Estimating the Irrigation Water Requirements at a Regional Scale: a Case Study in the North China Plain

Using the spline algorithm, this paper interpolates the site-based meteorological observations into a spatial domain which are then used as main input parameters for the CROPWAT model. By running the CROPWAT model, the reference evapotranspiration (ET0) is estimated in this paper for the case study area, the North China plain. And then by combining the estimated ET0 with the information on share of cultivated land decoded from the Landsat TM/ETM digital imagines covering the entire case study area of the North China plain, this paper estimates the amount of irrigation water requirements (IWRs) in the years of 1991 and 2000 and uncovers the characteristics of variability of the IWRs over space and time. The research result offers a scientific basis for the decision makings in the exploitation and utilization of climatic and water resources as well as the land use planning and the managements of irrigation water at the regional level.