41.3 Runoff into storages
Runoff into all storages was not explicitly calculated for the 2010–11 year. However, runoff into the Ord River upstream of Lake Argyle (20,908,921 ML) was calculated. Thus runoff is used as an estimate of the runoff into Lake Argyle. This runoff is further used to estimate the runoff into storages.
This is expected to be an underestimate of the true runoff to storages because none of the runoff to Arthur Creek Dam, Moochalabra Dam or Lake Kununurra are explictly calculated. Nevertheless, providing the magnitude of the runoff reported here is deemed to be useful to users of the account.
|River reach||Volume 2010–11 (ML)||Volume 2009–10 (ML)|
|Ord River downstream of Lake Argyle||10,259,733||1,623,419|
|Ord River upstream of Lake Argyle||20,908,921||2,131,562|
Runoff was calculated based on a water balance approach using measured data. Inflow is calculated using the following water balance equation:
Inflow = ΔS + O + E - Pb - T
ΔS is the change in storage
O is total outflow
E is evaporation
Pb is the volume of water pumped backed in
T is the volume of water transferred in.
Total outflow (O) is calculated using the following equation:
O = Sp + Sc + D + R
Sp is spillage
Sc is scour
D is volume of water abstracted
R is volume of riparian releases.
Assumptions, Limitations, Caveats and Approximations
Runoff assumes that all inflows and outflows are adequately quantified.
Runoff is derived from measured and modelled data. The uncertainty estimate was not quantified.