Falls in groundwater for southern Eyre Peninsula in South Australia force 2024 decision for plant to desalinate seawater
South Australia's southern Eyre Peninsula had its levels fall in Uley South groundwater basin, main supplier of drinking water, and in the Musgrave basin (top left). Eyre Peninsula Landscape Board monitored eco systems for flora changes, especially with many red gum trees (at right), due to groundwater levels and salinity.
Images courtesy Water Connect and Eyre Peninsula Landscape Board
Falling groundwater levels on the southern Eyre Peninsula, including its main city centre Port Lincoln, forced the decision in 2024 to build a seawater desalination plant to supplement the Uley South basin that supplied 75% of the region’s drinking water. The remaining supply was sourced from the River Murray via the extended Morgan-Whyalla pipeline.
The lack of a reliable surface water supply was a factor preventing Port Lincoln from being proclaimed the South Australia's capital city in the 1830s. Even as a small town, Port Lincoln outgrew its fresh water supplies. It became largely dependent on water from groundwater basins in the south of the peninsula.
Southern Eyre Peninsula groundwater had two prescribed or regulated wells areas: The Southern Basin (Unley and Wanilla) and Musgrave (Polda, Bellevue, Bramfield). The largest and most reliable supplies of low-salinity groundwater were found in the Quaternary limestone, widely used in the Southern Basin, including for the Port Lincoln public water supply.
The need for a new water source for southern Eyre Peninsula was identified in South Australia government-owned utility SA Water’s 2008 long-term plan. The need became urgent in 2023 from analysis of Eyre Peninsula’s underground water sources. Despite several years of La Nina weather patterns, rainfall wasn’t enough to restore water levels. Uley South Basin, supplying most water used in homes and industries such as agriculture and mining, recorded water levels “below” or “very much below average”.
The lower trend was seen in other groundwater resources across the region, including the Robinson Lens near Streaky Bay, the Polda Lens and Bramfield Lens near Elliston, and the Lincoln Basin and Uley Wanilla Lens. Downward trends were seen in aquifers regardless of being extracted from or not.
Eyre Peninsula Landscape Board also was monitoring eco systems for changes in the condition of flora due to groundwater levels and salinity. Particular forus was on the many red gum (eucalyptus camaldulensis) trees that relied on groundwater for some or all of their water needs. The state government decided to build a seawater desalination at Billy Lights Point, a controversial site choice, near Port Lincoln.
Elsewhere on Eyre Peninsula, Ceduna on the west coast had its water supply via a pipeline, opened by public works commissioner M. McIntosh in 1928, bringing water from the Tod Reservoir, formed from an earth embankment dam taking water from the Tod River, 27 kilometres north of Port Lincoln, between 1918 and 1922. It was taken offline in 2001-02 due to concerns about rising agricultural chemical contamination and salinity.
South Australia Riverland fruit growers were angered when Ceduna was connected in 2009 to water from the Morgan to Whyalla pipeline via the Iron Knob through the Kimba to Lock link. In 2024, Ceduna’s water supply was from three relatively small local tanks north of the town on Kalanbi Road (0.91megalitres) and more remotely from the larger Pimbaacla Tank 80 kilometres to the east (9.09 megalitres).
In 2007, SA Water responded to the drops in groundwater levels by completing a 90 kilometres water pipelines linking Iron Knob to Kimba, on the upper Eyre Peninsula. The pipes' route followied the Eyre Peninsula Highway and delivered up to 1.4 gigalitees of water each day to SA Water customers between Kimba and Lock