Diente, Antonio C. creator Murty, V.V.N. Chairperson Harboe, Ricardo Examination Committee Kono, Yasuyuki Examination Committee Tran Thuc Examination Committee Government of Spain Scholarship Donor text series technical report th Bangkok Asian Institute of Technology 1994 continuing eng 123 leaves A computer model RIW AP (Real Time Irrigation Water Allocation Program) for water allocations in large irrigation system has been applied to simulate the water requirement of lowland paddy and upland crop maize in an irrigation system in the Philippines. The model accounts for all significant climatic and soil factors which influence the crop water requirement. The model has been modified to conform with the area's conditions and farming practices. The model was adjusted to address the present cropping pattern in the area. Dry season rainfall records for the past forty years were analyzed on weekly basis by the concept of conditional probability. For this purpose, a computer program using Markov Chain was purposely developed to generate the probable rainfall for each of the following week of the season. The model adopts the water balance method for the calculation of water requirement for lowland paddy, and soil moisture simulation approach for the upland crop maize. The model calculates the crop water requirement of the next following week by assuming the climatic values of the preceeding week except rainfall which will be generated by the model. After the end of each irrigation week, the model updates the climatic variables using the actual values that has transpired during the week. Comparison of model results were undertaken between this model and the one which was used by an irrigation system in Thailand called W ASAM (Water Allocation Scheduling and Monitoring Program). Results of both models were compared with the values gathered from the systems office. For the paddy crop, the two models showed a similar results. However, WASAM displays unfavorable results when applied in the upland crop maize. It suggests a continuous weekly irrigation which amounts to high water requirement, while the expanded model RIW AP exhibits a reasonable results. The discrepancy of the results is credited to WASAM's similar water requirement calculation procedure, both for upland crop and lowland paddy. While that for RIW AP which adopts the soil moisture simulation approach for upland crop. The extent of area that can be supplied by the present conveyance facilities under consideration as suggested by RIW AP is only about 70% of the total designed area which closely coincides with the actual scenario. A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Civil Engineering Thesis (M. Eng.) - Asian Institute of Technology, 1994 Water Philippines Mindanao Distribution Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B16040 http://203.159.5.9/ait-thesis/detail.php?q=B16040 951012 20260818084631.0