Agriculture provides the basis of sustenance for the population.But the challenge of maintaining a balance between human numbers and the capacity to produce food increases day by day.Furth more global climate change seems to make intra-annual rainfall distributions more erratic and inter-annual variations less predictable,resulting in greater uncertainty and risk for agriculture.Irrigation Scheduling according to crop water requirement at different stages not only minimizes the chances of under or over watering but also helpful to boost up crop output per unit of water.Apart of that it also gives idea to farmers and irrigation managers about the quantity of water needed to deliver to meet the peak demand of water.Present study is an attempt in this regard in which Water Balance according to Thornthwaite's method of Potential Evapotranspiration and Crop Water Requirements for different stages are computed on the basis of Penman-Monteith model for the study area of Samastipur, Bihar.These are the methods that require minimum effort and give maximum dividend.Hope that this book envisioned as a reference for those working in the field of achieving more crop per drop of water.