Groundwater levels in the South West
In the upper aquifers seasonal fluctuation occurs, however groundwater trends are fairly stable in all GMUs. Groundwater levels decline during summer and autumn when rainfall is low and pumping is high, however they generally recover during winter and spring when pumping stops and rainfall increases.
In the middle aquifers some seasonal fluctuation occurs in all GMUs. The greatest fluctuation occurs in the Condah GMU where the aquifer is confined and some long-term decline in groundwater levels is evident in the Glenelg and Condah GMUs.
In the lower aquifers groundwater level trends are fairly stable overall and are not influenced by rainfall or changes in climate.
What are the groundwater level trends in local areas across the region?
To view the data for any observation bore within the South West region visit the South West region map page. The data is presented as hydrographs. For basic guidance on how to read a hydrograph visit the How is groundwater monitored page.
Below is a summary of the groundwater level trend in a selected bore from each GMU.
Bungaree GMU: Bore 119337 is in the Newer Volcanics basalt aquifer south of the Western Highway and east of Ballarat. Groundwater levels in this bore and across the GMU fluctuate seasonally due to climate and pumping but are stable overall since monitoring began in the 1990s.
Cardigan GMU: Bore 54574 is in the Newer Volcanics basalt aquifer west of Ballarat. Groundwater levels in this bore and across the GMU fluctuate seasonally due to climate. During the millennium drought groundwater levels declined due to pumping by Central Highlands Water for Ballarat’s urban supply, however they have since recovered.
Colongulac GMU: Bore 89040 is in the Newer Volcanics basalt aquifer east of Camperdown on the western side of Lake Corangamite. Limited monitoring in this GMU indicates that groundwater levels fluctuate seasonally due to climate and pumping, however they are stable over the long term.
Glenormiston GMU: There are no monitoring bores in this GMU.
Hawkesdale (non-GMU): Bore 111522 is in the Newer Volcanics basalt aquifer near Hawkesdale. Groundwater levels fluctuate seasonally due to climate and pumping. During the millennium drought they showed some decline, however they are stable overall.
Warrion GMU: Bore 57694 is in the Newer Volcanics basalt aquifer near the centre of the GMU near Lake Beeac. Groundwater levels fluctuate seasonally due to climate and pumping but are stable overall.
Condah GMU: Bore 120248 is in the Clifton Formation aquifer east of Condah on Butter Factory Rd. Groundwater levels fluctuate by up to 10 metres seasonally due to pumping. Some decline occurred between the mid-1990s and mid-2000s as pumping increased, however groundwater levels have stabilised since.
Glenelg GMU: Bore 83447 is in the limestone aquifer east of Lake Mundi on Shanks Rd. Groundwater levels fluctuate seasonally but have been declining overall since the 1990s due to changes in pumping and the influence of plantation forestry.
South West Limestone GMU: Bore 78550 is in the limestone aquifer, east of Allansford on the Cobden-Warrnambool Rd (near The Great Ocean Rd). It shows a small amount of seasonal fluctuation, however groundwater levels are stable over the long term.
Gerangamete GMU: Bore 82841 is in the Dilwyn Formation aquifer on Birregurra-Forrest Rd. Recovering from three pumping cycles in the late 1980s, late 1990s and from 2006 to 2010 when the borefield was used as supply for Geelong.
Gellibrand GMU: Bore 47986 is in the Dilwyn Formation aquifer near Love Creek. This bore and GMU are mainly influenced by pumping by Wannon Water for supply to Warrnambool and other towns in the region. Groundwater levels were fairly stable before the 2000s, however there has been some decline since then due to increased reliance on this water for urban supply.
Jan Juc GMU: Bore 121768 is in the Eastern View Formation aquifer on Forest Rd. This bore and the GMU are mainly influenced by pumping for industrial use and urban supply. Groundwater levels were generally stable until the mid-2000s, however they have been slowly declining since then due to an increase in this pumping.
Newlingrook GMU: Bore 80230 is in the Dilwyn Formation aquifer on Gellibrand River Rd. The aquifer is quite close to the surface here and shows some seasonal variation. There is little pumping from this GMU and so groundwater levels are very stable.
Paaratte GMU: Bore 87250 is in the Dilwyn Formation aquifer on Port Campbell Rd. There is very little pumping from this GMU and so groundwater levels are very stable.
Portland GMU: Bore 307764 is in the Dilwyn Formation aquifer north west of Portland. Between the mid-1980s and mid-1990s groundwater levels declined by about a metre. Since then levels have remained stable. This bore has recently been refurbished so monitoring was discontinued for a short period of time, but will begin again in mid 2015.