Crop Water Budget - how is it calculated and what does it mean?
The Water Budget Forecast, provided as part of the Implexx Crop Water Use Forecast, is the amount of forecast crop water use minus forecast rainfall for the next 14 days.
Water Budget = Crop Water Use – Rainfall
When the Water Budget is a negative value, it means the crop water use is greater than rainfall. That is, the forecast demand for water by the crop exceeds the amount of forecast rainfall.
When the Water Budget is a positive value, it means that rainfall is greater than crop water use. That is, the forecast rainfall exceeds the amount of demand for water by the crop.
A Water Budget with a negative value suggests that another source of water is required to maintain crop water use. Typically, this supplemental water is supplied via irrigation.
Important information about rainfall
The Water Budget Forecast is an estimate only and actual values may vary. Rainfall is difficult to estimate precisely and the value provided in the Implexx Crop Water Use Forecast is an estimate based on a probability. In the section “Daily Implexx Forecast”, the probability of rainfall is provided in the table. It is recommended to use this information on the probability of rainfall to gauge how much actual rainfall may eventuate.
Other considerations for irrigation management
The Water Budget Forecast only includes two parameters: rainfall (input) and crop water use (output). In an ideal world, these two items will equal. In reality, there are many additional parameters to consider that will affect the water budget of a property or operation. For example, not all rainfall will be available to the crop as some rainfall will be intercepted by the canopy. There are other outputs to consider when irrigation is supplementing a shortfall in rainfall. For instance, leaky pipes, surface run-off, drainage beneath the root zone, and others. Overall irrigation management should take these additional factors into account.