An environmental flow method applied in small and medium-sized mountainous rivers

In small and medium-sized mountainous rivers, there are usually hydropower stations in upper reaches as well as widened and heightened river sections in downstream reaches that are close to settlements. The environmental flow (EF) ensures river connectivity and the survival of aquatic organisms. The Tennant and wetted perimeter methods were used to calculate the minimum EF, and the R2CROSS criteria were used to evaluate the rationality of hydraulic parameters. The result shows that downstream areas with large cross-sections may suffer from shallow water depths, insufficient wetted perimeters, and poor overall connectivity of the water bodies, even under the standard EF discharges. A novel method was proposed to ensure EF and sustain suitable hydraulic conditions. The minimum EF calculated by the Tennant method is adopted as the design flow, and a small trapezoidal trough channel is excavated on the wide riverbed of an artificial river section. The width and depth of the small channel are calculated with Manning's equation. As a study case, this method was applied in the Fenglingang River in Zhejiang Province of China. A trapezoidal groove with a depth of 0.74 m and a bottom width of 0.52 m was excavated in the center of Fenglingang River to sustain EF and maintain river connectivity. This small channel not only prevents the river from cutoff, but also enables the water depth and wetted perimeter to meet the demand of aquatic organisms.     

妫水河入官厅水库水污染成因及减排措施评估

为保障妫水河入官厅水库入流水质达标,分析水质成因,分步制订水质改善措施。采用MIKE21耦合植物作用的Ecolab生态水质模型,对妫水河下游入官厅水库断面至东大桥断面、支流三里河水域进行模拟。通过对丰水期和枯水期监测数据及模拟结果进行分析,流域上游来流水量及水质、区间污染源及河流湿地等自净作用是影响官厅水库入流水质的主要原因,其中:妫水河入流污染负荷对水库入流水质贡献率最大,丰枯水期氨氮、总磷和总氮的贡献率分别为18.32%～45.76%、9.31%～31.17%和29.34%～67.56%;区间入河污染源氨氮、总磷和总氮削减率分别为19.41%、31.31%和24.94%;丰枯水期河道自净对氨氮、总磷和总氮削减率分别为44.85%～61.29%、51.40%～77.92%和8.40%～23.06%。为改善官厅水库入流水质,在流经城市区的妫水河下游及三里河修建了河流湿地公园,对区域污染源进行截污,使得入库水质可达到Ⅲ类水。为长远确保官厅水库的水质,控制来流水质和加强流域治理是关键,同时营造岸带湿地,对水质改善有积极的作用。研究结果及方法可为水库污染防治及负荷量削减提供理论依据。     

一种自适应运动目标检测算法及其应用

针对ViBe算法在动态背景下存在鬼影消除时间长、算法适应性差、前景检测噪声多的问题,本文提出一种基于ViBe算法框架的改进算法.该算法采用鬼影检测法标记第1帧中的鬼影区域,并向位于鬼影区域的背景模型中强制引入背景样本,从而快速抑制鬼影;在像素分类过程中,引入自适应分类阈值,解决全局阈值易受动态噪声干扰的问题;在背景模型更新中,根据像素分类的匹配值来动态决定更新因子,提高算法适应场景变化的能力.定性与定量的对比实验结果表明,本文算法相较于ViBe算法能够有效地检测动态背景下的运动目标,应用于河流漂浮物检测场景中也有较好的效果.     

Planning for the Subernarekha river system in eastern India

The study describes the systems studies carried out to plan a river basin in order to determine the nature and size of water storage facilities and releases for irrigation and industrial uses, and the associated cropping pattern. The model has been formulated in the framework of a linear programming model for a specific target year. This model is developed in the context of planning the Subernarekha river basin. The results are discussed and these provide information and insight suggesting the need for more disaggregated analysis of interaction between irrigation and related agroeconomic parameters.     

西南山区交通工程弃渣的工程特性评价及其分类

山区交通工程弃渣力学参数的准确测定,一直是弃渣场边坡稳定性评价面临的基础科学问题。在山区交通工程弃渣场运行特点和弃渣固体废弃物特征认知的基础上,探讨弃渣取样和试验代表性问题的物理根源,依托实际工程累计数据尝试提出简单实用的弃渣工程特性评价和分类方法。结果表明:①常规交通工程弃渣的密度、颗粒分析和强度试验,由于弃渣的粒径范围差异大、颗粒空间分布不均、弃渣来源复杂等固体废弃物特征造成取样和试验代表性难题; 用多阶段坡角测量和颗粒分析试验代替传统的弃渣边坡试验,解决了试验和取样代表性难题。②利用弃渣粗细比可将弃渣分为细粒弃渣、混合型弃渣和粗粒弃渣。③根据弃渣粗细比、天然休止角和整形坡率,将西南山区交通工程弃渣分为细粒弃渣、混合型弃渣和粗粒弃渣等3类。细粒弃渣,弃渣粗细比小于0.3,天然休止角小于31.5°,整形坡率为1.00:2.00; 混合型弃渣,弃渣粗细比为0.3～1.0,天然休止角为31.5°～39.5°,整形坡率为1.00:2.00～1.00:1.50; 粗粒弃渣,弃渣粗细比大于1.0,天然休止角大于39.5°,整形坡率为1.00:1.50。④用多阶段坡角测量、颗粒分析试验和无黏性土边坡稳定性系数计算公式代替传统的弃渣边坡试验和稳定性系数计算方法,方法简单,结果保守,可以作为弃渣边坡稳定性评价和安全控制技术的有益补充。     

隐伏溶洞对隧道围岩稳定性影响规律及处治技术

以鄂西山区隧道工程实例为依托,在溶洞调查与统计分析的基础上,从岩溶的溶洞体积、形态特征、溶腔充填物特征以及涌水通道类型等方面,对鄂西山区岩溶进行分类,得到鄂西山区岩溶发育特征,即溶腔体积不等、形态多样、溶腔充填物种类多、涌水通道复杂。采用数值模拟方法,分析不同位置的隐伏溶洞对隧道围岩的应力场、位移场影响情况,得出随隐伏岩溶位置变化,围岩应力分布有所不同;溶洞位置由隧道顶部向隧道底部变化过程中,隧道顶部围岩最大沉降由大到小依次为拱肩延长线、边墙一侧、拱脚延长线、拱顶上方、底板下方;随着溶洞位置的降低,隧道拱顶围岩水平最大收敛值由大到小依次为拱肩延长线、拱顶上方、边墙一侧、底板下方、拱脚延长线;随着溶洞位置的降低,隧道周边围岩沉降量由大到小均为拱顶、拱腰、拱脚、底板。基于岩溶类型特征、数值模拟围岩应力场、位移变化情况结果,提出岩溶区隧道揭露溶洞处治原则。以花果山隧道为例,开展溶洞处治原则与方法应用,提出针对性的处治方案。     

基于水质模拟的水质在线监测站点布设研究

随着水质监测连续化的需求增加,河流水质在线监测站布设成为不可忽视的问题。本文采用水文模拟模型HSPF对台湾淡水河流域进行水量水质联合模拟。水文模拟以9个测站比对,纳什效率系数多数大于0.7;相关系数r皆大于0.7。水质模拟以27个测站比对,生化需氧量、氨氮、悬浮固体、溶氧的修正平均百分误差多数小于25%。基于水质变化率和水质超标率提出水质敏感河段概念,并以此确定为补充布设水质在线监测站点的优先河段。研究指出,淡水河流域水质在线监测站目前仍缺乏且位置不尽合理,应优先补充三峡河的三峡大桥、景美溪的宝桥、基隆河的江北桥水质在线监测站。     

森林植被改善对鄱阳湖流域径流和输沙过程的影响

以河流基流为切入点,研究流域植被调节径流、水土保持等微观作用影响大中型河流湖泊径流过程和水沙过程宏观效应的机理。鄱阳湖流域60年来天然降水没有发生趋势性变化。流域森林覆盖率由34.73%上升到63.00%,植被质量改善,赣江等入湖河流基流增加83 m~3/s,河流输沙量减少。2000年以后和2000年以前相比较,枯水期降水径流系数增大,年流量过程平坦化,一定程度上减小洪灾风险,有利于水资源利用和生态环境保护。2001年以后进入鄱阳湖泥沙平均每年减少1 007×10~4t;出湖泥沙增加314×10~4t。因此,鄱阳湖入江水道由淤积转变为冲刷,但出湖流量过程没有趋势性变化。     

Geomorphic diversity as a river management tool and its application to the Ganga River,India

Understanding of geomorphic processes and the determination of geomorphic diversity in catchments are prerequisites for the sustainable rehabilitation of river systems and for reach‐scale assessment of river health. The Ganga River system in India is a large, complex system consisting of several long tributaries, some >1,000 km, originating from 2 distinct hinterlands—the Himalaya to the north and the cratons to the south. Traversing through a diverse climatic regime across the Plain and through precipitation zones ranging from 600 mm/year near Delhi to 1,200 mm/year in the eastern plains, the Ganga River system has formed very diverse landform assemblages in 3 major geomorphic domains. We have recognized 10 different river classes for the trunk river from Gangotri (source) to Farakka (upstream of its confluence with the Brahmaputra) based on (a) landscape setting, (b) channel and active floodplain properties, and (c) channel planform parameters. The mountainous stretch is characterized by steep valleys and bedrock channels and is dominated by large‐scale sediment production and transport through hill slope processes. The alluvial part of the river is characterized by 8 different river classes of varying reach lengths (60–300 km) many of which show sharp transitions in landscape setting. We have highlighted the application of this approach for the assessment of habitat suitability, environmental flows, and flood risk all of which have been significantly modified during the last few decades due to large‐scale anthropogenic disturbances. We suggest that the diversity embedded in this geomorphic framework can be useful for developing a sustainable river management programme to “work with” the contemporary character and behaviour of rivers.     

Estimating discharge in gravel‐bed river using non‐contact ground‐penetrating and surface‐velocity radars

Discharge measurement is a critical task for gravel‐bed channels. Under high‐flow conditions, the elevation of the riverbed changes significantly by intensive torrential flow. The stage–discharge relations commonly used for stream discharge estimation may no longer be adequate. The contact‐type velocity measuring is also subject to measurement errors and/or instrument failures by the high‐flow velocities, driftwood, stumps, and debris. This study developed a new real‐time method to estimate river discharge in gravel‐bed channels. A systematic measuring technology combining ground‐penetrating radar and surface‐velocity radar was employed. The rating curves representing the relations of water surface velocity to the channel cross‐sectional mean velocity and flow area were established. Stream discharge was then deduced from the resulting mean velocity and flow area. The proposed method was examined in a steep gravel‐bed reach of the Cho‐Shui River in central Taiwan. The estimated stream discharge during three flood events were compared to the prediction by using the stage–discharge relation and the index‐velocity method. The proposed method of this study is capable of computing reasonable values of discharge for an entire flood hydrograph, whereas the other two methods tend to produce large extrapolation errors. Moreover, when the computed discharge is used in 2D flood flow simulation, the proposed method demonstrates better performance than the commonly used stage–discharge and index‐velocity methods.