Evaluation Spatial and Temporal Distribution of Maize Water Requirement Using Geostatistical Methods in Khuzestan Province

Maize cultivation is considered as one of the main crops in the Khuzestan province. Mostly, in planning water requirement is calculated as a point, while irrigation is preformed locally. Therefore, this data must be converted from the spot to the region. In this research, in order to determination irrigation scheduling in Khuzestan province were planted spring Maize in lysimeter at the Faculty of Water Sciences Engineering of Shahid Chamran University of Ahvaz. The aim of this cultivation were compared between the current methods of determination of water requirement and lysimeteric method and determine the appropriate equation. The results showed that the Blaney-Criddle equation is the best method to estimation evapotranspiration in case study area. After determining the appropriate equation of water requirement, mention equation and meteorological data were used for zoning Maize water requirement with geostatistical methods.The zoning was performed using ARC GIS 10.3. First, the data were normalized. Then, according to the lowest RMSE were selected the best semi variogram and zoning model. The results show that simple kriging with circular semi circular model in all months is considered optimal model. RMSE value of this model was calculated, the amount of it was 0.08, 0.17, 0.46 and 0.48 for March, April, May and June. The result of water requirement zoning showed that this parameter in south is more than north of Khuzestan province. Also, the amount of water requirement in last months is more than first months. During the study period (from March to June), water requirement was 1.98, 5.52, 11.78 and 11.97 (mm/day) monthly. Small amounts of RMSE was indicated the optimum of water requirement zoning.