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Estimation of Stream Flows from Guandaushi Forest Watershed
|關鍵字:||水文反應值;hydrological response value;前期降雨;突現性;稽延時間;尖峰到達時間;最大日雨量;直接逕流量;滲漏;antecedent precipitation;flashiness;lag time;time to peak;maximum daily rainfall;runoff;percolated||出版社:||水土保持學系||摘要:||
The main purpose of this thesis was going to set up a hydrological model between the main watershed and sub-watershed in Guandaushi watershed where located in the middle of Taiwan, in order to estimate the stream flow of main watershed.
The results were shown as follows:
1. According to the annual discharge and rainfall collected from 1996 to 1998, the average outflow rate in the sub-watershed was 35.2% and was 61.4% in the main watershed. The reason why the sub-watershed outflow rate less than the main watershed was that most of the precipitation percolated into the ground.
2. According to the collected 19 events of storms in the main watershed, the average hydrological response value was 15.3%;the range was 1.4%∼64.3%. The hydrological response value increased with the duration of storm. If the antecedent precipitation moistened the watershed damp, the rainfall of the storm would outflow more by runoff and made the hydrological response value increased with the duration of storm to show the higher flashiness.
3. According to the statistical analysis, the average lag time (TL) and the time to peak (Tp) of the sub-watershed were 1.7hours and 4.8hours but it took 1.6 days and 3.8 days in the main watershed which was 23 times of the TL and 19 times of the Tp in the sub-watershed . This showed that with the similar shape of these two watersheds, TL and Tp in the main watershed was shorter than the square times of watershed length ratio. The main watershed area was 47 times larger than the sub-watershed. TL and Tp in the main watershed were shorter in proportion to ratio of the area and the length of the stream. This might due to the average slope of the geography in the main watershed was steeper than that in the sub-watershed.
4. The regression analysis of rainfall and discharge flow on recession hydrograph in the main watershed, The result showed that rainfall did not have much influence on the recession hydrograph. Even if the extreme value of the discharge parameter was deleted,the regression analysis would showed that there was highly correlation between the maximum daily rainfall and runoff. However, we found that some rainfall events were over the threshold value, but there were no runoff occurred. This might be due to un-uniform rainfall distribution in space.
中 文 摘 要
三、由統計結果顯示，子集水區之平均稽延時間(TL) 及尖峰到達時間(Tp) 分別為1.7hr及4.8hr；主流集水區則分別為1.6天及3.8天，分別約為子集水區平均稽延時間之23倍與尖峰到達時間之19倍，顯示在兩集水區形狀相似之情況下，主流集水區之稽延時間與尖峰到達時間為略小於兩集水區最高點至出水口距離之比值之平方倍，而主流集水區面積約為子集水區面積之47倍，依此面積及溪流長度比例顯示主流集水區之尖峰到達時間及稽延時間較之子集水區均呈現較快之趨勢，此可能因主流集水區地形之平均坡度較子集水區為陡所致。
|Appears in Collections:||水土保持學系|
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