Serial discontinuities in a Rocky mountain river. II. Distribution and abundance of trichoptera

River regulation in the headwaters and middle reaches of the Gunnison River, Colorado, significantly altered distributions and abundances of Trichoptera fauna. Twenty-five species were collected from mainstream samples, with the greatest species richness occurring at an unregulated, rhithron segment above the central reach dams. At sites immediately below the three hypolimnial-release dams and a reregulation dam, species richness was reduced 35–90 per cent and abundance > 95 per cent. Net-spinning caddisflies were the dominant trichopterans at unregulated sites; Arctopsyche grandis in the upper reaches (218 organisms, 586 mg dry mass m^?2) and Hydropsyche cockerelli, H. occidentalis and Cheumatopsyche pettiti in the lower river (9041 total organisms, 6621 mg m^?2), downstream from the last dam. The observed distributional pattern of low trichopteran densities in dam tailwaters and high hydropsychid densities at sites 60–80 km below the central reach dams is a classic expression of continuum resets and adjustments in response to stream regulation as predicted by the Serial Discontinuity Concept.     

Assessing the impacts of stream regulation in the flathead river Basin,Montana, U.S.A. I. Simulation modelling of system water balance

A Fortran-based simulation model was written to predict water movement into and out of Flathead Lake. Since tributaries, the lake proper and downstream flows were either freeflowing or regulated by hydroelectric dams, it was necessary for the model to adjust simulated, regulated flows to account for predicted natural flows. Empirical input to the model consisted of daily discharge data or statistical summaries of data sets for an 80+ year period of record for gauging sites on major tributaries, the lake and its outlet river. The model produces graphical output of empirical observations or simulates lake levels and riverine flows on the basis of any selected period of the record. The model was successfully used to evaluate the feasibility of various water management scenarios to enhance or protect fish and wildlife and also permit various hydropower production quotas.     

Discontinuities in the distribution of invertebrates in impounded south island rivers,New Zealand

The invertebrate fauna of 10 river systems, five with impoundments and five without, were sampled. No significant difference was found either in taxonomic richness or invertebrate densities between impounded and unimpounded sites at similar positions along river continua. However, plecopteran species richness was significantly lower and plecopteran density reduced in post-impoundment sites. Densities of Deleatidium spp. (Ephemeroptera: Leptephlebiidae) were significantly lower at lake outlets compared with other sites. Two species of Zelandobius (Plecoptera: Gripopterygidae) and Eriopterini (Diptera: Tipulidae) snowed distributions apparently curtailed by impoundments, whereas Potamopyrgus antipodarum (Mollusca: Hydrobiidae) had an extended distribution. Margalef's, Menhinick's, Berger-Parker and Shannon indices, total taxa present and plecopteran taxa were plotted against stream order, stream width and distance from the source. Menhinick's and Shannon-Weaver indices produced statistically significant but weak regressions, and discontinuity distances and intensity could not be accurately calculated. The usefulness of diversity indices as a measure of the magnitude of impoundment effects in the South Island seems to be limited.     

Entrainment of riparian gravel and cobbles in an alluvial reach of a regulated canyon river

Many canyon rivers have channels and riparian zones composed of alluvial materials and these reaches, dominated by fluvial processes, are sensitive to alterations in streamflow regime. Prior to reservoir construction in the mid‐1960s, banks and bars in alluvial reaches of the Gunnison River in the Black Canyon National Monument, Colorado, USA, periodically were reworked and cleared of riparian vegetation by mainstem floods. Recent interest in maintaining near‐natural conditions in the Black Canyon using reservoir releases has created a need to estimate sediment‐entraining discharges for a variety of geomorphic surfaces composed of sediment ranging in size from gravel to small boulders. Sediment entrainment potential was studied at eight cross‐sections in an alluvial reach of the Gunnison River in the Black Canyon in 1994 and 1995. A one‐dimensional water‐surface profile model was used to estimate water‐surface elevations, flow depths, and hydraulic conditions on selected alluvial surfaces for discharges ranging from 57 to 570 m³/s. Onsite observations before and after a flood of 270 m³/s confirmed sediment entrainment on several surfaces inundated by the flood. Selective entrainment of all but the largest particle sizes on the surface occurred at some locations. Physical evidence of sediment entrainment, or absence of sediment entrainment, on inundated surfaces generally was consistent with critical shear stresses estimated with a dimensionless critical shear stress of 0.030. Sediment‐entrainment potential over a range of discharges was summarized by the ratio of the local boundary shear stress to the critical shear stress for d₅₀, given hydraulic geometry and sediment‐size characteristics. Differing entrainment potential for similar geomorphic surfaces indicates that estimation of minimum streamflow requirements based on sediment mobility is site‐specific and that there is no unique streamflow that will initiate movement of d₅₀ at every geomorphically similar location in the Black Canyon. Copyright © 2000 John Wiley & Sons, Ltd.     

Effects of stream and lake regulation on reproductive success of kokanee in the flathead river system,Montana, U.S.A

Kokanee (Oncorhynchus nerka) provided an important recreational fishery in the Flathead River-Lake system (Columbia River Basin, U.S.A.-Canada) until the late 1970s when populations declined dramatically. The declines coincided with peaking river discharge from Hungry Horse Dam during the autumn spawning period and an increase in the duration of lake drawdown caused by the operation of Kerr Dam on the outlet of Flathead Lake. Redds of both river and lakeshore spawners were, therefore, dewatered in winter, causing high freezing and desiccation mortality of eggs during the incubation period. It appeared that growth rates of kokanee were density dependent. Female kokanee from strong year classes (i.e., those produced during years of favourable water levels and flow conditions during the incubation period) were smaller than those from weak year classes when unfavourable conditions for incubation prevailed. A highly significant relationship (r² = 0.929, p < 0.001) was demonstrated between female kokanee spawner length, river gauge heights, and lake levels during years which produced each year class. The close fit of the relationship was further validated by the strong correlation (r = 0.964) between actual kokanee lengths and predicted lengths. Other factors which could have influenced kokanee year class strength include hatchery plants of kokanee fry, harvest of kokanee by anglers, variations in the carrying capacity of Flathead Lake, and natural fluctuations in egg and fry mortality.     

Distribution,abundance and development of trichoptera larvae in the river north tyne following the commencement of hydroelectric power generation

Following turbine installation at the Kielder dam, the River North Tyne downstream is now characterized by large daily fluctuations in flow. A survey of trichopteran populations (Hydropsychidae, Rhyacophilidae and Polycentropodidae) was carried out to assess the impact of hydroelectric power generation (Phase III), and to compare the results with similar pre-impoundment (Phase I) and post-impoundment (Phase II) surveys. Benthic samples were collected quarterly upstream from the reservoir and at four stations downstream. Although the same three species (Hydropsyche siltalai, Hydropsyche pellucidula and Rhyacophila dorsalis) continue to dominate, there were some notable differences found between sampling sites. Species diversity was drastically reduced at the station nearest the dam, where 99% of all larvae collected were R. dorsalis. At the next station 5 km downstream, where previously H. siltalai had been dominant, R. dorsalis now constitutes 65% of collections. At the two stations farthest away from the dam the former prevalence of H. siltalai was re-established. It is suggested that the unstable, high flows at the reservoir outlet are likely to favour the predatory R. dorsalis rather than the filter feeding hydropsychids whose nets may be susceptible to damage. Upstream from Kielder Water, R. dorsalis was prominent in benthic samples, whereas numbers of H. siltalai were 10 times lower than in Phase II and 60 times lower than in Phase I. The extent to which such upstream changes may be related to altered patterns of community structure below the dam is not known, but these observations may warrant a more cautious approach when considering upstream areas as unaffected ‘reference sites’. Instar analyses suggested that winter-warm, summer-cool discharges were continuing to modify larval growth rates, as noted in Phase II. The results of this study are discussed in relation to present trends in water resource development in Britain, especially with regard to future needs in monitoring and research.     

淳安县山区河道整治规划与设计探讨

淳安县位于浙西山区,地形地质复杂,源短坡陡,洪枯变幅大,洪水位高,水土流失严重.大部分城镇、村庄、良田和各种基础设施成点片状分布在溪沟两岸.随着保护对象的增多,洪灾造成的损失也逐年增大.该文结合淳安县几年来河道整治规划方面的经验,对河道整治规划设计的一些问题进行了探讨.     

Stable carbon and nitrogen isotope analysis of seston in a regulated Rocky Mountain river,USA

The δ¹³C and δ¹⁵N of seston, organic matter sources (riparian vegetation, algae, macrophytes, plankton) and an invertebrate detritivore were examined in a regulated Rocky Mountain river (fourth order). The isotopic composition of seston varied among sites and seasons for all size fractions; among-site variation was weakest for ultra-fine particulate organic matter (< 53 μm). Comminution of seston to ultra-fine size partially obscured isotopic differences among sites. Multiple isotope signatures of seston were distinct among sites at different distances from a dam (0.5, 5.3, 8.7 km) and between the river and a third order tributary. Seston (> 53 μm) from 0.5 km below the dam was relatively ¹³C-depleted (?30 to ?28°), reflecting the contribution of reservoir-derived plankton; seston from the site 8.7 km downstream was relatively ¹³C-enriched (?18 to ?23°), reflecting autochthonous inputs. Tributary seston had an intermediate δ¹³C value (?22 to ?26°), reflecting allochthonous inputs (conifer litter) and macrophyte (Elodea) detrital inputs. δ¹⁵N values of seston were generally similar among sites (4–8°) but were more depleted for the tributary (1–4°). Depleted δ¹⁵N values (0–2.5°) for seston from below the dam in late summer corresponded to a blue-green algae bloom in the reservoir. Isotopic shifts of organic matter incubated for 60–90 days in situ were small (< 2°) and varied in direction depending on isotope and litter type. The isotopic composition of stonefly larvae, Pteronarcys californica, varied among sites, and closely matched that of the local seston (especially FPOM), suggesting that with respect to detritus origin, larvae were opportunistic foragers. The origin of organic matter is influenced by flow regulation, resulting in compressed isotopic gradients.     

Fish populations of a small lowland channelized river in England subject to long-term river maintenance and management works

Fish populations in the River Perry, a small lowland channelized river in England, were affected by long-term river maintenance and improvement works. Habitat diversity at two ‘old channelized’ sites was low compared with a downstream ‘partially channelized’ site and an unmodified site, where natural river features such as the pool-riffle pattern were more apparent. The fish community was low in diversity at all sites, with two running-water cyprinids, dace Leuciscus leuciscus (L.) and chub Leuciscus cephalus (L.), being the dominant fish species. Relative species composition varied between sites, with dace predominating at the ‘old channelized’ sites and chub increasingly dominant at the ‘partially channelized’ and unmodified sites. Population density and biomass estimates of dace were similar at all sites, but chub were up three times more abundant at the ‘partially channelized’ and unmodified sites than at the ‘old channelized’ sites. Populations of dace and chub at the ‘old channelized’ sites contained a higher proportion of small fish than populations at the downstream sites, which exhibited a more balanced population structure. The growth rates of both dace and chub varied between sites. Low recaptures of marked dace suggested a highly mobile movement pattern while higher recapture rates of chub, particularly at the ‘partially channelized’ and unmodified sites, seemed to indicate a more sedentary activity pattern. The conclusion of the study is that long-term river maintenance and management works may delay the morphological and biological recovery of lowland channelized rivers.     

高度城镇化地区河网水系生态调控方案

为探究长三角高度城镇化地区河网水系生态调控方案,以秦淮河流域下游地区水系为例,采用生态功能设定法,计算了各河段生态水位和生态流量.通过构建一维水量水质模型,在枯水年非汛期水量调控及截污措施协同驱动下,对水位、流量及污染物浓度的时空分布特征进行多情景数值模拟,并对生态水量保障率及水质改善效果进行评估.结果表明,水位调控措...     

Effects of river discharge on abundance and instantaneous growth of age‐0 carpsuckers in the Oconee River,Georgia, USA

The Oconee River in middle Georgia, U.S.A., has been regulated by the Sinclair Dam since 1953. Since then, the habitat of the lower Oconee River has been altered and the river has become more incised. The altered environmental conditions of the Oconee River may limit the success of various fish populations. Some obligate riverine fishes may be good indicator species for assessing river system integrity because they are intolerant to unfavourable conditions. For example, many sucker species require clean gravel for feeding and reproduction. Further, age‐0 fishes are more vulnerable than adults to flow alterations because of their limited ability to react to such conditions. In this study, we investigated the relationship between abundance and growth of age‐0 carpsuckers to river discharge in the Oconee River. A beach seine was used to collect age‐0 carpsuckers (Carpiodes spp.) from littoral zones of the lower Oconee River from May through July of 1995 to 2001. Regression models were used to assess whether 12 river discharge categories (e.g. peak, low, seasonal flows) influenced age‐0 carpsucker abundance or instantaneous growth. Our analysis indicated that abundance of age‐0 carpsuckers was significantly negatively related to number of days river discharge was >85 m³ s^?1(r² = 0.61, p = 0.04). Estimates of instantaneous growth ranged from 0.10 to 0.90. Instantaneous growth rates were significantly positively related to summer river discharge (r² = 0.95, p <0.01). These results suggest that (1) moderate flows during spawning and rearing are important for producing strong‐year classes of carpsuckers, and (2) river discharge is variable among years, with suitable flows for strong year‐classes of carpsuckers occurring every few years. River management should attempt to regulate river discharge to simulate historic flows typical for the region when possible. Such an approach is best achieved when regional climatic conditions are considered. Published in 2007 by John Wiley & Sons, Ltd.     

河道治理工程水土保持监测方法探讨——以深圳河治理第4期工程为例

江河治理一直是我国生态文明建设的重点,开展河道治理工程的水土保持监测工作是预防其水土流失的重要举措。为提高生产开发建设项目水土保持监测数据的准确性和科学性,以深圳河治理第4期工程为例,探讨了江河治理项目中水土保持监测的内容、方法以及监测体系,并对监测结果进行了讨论。分析结果可为相关江河治理工程水土保持监测项目提供参考和借鉴。     

新情势下黄河口演变与整治研究思路

基于黄河口水沙变异的新情况以及经济发展和生态环境建设的新需求,提出新情势下黄河口演变与整治的研究思路。针对目前研究中需要突破的薄弱环节,瞄准国际河口学领域中的前沿问题,采用多学科交叉和多种研究手段,对黄河口开展创新研究。主要研究:黄河口水沙变异特征,尾闾河道枯萎机制及其演变响应,拦门沙演变响应过程及其反馈影响;河口泥沙通量,最大浑浊带、泥沙异重流形成机理,河口海岸淤进、蚀退及其动力平衡机制;黄河口陆海相互作用的整体数模,河口演变趋势与入海流路使用年限;新情势下黄河口治理对策及水土资源优化配置。     

Effect of mixing patterns and light dose on growth of Anabaena circinalis in a turbid,lowland river

Anabaena circinalis is common in the lower Murray River, Australia, and may compromise water quality due to the release of toxins. The water is turbid and thermal structure may significantly affect light availability. An in situ experiment was designed to represent complete mixing, diurnal stratification and persistent stratification and test the effect on growth of A. circinalis. To represent the mixing treatments, cells were incubated in diffusion chambers that were adjusted to different positions in the water‐column throughout the day. Populations exposed to persistent stratification over six days grew significantly faster than the other treatments at a rate of 0.65 day^?1. However, growth of the diurnally stratified populations was slower than (0.28 day^?1), or similar to (0.40 day^?1) the mixed population (0.40 day^?1). Therefore, the growth of the subpopulations exposed to the euphotic zone was insufficient to counteract the slow growth of the majority that were confined to darkness during the stratified period. A relationship between growth rate (G) and average daily light dose (I) was constructed and growth rate at optimal light dose (G_max), slope of linear section of G–I curve (α), and light dose where lines of G_max and light‐limited portion of G–I curve intersect (I_k) were solved as 0.66 day^?1, 0.12 day^?1 (mol^?1 m^?2 day^?1)^?1 and 5.4 mol m^?2 day^?1, respectively. Using these parameters, a model was developed to predict possible differences in growth between diurnal and mixed populations under varying conditions of vertical light attenuation, mixed depth and incubation time. Copyright © 2003 John Wiley & Sons, Ltd.     

冰期河流弯道冰水动力学行为研究

以黄河什四份子弯道为研究对象,基于2019-2020年度的凌情监测影像及现场试验数据,分析了河流弯道冰水动力学行为特征。结果表明:上宽下窄的河道形态是造成弯道卡冰的主要原因,流凌-封河阶段,弯顶节点工程对水流的顶托作用促进了上游回流区的形成;受弯道离心力作用,河冰聚集于河道凹岸一侧,并在回流区堆积形成冰桥,从而缩小了断面过冰面积,河道逐渐封冻;弯顶下游流速大且来冰量少,形成清沟,主流向河中发展;冰塞堆积于弯顶上游凹岸主河槽内,水流被挤压至凸岸非冰塞区,弯道主流易位;在稳封期,河道冰水动力特征基本不再变化,在解冻开河期,凸岸非冰塞区流速较大,主流区冰盖优先解冻且沿主流输移,回流区冰盖最后消融,河道主流逐渐恢复至畅流阶段,整体呈复归式。     

黄河源区弯曲河流滨河植被与河湾迁移的关系

为了解滨河植被对河湾横向迁移的作用,以及河湾迁移对滨河植被群落分布的影响,对黄河源区兰木错曲弯曲河段崩塌块、凹岸植被生物量和凸岸植被多样性进行现场调查统计,给出了河湾迁移速率的估算方法。结果表明:其迁移速率与凹岸植被生物量呈指数关系;河湾凸岸边滩的泥沙沉积在不同重现期洪水作用下,形成不同的植被条带,对应于5种典型的植被群落;河湾的横向迁移对滨河植被生态系统具有调节作用,形成一种牧草先增多后减少再增多的草场更新机制,原生演替不断循环进行,以维持草场的长期可持续放牧功能。     

The Sanaga discharge at the Edea Catchment outlet (Cameroon): An example of hydrologic responses of a tropical rain‐fed river system to changes in precipitation and groundwater inputs and to flow regulation

The Sanaga River is one of Sub‐Saharan Africa's largest and greatly regulated rivers. Available flow data for this hydrosystem largely cover the pre‐ and post‐regulation periods. From comparisons between unregulated (hypothetical) and observed scenarios, it has been possible to separate and to quantify hydro‐climatic (groundwater + rainfall) change effects from anthropogenic impacts (especially dam‐related alterations). To appreciate shifts in the river regime, discontinuity detection tests and the IHA model were applied to discharge data series reflecting average and extreme flow conditions, respectively. Results obtained principally from the Hubert segmentation method reveal that a major discontinuity occurred in 1970–1971 separating a surplus phase between 1945–1946 and 1969–1970, and a deficient and much contrasted one, from 1971/1972. This implies that the Sanaga catchment is dominantly affected by hydro‐climatic changes. However, wide land cover/land use changes experienced here since 1988 have resulted in an increase in surface runoff. Additional quickflows linked to these changes may have partly compensated for the substantial decline in the dry season rainfall and groundwater inputs observed from this date. Although at the monthly scale, dam‐related impacts on average flows increase with stage of regulation, the seasonal variability of the river regime remains generally unaffected. A comparison of the IHA statistics, calculated from unregulated and observed streamflow data, show that hydrologic shifts occurring in maximum and minimum discharges are mostly significant from 1971/1972 and are mainly due to the action of dams. Minimum flows appear, however, widely impacted, thus reflecting the prime objective assigned to the existing reservoirs, constructed to supplement flows for hydroelectricity production during the dry season. Copyright © 2010 John Wiley & Sons, Ltd.     

控水闸对通江湖泊水位及面积变化的影响分析——以升金湖为例

根据近3年来升金湖姜坝、黄湓闸闸上和闸下以及安庆水位站实测资料,探究控水闸对通江型湖泊水位及面积的影响。结果表明:受黄湓闸控水作用的影响,姜坝站水位在枯水期维持在11 m左右,远高于其他水位站,丰水期维持在15 m的警戒水位以内,与闸上水位波动一致,在特大洪水时河湖连通,水位不受控水闸影响;闸上水位在枯水期介于姜坝站和闸下水位之间,在水位高于11 m的平水期和丰水期,水位波动基本与姜坝站水位一致;闸下水位在枯水期介于闸上和安庆站水位之间,在平水期和丰水期与长江水位波动一致;估算并比较在河湖自然连通和黄湓闸控水状态下升金湖月均面积的变化,控水闸导致枯水期湖泊面积扩大,丰水期湖泊面积缩小。     

Distribution of Contaminants in Clams and Sediments from the Huron-Erie Corridor. I–PCBs and Octachlorostyrene

Samples of surficial sediments and the clam species Lampsilis radiata siliquoidea were collected from 102 sites covering all of Lake St. Clair and the Canadian shoreline of the St. Clair and Detroit rivers. The distribution patterns of both octachlorostyrene (OCS) and PCBs were mapped throughout this area. The mean level of PCBs in sediments of 3.9 μg kg^?1 (Aroclor 1254) was much lower than values for “total PCBs” reported in studies carried out in the early 1970s. This reduction does not appear to reflect a real decrease in PCB levels in the environment, but rather changes that have been made in sampling procedures and analytical techniques. Highest levels of PCBs in both sample types were found along the western shore of Lake St. Clair. Mean levels of OCS in whole clam tissue and surficial sediment (0–10 cm) were 43.0 and 5.1 μg kg^?1, respectively. The distribution pattern of OCS in the Huron-Erie corridor in both clams and sediments suggests that the primary source is in the St. Clair River. The mean chemical concentration factor was 59 for OCS, indicating considerable bioaccumulation in the biota of Huron-Erie corridor.     

Age,growth and non‐flood recruitment of two potamodromous fishes in a large semi‐arid/temperate river system

Golden perch Macquaria ambigua (Percichthyidae) and silver perch Bidyanus bidyanus (Terapontidae) are two potamodromous fish species of the Murray‐Darling river system in southeastern Australia. Ageing of these species using thin sections of the sagittal otoliths and validation with known‐age fish revealed: they live for over 26 years; male and female silver perch reach maturity at 3 and 5 years respectively; male and female golden perch reach maturity at 2 and 4 years respectively; both species exhibit sexual dimorphism with larger females; and growth varies (L_∞ silver perch 331–397 mm, golden perch 354–502 mm) among interconnected river systems. Longevity and opportunistic growth are characteristics that are well suited to the semi‐arid and temperate hydrology of this river system. A flood‐recruitment model for these two species, consistent with the ‘flood‐pulse concept’, has previously been assumed to be the main mechanism of recruitment. The model appeared appropriate for this large, low‐gradient river system with productive floodplains. However, in the middle reaches of the Murray River we found that golden perch recruitment was strong in non‐flood years and poor in flood years, and silver perch recruited in all years. These data do not preclude golden perch recruiting during floods as well, because downstream larval drift may have resulted in strong year‐classes being swept downstream of the sampling area during high flows. However, the recruitment models for these species need to be re‐evaluated to include within‐channel flows. Importantly, these flows can be manipulated by river regulation, unlike large floods, and therefore there is potential to enhance recruitment. Copyright © 2003 John Wiley & Sons, Ltd.