Winter wheat uses water for evapotranspiration (ET) and the requirements will depend on variety, growth stage, canopy, density, climatic conditions, and irrigation and crop management.
Optimal conditions for winter wheat are to be well-fertilized, well-irrigated, seeded in standing stubble, pest-free, and with a uniform and optimum canopy, and in optimal conditions, winter wheat requires 400 to 430 mm of water per growing season, based on conditions in southern Alberta.
When winter wheat is seeding in, if available water is at 60 to 100 per cent, it will germinate, grow rapidly, and reach a peak water use of between 1.5 to 2 mm per day in October prior to freeze-up. When winter wheat comes out of dormancy in April, it will use anywhere between 0.1 mm of water to 7mm during the flowering and fruit formation stages.
Soil water levels in the root zone can be used to measure when to start and stop irrigation.