Trend of long-term changes in precipitation and discharge in the River Yamato basin by pseudo-global warming experiment

Abstract:

Recently, it has the damage resulting from the severe flood in Japan, for the frontogenesis of the monsoon has caused heavy rainfall over a wide. On the other hand, some areas have the social problem of drought. In the future, changes in precipitation and evapotranspiration due to global warming may not only affect the water use system in the basin, but also increase the risk of drought. As a pseudo-global warming experiment, the data of hourly precipitation in the River Yamato Basin, which considered the ensemble climate change prediction data (4℃ rise experiment) were used . These data had been provided with evaluation the many impacts of climate change using the ensemble climate change prediction data (d4PDF) of 20 km² at a mesh for system of the River Yamato, where water resources were developed. The other parameters such as temperature, wind speed, solar radiation, irrigation water, pattern outlet discharge from dams pattern and sewage treatment data were adapted in the changing pattern or averaged values in past trends.

As a result, we expected the rainy season would be prolonged and heavy rain would occur that water resources might be more abundant than at present, and that floods would cause enormous inundation damage. In addition, the typhoons will make it difficult to save water in autumn, which may lead to a shortage of water resources from the winter to the spring at next year. We had developed a distributed runoff model that expects discharge from change trend of rainfall, and had conducted to prove the trend estimated from rainfall. We had collected precipitation by the quantile mapping method was applied to many ensemble data.

As a result, it was found that it not only expects the same change trend as the rainfall but also the increase of evapotranspiration due to the temperature rise may increase the risk of drought. It is necessary to evaluate the storage effect of water resource development facilities in order to evaluate the risk of drought and flood in the River Yamato Basin. Hourly discharge during 60years every ensembles had calculated by the runoff model. In this study, we evaluated the impact of climate change on the flow regime. The drought risk of water resources would be eliminated due to the prolonged rainy season. However, the possibility of flood risk due to typhoons and localized heavy rainfall were confirmed.