A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering at the Asian Institute of Technology, Bangkok, Thailand.

Thesis (M.Eng.) - Asian Institute of Technology, 1976

The diversion requirement for irrigation of paddy field is usually estimated as the summation of all the components concerned, i.e., consumptive use that corresponds to cropping pattern, growth stage, climatic condition, unavoidable deep percolation which is influenced by physical properties and structure of soil layer and ground water table, effective precipitation and other losses such as application loss (farm waste), conveyance loss [seepage and leakage from canals) and distribution loss. The integral method implies that each component mentioned above is known or at least, can be assumed by some extensiveness. However, at project level this modified and applied concept in estimating components such as effective precipitation, deep percolation and other losses is seem to be limited in practice. In this study, exploration of the records of the water management by means of screening the record has been analyzed in estimating the diversion requirement at the Chao Phya diversion dam, Screening the record is done by considering the amount of available data at that moment which is being caused by over -or under -supply for the demand have been skipped and actual diverted discharges are screened. Under conditions of different loss factors, the water needed for land preparation together with the average evapotranspiration and deep percolation for the transplanted rice and the average evapotranspiration and deep percolation in case of broadcast rice have been estimated,