Irrigation Water Operation and Water Quality Management in Large Scale Water System

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Land and water are essential resources for paddy agriculture.The purposes of the study are to clarify the performances of irrigation water system operation and to evaluate the contributions of the water system operation to water quality management in river basins.(1) The practices of irrigation water use were surveyed and the relationships among the water use and several concerning factors were considered by multivariate analysis in several river basin areas.(2) There arc, recently, remarkable changing of farmers' interests in their water associations, because of urbanization and modernization in rural communities. Surveys and analyses were conducted for clarifying the change in aspects and reasons concerning on it.(3) It was tried to investigate various functions of traditional creeks in tower river basin. Based on principles of water control, the roles of creeks were evaluated from environmental conservation side.(4) The water balance and concerning components were analyzed using a complex tank model for creek water system, The water quality was also examined.The existence of return flow in the creek water system improve the efficiency of water use, but may have severe impacts on water quality in creek networks.(5) There are rotational land use of paddy and other crops in creek area.The net effluent toad analsis was conducted for evaluating the status of water quality in the area.