Groundwater provides a valuable resource particularly in the West Wimmera for irrigation and town water supply. Many farms in the west of the region rely on groundwater for stock and domestic supply. Mining companies often utilise groundwater for their operations.

The characteristics of groundwater in the Wimmera are a function of the underlying geology which in turn influences groundwater quality and yield. The Wimmera’s groundwater is contained in layers of sedimentary sands, gravels, clays, limestone and fractured rock. Groundwater systems can be grouped into groundwater flow systems based on their characteristics. In the Wimmera, groundwater flow direction mirrors that of surface water, generally flowing from the southeast to the northwest.

For management purposes groundwater resources in the Wimmera are zoned into the following areas:

  • West Wimmera Groundwater Management Area (GMA)
  • Wimmera Catchment which includes the following groundwater management units:
    • Grampians East
    • Grampians West
    • Upper Wimmera
    • Wimmera Mallee Sedimentary Plains.

A 2009 West Wimmera socio-economic study investigated the value of groundwater for irrigated and intensive livestock systems. Combined with dryland systems reliant on groundwater for stock and domestic use, they were estimated to represent 40% of the value added in the agricultural sector of the West Wimmera GMA. The regional impact of the economic activity generated by using groundwater is in the order of $121 million per year.

Figure 8: Groundwater flow systems in the Wimmera

Groundwater flow systems in the Wimmera

Figure 9: Wimmera groundwater zones.
There are 5 Groundwater Management Zones in the Wimmera; West Wimmera, Wimmera Mallee Sedimentary Plains, West Grampians, East Grampians and Upper Wimmera.

Wimmera groundwater zones

The analysis found that groundwater is an extremely important and valuable resource to the community of the West Wimmera GMA being the only significant source of water in the region.(17)

Groundwater also provides water to groundwater dependent ecosystems such as saline wetlands in the Natimuk Douglas chain of lakes and rivers and streams where the groundwater meets the surface.

There is also good quality groundwater emanating out from Gariwerd (Grampians National Park).

In parts of the Wimmera Groundwater Catchment, particularly in the north, groundwater can be viewed as a threat due to its high salinity and impacts on waterways and low-lying land. For this reason, it is not often used as a resource.