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

在本研究中，在过去的102年，1895年至1996年，作为一个案例研究在日本中部的湿温带气候下，年降水量，流量和径流比的长期有效性的时间特征进行了讨论。本研究的主要目的是阐明长江流域水文极端事件发生频率和强度的变化趋势，并重点研究其与流域自然环境和社会经济环境的关系，主要结果如下：1.利用木曾河、长良河、伊比河和铃鹿河流域的仪器记录，研究了中空间尺度水平衡的长期有效性特征。(1)自20世纪80年代后半期以来，研究流域的年降水量倾向于低于平均值，其标准差自20世纪60年代以来持续增加。(2)年降水量的频数-量级分布的显著特征是干旱事件间隔的缩短和年际变化幅度的增大. 1895年以来的年降水量最小值记录在1994年。在此次极端水文事件条件下，河流水质与常年平均值相比发生了显著变化.这些趋势为降水的有效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础信息。

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.