Monitoring fish entrainment through riverine irrigation pumps in the Fitzroy River Basin has demonstrated that some pumps entrain very few fish and larvae, whereas others can entrain high numbers of fish (range 0 to 137 fish per ML) and fish larvae (range 0 to 1028 per ML). The position and depth (configuration) of the pump intake and the type of river flow being pumped have a greater influence on the number of fish entrained than the pumping rate.
Pumping from within bank natural flows tended to entrain twice as many fish as pumping from flows released from irrigation dams. Pumping from flood flows (overbank) entrained very few fish. Bankside pumps with shallow intakes tended to entrain fewer fish than other intake types. Pumping rate has some influence on entrainment rates, but the number of fish entrained per unit volume only increases marginally as pumping rate increases. The total volume of water extracted also influences the total number of fish entrained.
The relative impact of pumps can be determined by considering the pump inlet configuration, the types of flows that are licensed to pump, the total allocation that can be pumped and the capacity of the pump (pumping rate). This has led to the development of a prioritisation matrix that can be applied to pumps in a catchment, or a reach. The objective of the matrix is to aid selection of pumps for mitigation, so that available dollars can be allocated to where the greatest impact can be had for reducing loss of fish from our river systems. Although the work that led to this matrix was conducted in the Fitzroy Basin, this catchment shares many species and genera with the northern Murray-Darling Basin and the Burdekin River Basin, so the results are applicable more broadly.