对计算河道最小生态流量湿周法的改进研究

Improved research on wetted perimeter method to calculate minimum stream ecological discharge

在分析湿周法基本理论的基础上,探讨了湿周法确定河道最小生态流量的计算步骤。研究分析了几种典型河槽几何断面的湿周流量关系,采用斜率为1法和曲率最大法来确定湿周流量关系曲线上变化点所对应的最小生态流量。以长江中下游河道计算为例,分别选取长江中下游的宜昌、汉口水文站作为控制断面,对长江中下游河道最小生态流量进行了研究,并利用Tennant法对计算结果进行了分析评价。结果表明,曲率最大法确定准则计算结果合理,而采用斜率为1法确定准则计算结果则偏大。最后确定宜昌、汉口站断面的最小生态流量为2315m3/s、3124m3/s,分别占多年平均天然流量的16.7%、13.8%。该研究表明改进湿周法用于长江中下游河道最小生态流量研究是可行的。

Based on the analysis of the basic theory of wetted perimeter for the estimation of the minimum ecological discharge in river channels, the calculation procedures of wetted perimether method are introduced. The relationships between wetted perimeter and discharge of several typical stream channel shapes are analyzed and the critical point corresponding to the minimum ecological discharge at the relationship curve is determined based on slope （slope being 1） and curvature techniques. The improved wetted perimeter method is applied to determine the minimum ecological discharges in the middle and lower reaches of the Yangtze River. By choosing Yichang station and Hankou station at the middle and lower reaches of the Yangtze River as the hydrological control transects, the calculating result is evaluated by Tennant method. It is founded that the results calculated by curvature technique are reasonable and the results calculated by slope technique are langer than reasonable. The final results are determined that the minimum ecological discharges at Yichang station and Hankou station are respectively 2315 m3/s and 3124m3/s, respectively occupying 16.7% and 13.8% of average nature discharge. The study shows that the improved wetted perimeter method applied to analyze the minimum ecological discharges in the middle and lower reaches of the Yangtze River are feasible.