Crop water requirements for rainfed and irrigated wheat in China and Korea

The parametric crop water use model (WATER) was applied for winter wheat to China and its environs in order to examine the evapotranspiration requirements under rainfed conditions and the associated irrigation water applications necessary for optimal production. A network of 241 stations provided climatic data averaged over a 20 year period. Highest ET under full irrigation (first growing season) was observed in the northwestern inland sections of China and the eastern portions of the Tibetan Plateau, while lowest ET occurred in the southeast; under rainfed conditions, these tendencies nearly reversed. About 400 mm of irrigation water was required in the northwest in order to achieve near-optimum yields in contrast with no such water requirements in the central east of China. A sensitivity analysis was conducted to determine the errors introduced by faulty, uncertain, or missing station data.