Reference Evapotranspiration

The reference evapotranspiration (ET) is the rate of ET from a reference sur­face with an unlimited amount of water. Based on the FAO guidelines, the ref­erence surface is a hypothetical grass surface with specific characteristics. The reference ET value is independent of everything but climate and can be calculated from weather data. The FAO Penman-Monteith method is recom­mended for determining the reference ET value.

The Reference ET is multiplied by the Crop Coefficient to get the Crop Refer­ence ET. The Crop Coefficient is found in the Vegetation development table in the Vegetation database. If the vegetation database is not used, then the Ref­erence ET is the maximum ET rate.

The Reference Evapotranspiration item comprises both a distribution and a value. The distribution can be either uniform, station-based or fully distrib­uted. If the data is station-based then for each station a sub-item will appear where you can enter the time series of values for the station.

Related Items

·         Creating Time Series in MIKE SHE (V1 p. 145)

·         Working with Spatial Time Series (V1 p. 147)

·         Time Series Types (V1 p. 147)

·         Vegetation Properties Editor (V1 p. 403)

·         Evapotranspiration - Technical Reference (V1 p. 425)

·         Working with Evapotranspiration - User Guide (V1 p. 445)