Water requirement of crops using CROPWAT model- A case study of Buxar district in Bihar

India with a geographical area of nearly 3.3 million square kilometers is home to 16% of the population of the world whereas it has only 4% of the total freshwater resources of the world. Moreover, there is huge inequality in the distribution of water resources within the country. The scarce natural resource is fundamental to life, livelihood, food security and development. Sustainable management of this scarce resource has become a challenge nowadays owing to increased demands of increasing population, growing urbanization and rapid industrialization. It has become very important to define appropriate strategies for planning and management of irrigated farmland. One of the major practices adopted by the researchers for estimating water requirement of the crop is modeling. Understanding crop water requirement is essential for irrigation scheduling and selection of cropping pattern in any particular area. This study has been conducted to estimate irrigation requirement, crop evapotranspiration and yield responses in Buxar district of Bihar, using CROPWAT model. Historical climate data from weather stations in the region along with soil and crop data were used as input to FAO Penman-Monteith method to estimate reference evapotranspiration (ET_o). Effective rainfall was calculated using USDA soil conservation method.