Groundwater Resources
>> See also Victoria's Groundwater Resources.
Groundwater resources in the Wimmera are part of the larger Wimmera-Mallee stock and domestic supply system, which is thought to be the largest water supply system of its kind in the world. Storages in the Grampians, together with 16 000 km of distribution channels serve an area of 28 500 kmē of farmland. The Wimmera-Avon Basin region has large reserves of groundwater with varying salinity levels. Good quality groundwater is found in the far west of the Basin. Elsewhere, the groundwater is generally of poor quality, and therefore, it is of limited use.
The Wimmera River ends in terminal lakes partway down the basin and its groundwater systems continue north-west beneath the Big Desert to ultimately re-emerge in zones of regional groundwater discharge adjacent to the Murray River in South Australia and far north western Victoria. Where it turns northward, the Wimmera River downstream of Natimuk, marks a boundary between two major groundwater provinces (Source: Wimmera Mallee Water Website).
The divertible groundwater resource of the Wimmera-Avon Basin is estimated to be about 17 500 ML per annum, and the minor sources about 800 ML per year. Of the divertible resource, about 9 700 ML per year are considered to be saline; 4 500 ML per year fresh, and the remainder brackish.
Groundwater usage during early settlement of the Wimmera was infrequent due to its relative scarcity and salinity of resources. Therefore, during prolonged dry periods water was often transported into the region. The low volume and unreliable flow of the Wimmera River at the time prompted early settlers to improvise means of harnessing its meagre water yield. Their efforts constituted the foundations of the Wimmera-Mallee domestic and stock supply system.
Groundwater is heavily relied upon in the Wimmera region for domestic usage, particularly in towns such as Goroke, Kaniva and Serviceton and also for stock. The developed aquifer is the Duddo Limestone which underlies the Millicent Coast in the west of the Wimmera catchment at 80 to 180 m below the surface. Water from this aquifer system is generally of high quality and is used for domestic, stock, urban and irrigation purposes.
| The Parilla Sand is a shallow aquifer of littoral sand. It generally occurs as an outcrop in ridges, or lies beneath a cover of Quaternary deposits. Its watertable lies at depths of 0 to 45 m. This aquifer is also the uppermost saturated layer within the majority of the West Wimmera. Increasing salinity from east to west is the main constraint to utilising groundwater resources. It is also believed to be the most significant contributor to land salinisation in the Millicent Coast (Hocking, 1998). The deepest aquifer occurs in the Renmark Group, consisting of the lower units of the Cainozoic sequence. These sediments are continuous throughout the area at depths of 300 to 400 m below the surface. This deep sandy aquifer yields water of relatively low salinity, but water quality generally declines to the north of the basin, as with other basins in the region. Source: Dept of Water Resources Victoria, (1989) |  Parilla Sandstone outcrop near Kaniva. |
The Murray Group Limestone is one of the most valuable groundwater resources in the Wimmera. The relatively shallow depth of this aquifer allows economical groundwater extraction while yields are relatively high and salinity is low (Hocking, 1998).
Stranded Beach Ridge Aquifers in the Wimmera catchment region are of little use for groundwater extraction purposes due to low yields and high salinities. They are a significant contributor to land salinisation and hence should be targeted as a high priority for salinity control (Hocking, 1998).
References
Department of Water Resources Victoria, (1989) Water Victoria: A Resource Handbook, Melbourne, VGPO.
Hocking, M., (1998) Assessment of Salinity Risk in the West Wimmera, Centre for Land Protection Research Technical Report no. 46, DNRE, Bendigo
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© The State of Victoria, 1996 - 2009.
This document was last reviewed on 04/06/2009