A contingency drinking water supply for the Great Southern Towns Region
Following a number of dry winters, the Water Corporation was keen to develop and implement a contingency plan for the Great Southern Towns Water Supply Scheme. Lower winter rainfall meant that the region’s supply from Harris Dam was increasingly under threat.
The contingency strategy involved supplementing Harris Dam’s water levels by pumping water from nearby Stirling Dam. However, with a growing urgency to find a solution, there were many variables for the Water Corporation to consider – including the potential use of an existing pipeline running to Harris Dam – before a solution could be designed.
John Waters, Design Manager, Water Corporation
Two potential routes had been earmarked for the contingency pipeline. Our first task was to assess their relative merits and make a recommendation on the most efficient solution, including recommendations on pipe sizes.
Using models, we confirmed the most efficient route and steel (MSCL) pipe size – choosing from DN600, 700 and 800 – to pump water from Stirling Dam to a section of the existing pipeline. To minimise energy and installation costs, we also recommended discharging water into a stream that would then fill Harris Dam, rather than using the existing pipeline all the way to the dam wall.
With our recommendations accepted, we progressed to engineering the system and refining the details of the design. This involved steady-state modelling (to assess pump duty) and water hammer modelling (to assess the system in start-up and shut-down situations), as well as conducting field testing to assess how biological matter in the water would cause additional friction losses and impact on the system’s performance.
Our hydraulic modelling and design expertise enabled the Water Corporation to consider a host of variables before progressing with the most efficient and technically sound solution.
We were able to find the ideal balance between construction and pumping energy costs, bearing in mind the system would only be used in rare contingency situations, but almost continuously when it was required.
We also helped to minimise maintenance costs – the initial concept included surge vessels at the pumping station, but our water hammer analysis confirmed that the system would work effectively without these high-maintenance elements.