Managing Farm Water Supplies
ISBN 978-1-74264-655-8 (print)
ISBN 978-1-74264-656-5 (online)
Overview of farm water planning
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.
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, while poor water quality can restrict the type of stock run or inhibit their productivity.
This booklet is designed to provide information on range of water requirement and quality topics along with a series of tips on water management.
- Overview of farm water planning
- Farm water balance
- Stock water requirements
- Water quality
- Water salinity
- Water testing
- Sources of water
- Calculating dam volume
- Capturing runoff from roof areas
- Helpful tips
- Contacts and references
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.
For information on how to carry out a water budget, please refer to the farm water calculator at: www.agriculture.vic.gov.au/farmwater and click on the Online Farm Water Calculator button.
Stock water requirements
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.
|Livestock unit||Daily||Annual litres/ |
|Daily average |
|Nursing ewes on dry feed||10||6||14||3,650|
|Prime lambs on dry pasture||4||2.4||6||1,460|
|Mature sheep on dry pasture||6||4.2||10||2,190|
|Prime lambs on irrigated pasture||1.1||0.7||1.5||400|
|Mature sheep on irrigated pasture||3.5||2.1||4.9||1,280|
|Dairy cow, dry||80||48||112||29,200|
|Dairy cow, milking||150||90||210||54,750|
Note: To convert L/year to ML/year, divide L/year by 1,000,000.
Having water of a quality that is fit for purpose is important. Water quality can affect plant growth, livestock health, soil quality, farm equipment and 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.
|Calcium||40 mg/L||>1000 mg/L||Phosphorous deficiency|
|Magnesium||0-19 mg/L||> 1000 mg/L||Scouring and diarrhoea|
|Nitrate||10 mg/L |
|>1500 mg/L nitrate, |
>30 mg/L nitrite
|Vomiting, convulsions, death|
|Sulfate||250 mg/L||>1000-2000 mg/L||Diarrhoea|
|Aluminium||0.05-0.2 mg/L||5 mg/L||Phosphorous deficiency|
|Arsenic||0.5 mg/L||Diarrhoea, anaemia, poor coordination|
|Copper||1 mg/L||0.5 mg/L||Liver damage and jaundice, |
Copper accumulation in the liver
|Fluoride||1 mg/L||>2 mg/L||Tooth damage and bone lesions|
|Iron||0.3 mg/L||Low toxicity|
|Lead (notifiable disease*)||0.015 mg/L||0.1 mg/L||Reduced coordination, blindness, going off feed.|
(related to copper)
|0.15 mg/L||Scouring and loss of condition. Infertility, skeletal disorders, testicular damage.|
|Other minerals become available such as Copper and Aluminium|
|Total Dissolved Solids||500 mg/L||Variable generally |
> 5000 mg/L
|Poor production, diarrhoea, higher mortality rates|
* Notifiable disease - seek advice from DEDJTR 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).
Please refer to the later section on water testing.
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.
|Type of Livestock||EC (µS/cm)||mg/L* (ppm)|
|Poultry||Production decline begins |
|Pigs||Production decline begins |
|Horses||Health / growth affected |
|Dairy Cattle||Production decline begins |
|Beef Cattle||Production decline begins |
|Lactating Ewes, |
|Production decline begins |
|Production decline begins |
*Source: Victorian Department of Economic Development, Jobs, Transport and Resources
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
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), for example March, June, September and December.
- EC meters are relatively inexpensive and available at various water equipment dealers.
- EC measurements can be done free of charge at some Department of Economic Development, Jobs, Transport and Resources (DEDJTR) 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 booklet.
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.
If you don't know the bottom width or bottom length the following formula can be used.
- Lb = Lt – 2 (Depth x Batter Slope)
- Wb = Wt – 2 (Depth x Batter Slope)
Or alternatively, you can use the table below.
An online farm water calculator can be used for circular and gully dams and dam sizes outside the dimensions in Table 4. Refer to agriculture.vic.gov.au/watercalculator.
Table 4 Volume of a square/rectangle with a batter slope of (1:2.5 batter) and depth is in brackets.
|Width (m)||Length (m)|
*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, however not all of this 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) x Roof area (m²) x 0.95
*Note: for a rectangular roof the area is the length (m) x width (m)
For example: A shed with the dimensions 15m x 9m has a roof area of 135m² and an annual rainfall of 1000mm will yield 128,250 litres/year (1000mm x 135m² x 0.95).
Roof catchment area (m2)
- 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 doubling the pipe diameter will increase the flow rate four times.
- 50mm (2inch) 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 any salts 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, by fencing and revegetating around the dam and by restricting stock access.
- µS/cm ÷ 1.56 = ppm
- µS/cm x 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
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
General farm water information
Rural water corporations & services
Southern Rural Water
Phone: 1300 139 510
or (03) 5564 1700
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
20 Hotham Street, Traralgon
Phone: (03) 5172 1555
Irrigation and stock water analysis
NATA Facilities and Labs Deakin University, Warrnambool
Phone: (03) 5563 3481
Water testing service – Blue green algae and chemistry
ALS Water Resources Group
22 Dalmore Drive, Caribbean Business Park, Scoresby Phone: (03) 8756 8000
Domestic, stock and irrigation packages available
Constructing a domestic and stock bore
If you are planning to construct a domestic and stock bore, you will need a bore construction licence, apply for one online at www.mywater.waterregister.vic.gov.au or go to 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 www.adia.com.au.