This Note is to assist farmers to estimate water storage needs based on likely water requirements. The figures are broad guides only and should be tweaked for local conditions.
Initial considerations
Few rural properties are serviced by public water supplies. In most cases, the only option is to use water resources available on the farm. Careful planing is essential before embarking on costly constructions and other commitments.
There are three preliminary planning steps:
1. Determine the specific water uses of the farm.
2. Determine water needed for each proposed use, and in which seasons it will be needed most.
3. Determine what options are available to provide the required supplies at the level and timing wanted.
Factors affecting these differ considerably between properties. Look carefully at your own circumstances. It is important that all estimates be as accurate as possible.
It is convenient to work with average daily or average annual requirements for ease of planning, but be aware that specific daily requirements will vary considerably over the year and from year to year.
Any water storage not used for valid stock and domestic use now requires a license in Australia from your Rural Water Authority. Contact them to find out appropriate guidelines and requirements. It is especially important to get their interpretation of reasonable stock and domestic allowances for your area.
All figures given in this Note are based on general experience within Australia. They will benefit from local adjustment to meet specific circumstances, and have not yet taken climate change into account.
Annual water requirements are subdivided into household, garden, stock, and fire fighting uses. Irrigation needs are not dealt with in this Note.
Household requirements
Melbourne residents are encouraged to contain their daily water use to a maximum of 155 litre per day per person. However this does include an allowance for garden watering. If we assume 10 % of this is for the garden, then this becomes a working figure of 140 litre per day per person.
A reasonable working annual figure on this basis is in the order of 50,000 litre per person
Note however that evaporative air conditioners on hot dry days can use large quantities of water (up to 25 litre per hour).
Roof runoff into tanks provides high quality water for drinking, hot water services, household cleaning and various veterinary and crop spraying purposes.
Earthen dams however provide lower quality water, with turbidity as the most usual quality problem. Often dam water is settled, clarified and even disinfected (in a tank) and then transferred to dedicated house supply tanks. In other cases, a house may be plumbed to keep the two supplies separate.
Garden requirements
Typical supplementary water requirement (summer period) for gardens
This amount of water only supplements existing rainfall. It is not sufficient to meet all plant requirements, even for just the summer.
Annual average drinking water requirement of grazing stock
Stock requirements
Drinking
Drinking water requirements for a grazing animal will vary according to weather, water quality, nature and quality of feed, age of animal, condition of animal and even social behaviour. Summer water requirement is usually 125% of the average daily requirement. Winter requirement is usually 75% of average daily requirements.
The table to the right is as a starting point for estimating stock drinking requirements.
These figures are generalized. Stock will drink more with greater heat load, lower quality water, dryer food, and lower feed quality. They will drink less with the converse.
Additional water should be allowed for miscellaneous stock management activities, as exampled below. The figures will be dependent on equipment used and practices deployed.
Miscellaneous stock management
Dairies, piggeries, and sheep dips all have specific water requirements over and above stock drinking requirements. They are quite specific for each circumstance but need to be covered in a farm water plan.
The DPI publication (2009) Dairy shed water: How much do you use? provides a sound guide for dairy water use.
Typical reserve volumes for fire fighting
Fire fighting reserve
Rule-of-thumb figures are as shown in the table to the right.
However, chase specific recommendations from your local government or CFA office.
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