A study on the response of hydrologic extremes attendant upon climate change and its spatial-temporal characteristics

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In the present paper, components of hydroclimatological water balance were examined in the Ishikari, Shinano, Tone, Kiso-Nagara-Ibi and Shira Rivers basin. The purpose of this study is to elucidate the distinctive features both on spatial distributions and on secular changes in annual precipitation, potential evapotranspiration and runoff as a grounding in regional hydrology at basin-wide scale.The results are summarized as follows :As one of the temporal characteristics of long-term variability, it is pointed out that the annual precipitation in the Kiso, Nagara and Ibi Rivers basin is inclined to be below the average since the latter half of the 1980s. On the contrary, annual evapotranspiration has increased over a long period of time. According to the annual runoff as calculated by the remainder of annual values of evapotranspiration from precipitation, the observed value on discharge has a tendency to overestimation.Water quality of the Kiso River changed toward an extremely worse condition under the typical drought events as recorded in 1994.Although comparison of the result presented for this investigation with those for different climatic regions is left for further studies, the identified fact would provide a meaningful basic information from the comparative hydrological point of view.