Many dams on Kangaroo Island are starting to look a bit low and there may be concern as to whether there will be enough water for livestock

Not a drop to drink: The management of dam water supplies is critical for most livestock operations. Photo: Supplied.
Not a drop to drink: The management of dam water supplies is critical for most livestock operations. Photo: Supplied.

Many dams on KI are starting to look a bit low and you may be concerned whether you will have enough water to last you through until the break.

With most underground water on KI being too saline for stock use and limited access to mains water, the management of dam water supplies is critical for most livestock operations.

Two issues then arise: first, how to more effectively capture water in farm dams and second, how to prevent loss through evaporation once the water is harvested.  

Several farmers on KI have successfully installed ‘Graded Catchments’ to increase run-off and enable more reliable capture of rainfall into the dam.

While this requires a capital investment that may not be possible in the short term, simply constructing drains into a dam will help increase run-off.

The key to both graded catchments or drains is ongoing maintenance.

Ensure drains are clear and free of debris before the opening rains.

Also, check with Natural Resources KI (NRKI) before constructing any drains or graded catchments for necessary approvals.

Once the dam is full, you want to make sure you are not losing any water through unnecessary evaporation.

How much do we lose to evaporation?

Research shows that it varies from more than 1.6m inland to less than 1.3m along the coast. This is about 20 per cent of the volume of an average stock dam.

This evaporative loss has been shown to be minimised by appropriate dam design, including minimised surface area or management strategies such as windbreaks or evaporation control covers.

Less water will evaporate by reducing the dam’s surface area.

If constructing a new dam, try to make it as deep and as narrow as is practical.

Take care to ensure dams do not intercept the saline ground water that is present in many parts of the island.

Alternatively consider pumping water from smaller dams into one larger dam. Again, always talk to NRKI before constructing a dam.

Windbreaks planted near dams provide some protection from evaporation.

Trees planted directly on top of, or adjacent to dam walls, lead to roots destabilising dam walls and therefore can increase the risk of wall failure or even draw water out of the dam and may hinder cleaning out or enlarging dams.

At best, research shows evaporation rates could be reduced by 20 per cent by the use of trees as wind breaks.​

Whatever methods you chose appropriate for your business, the key elements of water supply for livestock are; planning early, minimise evaporation, and ongoing maintenance.