Clarification of Water Usage of Puddling Paddy Period Using Canal System Information and RADARSAT Data in Chikugo and Its Related Basin

Abstract

In Chikugo River basin and its neighboring basin, the adequate distribution of irrigation water is a great issue especially during puddling paddy period, so that at first grasp of present water use is needed. Therefore, the aim of our research is understanding the actual water use by analyzing the satellite data (RADARSAT), the existing GIS data, and the water intake records. The satellite data (RADARSAT), which showed the surface of rice paddies, was used for deciding irrigation starting time. The GIS data, which is water distribution area, canal networks and farm layouts, was used for understanding water flow of distributed water. The water intake records, which is significant quantitative data, is used for analyzing the actual water use during puddling paddy period. As a result, from the RADARSAT analysis, puddling paddies were found in the downstream area in early June, and the area were found in the middle basin area one week later. From the water intake records analysis, the peak timing of intaking volume for downstream area was around 1 week earlier than that for middle basin area. Thus, the trend of puddling paddy area expansion corresponded to the trend of intake water increase, so it was found that irrigation water was supplied to downstream area 1 week earlier than to the middle basin area. Our results implied that the analysis of the satellite data, existing GIS data, and water intake records were effective methods for understanding the actual water use.