Information of actual evapotranspiration (ET) is the key factor to determine the crop water requirements of a particular crop, which is an essential input for budgeting optimum irrigation water requirement. In order to quantify crop water requirement, this research focuses on finding out the ET of boro rice from remotely sensed image and meteorological data which may pave the way for better understanding of improved water management issues of paddy rice as well as efficient use of groundwater for irrigation purposes. MODIS satellite images were been geo-referenced and analysed using ILWIS 3.4. ET of boro rice was estimated using SEBAL algorithm and FAO Penman-Monteith method for the five selected upazilas in the North-west region of Bangladesh during the growing season. Comparing ET values from MODIS image with Landsat image, it was found that despite moderate resolution, MODIS is able to estimate ET of boro rice during the growing with substantial accuracy. Usually farmers use much water in the field compared to actual water crop needs, remote sensed data could be used for efficient irrigation water management, remote sensing data could be used for proper irrigation management. The estimated ET can be used for budgeting optimum irrigation water requirement of boro rice crop which will eventually decrease irrigation cost of farmers by reducing the lifting of excess water.
Key words: Evapotranspiration, Crop Water Requirement, MODIS, Landsat, SEBAL