How much water does my farm need?

A reliable supply of good quality water is critical for any mixed farming enterprise. Prolonged dry seasons over the 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 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
• management practices.

When calculating your water requirements it is important to consider:

• your future needs
• drought
• water quality
• available water resources.

Farm water needs

Unregulated water is utilised by approximately:

• 50% of dairy
• 98% of meat and wool production
• 96% of cropping
• 70% of potatoes
• 40% of vegetables
• significant areas of grapes and fruit crops.

It is used for farm production systems, including:

• stock water
• irrigation
• plant wash down
• production management processes.

To find out how much water you need within your business and how to calculate the water use for your enterprise, the basic planning steps are:

1. Determine the use for the water. For example:

• stock
• home garden
• dairy shed
• processing
• weed spraying
• irrigation
• fire fighting.

Peak water demand

The water requirement for plants and animals varies significantly from day to day as well as throughout the year.

It depends on climatic conditions and, in the case of animals, the amount of water in their feed:

• sheep on green feed in winter can drink less than 0.5 litres/day
• sheep on dry feed in summer may drink up to 10 litres/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
• pipelines.

The peak demand for:

• beef cattle is 100 litres/head/day
• dry sheep is 10 litres/head/day
• 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. This ensures 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

Water for livestock

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
• 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
• quality and temperature of the water.

The maximum water consumption for various classes of stock are listed in Table 1. For more details refer to Managing farm water supplies.

Water for spraying crops

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 to 200 litres/ha for each application.

Domestic water use

Domestic water use includes water used for:

• household
• home garden
• fire-fighting reserves.

Future water needs

When calculating water requirements it is vital that all future needs are considered. Changes that can require extra water include:

• enterprise
• an increase in stocking rates
• purchasing additional neighbouring land.

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 to upgrade the system at a later date.

Drought

In recent droughts, 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 high evaporation losses in small farm dams. A small farm dam with a depth of 3m 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 more information refer to Drought reserve dams.

Water quality

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
• organic contamination.

Salinity is the most common water quality issue. Refer to Water quality for farm water supplies for more information on salinity.

Water quality will determine just what the water may be used for. Cool and clean water of low salt content is best for stock health and for household use. Stock will require more water where salt levels increase.

Water sources

Water for agricultural use can originate from a variety of sources including:

• public pipelines
• groundwater
• rivers
• streams
• 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.

More information

More information is available from local Agriculture Victoria offices or our Customer Service Centre on 136 186.