Determination of Effects of Amounts of Water Use on Water Productivity and Yield Gap Using Landsat Imageries and CGM (Case Study: Sephid Rod Irrigation Network)

Crop Growth Models (CGMs) provide a tool for generalizing the results of water research from small scales to a larger ones. In this situation, using remotely sensed data is vital in order to reduce the inaccuracy derived from spatial variations. The present study was conducted to optimize water use in paddy fields of Guilan province using a combination of DSSAT model and Landsat satellite image. At first, the model was calibrated using the data of the small plot, then the accuracy of the model estimation was evaluated in 110 farmer fields of Some Sara. In the next step, using satellite imagery data, the model was calibrated and evaluated in the same area and the performance of each method was compared. Finally, using the model, the water productivity in the region was obtained in five water use scenarios. The results indicated that with water consumption of 400 mm during the growing season, maximum water productivity was obtained. The average water productivity based on water consumption in the rice growth period is 0.65 kg per cubic meter. In the areas, actual yield is less than potential yield. These areas represent a total of about 80% of the land in the region.