Chapter 9 Comparison of FAO56 and NDVI-Derived K c Curves for Major Crops in Pare Basin of Arunachal Pradesh Waikhom Rahul Singh, Khyoda Meema, Tana Matthew, A. Bhadra, and A. Bandyopadhyay Abstract This study compared the crop coefficients of major crops of the Pare basin acquired from the FAO56 with the NDVI-generated crop coefficients. The FAO56’s K c was modified using average monthly RH and wind speed of the study area and compared with NDVI-generated K c . The coefficient of determination (R 2 ) was determined to evaluate the NDVI-generated K c values. Results showed that sweet potato, mustard, and sugarcane results were satisfactory; cucumber and maize were moderate and paddy was not satisfactory which may be attributed to the presence of standing water for the most part of its life. The uncertainty involved with the results may be because of not incorporating the effects of parameters like crop height, crop canopy, and water management in the estimation of K c . This study illustrated the usefulness of the NDVI images to generate K c curves for various crops in a region where conducting field experiments are not feasible. Keywords Crop coefficient · NDVI-derived K c · FAO56 · Major crops of arunachal pradesh 9.1 Introduction The accurate calculation of daily crop evapotranspiration (ET o ) is a necessary requirement within the irrigation scheduling program. The crop coefficient values of different crops are important for estimating accurate crop evapotranspiration (ETc), water transfer planning, efficient irrigation management, and hydrological studies W. R. Singh (B ) Center for Flood Management Studies, National Institute of Hydrology, Dispur, Guwahati 781006, Assam, India e-mail: rahulwaikhom0@gmail.com W. R. Singh · K. Meema · T. Matthew · A. Bhadra · A. Bandyopadhyay Department of Agricultural Engineering, North Eastern Regional Institute of Science and Technology, 791109 Nirjuli (Itanagar), Arunachal Pradesh, India © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 A. Pandey et al. (eds.), Water Management and Water Governance, Water Science and Technology Library 96, https://doi.org/10.1007/978-3-030-58051-3_9 135