湿周法估算河道内最小生态需水量的理论分析

研究了不同河道几何断面的湿周法理论,分析了各种几何断面的湿周-流量关系。结果表明,当河道断面呈三角形、U型和抛物线型时,湿周-流量关系曲线可近似用幂函数拟合;当河道断面呈矩形和梯形时,湿周-流量关系曲线可近似用对数函数拟合。通过采用斜率为1法和曲率最大法确定曲线变化点,估算最小生态需水量发现,不论郡种断面,用斜率为1法和曲率最大法估算的结果差异很大,斜率为1法的估算结果均大于曲率最大法。分析同一流量下、不同断面形态对湿周法的适宜情况结果表明,在同一流量下,几何尺寸接近的不同断面,矩形和梯形断面有较大的湿周值,从湿周法初衷来讲,则更有利于生物生境的保护。

Theorrtical study of minimum instream flow requirement using the wetted perimeter method

This paper studied the theory of wetted perimeter method in different transection shapes ,analyzed the P-Q relation of different transection shapes. The results showed that the relation of P-Q fitted the power function when the transection was triangular geometry,U geometry and parabola geometry, the relation of P-Q fitted the logarithmic function when the transect was rectangular geometry and trapeziform geometry. Determining the minimum flow at an critical point where the slope equaled 1 and where the curvature was maximized indicated that the discharges at the breakpoints corresponding to the minimum flow was discrepant obviously at the point where the slope equaled 1 and the point where the curvature was maximized,but all results were higher at the point where the slope equaled 1 than the point where the curvature was maximized ; Meanwhile , analyze the feasibility of the wetted perimeter method to different transect shapes at the same discharge was analyzed. The results show that to the similar dimensions of different transect shapes,assuming the same discharge,rectangular geometry and trapeziform geometry respond to bigger wetted perimeter,so they are more propitious to protect aquatic habitat.