the corresponding line item in the 2010 Account.