The Changes of Stream Discharge under Low-flow Season

• Main Authors: Mei- Chih Lin, 林美志
• Other Authors: Shih- Chien Chan
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/62121985194798292977

碩士 === 國立彰化師範大學 === 地理學系 === 103 === Stream flow is vital to human life and terrestrial ecosystem, especially under low-flow season; it turns into a critical factor for water supply capability, water quality control and aquatic habitat sustainability. In Taiwan, recent reports indicate a general trend of increasing drought frequency, leading the stability of water resource in dry season to a highly concerned issue. This study aims to access changes of stream discharge under low-flow season and the relations with watershed parameters as the discussion of this link is still limited. Daily rainfall and stream flow records of 6 watersheds in Dahan River and Xindian Creek for 1970 to 2010 are analyzed in this study. All records are firstly divided equally into two periods and long term variations of low-flow are later drawn out through statistic analysis of flow duration curve (FDC) and frequency analysis (FA). The study reveals mean daily flow under low-flow season is decreasing except for Fu Shan, and the initial month of the season varies in watersheds. Through flow duration curve analysis, the flow discharge of San Hsia and Kao Yi stations are found decreasing under Q90 percentile while others increasing. At last the 100 year low-flow discharge dramatically declines on San Hsia, Kao Yi and Ching Mei stations, on the contrary Fu Shan is going up. The result indicates the changes of low-flow discharge are not unanimous in Danshui river basin because of diverse environmental characteristics in watersheds.Weak northeast monsoon caused by climate change has given rise to rainfall variances on watershed and could be responsible for less rainfall on Dahan river in low-flow season.Changes of land use over time lead to low-flow variation. Urbanization and water withdrawal affect extreme low-flow transform on San Hsia and Ching Mei. We believe rainfall variances, land use types, urbanization and water withdrawal are factors relating to changes of stream discharge under low-flow season.