Tools available to assess dam water levels

ALTHOUGH we have seen intermittent rain over the past couple of weeks, there has been very little run off into dams, for some, without an alternative source of water, its looking rather grim.

Carting water or selling off stock in a depressed market is the last thing any farmer wants to do.

Estimating how much water you have left and the time it may last, can be made easier using online tools available from Agriculture Victoria.

They have a range of online tools available to assist farmers in assessing the volume of water in their dams and how long that water may last.

Agriculture Victoria land management extension Officer Clem Sturmfels said assessing how much water there is in a dam can be difficult due to a dam’s odd shape and formulas used to measure their volume.

“Farm dams generally hold less water than expected and in a dry year, it’s important farmers have a good understanding of how much water is left in their dams and plan accordingly.

“The volume of a dam is closely related to its length and width, and a stable, well-built dam has gently sloping sides which nearly meet in the middle of the dam’s base.”

An example provided by Agriculture Victoria is that a rectangular dam measuring 33m by 22m has a depth of approximately 3m and volume of about 1 million litres or 1 megalitre.

A triangular shaped dam with similar measurements has a volume of approximately half this amount.

The tool shows that evaporation will cause a loss of around 60 per cent of this volume, leaving the dam with enough water to carry approximately 200 sheep or 20 cattle for one year.

Mr Sturmfels said many dams relied on a regular top-up of water during autumn or spring, but this year had seen dry seasonal conditions, making the chance of a top up less likely due to depleted soil moisture and less runoff.

Agriculture Victoria has several tools to help farmers calculate dam volumes based on shape, length, width and depth, including the Farm Water Calculator and the Summer Water Calculator.

The Summer Water Calculator also helps to calculate how long the remaining water may last.

The depth of a dam can be measured using a depth sounder or fishing line measuring device.

For a ‘how to’ video for making and using the fishing line measuring device, and information on preparing your farm for dry seasonal conditions, head to the Agriculture Victoria website.