Computer simulation for water uses and water managerment in the Bangpakong river basin

Abstract

Several medium and large scale irrigation projects had been developed in Bangpakong river basin, the largest river basin in the eastern part of the country. They are inundation schemes (without reservoir upstream) namely Nakornneyok, talad, Bangpluang, Tahae, Kokkacha, Banna, Huai Krai and Prachantakarm. The existing reservoir is only Khlong Rabom with the capacity of 40 mcm while the reservoirs under construction are the Upper Praprong, Khlong seeyad and Khlong Tadarn. Only one diversion dam is under construction on Bangpakong river about 10 km. upstream of ChaChaengsao city. Besides, there still be 8 potential sites suitable for reservoir construction with irrigation area development downstream. Percolation on wet season paddy area of every existing irrigation projects has been monitored. Two pilot areas have been selected in talad irrigation project. Percolation, water use for land preparation and effective rainfall of rice cultivation have been monitored in these pilot areas both wet and dry seasons. The computer models namely : Effective Rainfall Model, Irrigation Demand Model and System Simulation Model have been developed to simulate water uses and water management strategies in the Bangpakong river basin. These computer models have been calibrated by field monitoring data. Twenty development alternatives have been studied and recommends. The result of the study reveals that after completion of the Bangpakong Diversion Dam, water will be enough to irrigate the irrigation area on both banks in the wet season. But water will not be enough to irrigate during the dry season because there is no large reservoir upstream. This might create conflict of water uses among the various agencies concerned in front of Bangpakong Diversion Dam especially during the dry season.