| Budget Amount *help |
¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1998: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1997: ¥600,000 (Direct Cost: ¥600,000)
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| Research Abstract |
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.
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