Influence of habitat heterogeneity and bed surface complexity on benthic invertebrate diversity in a gravel‐bed river

Maintaining or restoring physical habitat diversity is a central tenet of sustainable river management, yet a link between habitat and ecological diversity in fluvial systems has long remained equivocal. The lack of consistent evidence partly reflects the problems of characterizing habitat in ways that are ecologically meaningful. This paper assesses the influence of habitat heterogeneity and complexity on macroinvertebrate assemblages in a mountain gravel‐bed river. With the use of 0.1‐m resolution data obtained from an acoustic Doppler current profiler, heterogeneity and complexity in hydraulic conditions and bed topography were characterized using 13 metrics applied to 30 areas, each 1 m², with an invertebrate sample collected from each area. Turnover of invertebrate taxa (i.e., β‐diversity) between sampled areas was rather limited, but observed differences in diversity were related significantly to several metrics of habitat heterogeneity. Invertebrate abundance was related to habitat diversity, patch size coefficient of variation, and patch size, whereas the Shannon diversity was related to the number of patches and patch size. None of the habitat complexity metrics accounted for a significant amount of observed variation in invertebrate communities between sampled areas. The paper demonstrates that high‐resolution data can help reveal relationships between habitat and benthic invertebrate diversity.     

In‐stream construction‐induced suspended sediment in riverine ecosystems

Construction activities within the wetted‐perimeter of rivers, referred to as in‐stream construction, are prevalent economically and environmentally motivated activities having direct interactions with sensitive lotic environments. Currently, there is a paucity of research related to in‐stream construction activities and their effects on aquatic ecosystems. In‐stream construction‐induced suspended sediment may result in harmful effects to aquatic flora and fauna. Regulatory frameworks worldwide focus primarily on concentration, with limited consideration for duration and no consideration for spatial extents of suspended sediment exposures. This research develops theoretical concentration, duration, and spatial extent exposure risk relationships for riverine ecosystems to demonstrate the influence of each mechanism during typical in‐stream construction activities. To reduce exposure risk, concentration and duration may be considered pragmatically, based on anticipated activity characteristics and site conditions. Spatial exposure characteristics are important to consider, as illustrated by our finding that activities located near the channel centerline may result in greater exposure risk than similar activities conducted near the streambank. Current regulatory frameworks worldwide do not sufficiently consider all exposure risk mechanisms present during in‐stream construction‐induced suspended sediment releases, possibly inhibiting efforts to reduce adverse environmental effects. This research improves our understanding of suspended sediment in lotic environments and may help environmental managers better evaluate and manage in‐stream construction activities.     

照片数量对SfM动床河工模型地形三维重构的影响研究

SfM是摄影测量领域近年来飞速发展的三维场景重构技术,目前已在地貌勘测、文物勘察、冰川演化、岩石勘探、土壤侵蚀等研究领域开展了大量尝试和应用,而在河工模型方面的应用研究尚处于起步阶段。本文开展了输入照片数量对SfM法动床河工模型地形三维数字高程地形(DEM)重构精度影响研究,采用4个不同视角对河工模型动床冲淤地形进行拍摄,选取不同数量照片作为输入开展SfM法三维地形DEM重构,然后将每组DEM重构结果与传统测针法测量进行对比。结果表明,当照片数量较少时,增加照片数量可改善SfM重构精度,但当照片数量较多时,虽可为SfM提供更多的床面变化图像信息,但同时带来由于特征点成像变化而引起的误匹配现象,反而可能导致SfM重构精度下降。鉴于不同动床模型的模型沙和光照等外部条件不同,实际应用时须针对不同模型的特点进行深入对比和分析,选取合理的照片张数开展SfM法动床冲淤地形测量。     

基于Landsat的淮河干流水质监测的可行性分析

流域水体污染已成为影响岸边带经济社会发展的热点问题,明确流域水质变化趋势是实施水体污染控制和综合治理的前提。针对流域水质状况及其发展趋势的监测问题,以淮河干流为研究对象,在现有的流域水质监测手段的基础上,结合实测水质数据和同步Landsat数据,采用多元统计分析方法,建立了TM、OLI水质遥感监测模型,开展了2006-2017年淮河干流水体污染趋势分析。结果表明：TM、OLI水质综合污染指数遥感监测模型计算值与实测值之间绝对误差不超过 0.17,相对误差不超过7.11%;模型计算的2006-2017年淮河干流各类污染水体面积占比变化情况与实际监测结果一致,模型可用于淮河干流水质动态监测中;将遥感影像数据与典型断面监测数据相结合,建立流域水质监测模型的思路是可行的。研究结果为大尺度流域水质动态监测和生态环境保护提供了一种新的思路。     

对构建国际流域治理体系的思考：以澜沧江-湄公河为例

由于“湄公河治理”是一个自主运作却又开放的组织集合,这种集合不仅仅是主权国、更是各类型组织组成的,因此它的治理直接面临着两个“根本性的难题”,即国际流域治理碎片化与各成员参与合作的约束与激励问题。因此如果单独采取科层制、市场机制或网络机制来协调澜沧江—湄公河治理中的矛盾都可能导致“囚徒困境”。根据西方各国经验并结合各流域国的国情,“澜沧江—湄公河治理”应着力于“整体性安排”,基本包括：完善合作的组织机构及机制、改善中国参与澜沧江—湄公河治理的方式、流域政府的政绩评价、流域生态补偿与政府间平权机制、多中心的混合制治理制度。     

GIS支持下的凡河流域农业非点源污染物时空特征分析

为了解铁岭县凡河流域农业非点源污染现状,本文以铁岭县多年乡镇统计报表为基础,结合输出系数法及源强系数法分析了凡河流域2007-2009年四种农业非点源污染物排放量及其排放强度的时空分布特征。结果表明:(1)流域内农业非点源污染物排放总量呈持续上升趋势,总氮、总磷、化学需氧量及氨氮的平均排放量为3174.5、361.4、16624.5和3980.3t/a;(2)流域内主要污染物为化学需氧量,主要污染源为畜禽养殖;(3)污染物排放总量及强度空间上大致呈中、西部高,东部低的特点,李千户乡及铁岭市区为主要污染区域。为有效地控制凡河流域农业非点源污染,当地政府应把重点放在畜禽粪便及居民生活垃圾的处理方式上。     

岷江全流域水资源量化配置研究

针对岷江流域的生态功能,本文采用多准则的层次分析法,构建了社会发展、经济发展和生态保护三维度的评价指标,以流域内行政区域作为分配对象,建立了科学合理的岷江流域水资源量化分配模式。结果表明:水资源分配不但要根据区域用水量、经济总量等社会、经济指标,也要根据生态保护的量度来进行相应的补偿,才能使水资源量化分配模型更加科学合理,各方均可接受,从而使得流域水资源的利用具有可持续性。     

西控工程对望虞河西岸地区防洪的影响

为了评估西控工程对望虞河西岸地区造成的防洪影响,以望虞河西岸为研究区域并结合其水文特性,构建了适合于模拟平原河网地区产汇流过程的MIKE11水文水力模型并利用当地降雨、水位等实测资料进行了率定。通过模拟50年一遇设计暴雨情况下的不同工况,得到研究区域内水系各节点的水位等要素变化情况,并依此分析了西控工程对望虞河西岸地区造成的防洪影响。结果表明:西控工程运行后,研究区域内重要节点的最高水位抬升明显,部分地区有遭受洪水淹没的风险;MIKE11水文水力模型对于分析平原河网地区河流沿线闸控影响具有较高的应用价值。     

群居蜘蛛优化算法在水位流量关系拟合中的应用

针对水位流量关系拟合中相关参数难以确定的不足,利用一种新型群体智能仿生算法——群居蜘蛛优化算法(SSO)优化水位流量关系的相关参数,以云南省丽江仁里站和总管田站水位流量关系拟合为例进行实例研究,并与粒子群优化算法(PSO)、最小二乘法(LSM)拟合结果进行对比。结果表明:SSO算法对仁里站和总管田站水位流量关系拟合的平均相对误差绝对值分别为0.57%、0.53%,拟合精度优于PSO、LSM算法。SSO算法具有收敛速度快、全局寻优能力强等特点,利用SSO算法优化水位流量关系可以获得更好的拟合效果。     

闽江下游径流量和北港分流比变化及其对水龄的影响研究

利用闽江下游多年水文资料,分析了干流流量时空变化和北港分流比变化趋势,并借助EFDC模型研究水口水库下泄流量和北港分流比对闽江下游水体水龄的影响。分析表明:闽江干流径流量年际变化不均匀,北港分流比则经历了由小变大再变小的趋势。模拟的闽江水龄结果可知水龄与下泄流量成反比关系,北港分流比减小将增加北港水体交换时间,同时减少南港水体交换时间;水龄可以定量地描述污染物在北港河道的停留时间,为保障北港水源地水质安全,需要增大枯水期上游水口水库下泄流量和增大北港分流比。