湿周法估算河道内最小生态需水量——以滦河水系为例

Wetted Perimeter Approach to Estimate Instream Flow Requirements:A Case Study in Luanhe Water System

湿周法是以湿周作为衡量栖息地质量的指标来估算河道内流量的最小值。通过建立河道断面湿周与流量的关系曲线,依据该曲线确定变化点的位置,估算最小需水量的推荐值。根据国外对湿周法的研究应用,分别采用对数函数和幂函数关系对湿周—流量关系进行拟合。从理论上分析了湿周法采用斜率为1法和曲率最大法确定变化点的不同,得到不论采用对数函数还是幂函数关系拟合流量—湿周关系,斜率为1法的估算结果都要大于曲率最大法的估算结果。把湿周法应用到滦河流域两个水文站,以曲率最大法确定变化点,估算了两个站点的最小生态需水量。结果表明:①对数函数拟合流量-湿周关系得到的最小生态需水量都要大于幂函数拟合流量-湿周关系的结果;②湿周法估算的生态需水量都能满足河道内最小生态需水的要求,且较小河流对生态需水量的要求相对较大河流更高。

Wetted perimeter approach estimates instream flow using wetted perimeter as an index to scale the habitat quality. It estimates minimum environmental flows via determining break point on curve of the relation- ship between wetted perimeter and discharge. This paper adopted logarithmic and power function methods respectively to simulate the relationship between wetted perimeter and discharge based on the foreign experience of research and application. The difference of determining breakpoint using slope equaling 1 method and using maximal curvature method was analysed in theory when the wetted perimeter method was used. The results showed that all calculating results from slope equaling 1 method were higher than those from maximal curvature method. The wetted perimeter method was used at two hydrological stations of the Luanhe drainage basin. The results were： （1） The minimum instream flow results were all higher when discharge and wetted perimeter relation fitted by the logarithmic function than that when discharge and wetted perimeter relation fitted by the power function; （2） The minimum instream flow calculated by the wetted perimeter method could satisfy the minimum instream flow requirement, and the minimum instream flow requirement for small rivers is correspondingly higher than that for big rivers.