MODEL VALIDATION AND CROP COEFFICIENTS FOR IRRIGATION SCHEDULING IN THE NORTH CHINA PLAIN

ISAREG is a model for simulation and evaluation of irrigation scheduli ng. The model performs the soil water balance and evaluates impacts of water stress on yields for different crops. It is now being used to s upport a water saving irrigation scheduling program in a pilot area in the North China plain. This paper reports on the calibration and vali dation of the model using independent data sets relative to winter whe at and summer maize, Data are originated from the Wangdu experimental station and concern a set of drainage lysimeters where diverse irrigat ion treatments were applied representing different strategies of defic it irrigation. The calibration of the model was performed by deriving the crop coefficients adapted to the local climatic conditions, and co nsidering the soil freezing during winter. The validation of the model was performed using different data sets. Results show that the relati ve errors to estimate the soil water content averaged 5.3% for summer maize and 7.3% for the winter wheat. These results support the use of the model in the practice. (C) 1998 Elsevier Science B.V.