| Summary: | 碩士 === 國立臺灣大學 === 地理環境資源學研究所 === 101 === Streamflow characteristics are the intricate response of climatic system, landuse change, and other environmental changes. Meanwhile, they are also the basis for flood and drought warning, design and operation of hydraulic constructures. Previous studies analyzed historical rainfall records showed that the intensity of heavy rain increased doubled and light rain became about half worldwide. The signification rainfall intensification implies the droughts and floods may threat to natural and anthropogenic system frequently. This study analyzed the streamflow characteristics, including frequency, magnitude, duration, timing and varibility, of 48 mountainous catchments in Taiwan since 1970 to 2010. Besides, the possible rainfall projections are generated and inputted to 2 distributed hydrological models (HBV and TOPMODEL) for assessing the streamflow responses to rainfall intensification.
Results revealed the mean of daily flow and baseflow in mountainous catchments is higher, but lower in variability. In contrast, the stormflow and varibility in lower and southern catchments are higher. The timing of wet season circulates from north-western with counter-clock. Besides, flow characteristics are found to highly correlated to drainge density and relief-relevant geomorphologic chacteristics. In trend analysis, the baseflow in central and southern low-land and Ilan region is increasing. On the other hand, the baseflow decreases in important water resources region, such as Danshui, Dajia, Tzengwen, Gaoping. In simulation between historical and projected rainstorm, accmulated rainfall increase 1.79-folds, and maximum 6-hr rainfall increase 2.32-folds. Under this circumstance, the accumulated flow may increase 2.27-folds, peak flow increase 3.52-folds, and the surface flow increase 4 to 6-folds. The amplification in peak flow is significant which should be the foundation of disaster prevention and water resources plan, and improve the understanding of hydrological cycle under environmental change.
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