A study on changes in annual runoff ratio resulting from the global warming and their regional characteristics

本文以日本中部湿润温带气候为例，研究了近102年(1895~1996年)年降水量、流量和径流比长期可验证性的时间特征。本研究的目的是阐明水文极端事件的发生频率和严重程度的趋势及其与流域物理和社会经济环境的关系。研究结果如下：1.利用仪器记录研究了基索河、长加拉河、伊比河和铃鹿河流域中空间尺度上水量平衡的长期可验证性特征。(1)自20世纪80年代后半期以来，研究流域的年降水量有低于平均水平的趋势，其标准差自20世纪60年代以来持续增大。(2)当前年降水量频率-震级分布的显著特征是干旱事件的间隔时间缩短，年变化幅度增大。自1895年以来的年降水量最低值记录在1994年。在这次极端水文事件发生的情况下，河水水质与常年平均值相比发生了显著变化。所确定的趋势对降水的可验证性提供了有意义的视角，并可作为评估气候变化对水文环境影响的基本信息。

In the present study, the temporal characteristics of long-term valiability in the annual precipitation, discharge and runoff ratio are discussed for the last 102 years, 1895 to 1996, as a case study under the humid temperate climate in central Japan. The purpose of this study is to elucidate the trends in frequency and severity of hydrological extremes with a research focus of their relationsto physical and socio-economic environment of the basin.The results are summarized as follows :1. Characteristics of long term valiability in water balance at meso-spatial scale were investigated by using instrumental records in the Kiso, Nagara, Ibi and Suzuka River Basins.(1) Annual precipitation in the study basin is inclined to be below the average since the latter half of the 1980s, and its standard deviation has continued to increase since the 1960s.(2) The notable characteristics on current frequency-magnitude distributions in annual precipitation are both the reduction of interval of drought events and the increase of range in each year.2. The minimum value of annual precipitation since 1895 was recorded in 1994. Under the condition of this extreme hydrological events, the quality of river water showed the remarkable change as compared with the average value in normal year.3. The trends identified provide a meaningful perspective on the valiability of precipitation, and are useful as basic information to evaluate the effect of climate change on hydrologicalenvironment.