Abstract
A questionnaire investigation of the water management was done in two pipeline irrigation districts of paddy fields in the Niigata plains. From the investigations, it was made clear that careless water management was done at the fields of the farmers who felt that the supply volume of the water from the pipeline valves was enough. At such hydraulically advantaged paddy fields, visits to check the water supply from the valves were less frequent. By the time the hydraulically disadvantaged fields had enough water, a lot of excess water was generated at the fields with less frequent visits. This excess water became the management water requirement, increasing the demand for irrigation water supply.
Using the expanded node energy method, the volume of water from the valves in the pipeline network was calculated to show that careless water management caused the increase in the management water requirement. The management water requirement was simulated by changing the time interval between field visits for checking the water supply, and by adjusting the valve at every field. As a result, it was proved that lengthening the time interval between field visits has a tendency to increase the management water requirement, while partially closing the valves at the hydraulically advantaged nodes was able to reduce it.
In the future, such pipeline network simulations done using the expanded node energy method will become useful means for investigating various water management methods.
