Author
Assistant professor AREO Agricultural engineering research institute, Karaj;
Abstract
Cropped area, cropping pattern, and cropping intensity are among the most important information needed for determining the water requirements in a basin or at an irrigation scheme scale, and they are difficult to measure. Conventional methods are very local, ranging from region- to field-scale. Estimates of such information over an entire area, especially for irrigated areas, are essential, as these can differ substantially depending on the cropping pattern and the management applied. Today, actual cropped area, cropping pattern and intensity under different conditions can be estimated by using satellites and remote sensing (RS) techniques. In order to obtain the required data, it was attempted to upscale the accuracy of NOAA satellite images by using Landsat 7 images. From a time series of NOAA images during one growing season, NDVI and SAVI indicators were established. Based on these indicators the actual cropped area and cropping intensities were evaluated for each irrigation network in the Zayandeh Rud basin. Results indicated that the actual cropped area using RS data was more than the designed command area in most irrigation districts of Zayandeh Rud. The designed command areas for Nekouabad-Right and Abshar-Right are 13,500 and 15,000 ha, while the actual cropped areas are 16,700 and 16,250 ha, respectively. Cropped area of Nekouabad and Abshar irrigation networks are between 72% and 81%, but cropping intensities can be much higher as an extensive area is used to grow two crops per season. Main winter crops are wheat and barley, summer crops are rice and vegetables. The main advantage of RS approach applied here is that it is nonspecific and can be easily adapted to other conditions in terms of soil, weather, and crop. Besides the benefits of this non-specific approach, the methodology applied here gives a wealth of information in comparison to field surveys, in terms of spatial and temporal resolution, and it overcomes the difficulties of field work.
Keywords
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