Farm Water Security

Thursday, November 01, 2018

Water is an essential requirement for running a farm business and has a significant impact upon the livestock enterprise with relation to stock welfare, farm productivity and business profitability. Knowledge of livestock water requirements and potential sources of water are important for planning on a daily, as well as an annual and long term basis.

The goal of farm water planning is to have the water you need, where you need it, when you need it. 

Farm water planning also takes into account the levels of risk associated with water supply reliability. The short term and long term economics and impacts on the farm business are particularly important when considering alternative sources.

 Essential elements of farm water planning include:

  • understanding total farm water requirements,
  • evaluating the reliability of water sources,
  • determining the cost benefit of alternative options,
  • determining the sizes of storages (dams or tanks) needed,
  • matching stocking rates to water availability,
  • designing farm water supply and reticulation systems,
  • determining how long water supplies will last during times of prolonged dry conditions.

There are a number of factors to consider when determining total water requirements. This will include not only the requirements of your livestock, but also requirements for other enterprises (e.g. crop spraying), firefighting and domestic requirements. Allowances also need to be made for evaporation, potential leakages and other non-domesticated grazing animals using watering points.

Daily water intake varies widely among different types of livestock and according to the activity level of the animal. A mature sheep (on dry pasture) requires 2,190 litres/year, with an average daily requirement of 6 litres/day (however this daily requirement will vary between winter and summer).  Commonly, two thirds of a grazing animals water requirement in summer comes from drinking water, but in winter up to 90% of its requirement may come from pasture. The amount of drinking water required by an animal depends on what type of feed it is eating and the ambient temperature. On dry feed animals require two and a half to three times the weight of dry matter eaten. On salty feeds (i.e. a pure stand saltbush) sheep require up to 14 litres a day.

Water source strategies and alternatives

Access to mains water, ground water and/or surface water varies greatly across the State. Consideration needs to be given to cost effective strategies and/or alternatives if there is any risk of the existing source not being reliable, both in quantity and quality.

Strategies may include the blending of water from different sources to ensure adequate quality.

Alternative sources may include opportunities such as sheeted catchments or desalinisation.

Blending or shandying are the terms used to describe the mixing of water sources to a predetermined standard. Water sources may include mains, dam, rain, bore or recycled. Depending on your requirements the blending system can be manual to fully automatic, or combinations. The fully automatic system generally provides better control and accuracy in blending, and they have functions to shut off the system if problems arise.

Blending in tanks is possible but care will need to be taken that adequate mixing is being achieved. It is a known phenomenon that waters of different salinity will stratify and not readily mix as would be supposed. Therefore, if the addition of the mixing water can be added prior to a pump, or an inline static mixer, that will ensure a homogenous result.

Sheeted catchments are becoming a popular option in some areas of the State. Sheeted catchments work on the ability to harvest 1 litre of water per mm rainfall per square metre of catchment. So, with a rainfall of 400 mm a 10,000 m2 catchment could harvest 4 megalitres of water.

An area to ‘catch’ the required amount of rain is lined with 1-1.5 poly liner; this slopes off into a lined dam. Given the catchment is lined its location is somewhat flexible. Many systems are being constructed on higher areas allowing water to be gravity-fed across a property. Tyres are used to hold the catchment area liner down. The sheeted catchment area needs to be well fenced to keep kangaroos and other vermin out, to avoid any potential damage to the poly liner.

The cost of a sheeted catchment area will depend on a number of factors, however some systems in place have cost $80,000 plus.

Evaporation from the dam is an issue. Whilst there are a few commercial systems available they tend to be quite expensive.

Desalinisation plants have improved over time with the cost of a unit being governed by the quality of the water you are treating. Units can be manual or automatic, the latter providing the ability to remotely monitor flows and quality.  Using reverse osmosis, the units use a series of filters to remove the unwanted components. Some consideration needs to be given to disposal of the waste discharge from the process.

Source: Managing Farm Water Supplies, Agriculture Victoria