bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tributary response to local base level lowering below a dam
Authors: Germanoski Dru , Ritter Dale F. 
Published: February 2007

AbstractTributaries located immediately downstream from a dam responded to lowered local base level by incising vertically, widening, and expanding headwardly. The eight tributaries examined, join the Osage River along a 17 km reach directly below the Bagnell Dam in central Missouri. These tributaries flow through unconsolidated alluvium, and respond rapidly to base level lowering.Local base level lowering below Bagnell Dam is believed to result from a combination of factors, including an increase in channel cross‐sectional area caused by degradation and channel widening, and hydrological desynchronization of the trunk river and the tributaries during periods of high discharge. Of these, degradation appears to be the most important cause of tributary incision. Age dates from cores of trees which project cross‐channel roots indicate that tributary entrenchment has occurred after the closure of Bagnell Dam in 1931.Root‐armoured knickpoints, subaerially exposed cross‐channel tree roots, broken‐off roots, and ‘within channel’ terraces provided the basis for reconstruction of relative pre‐entrenchment tributary profiles which, when extended to the Osage River confluence, reveals the magnitude of entrenchment at the tributary mouth. The tributaries incised on average, 2·2 m and widened approximately 2·3 m at their mouths. Root armouring protracts the adjustment period of the tributaries and results in stepped longitudinal profiles. Tributary incision is episodic, and the influxes of high sediment discharge are out of phase from tributary to tributary.
Changes in the physico‐chemistry and benthic invertebrates of the great fish river, South Africa, following an interbasin transfer of water
Authors: O'Keeffe J. H. , De Moor F. C. 
Published: February 2007

AbstractData on the hydrology, chemistry, and benthic invertebrates of the Great Fish River prior to the opening of the Orange River/Fish River interbasin water transfer scheme in 1977, are compared with similar data for post transfer conditions. As a result of the transfer of water the once irregular seasonal flow of the Fish River has now become perennial. The mean annual runoff of the upper river has increased by between 500 and 800 per cent. Mainly because of abstractions for irrigation, the mean annual discharge of the lower river has changed little, but seasonal flow variation in the lower river has been considerably reduced. The inflow of low salinity water from the Orange River has diluted the highly mineralized Fish River water, reducing concentrations of sodium, magnesium, chloride, and sulphate, but not of calcium or total alkalinity. The invertebrate communities of riffles have changed substantially as a result of the water transfer, and only 33 per cent of taxa identified were common to both pre‐ and post‐transfer surveys. In particular, the dominant chironomid, hydropsychid, and simuliid species have changed, although there is no evidence that overall invertebrate densities have been altered. The most striking change in the fauna has been the replacement of the pre‐transfer dominant simuliids (Simulium adersi and S. nigritarse) by S. chutteri, a blood‐feeding pest of livestock, which now causes considerable problems to farmers. The major changes in invertebrate species can be attributed to the more permanent flow and increased area of erosional habitats.
Effects of river regulation on flooding of a riparian red gum forest on the River Murray, Australia
Authors: Bren L. J. 
Published: February 2007

AbstractForests of river red gum (Eucalyptus camaldulensis Dehnh.) occur along the River Murray in Australia. These forests are important for biota, recreation, grazing, and wood products. They occur in a sub‐humid to semi‐arid environment and require flooding for adequate growth and regeneration. The largest continous area is the Barmah (Victoria) and Millewa (New South Wales) forest near Echuca (Vic.). Information from maps showing the extent of inundation of Barmah Forest for particular floods was related to flow data upstream of the forest, and maps showing the distribution of vegetaton and forest site quality. Vegetation associations were shown to occur in characteristics flood frequency ranges, with red gum being the dominant species on all but the highest and lowest flood frequency sites. In general, higher red gum site quality was associated with higher frequency of flooding. The extent of flooding depended on the magnitude of peak flows in the river. Regulation of the river since the first filling of Hume Dam in 1934 has caused a reduction in the frequency of flows associated with partial flooding and an increase in the occurrence of small summer floods. Areas with a high flood frequency were most affected. It is possible that the forest may change to types associated with reduced duration of inundation in the long‐term unless ameliorative action is taken.
Instream flow studies in perspective
Authors: Gore James A. , Nestler John M. 
Published: February 2007

AbstractThe Instream Flow Incremental Methodology (IFIM) has been subject to criticisms, including its apparent imprecision, inability to predict discharge‐biomass relationships, lack of independence of hydraulic variables, and omission of predation/competition as variables in assessing the dynamics of aquatic populations and communities. This paper addresses criticisms of the methodology, stressing three themes. First, the development of IFIM to its present form is described. The goal of the method is to relate biotic values in equivalent terms to those used to estimate other beneficial uses of water. As such the engineering concepts of hydraulic simulation and suitability criteria play a strong role in the model. Previous studies suggest that IFIM appears to perform defensibly in coldwater systems but less well in more complex coolwater and warmwater systems. Second, the strengths of IFIM are considered and the type of environmental of IFIM are considered and the type of environmental problems it is suited to address are described. Research suggests that biotic responses vary dramatically as certain threshold discharges are approached and it is suggested that biomass predictions are inappropriate with current versions of IFIM. Its greatest utility is shown to be in assessing the impacts of water resources development on habitat availability for aquatic organisms. Third, the limitations of IFIM are presented; those that appear to have merit and those that arise from misapplication or misunderstanding of the methodology. We suggest that suitability criteria be developed on a site specific basis and include depth‐velocity dependent functions. The added predictive power by incorporation of coefficients of biological interactions to this management model is probably not justified by the expense required to obtain the data. As a tool, IFIM maximizes generality and precision at the expense of ecological reality but this does not detract from its utility to analyse water resource issues.
The importance of streamlining in influencing fish community structure in channelized and unchannelized reaches of a prairie stream
Authors: Scarnecchia Dennis L. 
Published: February 2007

AbstractChannelized and unchannelized sections of a prairie stream in northwestern Iowa were compared to determine how differences in microhabitats affected fish species abundance and diversity and the incidence of streamlined species. Channelized sections had significantly more fish per unit area (P < 0.05) but significantly less biomass (P < 0·05). Green sunfish (Lepomis cyanellus) and stonecats (Noturus flavus) were common in the unchannelized sections but rare or absent in the channelized ones. Small native minnows (Cyprinidae), especially the bigmouth shiner (Notropis dorsalis), dominated channelized sections. Species diversity was lower in channelized sections, but differences were not statistically significant (P = 0·06). Family diversity was significantly lower in channelized sections (P < 0·05). Channelized sections exhibited less heterogeneity of widths, velocities and substrates and contained more stremlined forms than did unchannelized sections. Unchannelized sections, characterised by greater diversity of velocities and substrate types, supported more centrarchids and ictalurids, fishes that are not optimally streamlined. Although many other factors besides streamlining influence the fish community structure in streams, in reaches without refuges from the current, streamlining may be a factor determining which species persist there.
A note on the problem of using biological surveys to assess water quality in small alpine torrents
Authors: Crosa G. , Ramusino M. Cotta 
Published: February 2007

AbstractBiological surveillance techniques have been widely used to assess river water quality. A biological survey using the E.B.I. method has been carried out in the Viola Torrent, a mountain stream subject to water transfers from hydroelectric power plants and receiving the aqueous effluents from some villages. The investigation shows that the oligotrophy of the torrent brings about a simplification of the macrobenthic community and leads to an inaccurate assessment of the quality of the water. It has therefore been necessary to adopt a critical application of the mapping method used.
Hydropower development on rivers in Scotland
Authors: Johnson F. G. 
Published: February 2007

AbstractThis paper reviews the development of Britain's limited hydropower resources, most of which is concentrated in Scotland producing on average some 4000 GWh per year. The Scottish schemes are dominated by the reservoir storage type although pumped storage plants have been constructed since the 1960s. These latter also occur at two sites in Wales. The performance of existing schemes is examined, with particular reference to environmental aspects, and the potential and prospects for future hydropower development are considered.
The impact of river regulation on invertebrate communities in the U.K.
Authors: Boon P. J. 
Published: February 2007

AbstractThe impact of river regulation on invertebrates has received comparatively little attention in the U.K., with most studies concentrating on the effects of impoundment. During dam construction invertebrate diversity and abundance decreases. Longer term alterations in community structure (which usually extend for a relatively short distance downstream) reflect changes in flow, substrate, temperature, and water quality. In particular adverse effects on invertebrates have been attributed to a reduction in substrate heterogeneity together with an accumulation of sediment. Responses to impoundment within and between taxonomic groups are highly variable. In general Ephemeroptera and Coleoptera are reduced. Of the Plecoptera the Perlodidae and Chloroperlidae are more likely to be adversely affected than the Nemouridae or Leuctridae. The impact of impoundment on net‐spinning Trichoptera varies with reductions in some populations and enhancement in others. Simuliids are usually restricted, probably because of a lack of suitable oviposition or attachment sites. Freshets released from reservoirs increase the level of invertebrate drift. However, the full consequences of impoundment on drift, recolonization, and upstream migration have yet to be assessed. There is some evidence that modified temperature regimes cause extended egg hatching periods and alter larval growth rates but further studies are needed.Little is known of the effects of inter‐river transfers on invertebrates, but it has been suggested that changes in flow velocity, water chemistry, suspended solids, and temperature together with translocation of organisms are all likely to be important. The limited information available for groundwater schemes indicates that they are not detrimental to invertebrates. Their impact, however, is dependent upon factors such as the extent and timing of flow augmentation. It is suggested that there is scope for positive management of invertebrate communities through river regulation, although at present attitudes and practices do not encourage this. Many gaps in our knowledge still remain and these are discussed in relation to future research needs.
River regulation and nature conservation
Authors: Hellawell John M. 
Published: February 2007

AbstractThe basic tenet of nature conservation is the protection and management of the environment so as to maintain its wildlife. Much of the effort is presently expended in securing the continued existence of rare, endangered or threatened species, communities, and habitats.River regulation involves considerable environmental manipulation. This extends beyond the modification of discharge regimes through the need for ancilliary operations, including the construction of dams, channel modification and transfer of water between catchments. The imposition of regulation modifies the natural environment in which the original communities of organisms became established. Where the ecological requirements of these organisms are destroyed or modified beyond the limits of their adaptations or tolerances they are unable to survive. The communities are thus changed and replaced by others, perhaps of lesser conservation value. Since the aims of nature conservation and river regulation are intrinsically incompatible the best that can be hoped for is that regulation schemes are designed, constructed, and operated so as to ameliorate environmental damage.
Environmentally sound river engineering: Examples from the thames catchment
Authors: Gardiner John L 
Published: February 2007

AbstractThis paper views new approaches to river channel engineering works and examines the constraints to the achievement of environmentally sound schemes. The approaches are being developed by an inter‐disciplinary team at Thames Water. Before 1981, institutional demarcation passively encouraged the tendency toward treating symptoms of such catchment problems rather than investigating and dealing with the causes. Environmentally sound river engineering is shown not to be achieved solely by application of a range of sensitive design and construction techniques. These affect only the cross‐sectional or at best local plan‐form design and must themselves be underpinned by thorough knowledge of what constitutes the river environment and the associated geomorphological processes. Long‐term environmental soundness can only come through sustaining the dynamism of the river system. Such management is shown to require a recognized structure of multidisciplinary, interorganizational teamwork, supported by appropriate legislation, institutional policy and strategy, individual awareness of the issue, and a facilitating methodology. The latter should plan the progress of major projects from a base level of thorough problem definition through successive levels of iterative refinement, involving interactive teamwork fully supported by appropriate use of new technology to define the best practical environmental option available. The resulting river engineering should be environmentally sound: a programme of post‐investment appraisal is necessary to provide feedback for the judgement to be made.
Outstanding problems in river regulation
Authors: Wood Richard 
Published: February 2007

AbstractIntegrated river basin management has been the backcloth against which river regulation has been practiced in England and Wales for the past 14 years. Its success is reviewed and the forthcoming changes in legislation are critically examined. A number of problems facing the emergent National Rivers Authority are discussed. The need for co‐operation rather than conflict is advocated wherever environment is to be protected and when competing pressures impact on river resources. A number of technical issues remain unresolved and the need for continuing work is recognized.
Effects of hydroelectric scheme on fluvial ecosystems within the Spanish Pyrenees
Authors: De Jalon Diego Garcia , Montes Carlos , Barcelo Elena , Casado Carmen , Menes Felicidad 
Published: February 2007

AbstractThe effects on faunal communities of a high head, low capacity hydroelectric power project are evaluated for the River Cinca, a Pyrenean tributary of the River Ebro (North East of Spain). The macrobenthic fauna of the regulated Cinca river is compared with the unregulated River Ara. Colder summer water temperatures in the River Cinca are shown to have caused a reduction in species richness of the macrobenthic community as a consequence of the elimination of thermophilous species. Reduced temperatures may also explain the lower growth rate and productivity of the trout populations. Sudden flow fluctuations caused by hydropower generation influence the downstream macrobenthic communities; their populations are less abundant (reduction in densities and biomass) and their structure is less diverse. Although trout fisheries do not seem to be directly affected by sudden flow fluctuations, the limitation of their food resources (benthos), has reduced trout production and turnover ratio.
Effect of impoundment on the growth and fishery of Bagrus docmac in lake Nasser
Authors: Khallaf Elsayed A. 
Published: February 2007

AbstractChanges of faunistic composition in impounded reaches of regulated rivers have been related to changes in environment from lotic to lentic. Rarely has this assumption been tested, however, Bagrus docmac is a long‐lived freshwater catfish and was once a commercially valuable species in Lake Nasser. Its production declined abruptly following the early years of impoundment of the lake. This decline is significantly correlated to the increase of Tilapia catch. A modified model for the surplus production is introduced and estimated the potential yield as 195·7 metric tonnes. Relative growth rate of weight over length interval showed that the fish ranging between 20 to 40 cm in standard length have had the highest rate of weight gain which is attributed to gear selective mortality. Fish (18‐83 cm in standard length) vertebrae (N = 105) are used for growth analysis, after their annuli are validated. Age‐groups ranged between I to VI with an average age of 3·14. Age‐groups II suffered high selective mortality which caused a fishing‐up effect that took about four years to appear in the catch. Thus, the problem of Bagrus may be safely attributed to the effect of fishing gears which are mainly used to catch the relatively smaller Tilapia.
Some alternative approaches to mathematical modelling of reservoir systems
Authors: Tollow Anthony J. 
Published: February 2007

AbstractFour basic methods of devising an operating policy for reservoirs exist, namely dynamic programming, linear programming, non‐linear programming, and simulation. Dynamic programming has been found on the whole to be too cumbersome in use for multiple reservoir operation. Linear programming has been successfully used, as has non‐linear programming. Both have developed hybridized subsets such as ‘adaptive programming’. However, the most popular is simulation, as its methods of operation are relatively easy to understand. Its major drawback is that it does not in itself produce an optimal solution. In practice this may not be a disadvantage, especially when simulation is used to create a set of ‘control bands’. All the methods at one stage or another permit cost functions to be incorporated. The ability of simulation to include water quality constraints, as well as costs, will be of increasing benefit as the quality of the available water resources deteriorates. Other non‐quantifiable aspects of the ecological cycle may also be included.The use of control bands and the relative simplicity of the basic simulation program permit the day‐to‐day operation to be delegated. Microcomputers may be used even though the programme may require running in several discrete parts. The ease with which the segment containing costs can be changed is of major benefit. Control bands can be derived from median and low flows. However, during a drought additional monitoring is likely to be needed if control bands derived on hindsight are used for forecasting.‘Conjuctive use’ can enhance yield, surface water being relied upon and groundwater during the drier periods, this being a form of multiple reservoir system. Other forms may be single large reservoirs, possibly by pumping, from several different sources. A single resevoir may be operated in conjunction with several others, each having its own individual operating control band, but conforming to a group policy. To achieve full benefit from multiple operation, a linking of outputs may be needed, either by pipelines or natural river systems. Simulation has been suggested as one method of operation; others are being continually developed. The object is to introduce a degree of optimization. However, by so doing the alternative method tends to become mole obscure to the user, and therefore is seldom used.
Effects of hydropower development on aquatic macrophytes in norwegian rivers: Present state of knowledge and some case studies
Authors: Rørslett Bjørn , Mjelde Marit , Johansen Stein W. 
Published: February 2007

AbstractA multitude of Norwegian rivers are managed for generating hydroelectric power (HEP). The hydrology of these hydrorivers changes in various ways which reflect the implemented HEP schemes. Increased winter flows and a concomitant lack of ice‐cover are features found downstream of power installations on many Norwegian hydrorivers.Our study objectives were (1) to assess the changes in aquatic macrophyte abundance subsequent to HEP development; and (2) to evaluate the environmental conditions under which nuisance growths of macrophytes are likely to occur. Towards these ends, Norwegian literature data were compiled and assessed. Some case studies are outlined showing the variety of situations under which prolific growths of macrophytes might result. Unfortunately, available data on macrophyte‐associated problems proved deficient in many respects. This occurred chiefly because most macrophyte studies are conducted either before, or after, an HEP scheme is completed. Evidently, no concerted efforts are made for assessing the likelihood of macrophyte‐dominated nuisance growth in the planning stage of a Norwegian HEP scheme.
Instream flow predictions and management options for biota affected by peaking‐power hydroelectric operations
Authors: Gore James A. , Nestler John M. , Layzer James, B. 
Published: February 2007

AbstractRecent studies on the impact of peaking hydropower have indicated that impacts directly associated with peaking releases can be categorized as those which result from the hydraulic surge during start‐up of generation and the chronic effects of frequent flow fluctuations to biota occupying the fluctuation zones. The instream flow incremental methodology (IFIM) was not designed for application to dynamic flows. In order to determine if such an application was appropriate, we chose to conduct exacting habitat descriptions at the unique zones associated with peaking hydropower (degradation, aggradation, and recovery) and combine this information with suitability criteria for the banded sculpin (Cottus carolinae) and stage/discharge records to obtain weighted usable habitat estimates under typical peaking releases. The results demonstrate that habitat declines as the peaking surge passes an area and rises during low flow periods. However, the difficulties in interpretation of the results remain. That is, the biological response (lateral or longitudinal movement or entrainment) as well as the refuge value of certain hydraulic conditions remain to be investigated. This suggests that the present management value of IFIM applied to peaking hydropower is in examining minimum habitat values that occur during the generation cycle and a comparison of gains or losses in the minimum (greatest amount of hydraulic refuge available) WUA estimates under various proposed release scenarios.