9.7 Delivery of water from outside region
This line item refers to bulk deliveries of water from outside the Perth region boundary into surface water storages within the Perth region.
The volume reported in the water accounting statements (4,569 ML) represents the water transferred from the Collie River Irrigation District, which lies outside the Perth region boundary, into the Harvey Reservoir during the 2011–12 year.
The total volume of water transferred into Harvey Reservoir from the Collie River Irrigation District is based on measured data observed at the pump station located at the border of the Collie River and Harvey irrigation districts.
Assumptions, limitations, caveats and approximations
It is assumed that the volume of water measured at the flow meter at the border of the Collie River and Harvey irrigation districts is equal to the inflow at Harvey Reservoir (i.e. no leaks or transmission losses). This is a reasonable assumption given the transfer occurs via a closed pipe.
Expected error for water meters is +/– 5%.
The Department of Water requires that all water meters, when tested under in situ conditions, must be within 5% accuracy across the full flow rate range (Guidelines for water meter installation 2009).