Zooplankton density and community composition following an experimental flood in the Colorado River,Grand Canyon,Arizona

Zooplankton density and community composition were examined before and after an experimental flood (22 March–7 April 1996) in the Colorado River, Grand Canyon, north‐central Arizona, USA, and comparisons were made across sampling locations and habitat types. The flood primarily affected longitudinal distribution and community composition of zooplankton. Prior to the flood, zooplankton density declined linearly below Lee's Ferry (R²=0.79) but declined with the fourth power of distance downriver following the flood (R²=0.59). Zooplankton community similarity indices between mainchannel and backwater habitats ranged from 0.08 to 0.89 prior to the flood but increased significantly to 0.64–0.98 after the flood, indicating increased homogeneity between habitat types. The flood displaced resident (i.e. benthic, littoral and/or phytophyllic) taxa from backwater habitats and replaced them with limnetic organisms. Total zooplankton density was greater after the flood (4174/m³) than before (2733/m³), but the increase may have been an artifact of normal seasonal cycles in the Colorado River and/or the upstream reservoir (Lake Powell). Copyright © 2000 John Wiley & Sons, Ltd.     

Desiccation and recolonization of phytobenthos in a regulated desert river: Colorado River at Lees Ferry,Arizona, USA

We tested the recolonization of the phytobenthic community in the tailwaters of Glen Canyon Dam following long- and short-term experimentally induced desiccation. The response of Cladophora glomerata, Oscillatoria spp., miscellaneous phytobenthos species and periphyton was studied over 18 weeks using three treatments: (1) undisturbed control cobbles from the submerged zone; (2) cobbles desiccated and replaced into the submerged zone; and (3) cobbles desiccated and replaced into the varial zone. Periphyton density and compositional response resulting from these treatments were also examined. Desiccation treatments were significantly different in biomass from controls throughout the study. The biomass of desiccated and replaced river cobbles averaged <30% of the controls for C. glomerata and periphyton during the 18-week recolonization period. In contrast, the biomass of the control Oscillatoria and miscellaneous phytobenthos species averaged only 3 and 50% of that in the desiccation treatments, respectively. Cladophora, the dominant alga, comprised 77% of the phytobenthic biomass. A significant positive relationship between discharge, Cladophora and periphyton biomass was present in all treatments, while there was a negative relationship with discharge for Oscillatoria and miscellaneous phytobenthos species. There was a significant inverse correlation, as well as a pattern of separate biomass dominance, between C. glomerata and Oscillatoria. Cladophora was the dominant phytobenthos species on cobbles below the baseflow and Oscillatoria was dominant on cobbles in the varial zone. In general, the Cladophora biomass decreased under intermittent drying conditions, while Oscillatoria declined under permanently wet conditions. Diatom composition was not significantly different between treatments; however, their density was lower on desiccated cobbles. Diatom density on desiccated cobbles in the submerged and varial zones averaged 69 and 42% of that of the controls, respectively. Recovery and maintenance of benthic resources are hindered by fluctuating flow regimes driven by electricity and irrigation requirements. Repeated desiccation of the phytobenthos has major effects on the bottom-up interactions in the Colorado River ecosystem. © 1998 John Wiley & Sons, Ltd.     

Application of wavelet analysis for monitoring the hydrologic effects of dam operation: Glen Canyon Dam and the Colorado River at Lees Ferry,Arizona

Wavelet analysis is a powerful tool with which to analyse the hydrologic effects of dam construction and operation on river systems. Using continuous records of instantaneous discharge from the Lees Ferry gauging station and records of daily mean discharge from upstream tributaries, we conducted wavelet analyses of the hydrologic structure of the Colorado River in Grand Canyon. The wavelet power spectrum (WPS) of daily mean discharge provided a highly compressed and integrative picture of the post‐dam elimination of pronounced annual and sub‐annual flow features. The WPS of the continuous record showed the influence of diurnal and weekly power generation cycles, shifts in discharge management, and the 1996 experimental flood in the post‐dam period. Normalization of the WPS by local wavelet spectra revealed the fine structure of modulation in discharge scale and amplitude and provides an extremely efficient tool with which to assess the relationships among hydrologic cycles and ecological and geomorphic systems. We extended our analysis to sections of the Snake River and showed how wavelet analysis can be used as a data mining technique. The wavelet approach is an especially promising tool with which to assess dam operation in less well‐studied regions and to evaluate management attempts to reconstruct desired flow characteristics. Copyright © 2005 John Wiley & Sons, Ltd.     

Flood frequency and routing processes at a confluence of the middle Yellow River in China

Floods cause environmental hazards and influence on socio‐economic activities. In this study, we evaluated the historic flood frequency at a confluence in the middle Yellow River, China. A non‐parametric, multivariate, empirical, orthogonal function matrix model, which consists of time correlation coefficients of flood discharge at different gauge stations and flood events was used for the analysis of flood frequency. The model addresses the characteristics of confluent floods such as frequency and the probability in multiple tributary rivers. Flood frequency analysis is often coupled with studies of hydrological routing processes that reduce the flood capacity of the rivers. Flood routing to the confluence were simulated using kinematic wave theory. Results of this flood frequency analysis showed that flooding frequency has intensified in the past 500 years, especially during the 19th century. Flooding in streams above the confluence was more frequent than in streams below the confluence. Over the last 2000 years, concurrent flooding in multiple tributary rivers accounted for 67.5% of the total flooding in the middle Yellow River. Simulation of flood routing processes shows that the decreased flooding capacity and elevated river bed of the shrunken main channel leads to an increased flood wave propagation time (24–52.3 h) in the study area after 1995. The model indicates that human activities, such as constructions of the Sanmenxia Dam, have changed flood routing boundary conditions and have contributed to the increased flood frequency at the confluence. Copyright © 2007 John Wiley & Sons, Ltd.     

Modelling effects of discharge on habitat quality and dispersal of juvenile humpback chub (Gila cypha) in the Colorado River,Grand Canyon

A two‐dimensional hydrodynamic model was applied to seven study reaches in the Colorado River within Grand Canyon to examine how operation of Glen Canyon Dam has affected availability of suitable shoreline habitat and dispersal of juvenile humpback chub (Gila cypha). Suitable shoreline habitat typically declined with increasing discharges above 226–425 m³/ s, although the response varied among modelled reaches and was strongly dependent on local morphology. The area of suitable shoreline habitat over cover types that are preferred by juvenile humpback chub, however, stayed constant, and in some reaches, actually increased with discharge. In general, changes in discharge caused by impoundment tended to decrease availability of suitable shoreline habitat from September to February, but increased habitat availability in spring (May–June). Hourly variation in discharge from Glen Canyon Dam substantially reduced the amount of persistent shoreline habitat at all reaches. Changes in suitable shoreline habitat with discharge were shown to potentially bias historical catch per unit effort indices of native fish abundance up to fourfold. Physical retention of randomly placed particles simulating the movement of juvenile humpback chub in the study reaches tended to decline with increasing discharge, but the pattern varied considerably due to differences in the local morphology among reaches and the type of swimming behaviour modelled. Implications of these results to current hypotheses about the effects of Glen Canyon Dam on juvenile humpback chub survival in the mainstem Colorado River are discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

Rodent use of anthropogenic and ‘natural’ desert riparian habitat,lower Colorado River,Arizona

The role of native trees, Fremont cottonwood (Populus fremontii) and Goodding willow (Salix gooddingii), in structuring the riparian small mammal assemblage on rivers in the American desert southwest is unclear. It is unknown, for example, whether these trees directly or indirectly provide the food or shelter necessary for the presence of any species. Because of the rapid and widespread decline of gallery forest, due in part to river regulation, the retention of remnant stands and replacement of lost stands are major regional conservation issues. To elucidate small mammal–forest linkages, we compared patterns of macrohabitat use among terrestrial small mammals at two rehabilitated and one unmanipulated alluvial floodplain site along the highly regulated lower Colorado River. We also compared current patterns to the Colorado River faunal associations Joseph Grinnell documented in 1910, prior to significant flow regulation. We used grid‐based, capture‐mark‐recapture techniques at two revegetation sites, each a mosaic of six distinct macrohabitats, including planted cottonwood/willow, to associate species with specific macrohabitats. We also trapped a ‘reference’ grid containing naturally regenerating cottonwood and willow at a site on the lower Bill Williams River floodplain. Despite very poor development of cottonwood plantings at one of the revegetated sites, each supported at least nine species and harbored all seven species that Grinnell associated with areas flooded nearly every year. The set of species Grinnell associated with cottonwood/willow stands (Peromyscus maniculatus, Reithrodontomys megalotis, and Sigmodon arizonae) was trapped at both revegetation sites but entirely absent at the reference site. The Bill Williams site may be inaccessible to Sigmodon, but the absence of the other two species is probably a consequence of differences in floodplain structure and functioning among the study sites as well as between the Bill Williams site and historic Colorado River riparian areas. Our data suggest the richness of the native lower Colorado River riparian small mammal assemblage is unrelated to the presence or absence of cottonwood/willow trees, but does depend in part upon the presence or absence of dense herbaceous vegetation. Resource managers attempting to rehabilitate degraded desert riverine ecosystems need to consider understory as well as overstory plant species in revegetation efforts. Copyright © 1999 John Wiley & Sons, Ltd.     

水文监测创新在2016年长江洪水测报中的作用

2016年,长江中下游发生了区域性大洪水。为保证洪水预报的水文资料需求,长江委水文局通过建立的由水文监测管理体系、水文监测服务体系、水文监测技术支撑体系、水文监测质量保障体系等四大部分组成的水文监测体系创新与关键技术,以“巡测优先、驻巡结合、测报自动、应急补充”的新型水文监测模式,大大提升了防洪监测的能力和水平。与往次防洪监测比较,在应对2016年的大洪水的过程中,长江水文测验的新型模式带来了测洪能力、技术水平、准确度、时效性的系统性提升,其中,流量测验时间缩短了73%~83%,水情信息到报率和准确率达到99.95%,远远高于国家标准。     

Regulation leads to increases in riparian vegetation,but not direct allochthonous inputs,along the Colorado River in Grand Canyon,Arizona

Dams and associated river regulation have led to the expansion of riparian vegetation, especially nonnative species, along downstream ecosystems. Nonnative saltcedar is one of the dominant riparian plants along virtually every major river system in the arid western United States, but allochthonous inputs have never been quantified along a segment of a large river that is dominated by saltcedar. We developed a novel method for estimating direct allochthonous inputs along the 387 km‐long reach of the Colorado River downstream of Glen Canyon Dam that utilized a GIS vegetation map developed from aerial photographs, empirical and literature‐derived litter production data for the dominant vegetation types, and virtual shorelines of annual peak discharge (566 m³ s^?1 stage elevation). Using this method, we estimate that direct allochthonous inputs from riparian vegetation for the entire reach studied total 186 metric tons year^?1, which represents mean inputs of 470 gAFDM m^?1 year^?1 of shoreline or 5.17 gAFDM m^?2 year^?1 of river surface. These values are comparable to allochthonous inputs for other large rivers and systems that also have sparse riparian vegetation. Nonnative saltcedar represents a significant component of annual allochthonous inputs (36% of total direct inputs) in the Colorado River. We also estimated direct allochthonous inputs for 46.8 km of the Colorado River prior to closure of Glen Canyon Dam using a vegetation map that was developed from historical photographs. Regulation has led to significant increases in riparian vegetation (270–319% increase in cover, depending on stage elevation), but annual allochthonous inputs appear unaffected by regulation because of the lower flood peaks on the post‐dam river. Published in 2010 by John Wiley & Sons, Ltd.     

淮河蚌埠以下河道疏浚对降低洪水位的可行性及长效性研究

目前淮河中游洪涝灾害仍然严重,为了减轻灾害损失,迫切需要找到更加有效的治理措施。疏浚虽然是一种常用河道治理措施,可以理顺河势,降低洪水位,但是由于担心疏浚后回淤,效果不能维持,一直没有作为主要措施在淮河治理中使用。为此,首先从研究淮河中游河道演变规律出发,量化第二造床流量,揭示第二造床流量与平滩流量关系的机理,探寻淮河治理的新方法,为采用河道大规模疏浚来降低洪水位提供理论依据。然后采用非均匀不平衡输沙数学模型就上段疏浚、下段疏浚以及全河段疏浚对降低淮河干流洪水位的效果以及长期维持情况进行了计算研究。研究结果表明,长距离河道疏浚不仅能够大幅度地降低干流河道的洪水位,而且不会发生明显回淤,疏浚效果可以长期保留,为淮河的洪涝灾害治理提供了新思路和新措施。     

Angler Harvest,Hatchery Return,and Tributary Stray Rates of Recycled Adult Summer Steelhead Oncorhynchus mykiss in the Cowlitz River,Washington

Hatchery ‘recycling’ programs have been used to increase angling opportunities by re‐releasing fish into a river after they returned to a hatchery or fish trap. Recycling is intended to increase opportunities for fishermen, but this strategy could affect wild fish populations if some recycled fish remain in the river and interact with wild fish populations. To quantify hatchery return and angler harvest rates of recycled steelhead, we conducted a 2‐year study on the Cowlitz River, Washington. A total of 1051 steelhead were recycled, including 218 fish that were radio‐tagged. Fates of recycled steelhead were similar between years: 48.4% returned to the hatchery, 19.2% were reported captured by anglers, and 32.4% remained in the river. A multistate model quantified the effects of covariates on hatchery return and angler harvest rates, which were positively affected by river discharge and negatively affected by time since release. However, hatchery return rates increased and angler harvest rates decreased during periods of increasing discharge. A total of 21.1% (46 fish) of the radio‐tagged steelhead failed to return to the hatchery or be reported by anglers, but nearly half of those fish (20 fish) appeared to be harvested and not reported. The remaining tagged fish (11.9% of the radio‐tagged population) were monitored into the spawning period, but only five fish (2.3% of the radio‐tagged population) entered tributaries where wild steelhead spawning occurs. Future research focused on straying behaviour, and spawning success of recycled steelhead may further advance the understanding of the effects of recycling as a management strategy. Copyright © 2016 John Wiley & Sons, Ltd.     

有关黄河下游流量沿程增大的各种观点评述

对包括黄河下游“04．8”洪水在内的各场高含沙洪水异常现象的观点做了系统总结,认为已有的各种观点可以分为（1）局部沙坝和浆河、阵流类;（2）主槽冲刷类;（3）“挤压”和“积聚”类。分析总结各种观点,对于认识2004年“04．8”洪水的形成机理具有重要意义。     

黄河下游洪水期输沙用水量与河道泥沙冲淤分析

本文从１９７３－１９９０年，共选取１０６个洪峰时段。分析了洪水期，三门峡出库不同含沙量级中，输沙用水量与黄河下游河道泥沙冲调整的关系。所得成果对三门峡水库今后的运用，以及下游河道减淤均有参考价值。     

黄河洪水演进洪峰增值现象及其机理

2004～2006年小浪底水库异重流排沙期间,在小浪底～花园口区间出现了下断面的洪峰流量明显大于上断面洪峰流量的洪峰增值现象.本文详细描述了洪峰增值现象发生过程和主要特征.通过对黄河小浪底水库及其下游河道实测资料的研究和水力学理论分析认为,洪水发生洪峰增值的主要原因是河道糙率的大幅度减小.河道糙率与水流含沙量、悬沙级配、床沙级配、床沙床面形态、河道断面形态及河岸周界情况等因素有关.在小浪底水库异重流排沙之前有清水下泄过程,使河道床沙粗化,糙率大幅度增大,当异重流出库后,高浓度细颗粒泥沙使水流黏性增加、紊动削弱,河床被极细沙填附,河道糙率大幅度减小,导致后续水流流速加大,并赶上前方水流,发生洪峰叠加.     

黄河内蒙古段开河流量预测

封冻河段开河时,冰、水情变化剧烈,预报难度大、精度低。马斯京根法及其衍生方法在推算明流条件下的流量演进方面取得了很大成功,但如何反映凌汛期流量演进特点还需进一步研究。以黄河内蒙古河段为例,类比有支流的河道洪水进行演算,并考虑流量传播时间,将区间的槽蓄水增量加入计算,采用改进的马斯京根法,推求完全开河时的凌峰流量。采用均方根误差、平均绝对百分比误差作为预测结果的评价指标,与往年实测流量相比较,演算流量的平均绝对百分比误差在10.29%以内。结果表明,此方法应用于凌汛期开河流量演进具有较好的预测效果,通过冰凌洪水的特点判别洪水类型,揭示了凌汛期开河流量的突变主要是由冰坝洪水造成的。研究结果可为河流开河的流量预报和防凌减灾提供参考思路。     

黄河下游河道输沙泄洪机理、能力及治理前景

经过我国几代人对黄河泥沙输移的研究和实践,认识已有重大突破。围绕黄河高含沙水流运动规律及应用前景这个中心,研究了高,低含沙水流运动规律多方面问题,为多沙河流防洪规划提出了新的指导原则。其中黄河下游可以利用高含沙洪水输沙入海,窄深河道洪水的非恒定性输沙泄洪机理是新的治黄主张的理论基础。     

山东黄河、东平湖排蓄洪能力分析与建议

黄河自2002年以来,已连续5年进行了调水调沙,黄河下游河道得到明显冲刷,河道行洪能力有了较大提高。东平湖也加大了治理力度,大大改善了防洪工程的薄弱环节,排蓄洪能力有了明显提高。但山东省黄河的防洪形势依然严峻。通过对山东黄河、东平湖排洪能力的分析研究,提出了山东黄河、东平湖滞洪区的防洪措施。     

山东黄河泥沙特性及沙峰运移规律

在论述黄河山东段泥沙时空分布及不同时期泥沙粒径变化的基础上，重点分析了洪水过程中沙峰的运移规律：山东河段沙峰的削峰率为沿程向下游递减，且与沙峰的大小成正比；沙峰沿程输沙量变化，高村至艾山段沿程减小。艾山至利津段基本稳定。沙峰运移过程中与相应洪峰发生的时间一般是不同步的，高村至艾山段，沙峰常超前于洪峰，而艾山至利津段，沙峰常滞后峰；不漫滩洪水，沙峰一般滞后于洪峰，漫滩洪水，沙峰一般超前于洪峰。     

近60年渭河下游自然裁弯成因分析

渭河下游是典型的弯曲型河道,过去60年频繁地发生自然裁弯,其触发原因、形成过程和演变规律缺少深入的研究。渭河下游的裁弯是河湾横向演变到一定阶段后在汛期洪水冲刷作用下发生临界突变,直接影响河道平面形态、上下游河床冲淤和局部河段的防洪安全。基于原型观测、水沙数据(1960-2013)和遥感影像(1990-2015),分析了渭河下游裁弯事件的水沙条件、影响因素和裁弯时空演变过程及其原因。渭河下游发生的18次裁弯的主要原因是受三门峡建库后渭河下游边界条件的改变,包括潼关侵蚀基准面淤积抬高,凸岸边滩及内侧平原缺少粘性成分,抗冲性差,同时也受渭河下游来水来沙条件的变化及其高含沙洪水的影响。     

黄河山东段河床糙率分析

在洪水演算、河道冲淤计算中糙率起重要作用。本文利用历年实测资料，对黄河山东段主要断面的滩、槽及全断面糙率值进行了对比，分析了不同类型河段糙率特性以及糙率与有关水沙因素之间的关系。