Farm Water Calculator: the annual balance

The Farm Water Balance

During periods of low rainfall, dams and farm catchments receive limited run-off and creeks can run dry. Dam and tank water then becomes a limited resource. The Farm Water Balance is a calculation that compares the Water Storage on-farm (dams and tanks) to the water use on-farm over a year. It is a useful calculation where water supply is intermittent.

Farm Water Balance =	Water Storage on-farm - Water use on-farm
Farm Water Balance =	No Value set  - No Value set
Farm Water Balance =	0 megalitres/year

Surplus

A surplus means that the volume of storage available is more then the amount of water required on-farm for a year. Providing the storages are full at the start of the year, the yearly water requirement for the property can be met.

Deficit

A deficit means that the annual water requirement has exceeded the storage available on-farm. If the Water Balance is a deficit the following should be considered;

• Does the water source (potential water supply) provide frequent refilling of the storage so the property does not experience an actual water shortage in most years, or,
• There is sufficient water available, in some years, but not others, and it occasionally runs out of water, or
• The property regularly runs short of water on an almost annual basis.