Managing farm water supplies

Water is an essential requirement for running a livestock business and has a significant impact upon stock welfare, farm productivity and business profitability.

Knowledge of stock drinking water requirements and potential sources of water are important for planning on both an annual and daily basis.

Overview of farm water planning

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.

Essential elements of farm water planning include:

• understanding total farm water requirements
• evaluating the reliability of water sources
• 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.

Stock water shortages can be a significant limitation to productivity. A lack of water can mean destocking the property or carting water in. Poor water quality can restrict the type of stock run or inhibit their productivity.

Farm water balance

A key component of farm water planning involves undertaking an annual farm water balance.

A water balance considers:

• water requirements (uses of water)
• water supplies on-farm (water available)
• the balance between water supply and use
• storages (actual and potential).

The information provided by the water budget along with an understanding of water distribution, quality and seasonal weather patterns can help guide decision making on-farm.

Stock water requirements - daily intake

Daily water intake varies widely among different types of livestock and according to the activity level of the animal. It is also influenced by factors such as climate, environmental conditions and the type of feed and water being consumed. It is important to remember that the peak consumption for your local area could be significantly higher than the figures given.

Table 1: Daily average and yearly as well as winter and summer stock drinking requirements

Sheep

Cattle

Horses

Pigs

Poultry

Alpaca

Deer

Goat

Note: To convert L/year to ML/year, divide L/year by 1,000,000.

Water quality

Having water of a quality that is fit for purpose is important. Water quality can affect:

• plant growth
• livestock health
• soil quality
• farm equipment
• domestic use.

The quality of a water source is also variable depending upon weather and external inputs.

Evaporation increases the concentrations of salts while a flush of water dilutes salts but may increase sediment and fertilisers, and manure or nutrient runoff.

Monitoring should be done regularly and more frequently in summer or in periods of prolonged moisture stress.

Table 2: Water quality stock tolerance levels

* Notifiable disease — seek advice from DJPR Animal Health.

The upper limits of mineral and metal levels described will vary due to specific geology weathering and acid conditions, in conjunction with high salinity levels or specific management. If feed contains the particular minerals, limits are lower. Guidelines from the ANZECC (2000).

Water salinity

Salinity is a major water quality issue in areas where accumulated salts are mobilised in the landscape and make their way into waterways and dams. Evaporation of these water sources increases the concentration of the salts and the problems associated with them.

Salinity refers to all the mineral salts present in the water including sodium, calcium, magnesium, chloride, sulphate and carbonate. High salinity levels can make water unsuitable for drinking or irrigation. Electrical conductivity (EC) of water can be used as a measure of salinity. The higher the value the higher the salt content. Units are micro siemens/centimetre (µs/cm).

Table 3: Salinity tolerance levels for stock water

*Source: Victorian Department of Jobs, Precincts and Regions

Production decline begins = upper limit salt concentration for healthy growth.
Maximum = maximum salt concentration that may be safe for limited periods.
Seawater = 55,000 µs/cm
Rainwater = 100-300 µs/cm

Water testing

The best way to be certain about the quality of your water is to have it tested. When testing water:

• Rinse meters and container in water to be tested.
• Read off numbers taking note of units.
• Stock bores can be tested on freshly pumped water at the trough.
• Bores should be monitored at regular intervals, monthly or quarterly.
• EC meters are relatively inexpensive and available at various water equipment dealers.
• EC measurements can be done free of charge at some Department of Jobs, Precincts and Regions  locations. Contact the Customer Service Centre 136 186.

For more in depth water tests including mineral analysis contact testing labs listed in the contacts section of this page.

Sources of water

Water supply can be extremely variable both seasonally and annually. In farm water planning it is important to consider all available sources of water and how much of this can be stored.

It is also important to note that the amount of run-off might not match amount that can be stored. For example, once a water tank or dam fills, the water overflows and goes back into the environment.

Calculating dam volume

Knowing the volume of a farm dam is useful for estimating how long the dam will last during prolonged dry periods. Below is a simple calculation used to calculate the volume of a dam.

Plan of a linear sided dam, dimensions  in metres, where:

• Depth of excavation = D
• Bottom length = Lbc
• Bottom width = Wb
• Top width = Wt
• Top length = Lt

Volume (ML) = [LtWt + LbWb + [9Lt+Lb)(Wt+Wb)]] × D / 6000

If you don't know the bottom width or bottom length the following formula can be used.

• L^b = L^t – 2 (Depth x Batter Slope)
• W^b = W^t – 2 (Depth x Batter Slope)

Alternatively, you can use Table 4. An online farm water calculator can be used for circular and gully dams and dam sizes outside the dimensions in this table.

Table 4: Volume of a square/rectangle with a batter slope of (1:2.5 batter) and depth is in brackets

*ML = Mega litre = 1,000,000 litres

Capturing runoff from roof areas

Rainfall runoff from shed and house roofs can be a reliable, efficient water source that is easily overlooked. Roofs are high yielding and can turn even minor rainfall events into a useful supply of good quality water. Such supplies are ideal for stock and domestic consumption or for use in spraying equipment.

The yield from a roof is dependent upon the area of the roof and the rainfall received. Not all rain is always captured, as at times the tank may overflow.

To calculate the volume of rainfall that can be collected from roof area the following formula is used: Volume of water (litres) = Annual average rainfall (mm) × Roof area (m²) × 0.95

*Note: for a rectangular roof the area is the length (m) × width (m)

For example: A shed with the dimensions 15m × 9m has a roof area of 135m² and an annual rainfall of 1000mm will yield 128,250 litres/year (1000mm × 135m² × 0.95).

Table 5: Rainfall captured by different roof areas (m2)

Helpful tips

• Water loss through evaporation is substantial. If you have a number of shallow dams, think about pumping water to a single dam to minimise evaporative losses.
• Water collected from farm sheds, in excess of domestic requirements, can contribute to overall stock supplies by reticulating to nearby paddock troughs from tanks.
• When piping around the farm, remember that doubling the pipe diameter will increase the flow rate by four times.
• 50mm (2 inch) pipe will deliver four times the supply compared to 25mm (1inch) pipe.
• Large water troughs located centrally in paddocks can reduce the walking distances for stock and reduce erosion.
• Air pressure or solar pumps provide an alternative option where there is no power supply. These pumps can supply water around the farm from a reliable source, either dam or bore without any requirement for wind. They also have the capacity to pump water to considerable heights.
• Water troughs with low usage need to be flushed out periodically as evaporation will lead to a concentration of salt present.

Gully dams with bare paddock catchment areas need to be protected from manure 'runoff' into dams after heavy rainfall.

This can be done by:

• constructing silt traps with small hay bales or various types of mesh upstream of the dam
• fencing and revegetating around the dam
• restricting stock access

Conversions

• µS/cm ÷ 1.56 = ppm
• µS/cm × 0.001 = mS/cm
• mS/m = dS/cm
• 1mg/L = 1ppm = 1g/m³
• 1 ML = 1 000 000 L = 1000 m³

Seawater = 55 000 µS/cm
= 55 mS/cm
= 55 dS/m

* ppm stands for parts per million

Note:

L = litre

ML = megalitre

mg = milligram

m³ = cubic metre

mm = millimetre

ha = hectare

µS/cm = microSieman/centimetre

mS/cm = milliSieman per centimetre

dS/m = deciSiemens per metre

Contacts and references

Rural water corporations and services

Southern Rural Water
Phone: 1300 139 510
or (03) 5564 1700

Goulburn-Murray Water
Phone: 1800 013 357
or (03) 5826 3500

Grampians Wimmera Mallee Water
Phone: 1300 659 961

Lower Murray Water
Phone: (03) 5051 3400

Water quality testing services

SGS
20 Hotham Street, Traralgon
Phone: (03) 5172 1555
Irrigation and stock water analysis

NATA Facilities and Labs Deakin University, Warrnambool
Phone: (03) 5563 3481
Email: wql-info@deakin.edu.au
Water testing service – Blue green algae and chemistry

ALS Water Resources Group
22 Dalmore Drive, Caribbean Business Park, Scoresby Phone: (03) 8756 8000
Email: melbournewrg@alsglobal.com
Domestic, stock and irrigation packages available

Groundwater

Groundwater is a component of property hydrology and it can be a major asset if it is available to extract. Supplies are never limitless and will often vary in both quantity and quality, and with time. Groundwater testing is essential before development. Licenses are needed both to construct a bore (bore construction licence) and operate a bore (groundwater extraction licence). Visit your relevant water authority website.

It is recommended that you utilise a licensed driller — you can find a list of licensed drillers at the Australian Drilling Industry Association website,

The department is responsible for monitoring and caring for groundwater in Victoria.

Groundwater monitoring — how and why?

Southern Rural Water has produced a series of groundwater maps for southern Victoria. There are links to maps about groundwater resources; including yield and quality.