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What is groundwater yield?

What is groundwater yield?

Yield is a measure of how much and how quickly groundwater can be extracted from an aquifer.  Yield is generally higher in large aquifers that have greater storage capacity, well-connected spaces within the aquifer material (i.e sand or gravel) and where the pressure is high.
For those reasons yield tends to be lower and more inconsistent in the shallow upper aquifers, and better in the deeper middle and lower aquifers.

Aquifer material and yield

The material of an aquifer is the primary driver of yield. The list below shows the type of aquifer material in order from most permeable to least permeable or higher yielding to lower yielding.

  1. Gravels
  2. Sands
  3. Fractured basalt and limestone
  4. Silts and clays
  5. Shale and granites

Infographic showing how the material of an aquifer is the main driver of yield. Gravel, sand, basalt and limestone are shown as having higher yields compared to clay, silt, shale and granite.

What else can affect yield?

Bore yields can also be affected by the condition of your bore, clogging or fouling, bore interference and timing. 

Bores generally have a lifespan of around 30 years.  It is important to perform regular and proper maintenance on your bore.  This will help prevent clogging. 

In some areas fouling from iron bacteria may occur.  This is commonly seen in bores along the coast near Warrnambool.  Iron bacteria can be treated with chemicals.  If you suspect you have an problem with iron bacteria in your bore please contact us.

In other cases the pumping activities of your neighbours can impact your bore. This is called interference and more can be found out on this subject on our What impacts groundwater levels page.  If you suspect bore interference is occurring, please contact us.

The timing of any changes in yield is important as well.   Aquifers that are close to the surface generally show seasonal groundwater level patterns that are impacted by rainfall and pumping. During winter and spring when pumping is low and rainfall is high, groundwater levels and yields will be better.  In summer when rainfall is lower and pumping increases the groundwater levels may drop and impact your yield.

Yield across the region

To see how groundwater yield varies across the region and in different aquifer, visit our Southern Victoria map.

Page last updated28th April 2015
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