台湾地区溪流生态基础流量推估——和平溪上游案例研究

The Estimation of Minimum Flow in Streams of Taiwan--A Case Study of Eastern Taiwan

在研究山区河川的水理计算方法时有争议 ,尚未有定论 ,一般研究河川基础流量以采用历史流量评估法及水理评估法为常用的量化方式。本研究主要以“历史流量评估法”进行生态基础流量分析。依据面积与流量经验值估算 ,本研究推估之最小生态基础流量约为 0 .32～ 0 .95 cms;依照日本一般生态基础流量计算标准 ,则维护生态最小放流量应为 1.0 6 cms。利用 Tennant法计算生态基础流量时应随时间季节及水文条件变化。推估值于丰水期之基础流量应为 1.46 cm s,枯水期应为 0 .6 1cms。若按日流量延时曲线之 95 %为分析基础 ,则查询历年最低日流量为 3.12 cm s;若按日流量延时曲线之最低标准 10 0 %为分析基础 ,则推估之基础流量应至少为 1.87cm s。依水理评估法分析结果 ,最小生态基础流量应在 2 .0 cms至 3.0 cm s之间 ,如此河道水深为主要鱼种生存之最低限。有鉴于山区陡坡河道水理计算迄今于学术界仍未具定论 ,计算成果仍需辅以现地实测成果予以验证。

The flow assessment methods have been extensively discussed but have no real resolution. Minimum flow in rivers and steams provides a certain level of protection for the aquatic ecosystem. Therefore, the estimation of minimum flows becomes one of the major considerations in dam construction. Three major categories of quantitative instream flow assessment methods, including historic flow, hydraulic geometry, and habitat have been examined last decade. Historic flow and hydraulic geometry methods are used in this study to estimate the minimum flow in the upstream of Hoping Stream. The historic flow methods rely on the recorded or estimated flow of the river. Tennant method, flow duration curve and the watershed area estimation are the most widely known methods. The estimations of the minimum flows are 1.46 cms in the flooding season and 0.61 cms in the dry season. The results based on the daily flow duration curve are 3.12 cms to 1.87 cms while the exceeding probability from 96%to 100%. According to the watershed areas versus flow experience value estimation method, the estimations of the minimum flows are 0.95 cms and 1.06 cms by using different parameters. Hydraulic geometry methods based on various parameters such as width, depth, velocity, and wetted perimeter. The estimation of this study is from 3 to 2 cms in different parameters. Habitat methods are not examined in this study due to the complicated procedure to establish the habitat suitable curves.