The Centre For Water Research

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Mundaring Weir (Helena Reservoir), located 30km east of Perth, Western Australia, is a 63.5GL drinking water storage servicing the Goldfields and agricultural regions of Western Australia. Increasing demand for water from this storage has required that water be transferred to the reservoir to supplement its stream inflows. A pumpback transfer system brings water into Mundaring Weir from the Lower Helena Pipehead Dam, a small (133ML) reservoir 10km downstream of Mundaring Weir. Water can be transferred into the Pipehead Dam from other local storages and subsequently transferred into Mundaring Weir through the pumpback transfer system. The pumpback transfers enter Mundaring Weir through a submerged multi-port outlet, which was found to act as a horizontal jet.

Analysis of field data and modelling results indicated the pumpback transfer system acted as a destratification device, significantly improving water quality conditions in the reservoir. A parameterisation of the outlet configuration was included into DYRESM, and used to generate a number of potential operating scenarios for the management and use of the pumpback system as a destratification device to improve water quality.

FIGURE : Time for destratification as a function of flow rate through the pumpback system, generated from modelling results. The field measurement of this process is also shown.