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1.
Svein Jakob Saltveit 《河流研究与利用》1990,5(4):295-303
The lowermost 20 km of the River Surna, northwestern Norway receives cool water during summer from a hypolimnetic release mountain reservoir. In this part of the river, yearlings of both Atlantic salmon and brown trout are significantly smaller compared with those in the upper section of the river, which is unaffected by the cold water release. The slower growth below the power station causes both Atlantic salmon and anadromous brown trout to smoltify one year later compared with fish in the upper section of the river. This leads to higher mortality and therefore lower production of both adult salmon and trout. 相似文献
2.
Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river. 相似文献
3.
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. 相似文献
4.
George A. Swan 《河流研究与利用》1989,4(4):355-370
In 1986 research divers surveyed and mapped deep-water spawning redds of fall chinook salmon (Oncorhynchus tshawytscha) in selected sites within an impounded segment of the main-stem Columbia River, Washington State, U.S.A. In velocities over 3m s?1 and depths up to 11 m, two divers riding a manoeuvrable sled made cross-current transects communicating observations of substrate materials and deep-water spawning sites. Surface personnel tracked the position of the sled with a laser locating system that logged the information into data storage. Subsequently, the computerized data were translated into overlaying maps depicting location of redds, substrate materials, and depth contours. Deep-water spawning (>3m) occurred at most survey sites in velocities between 0.6 and 0.8m s?1. The average depth of spawning was 6.5 m, and the maximum was 9.1 m-deeper than the depth redds can normally be detected by aerial observation (3–4 m). Deep-water spawning ranged from none to substantial in areas of near identical physical characteristics. A method for estimating abundance and density of deep-water redds, based upon the data collected with this mapping technique, is presented. This study combined with current limited information concerning deep-water spawning suggests that up to 80 per cent of the escapement of fall chinook salmon in this reach may spawn in deep water. 相似文献
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Riverine trichopteran (caddisfly) communities were sampled seasonally at eight locations over a two-year period to determine if a multiple-level release hydroelectric dam created a faunal discontinuity along the longitudinal profile of the Clearwater River in northern Idaho. The confluence of a non-regulated river with a regulated reach provided an unusual opportunity to examine the recovery of community parameters in a semi-regulated river. A marked discontinuity in the caddisfly community occurred in the regulated reach immediately below the dam, reflected by greatly reduced diversity and abundance values, and by shifts in functional relationships. These faunal changes are primarily attributable to the modified temperature, discharge, and food resources induced by river regulation. The non-regulated river exerted a major mitigative effect on the trichopteran fauna below its confluence with the regulated reach, despite maintenance of semi-regulated conditions. Trichopteran community parameters approached near normal levels concomitant with partial reductions in flow fluctuations, and partial recovery of temperature and food resources. In addition, the non-regulated river provided an important colonization pathway for riverine species to enter the semi-regulated lower reaches. 相似文献
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安庆河段为长江中下游一类重点整治河段 ,安庆江堤为I级堤防 ,分析了安庆河段的河势演变情况和拟建的安庆长江公路大桥对水位、流速、分流比及河势的影响 ,综合河演分析及试验成果 ,桥位附近的流向、流速分布规律基本未变 ,且变幅较小 ,汊道分流比变化亦较小 ,大桥建成后对安庆段的河势不会产生明显影响。但是 ,大桥对上游水位有一定的壅高值 ;各频率流量下近岸流速有所增加 ,同时近岸副墩和主墩附近的局部冲刷现象会影响到近岸岸坡的稳定 ,在此基础上提出了防护工程的必要性和防护范围。 相似文献
9.
P. J. Boon 《河流研究与利用》1987,1(2):95-109
Impounding the North Tyne has reduced the frequency of high peak flows, eliminated periods of extremely low flow and modified the temperature regime downstream from the Kielder dam. This paper compares the results of a recent survey of North Tyne trichopteran populations (Hydropsychidae, Rhyacophilidae, and Polycentropodidae) with those from previously published work in order to assess the impact of river regulation. Benthic samples were collected monthly upstream and downstream from the reservoir. Although nine out of the ten species found previously were also collected in the post-impoundment survey, species diversity was reduced downstream from the dam. This was mainly the result of disproportionate increases in Hydropsyche siltalai population densities which were up to 9.6 times greater than before; flow regulation and its effect on substrate stability may be largely responsible for this. Rhyacophila dorsalis also increased in abundance downstream probably in response to the altered flow regime. In contrast Hydropsyche pellucidula constituted a smaller proportion in downstream samples with population densities in places only a fifth of pre-impoundment levels. The differential effect of regulation on these two hydropsychid species may be explained by their different flow velocity preferences. Upstream from the reservoir, standing crops were frequently lower than before possibly due to the disruption of colonization cycles. Growth rates of H. siltalai, H. pellucidula, and R. dorsalis below the dam were accelerated at certain times of the year and retarded at others, apparently correlated with the winter-warm, summer-cool discharges from the reservoir. Since this study was completed Kielder Water has now begun generating hydroelectricity, and the flow regime downstream has consequently changed to one of regular, daily fluctuations. It is suggested that any adverse effects of this on the benthic community are likely to be offset by the continued benefit of eliminating flash floods with high peak flows. 相似文献
10.
Impoundment and diversion of watercourses for power production and water supply can have profound effects on the mayfly fauna. To explain such effects a species-specific approach is adopted on account of differing habitat requirements and life histories in the order and even within genera. Environmental conditions such as discharge and flow patterns, temperature, food availability, and predation may be changed. This leads to changes in the density and species composition of the mayfly community, especially when there is a hypolimnion drain from reservoirs. Temperature changes below such reservoirs may remove obligatory life cycle thresholds. Prolonged periods of low discharge lead to the dominance of genera, such as Paraleptophlebia, Choroterpes, Siphlonurus, and Pseudocloen, typical of slow-flowing and lentic habitats. The life cycle plasticity and opportunism shown by Baetis rhodani in Europe and B. tricaudatus in North America have undoubtedly contributed to their success in regulated rivers. The life history characteristics of Tricorythodes are also advantageous below dams. The increased growth of periphyton and mosses below many dams favour certain Ephemerellidae, but restrict or eliminate many Heptageniidae. In order to survive adverse conditions, flexible life cycles or a short period of rapid nymphal growth coupled with a long period of egg development, are advantageous. 相似文献
11.
The regulation of the Ebro River in the 1960s has changed the discharge pattern: spring floods have been reduced and, as the reservoirs are used for hydroelectrical purposes, discharge varies daily. The last 50 km of the river have been studied for two years (1986 and 1987). Our main purpose was to establish the particulate organic and inorganic transport of the river and its seasonal changes. Particulate material was sampled in surface and deep waters. Water conductivity ranges between 0.9 and 53 mS, and anoxia is common in summer situations. Particulate C ranges between 1 and 3 mg l?1 with higher values in summer; particulate N is very similar along the year with values between 0.1 and 0.5 mg l?1. Effects of regulation seem to be important in supplying very high nutrient content to algae and producing a high biomass and production in the lower part of the river, especially in summer. Diatoms and Chlorophyta are the most abundant groups. Phosphorus is higher than 5 μmol l?1, with lower values in summer. Most of particulate material is very fine (between 0.45 and 50 μm). The high biomass also explains the presence of abundant filter-feeders, such as Hydropsyche and Ephoron virgo. In some parts, where light reaches the bottom, stones and boulders are covered by Cladophora. In this case, grazers such as the gastropods Melanopsis and Theodoxus are abundant. 相似文献
12.
Changes in the faunal composition and density of communities of chironomid larvae were studied over a four year period in a newly regulated stream and compared with those in an adjacent unregulated stream, with a view to examining “stability” in contrasting environments. A total of 68 chironomid taxa were recorded from all sites. Faunal diversity was lowest closest to the dam and highest in the unregulated site. Within the study period values of H were highest in the fourth year of study (five years after dam closure). Species increments were tending to level out at the three totally regulated sites whereas at the partially regulated and unregulated sites new taxa continued to be recorded in samples. Clustering techniques and similarity indices clearly separated the study sites based on the composition of the chironomid fauna and there were indications that the unregulated sites were more variable in faunal composition between years than the regulated sites. The data are used to develop a conceptual model of fluctuations in faunal parameters under steady or reduced flow regimes. It is suggested that environmental stability brought about by regulation has structured the composition of the chironomid community and further that the changes occur very rapidly after impoundment. The model identifies key areas of faunal change and the question of environmental stability is discussed in relation to the scale of observation. 相似文献
13.
Survey data from 1906 and 1988 for the lower River Murray, Australia, reveal changes in channel morphology associated with the construction of Locks 2 and 3 (1925–8), which form contiguous pools in the Valley and Gorge sections, respectively. Regulated annual flows are less than half the volume of natural flows, and the frequency of maximum flows has decreased. Upstream weirs have reduced the sediment supply to the study reach by 1.05 × 106 tonnes per annum. The trap efficiencies of Pools 2 and 3 from 1906 to 1988 were 8 and 13% respectively, with retention channel of 80723 and 267470 tonnes. Responses over the past 60–70 years have differed between the pools-some channel characteristics have attained a new dynamic equilibrium and others have not. In Pool 3 the average bed slope has been reduced by 000004 (44%) and has attained equilibrium, but in Pool 2 the supply and redistribution of sediment have not been sufficient to reduce the bed slope. There are continuous areas of degradation and aggradation in Pool 3 but discontinuous areas in Pool 2, reflecting different stages in slope adjustment. Cross-sections have become wider and shallower in Pool 3 but narrower and deeper in Pool 2. These adjustments are influenced by local boundary conditions, floodplain morphology and the position of the study reach in the sequence of weirs. In general, the situation in the lower Murray does not conform to conventional models of the impact of regulation, which are based on data from upland dams. The Murray's gross morphology remains as a relict of the natural, semi-arid regime. Low contemporary stream energies and cohesive bank materials restrict the initiation of channel metamorphosis and prolong the time required for the completion of channel adjustment. 相似文献
14.
Tharan Fergus 《河流研究与利用》1997,13(5):449-461
The River Fortun is situated in south-western Norway and is typical of the fiord landscape catchments with large areas above 1000 m a.s.l, steep valley walls and an alluvial river plain at the valley floor. It was regulated for hydropower in 1963 and is Norway's 10th largest regulation scheme. The hydropower scheme has resulted in a large reduction of the frequency of large magnitude flood events. This paper describes the long-term geomorphological response of a gravel-bed river channel to this regulation. The study was initiated after complaints from local farmers of an increase in flooding of farmland after regulation. Forty-seven cross-profiles of the river repeatedly measured in 1973, 1989 and 1995 along a 1600 m reach have been used to quantify aggradation and degradation in the reach. The profiles show a reduction in channel size and capacity since 1973, with a net aggradation of 12000 m3. The upper part of the reach has been subject to the greatest amount of aggradation, with the river bed being raised by up to 1.5 m, while the lower part has degraded, with lateral erosion cutting banks back by up to 30 m. Aerial photographs from 1964 and 1984 show that former gravel-bars and flood channels have been subject to vegetation encroachment. The hydraulic model HEC-2 was used to compute the water level in 1973 and 1989. The water level has been raised by 0.6 m at low flows in the upper parts of the studied reach. This corresponds to an increase in discharge of between 20–303/ s. Overbank flow therefore occurs at lower discharges today than prior to regulation. © 1997 John Wiley & Sons, Ltd. 相似文献
15.
The effects of flow regulation on temperature behaviour in the River Exe, Devon, U.K. have been studied, and attention is given to the local impact of impoundment and its downstream persistence. Temperature levels and seasonal thermal regime are considered as well as diel temperature fluctuations and temperatures during extreme weather conditions. Variations in temperature during individual reservoir releases have also been monitored. The impact of impoundment has been to make the stream environment immediately below the dam more homothermous so that temperatures rearely rise above 17·5°C or fall below 2·0°C, and monthyl average diel ranges are < 3 and < 1°C in summer and winter months respectively. In contrast to other reservoirs in Britain and abroad, this effect has been largely caused by increased groundwater flow downstream from the reservoir following impoundment. Regulation has also affected downstream temperature behaviour and has moderated the thermal regime of the Exe mainstream. This influence is generally restricted to a distance of up to 20 km from the dam, but in conditions of hot weather and low flows it may extend to almost 40 km from the impoundment. 相似文献
16.
Investigations were carried out into the contemporary distribution and structure of the vegetation communities at Gunthorpe, Nottinghamshire on the floodplain of the River Trent. A 60 km reach of the river was examined to determine the overall distribution and structure of vegetation communities; the Gunthorpe site was chosen as a representative example. Three hundred and thirty-nine separate plots were examined and the site contained 132 species. It is clear that the extent of zones of discontinuity or transition (ecotones) between different vegetation patches has decreased due to long-term land-use management. The overall number of vegetation patches has also been reduced. A hierarchy relating boundaries to external influences is proposed and the relationship of ecotones to more clearly differentiated patch habitats identified. Highest species diversity is seen to be associated with the transition zones or ecotonal habitats, particularly under conditions of moderate disturbance intensity. It is concluded that the ecotones remaining still provide a habitat for a wide range of species with differing autecological requirements, but all typical of less disturbed alluvial meadows and marshes. These zones of transition potentially provide a pool for species expansion given improved ecological conditions following river restoration measures. 相似文献
17.
Although most of the world's river systems are regulated, the effects of river regulation on mammals and birds are little known. In fact, speculations are more common than empirical data. A review of this topic is presented, emphasizing northern rivers where most impacts have been described. Effects are related to the major causes of change. It is concluded that the two most disastrous effects of river regulation on mammals and birds are the permanent inundation of vast areas of land, and the disruption of the seasonal flood regime along the river. The design of future investigations to improve our knowledge is considered. 相似文献
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19.
Ya. L. Gotlib A. I. Khudyakova 《Power Technology and Engineering (formerly Hydrotechnical Construction)》1992,26(7):462-468
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 7, pp. 47–51, July, 1992. 相似文献
20.
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. 相似文献