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Groundwater levels in Port Phillip & Western Port

Groundwater levels in Port Phillip & Western Port

In the upper aquifers seasonal fluctuation occurs, however groundwater trends are fairly stable in all Groundwater Management Units except Deutgam. 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 aquifer some seasonal fluctuation occurs in all GMUs. The greatest fluctuation occurs in the Koo Wee Rup GMU where the middle aquifer is confined, however groundwater level trends are generally stable.

In the lower aquifers groundwater level trends are fairly stable overall.

What are the groundwater level trends in specific bores across the region? 

To view the groundwater level data for any observation bore within the Port Phillip & Western Port region visit the Port Phillip & Western Port region map. The data is presented as hydrographs. For basic guidance on how to read a hydrograph visit our How is groundwater monitored page.

Below is a summary of the trend in a selected bore from each GMU.

Upper aquifers

Deutgam GMU: Bore 59534 occurs in the recent sediments aquifer at the mouth of the Werribee River. Groundwater levels in this bore and across the GMU vary significantly and were below sea level in some bores at times during the millennium drought.

Lancefield GMU: Bore 144974 occurs in the shallowest part of the basalt aquifer in the eastern part of the GMU. Groundwater levels in this bore and across the GMU vary seasonally but the overall trend is fairly stable.

Merrimu GMU: Bore 144972 occurs in the recent sediments aquifer near the Werribee River. Groundwater levels in this bore and across the GMU vary seasonally but the overall trend is generally stable.

Nepean GMU: Bore 84892 occurs in the recent sediments aquifer close to Port Phillip Bay between Blairgowrie and Rye. While there is some seasonal fluctuation in this and other bores, the overall trend is fairly stable across the GMU.

Middle aquifers

Frankston GMU: Bore 62949 occurs inland in the north-eastern part of the GMU. In this bore and across the GMU there is some seasonal fluctuation but the overall trend is stable.

Koo Wee Rup GMU: Bore 71184 occurs in the centre of the GMU where the middle aquifer is confined. There is significant seasonal fluctuation
in the area where extraction is concentrated. However, seasonal fluctuation has lessened and levels have stabilised in recent decades across the entire GMU and the overall trend is stable.

Moorabbin GMU: Bore 80245 occurs near the coast in the southern part of the GMU. In this bore and across the GMU there is some seasonal fluctuation and the trend is an overall decline of about one metre.

Lower aquifers

Boneo (non-GMU): Bore 84887 occurs in the Werribee Formation which is a confined lower aquifer. The levels in this bore show very little seasonal fluctuation. Other bores in the area which are closer to extraction points are more affected by pumping. The overall trend in this bore and across the GMU is stable.

Corinella GMU: Bore 56922 occurs in the Older Volcanics aquifer which occurs at the surface and is unconfined. Levels in this bore fluctuate slightly but are stable overall. There is only one SOBN bore in this GMU.

Parwan GMU: Bore 144963 occurs in the Werribee Formation which is a confined lower aquifer and has been influenced by pumping for irrigation since 2003. Levels in this bore and across the GMU fluctuate seasonally but there is a slight downward trend overall.

Wandin Yallock GMU: Bore 98404 occurs in the Older Volcanics aquifer which is unconfined and occurs at the surface. It is influenced by climate and irrigation. Levels in this bore and across the GMU fluctuate seasonally but the overall trend is fairly stable.

Learn the basics

To find out more about how we monitor groundwater visit our How is groundwater monitored page.

Page last updated27th May 2015
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