How much water does my farm need?
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AgNote: AG1406 – This AgNote replaces AG1406 (2010).
Version: September 2018
A reliable supply of good quality water is critical for any mixed farming enterprise. Prolonged dry seasons over recent years have highlighted the value of this precious resource. Water is needed for stock, garden and domestic use, as well as for a variety of other purposes. Knowing water requirements is needed to inform whole farm planning, drought preparation and upgrading of water infrastructure. Figures provided in this AgNote are based on the water requirements for an average farm in Central Victoria. The figures will vary significantly depending on farm location, type of stock and management practices.
When calculating your water requirements it is important to consider your future needs, drought, water quality and available water resources. These topics are covered later in this AgNote.
The water requirement for plants and animals varies significantly from day to day and throughout the year depending on climatic conditions and in the case of animals the amount of water in their feed. Sheep on green feed in winter may drink less than 0.5 L/day, while sheep on dry feed in summer may drink up to 10 L/day.
Knowing the peak demand is essential when designing a reticulated water supply system. This information is needed to ensure the correct size of pumps, tanks, troughs and pipelines. The peak demand for beef cattle is 100 litres/head/day while the peak demand for dry sheep is 10 litres/head/day. The peak demand for a garden might be 45 litres/minute based on 3 taps running simultaneously.
It is important to note that the peak demand for stock needs to be supplied within a 4 hour period to ensure all stock have a chance to drink on a regular basis. A shortage of water can result in damage to float valves, troughs and livestock.
Table 1: Average livestock water requirements
Livestock water requirement
Landholders have a legal and moral responsibility to provide stock with an adequate supply of good quality water.
The amount of water used by stock varies depending on the breed, type, age and weight. Female stock will have an increased demand during pregnancy and lactation. Stock water requirements will also be affected by temperatures, feed type, distances stock are walking, availability of shade and the quality and temperature of the water. Table 1 lists the maximum water consumption for various classes of stock. For more details refer to the booklet “Managing farm water supplies”.
A significant amount of water is required for spraying crops and pastures. While some chemicals will tolerate lower quality water, it is recommended that an adequate supply of high quality water be kept for this purpose. Typically this would consist of water captured off a roof, a town water supply or high quality groundwater. Volumes of water required for crop spraying range from 40–200 L/ha for each application.
All farms need to have a store of water for firefighting purposes. This should consist of one or more stand-alone tanks fitted with a standard CFA outlet connection. A good supply of firefighting water for a farm dwelling and associated buildings may consist of a 25,000 litre concrete or steel tank. In some areas councils require landholders to have a water supply for firefighting purpose. Landholders in high risk fire areas should check with their local council for more details.
With the increased use of aerial firefighting resources, a suitable dam will provide additional protection to a farm dwelling and associated infrastructure. It may also be used to protect neighbouring properties. The dam should be at least 3m deep and be free of obstacles such as wires, pipes and trees.
Gardens can consume a large volume of water. Lawns use the most water closely followed by vegetables, introduced ornamental plants and fruit trees. The amount of water required varies depending on the type of plant, climate and soil characteristics. A typical farm garden can easily use 0.3 ML of good quality water each year.
Having an area of green grass around the house provides increased fire protection and is often used to assist with mental well-being during periods of drought.
Table 2 shows the garden water requirements based on an irrigation period of 105 days. During periods of drought, water requirements can be significantly higher than the figures shown in this table.
Table 2: Average garden water requirements
Type of garden
Annual water requirement
Example: Annual water requirement for a 400 m2 area of lawn with an annual rainfall of 600 mm is 400 m2 x 300 = 120,000 L or 120 kL.
Domestic use includes drinking, washing, laundry and flushing toilets, as well as air conditioning systems, spas and swimming pools. Typical water usage for a rural property is 120 – 180 litres/person/day or 50 kilolitres/year. Evaporative air conditioners can use up to 25 litres per hour on a hot day.
Roof runoff into tanks provides high quality water for drinking, hot water services, household cleaning and various veterinary and crop spraying purposes. Tanks are now readily available up to 250,000 litres.
Table 3 lists the minimum recommended flow rates required for domestic and garden use.
Table 3: Minimum recommended flow rates for domestic and garden use.
Minimum flow rate (L/minute)
Evaporative air conditioner
Source: GWMWater 2005, On-farm water reticulation guide.
When calculating water requirements it is vital that all future needs are considered. A change in enterprise, an increase in stocking rates or purchasing additional neighbouring land may require extra water. Upgrading water infrastructure is an expensive and time consuming activity. It is vital than new dams, tanks, pumps and pipelines are designed to meet anticipated future needs. It is much cheaper to add extra capacity to a dam or pipeline during construction than attempting to upgrade the system at a later date.
During the drought of 2013–2016 the majority of farm dams and many streams and rivers went dry. A small reduction in rainfall resulted in a significant reduction in surface runoff. This issue was compounded by the high evaporation losses that occur in small farm dams. A small farm dam with a depth of 3 m can lose up to 60% of its capacity over 12 months due to evaporation. When planning water needs it is important to consider drought strategies. This might include destocking, carting water for a short time or constructing a large drought reserve dam.
For further information refer to AgNote AG1400: Drought reserve dams.
Good quality water is essential to maintain stock health and maximise animal and plant production. Water quality issues that need to be considered include salinity, turbidity, hardness, pH and organic contamination. Salinity is the most common water quality issue. As a general rule the salinity of water should be below 6,000 EC (µs/cm) for stock and below 1,000 EC (µs/cm) for garden use. These figures vary significantly depending on the type of stock, plant species and soil texture.
For further information refer to AgNote AG1402: Water quality for farm water supplies.
Table 4: Abbreviations
parts per million
microSiemens per centimetre
Total Dissolved Solids
milligrams per litre
Water for agricultural use can originate from a variety of sources including public pipelines, groundwater, rivers and streams, and farm dams. When planning for future needs it is important to consider reliability. Public pipelines tend to have the highest level of reliability closely followed by groundwater. Rivers, streams and farm dams on the other hand tend to dry up during periods of drought. The roof of dwellings and farm sheds can provide a reliable and valuable source of high quality water even during periods of drought.
Table 5: Relationship between units
1 kL = 1000 L
1 m 3 = 1000 L
1 ML = 1000,000 L
*1 ppm = 0.6 EC (μS/cm)
1 ppm = 1 TDS (mg/L)
1 ha = 10,000 m2
The units – litres and kilolitres – are used in this AgNote to specify water volumes. Both units are used to avoid excessively large (or small) figures in subsequent tables. The prefix kilo designates a factor of one thousand; the prefix mega designates a factor of one million. Table’s 4 and 5 show a variety of units mentioned in this AgNote.
Further information is available from local Agriculture Victoria offices or our Customer Service Centre on 136 186.
Agriculture Victoria has an online calculator for estimating water requirements and to prepare a complete farm water budget. See the farm water calculator.