GeWasbehoefte

GeWasbehoefte is a Dutch term that refers to the water demand of a crop during a growing season. It describes the amount of usable water the crop requires to grow and produce a harvest, considering both rainfall and irrigation, as well as the soil’s ability to store water.

The concept encompasses the crop’s evapotranspiration needs and the contribution of rainfall. The core of geWasbehoefte is the crop evapotranspiration (ETc), which depends on the reference evapotranspiration (ET0) and a crop coefficient (Kc) that varies with crop type and growth stage. ETc can be estimated as ETc = ET0 × Kc. The effective rainfall and the soil’s water-holding capacity influence how much of ETc must be supplied by irrigation. Soil water depletion and root depth determine how quickly water is removed from available storage.

Estimation and calculation typically use climate data and standard methods such as the FAO Penman–Monteith approach to determine ET0, combined with crop-specific Kc values for different growth stages (initial, development, mid-season, late-season). The irrigation requirement is the portion of ETc that is not met by effective rainfall and soil storage, adjusted for irrigation efficiency to yield the gross irrigation depth.

In practice, geWasbehoefte informs irrigation planning and scheduling, helping farmers and water managers determine when and how much to irrigate, avoid water stress, and optimize yields. It can be influenced by soil type, rooting depth, crop variety, climate variability, and management practices, and should be interpreted with local conditions in mind.