Abstract
To elucidate the water balance in the Hetao Irrigation District of the Yellow River Basin, the evapotranspiration (ET) from an irrigated field of wheat, which is one of the main crops of this district, was estimated by the Bowen ratio energy balance method. As the observation results, the ET was measured as 456 mm during the observation period from 5 May to 27 July. In the same period, the rainfall was measured as 24 mm, the irrigated water was measured as 289 mm. Thus not only the water which was irrigated from the ditch to the wheat field, but also the water which infiltrated from the ditch to the deep soil layers were evapotranspired from the wheat field. Furthermore, to predict the evapotranspiration in different condition of solar radiation and vapor pressure deficit, the parameter of canopy resistance was modeled by the Penman Monteith method and the Bulk method respectively. Modeled ET by both two methods could reproduce actual ET successfully, whereas the Bulk method could reproduce ET more appropriately.
