A case study of the Mahanadi-Kathjori-Devi delta of Orissa, India was undertaken for the formulation of irrigation water requirement models of some major crops. Principal crops such as paddy (both during the Kharif and Rabi Seasons), sugarcane, jute, chilly, mustard, groundnuts, etc., which are mostly grown in the delta, were taken into account for the present study. Effective rainfall and irrigation water requirements are the two basic parameters of the developed models. The models help in predicting irrigation water requirements for different crops once the values of effective rainfalls are ascertained. This irrigation water requirement, estimated by models so developed, includes water requirements for consumptive use only and when any other water used for special requirements such as leaching, seed bed preparation, etc., is added to it, the total irrigation water requirement is determined. The models so developed can be used for the same crops grown in other areas having the same hydrometeorological characteristics.