湿周法估算巴音河河道内最小生态需水量

文中采用湿周法估算巴音河最小生态需水量。选用巴音河德令哈水文站作为控制断面,用对数函数和幂函数关系对湿周~流量关系进行拟合。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。分别用斜率为1法和曲率最大法对巴音河的德令哈断面的最小生态需水量进行定量估算。     

基于改进湿周法的贾鲁河河道内生态需水量计算

针对贾鲁河实际情况,选取中牟和扶沟水文站作为控制断面,利用斜率法、曲率法和多目标评价法3种改进湿周法计算分析贾鲁河不同频率年河道内生态需水量。结果表明,采用多目标评价法(r=2)计算结果最大,曲率法最小,中牟断面用多目标评价法(r=2)计算生态需水量较为合理,扶沟断面用斜率法计算生态需水量较为合理。     

河流生态需水量计算的湿周法拐点斜率取值的改进

现行计算生态需水的湿周法在相对湿周相对流量曲线上判定拐点时,常以斜率为1的点为拐点。在应用于标准抛物线形河道断面计算河段的生态需水时发现,在采用该拐点确定生态需水流量时,不同形状断面的需水流量比例都非常接近,没有反映出河段特征的差异。在对其原因分析后建议将拐点的斜率取为多年平均流量与相应湿周长比值的平方根。并以此进行计算,结果表明：河道断面越宽浅生态需水量占多年平均流量的比例越大;河流多年平均流量越大生态需水量所占的比例越小。反映出河流特征的差异,其变化趋势符合对河流生态需水规律的一般性认识。同时在计算     

用改进湿周法计算河道内最小生态流量

在探讨总结国内外计算河道内最小生态流量(minimum instream ecological flow)方法的基础上,针对汉江流域的实际情况,选用改进湿周法对汉江上游石泉、安康和白河3个水文断面的最小生态流量进行定量估算。与Tennant法相比较,表明采用曲率湿周法计算的汉江上游河道内最小生态流量是比较合理的。计算结果为：石泉、安康、白河3个断面的最小生态流量依次为40,70,100 m3/s,分别占各断面多年平均天然流量的11.23%,11.08%,12.55%。     

基于栖息地模拟的河道生态需水量多目标评价方法及其应用

本文提出基于栖息地模拟法的多目标评价法计算河道生态需水量,以加权可利用面积(WUA)最大和流量最小为目标,采用理想点法进行求解.该方法综合考虑了生态用水和经济用水,提供了一个栖息地保护和经济用水相协调的最优河流生态需水量.最后以鱼类作为指示物种,对新疆额尔齐斯河中游鱼类产卵期的河道生态需水量进行了计算.计算结果表明,其生态流量为78m3/s,占该河段多年平均流量的74%.该结果比直接采用栖息地模拟法计算的结果小,但该生态流量可以对河流栖息地提供足够的保护,且较好地协调了生态用水和经济用水的矛盾.     

蒲河中上游河道最小生态流量研究

以蒲河中上游河道为研究区域,运用曲率湿周法对河道内2个控制断面的最小生态流量进行了推算,并与采用Tennant法的估算结果进行比较分析.结果表明:运用曲率湿周法推算的2个控制断面的最小生态流量分别为0.227、0.239 m3/s,占多年平均流量的9.83%和10.35%;采用Tennant法估算的河道最小生态流量为0.231 m3/8,占多年平均流量的10%,两种算法结果吻合较好.     

湿周法确定河流生态环境需水量临界点的应用

湿周法是河流生态环境需水量的确定方法之一。文章针对其应用中对多组实测数据确定临界点困难的实际情况,对该法进行了改进。提出了湿周法确定临界点理论公式,并利用实测数据对选定的西南岔河流域的三个河段进行生态环境需水量计算。     

湿周法在超宽浅型河道生态需水计算中的应用

采用湿周法计算河道生态需水量是通过建立湿周—流量关系,利用斜率法或曲率法来确定湿周—流量关系曲线上的拐点,进而确定河道生态需水量的。当河道水浅、宽深比特别大时,该方法建立的湿周—流量关系曲线会出现明显的分段转折点,分析表明它并非确定生态需水量所需的拐点。为此,引入"计算水深"概念,根据河道断面几何形态进行概化,转化得到新的湿周—流量关系,能够有效、合理地利用斜率法和曲率法计算河道生态需水量。     

确定河流生态流量的几种湿周法比较

为比较不同湿周法在计算河流生态流量中的适用性,采用幂函数描述无量纲化的湿周～流量关系,利用曲率法、斜率法及多目标评价法中的线性加权和法、理想点法(尺度系数r分别取1,2,∞)、乘除法等7种方法计算河流生态流量。结果表明:曲率法的结果偏小;斜率法、理想点法(r=1)、线性加权和法的结果相同,且位于各方法的中间;另外3种多目标评价方法得到的河流生态流量大于斜率法等的结果,但湿周的增加比例明显小于流量增加比例。在湿周～流量关系符合幂函数关系时,利用斜率法或理想点法(r=1)、线性加权和法确定河流生态流量的方法是适宜的。     

引水式电站减水河段最小生态需水量模型研究

为了保护引水式水电站大坝与厂房之间减水河段的生态环境,需要确定河道最小生态需水量,以反映河道特征的差异.以湖南省一些典型引水式水电站下游减水河段为例,应用改进的湿周法计算了河道最小生态需水量,并通过单变量影响分析,研究河道最小生态需水量的影响因素;以幂函数对最小生态需水量与各单变量的关系进行了拟合分析,得到了合适的最小...     

A multiple criteria decision‐making approach to estimate minimum environmental flows based on wetted perimeter

Minimum environmental flows in rivers provide a certain level of protection for the aquatic environment. The relationship between wetted perimeter and discharge can be used to define the minimum environmental flows by the slope method (SM), or curvature method (CM), especially for cases with poor understanding of the aquatic ecosystem. SM and CM derived inconsistent values of minimum environmental flows. It was not clear which method better defined minimum environmental flow. Moreover, the computation and optimization procedures are both time consuming and error‐prone, especially for complicated wetted perimeter–discharge relationships. In this study, flow regulation for rivers was regarded as a multiple criteria decision‐making problem, with the objectives of minimum river discharge and maximum wetted perimeter. Ideal point methods (IPMs) with the scaling coefficient r = 1 (IPM1) and r = 2 (IPM2) were used to solve this model to determine optimal environmental flows. IPM was simple in computation, especially when the wetted perimeter–discharge relationship was given as scattered data pairs. Meanwhile, it was applicable to a wider range of wetted perimeter–discharge relationship than SM and CM. Environmental flows estimated by IMP1 are the same as that by SM. The analytical results for environmental flows using SM, CM, IPM1 and IPM2 were compared for wetted perimeter–discharge relationship expressed as power or logarithmic function. It showed that CM is not a good method to define environmental flows. SM with unity slope and IMP1 were recommended. CM, SM and IPM were examined for the determination of environmental flows in a river in North Xinjiang, China. Environmental flows for different transects of the studying river reach were estimated to be 21% of the mean annual flow by SM or IPM1, which provided the satisfactory wetted perimeter, water depth and average velocity for aquatic organisms. Copyright © 2007 John Wiley & Sons, Ltd.     

Refinement of the wetted perimeter breakpoint method for setting cease‐to‐pump limits or minimum environmental flows

Analysis of inflections or breakpoints apparent in relationships between measures of wetted perimeter and discharge can be used to assist in the determination of minimum environmental flows for perennial rivers. This paper suggests refinements and provides an example application of the wetted perimeter method for the determination of cease‐to‐pump limits in a perennial, unregulated gravel‐bed river subject to increasing levels of surface water extraction. HEC‐GeoRAS modelling outputs of riffle wetted area are used to illustrate that the magnitude of the discharge selected to represent 100% habitat availability is of crucial importance to the breakpoint method. Because of the dependence of the technique on this assumption, we suggest that it is prudent to use an upper and lower limiting discharge based on an assessment of the degree of flow variability to develop a flow range around the zone of diminishing return in the wetted perimeter to discharge relationship. For rivers exhibiting a low degree of flow variability, the mean and median daily flows are likely to provide appropriate discharges for representation of 100% habitat availability. For perennial rivers with a higher degree of flow variability and considerable differences between the mean and median daily flows we suggest use of the 50th and 80th flow duration percentiles. Wetted perimeter breakpoint results are also influenced by the degree to which areas of non‐riffle habitat are included in the analysis. Inclusion of excessive pool areas can lead to significant reductions in resultant recommendations for cease‐to‐pump limits or minimum environmental flows. Integration of hydraulic model outputs with GIS for wetted perimeter analysis of riffles provides a useful, rapid, field‐based approach that can assist with determination of cease‐to‐pump limits or minimum environmental flows in gravel‐bed rivers. However, care is needed in its application and interpretation as the technique is prone to numerous subjective choices that have a substantial influence on results. Copyright © 2004 John Wiley & Sons, Ltd.     

湿周法的改进和应用

由于湿周法在确定突变点中存在主观性的缺陷，而最大曲率法可客观的确定河流生态基流，避免了主观性。在湿周法的基础上，研究了河流生态基流的概率分布，同时研究了径流特征值和生态基流之间的关系，为河流生态需水的预测提供了解决方法。     

河流最小生态基础流量计算方法研究

为了能够计算几何断面复杂、泥沙淤积、河宽大、水深浅的河道生态基础流量,本文以渭河关中地区的生态基础流量计算为例,通过综合水力学中的湿周法和R2CROSS法建立了一套简单、适合管理的最小生态基础流量方法——综合法。该方法计算出的5个站的生态基础流量占多年平均流量的比值都在10.8%～14.9%之间,满足生态基流的合理要求。通过与Tennant方法比较,结果表明:综合法计算确定的生态基础流量更为合理、是一种在管理上更值得推广应用的方法。     

二维水力模拟在河流生态需水湿周法中的应用

湿周法是河流生态需水量计算中使用较为常见的一种水力学方法,通常采用一维的水力分析结果作为计算依据。二维水力模拟能提供更为细致全面的河道水力参数分布,通过对某水电站坝下13.3 km河道进行平面二维水力模拟,对其在湿周法中的应用进行了探讨。采用弗汝德数(Fr)作为浅滩生境划分标准,把浅滩生境较为集中的河段作为湿周法分析的浅滩河段。随后根据平面二维水力模拟结果,给出了浅滩断面相对湿周-流量关系曲线,采用斜率为1的斜率法计算得到了各浅滩断面的生态需水量。结果表明,采用二维水力模拟结果给出的曲线更为合理。     

清潩河流域河流环境流量计算与应用

针对北方地区河流环境流量短缺和污染并存的现状,在综合考虑水质保护与水量维持的情况下界定了河流环境流量的概念和内涵,并探讨不同功能目标下河流环境流量的组成。通过分析河流水系特征及河段的空间结构特征,建立了改善河流水质所需环境流量计算模型,同时建立了Tennant和湿周模型计算河流生态系统所需环境流量。利用临颍高村桥的水文水质数据,对清潩河为改善河流水质和生态系统所需环境流量进行了初步评价,为河流应急补水提供了调控建议,并提出了河道应常年保持的流量水平。