| dc.description.abstract | In the recent years, the rainfall intensity rises sharply in Taiwan due to global climate variations, and it may result in the situations such as increased flooding and droughts, the reservoir storage volume is insufficient, and it causes the management and the distribution of water resources more and more difficult in the future. This study discussed the influence of floods and drought under climate change, and analyzed rainfall by the Mann-Kendall method for the trends in year 1961-1990 and that in 1991-2010.
First, this study analyzed 50 years long-term rainfall data to discuss the change of trend, and to calculate the total rainfall and the rainfall patterns in spatial. Second, this study analyzed the return period of the single day maximum rainfall and the maximum continuance days without rainfall by frequency analysis in year 1961-1990 and 1991-2010. Last, this study discussed the effect of the extreme rainfall and the drought under climate change in Taiwan.
According to the analysis result of Mann-Kendall method, there was an obvious trend appeared in the alternate drying and wetting month. The average annual rainfall showed an increasing trend in both central and southern Taiwan. Analyzing average annual rainfall and average amount of water by the Kriging method, the rainfall patterns had changed in spatial in northern Taiwan. The average annual rainfall decreased between the elevation of 200 meter above sea and that of 1000 meter above sea, and the average annual rainfall increased for the elevation above 1000 meter. In central and southern Taiwan, the average annual rainfall increased for region above the elevation of reservoir sites. In addition, the frequency analysis result showed that the rainfall intensity increased sharply in the central and south area under climate change. Extreme rainfall had changed the return period, i.e., more sever rainfall is expected in 1991-2010 than that in 1961-1990. In Central and Southern Taiwan, the range of small-scale and large-scale drought would spread gradually to inland in 1991-2010. During this period, the probability of large-scale drought occurring is 0.02 in the central and south area along the coast, while the probability is less than 0.01 in Northern Taiwan.
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