| Summary: | 碩士 === 國立成功大學 === 水利及海洋工程學系碩博士班 === 92 === Drought is referred to the phenomenon of lacking rainfall. Because the global and regional climate has changed in resent years, the average temperature and drought situation in Taiwan has been more serious day by day also. The objective of this study is to investigate the regional caracteristics and its frequency under the situation of global climate has changed.
In this research, four kinds of statistical methods, including normal distribution, log-normal distribution, the first kind of extreme value distribution and log-pearson type III distribution, were used to analyze the frequency of the drought, with those satations, up to 2001, have over 20 years records in northern, central, northern and eastern part, four regions of Taiwan. By using the erected frequency equations from each gauged station it can be hoped to afford for estamiting the no rainfall days and that will be helpful to be the basic data on planning irrigation and public water supply.
The 3ird type of extreme value distribution is the most suitable method after the four distribution methods were used for investigating, and the regressive formular were erected with 2, 5, 10, 50 and 100-year return period. The results show: (1) The frequency of drought that occurred on plain area was more than withch on mountain area amd the western sea shore area was more than eastern shore area, totally, the central part and northern part are the most frecquent area in Taiwan. (2) In plain area of central and northern part of Taiwan, once per two year will occurr one small scale drought, on the more eastern hill area, once per five year will occurr one small scale drought. (3) In the same watershed, the lower stream area will be influenced more than the upper stream area. (4)For all basins of Taiwan，the days of drought has increase 20% in resent thirty years it shows that drought phenomenon has increased and the eastern part of Taiwan is the most one. (5) In the area of central and northern part, the occured drought days on autumn and winter are more over than those of spring and summer. Oppositively, spring and summer are more over than those of autumn and winter in the northern part of Taiwan. The eastern part is meanly equal in all seasons.
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