bluuebunny/crossref_metadata_2025 huggingface dataset:
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

Data 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

Forests 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

The 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

Channelized 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

Biological 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

This 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

The 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

The 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

This 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

Integrated 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

The 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

Changes 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.
Environmental management of the Zambezi river system
Authors: Mbumwae L. L.
Published: February 2007

In order to achieve environmentally sound management of the Zambezi River and its basin, an Action Plan — involving the cooperation of the eight countries of the basin — has been produced. This paper introduces this Action Plan.
Some alternative approaches to mathematical modelling of reservoir systems
Authors: Tollow Anthony J.
Published: February 2007

Four 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

A 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

Recent 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.
Biotic and abiotic gradients in a regulated high elevation Rocky mountain river
Authors: Voelz Neal J. , Ward J. V.
Published: February 2007

Samples were collected year‐round over a one‐year period at sites 250m, 500m, 1000m, 2300m, 5200m, and 11000m downstream from a hypolimnetic‐release reservoir on the Blue River, Colorado, to examine biotic and abiotic gradients induced by river regulation. The impoundment had only minimal effects on river chemistry and chemical variables failed to exhibit discernible downstream patterns. The temperature regime was markedly altered by regulation and exhibited a distinct downstream recovery gradient. The progressive downstream increase in zoobenthos species diversity is attributed, in part, to the thermal recovery. The average size of mineral substratum particles was greater at sites nearest the dam, although cobble and pebble predominated at all sites. A downstream decrease in bed stability was accompanied by decreased water clarity and increases in scour and ice action. These factors may have accounted for the higher standing crops of periphyton near the dam and a shift from filamentous chlorophytes to a predominance of diatoms with increasing distance downstream. The amount of leaf detritus in the substratum increased downstream. The abundance of shredders, zoobenthic species that feed on leaf detritus, tracked the downstream increase in coarse sedimentary detritus. Spatial patterns of organic seston within the study reach, influenced partly by sloughing of periphyton, are thought to account for the downstream species replacement patterns exhibited within the filter‐feeder guild.
Serial discontinuities in a Rocky mountain river. II. Distribution and abundance of trichoptera
Authors: Hauer F. Richard , Stanford Jack A. , Ward James V.
Published: February 2007

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.
Exploitation rate, survival and movements of brown trout (Salmo trutta L.) stocked at takeable size in the regulated rivers Lågen and Otta, southern Norway
Authors: Skurdal J. , Hegge O. , Hesthagen T.
Published: February 2007

Takeable size (age 4+, length 27–67cm), hatchery reared brown trout (Salmo trutta L.) were released into the rivers Lågen and Otta, the Glomma River System, southern Norway, in May‐July 1981 and 1983–87. The brown trout released in May gave significantly lower recapture rates compared to those released in June/July, i.e. 22.8 per cent compared to 41.6–58.0 per cent, respectively. Mean exploitation rate and survival rates ranged from 0.23 to 0.58 and 0.2 to 0.4, respectively, Within 15 days after release 50 per cent were recaptured, and 90 per cent were caught within 67 days. The frequency of recapture increased significantly with fish length in the length interval 30–45 cm, but decreased for bigger fish. The stocked brown trout were stationary and 95 per cent of the recaptures were caught less than 1 km from the site of release. Frequency of recapture ranged from 19.2 to 54.7 per cent in 6 experiments with takeable sized brown trout in different tributaries of the Glomma River System, and the variations are probably mainly due to differences in fishing pressure.
Problems in management of the Yellow river
Authors: Changming Liu
Published: February 2007

This paper deals with the management of the Yellow River, and particularly the main problems of flood and sedimentation control in the river's lower reaches. The available and adoptable measures for managing the river are itemized. These various measures can be coordinated to obtain an integrated effect on flood prevention.
Water quality management in the Ruhr area
Authors: Imhoff Klaus R.
Published: February 2007

The Ruhr River is the major source of water supply for the North Rhine‐Westphalian industrial district. To ensure drinking water supply from the river a system of reservoirs has been constructed for low flow augmentation. Five additional river impoundments have been built for the abatement of nonpoint pollution.

The Ruhr River Association was established in 1913. Its first task was the reduction of coarse pollution by mechanical treatment plants. Activated sludge plants were introduced as early as 1926. Developments continued and presently tertiary treatment is performed by polishing lagoons on one‐third of the Ruhrverband plants and a programme of storage and subsequent biological treatment of stormwater is underway. One important future task is nutrient removal from municipal wastewater by chemical precipitation and biological processes. Phosphorous concentrations in river water have to be diminished to fight eutrophication while nitrogen must be reduced because of drinking water considerations. Heavy metals have to be further controlled and organically attached halogens have to be diminished.
Observations on feeding relationships between fish predators and fish assemblages in a Mediterranean stream
Authors: de Sostoa A. , Lobon‐Cervia J.
Published: February 2007

The diet of native and introduced fish predators has been examined in two contrasting localities of a very fluctuating, Mediterranean stream, in relation to fish (prey) assemblage structure. The general patterns of all the species studied (Lutra lutra, Natrix maura, Salmo trutta, S. gairdneri, Esox lucius, and Leuciscus cephalus) seem to be the result of a generalist‐opportunist behaviour as their diets reflect the relative abundance of prey (fish) in the environment. The trophic levels are not well defined because of the opportunistic feeding of the predators and are also subjected to environmental changes. Non‐competitive dynamics is suggested to operate throughout the trophic web.
Effect of stream regulation on population parameters of atlantic salmon [Salmo salar L.] in the river Lærdalselva, western Norway
Authors: Brooks R. J. , Nielsen P. S. , Saltveit S. J.
Published: February 2007

The river Lærdalselva, West Norway, was regulated in the autumn of 1974. Regulation led to an increase in winter flow and a decrease in summer flow in a section where there was natural production of salmon. A slight decrease in summer temperature was also recorded in the uppermost part of this section. No data existed on juvenile Atlantic salmon before regulation and the regulation effect on juvenile fish population parameters is therefore based on samples taken from adult salmon in the period 1969 to 1984.

No differences in growth, smolt age, and smolt size which could be related to the regulation of the river were found. The smallest mean sizes of yearlings (0+) were found in 1964 and 1967. After regulation the mean size was never lower than before. Mean smolt age was between 3–1 and 3–9 years, but after regulation never exceeded that found before. River growth was slow, three year old smolts growing faster than four year old smolts. However, there were no differences in river growth before and after regulation.
The impact of channelization on the hydrology of the upper river main, county antrim, northern Ireland—a long term case study
Authors: Essery Charles I. , Wilcock David N.
Published: February 2007

The impact of an arterial drainage scheme on the water balance of a 200 km2 catchment in Northern Ireland is quantified. Monitored changes in groundwater storage act as an independent check on conclusions about storage change derived from measurements of surface hydrology. Three subcatchments of the study area and one other independent experimental catchment constitute controls against which the impact of arterial drainage can be assessed. Fiver years' predrainage data and three years' post‐drainage data are examined.

Stream flow from the floodplain area of the catchment has increased, especially low flows. Catchment water‐tables, however, as monitored in floodplain transects and disused farm wells have not been drawn down. Any immediate drainage benefits deriving directly from arterial drainage are difficult to detect. Groundwater evidence indicates that the likely source of the excess discharge is an underlying gravel aquifer that has been punctured by the deeper arterial channel.
Restoration and enhancement of engineered river channels: Some european experiences
Authors: Brookes Andrew
Published: February 2007

As government and organizations responsible for river mangement throughout the World become increasingly aware of the need to reconcile engineering objectives with nature conservation, alternative strategies for river management such as channel restoration are likely to continue to be developed and applied to particular areas.

Based on the experiences of 15 restoration projects in Denmark and Britain the criteria which determine the success of such projects are outlined. The essential precursor to a successful restoration project is a thorough feasibility and planning study. The type of restoration work included in a project is constrained by a variety of factors, including the physcial environment and the project objectives. The detailed design needs to be tailored to the individual river reaches under consideration. Project planning should consider the timing and supeervision of construction and make recommendations on the nature of maintenance. A management plan is desirable and post‐project appraisal is essetnial to evaluate the long‐term hydraulic and environmental performances. These criteria have been applied to two recent projects carried out on the River Lambourn in Berkshire, England, and on the Elbaek in central Jutland, Denmark.
Engineering operations and invertebrates: Linking hydrology with ecology
Authors: Smith Colin D. , Harper David M. , Barham Peter J.
Published: February 2007

This paper describes a study of a river regulated by past engineering schemes carried out for land drainage purposes: the River Welland in the East Midlands of England. Benthic invertebrate family richness and total biomass was measured in riffles, pools, and runs separately and then related to the frequency of these physical parameters. Changes which have occurred as a consequence of (a) loss of channel length through meander cut‐offs and (b) alteration of substrate characteristics through dredging and lowering of the river bed, were quantified. Riffles comprised 20‐30 per cent of the channel in reaches not seriously altered by engineering; elsewhere dredging has reduced or eliminated riffles and pools, leaving uniform sandy runs as the dominant channel feature. Riffles, pools, and runs all contribute to overall ecological value but the riffle and pool biotopes supported higher macroinvertebrate biomass and family richness. We show that proposals for river management that address the ecological needs of invertebrate communities can thus be expressed as numerical recommendations for maintaining or enhancing the key physical features of a river. In consequence, conservation recommendations can be simplified and considered in the same form as the engineering requirements of land drainage.
The effects of impoundment on the physicochemistry of two contrasting southern african river systems
Authors: O'Keeffe J. H. , Palmer R. W. , Byren B. A. , Davies B. R.
Published: February 2007

The downstream effects of six impoundments on their respective physicochemical conditions over two years are compared for two contrasting for two contrasting rivers. The impoundments studied included two on a cool, clear, clean, acid, and short system with a steep gradient (Palmiet River), and four on a warm, turbid, polluted, alkaline, and relatively long system (Buffalo River). Where possible, results are also compared against predictions of the Serial Discontinuity Concept (SDC) of Ward and Stanford (1983), and the ‘recovery’ (discontinuity) distances are estimated for a number of variables.

Major effects centred on changes in median spot temperatures and annual temperature ranges, particularly for dams regulating the upper reaches of both rivers. These upper river impoundments behaved similarly despite different release patterns; and caused only weak chemical effects, most of which recovered rapidly (within 3 km). Middle reach impoundments also behaved similarly despite different release characteristics, but they caused more pronounced changes and recovery distances were longer (up to 30 km).

Observed exceptions to the predictions of the SDC included alterations to nutrient regimes of receiving reaches downstream of all dams, annual temperature range was affected downstream of headwater dams on both rivers, and all impoundments on both systems depressed flow fluctuations. Although the specific predictions of the SDC model are not generally borne out, it is regarded as a useful tool for testing the effects of impoundment on rivers, and the concept of ‘recovery distance’ forms a useful practical framework for management of releases.
Comparison of discharge methods and habitat optimization for recommending instream flows to protect fish habitat
Authors: Orth Donald J. , Leonard Paul M.
Published: February 2007

Reliable methods are urgently needed for recommending minimum instream flows to protect aquatic life. For basinwide planning purposes, simple methods, which require little or nor field investigations, are required. While these methods tend to be conservative, the degree to which they protect habitat for fish is seldom determined. We applied physical microhabitat models (PHABSIM) for nine target fish species in four streams in the upper James River basin, Virginia, U.S.A., to (1) identify optimum flows to protect the fish fauna, (2) investigate the relationship between optimum flow and average discharge, and (3) compare our findings with recommendations based on simple discharge methods. Micohabitat availability for riffle‐dependent species was most limited at low flows while microhabitat availability for pool‐dependent species was most limited at high flows. At each study site there was a rapid increase in riffle habitat as discharge increased above zero. Optimum flow was the flow that maximized habitat for the most habitat‐limited species or life stages. The recommended optimum flow increased with increased stream size but the slope was not constant; as stream size increased lower proportions of average discharge were required to maintain optimum habitat. Aquatic Base Flow recommendations (i.e. September median flow) provided varying, but reasonable degrees of habitat protection. The Montana method 10 per cent average discharge recommendation correctly identified degraded or poor habitat conditions and the 30 per cent recommendation corresponded to near optimum habitat in small streams but greater than optimum flow at the large stream site. Seven‐day, 1‐in‐10‐year low flows (7Q10) provide very limited amounts of physical habitat for riffle‐dwelling fishes. The results provide a basis for making preliminary flow recommendations in this region with readily available data. Future studies will be needed to test the assumptions that need to be made.
Management of the sai river and the Tatsumi Canal, Japan
Authors: Nakagawa Takeo , Miyae Shin‐Ichi
Published: February 2007

The Tatsumi canal, Japan, constructed by Hyoshiro Itaya in 1632, is of immeasurable cultural value. It has become evident that the canal will be destroyed by construction of a new dam planned by Ishikawa Prefecture. The Tasumi canal is described and an alternative measure that fulfills the purposes of the dam construction and preservation of the Tatsumi canal is proposed. The alternative measure consists of widening the channel of the Sai River for flood control, and modification of the existing Heraso checkdam so as to fulfil the requirements for hydroelectric power generation and water storage. The proposed alternative also allows the preservation of the natural environment around the dam site and maintenance of water‐quality in the Tatsumi canal.
The downstream impacts of the burgomillodo reservoir, Spain
Authors: Camargo Julio A. , de Jalon Diego Garcia
Published: February 2007

The Burgomillodo Dam, located in the middle Rio Duraton (north Spain, Duero Basin), has created a small eutrophic reservoir with a capacity of 15 × 106 m 3 and a maximum depth of 40m. Burgomillodo Reservoir is solely used for producing hydroelectric power. The regulated flow pattern of hypolimnial waters is characterized by higher daytime flows than those by night, with low flows at weekends all the year round. The environmental impact generated by this hydropower scheme on the river downstream was assessed by comparing physiochemical characteristics and aquatic communities of an upstream site (reference station) with those of three downstream stations, which were located 0–2, 2–5, and 7–6 km below the dam.

Water temperature, pH and dissolved oxygen were significantly lower downstream from the reservoir. Hardness, alkalinity, suspended inorganic matter, and conductivity had reduced annual variability below the dam. Photosynthetic activity was directly involved in the recovery of dissolved oxygen and pH values.

Species richness and abundance of macrophytes increased just below the dam. Macrobenthic and fish communities were composed of higher numbers of potamic species. Number of taxa, density, biomass, and diversity were higher at the reference site, recovering their values as the distance below the reservoir increased. Macrobenthic trophic structure was changed by an increase in predators and filter feeders and a decrease in shredders. Environmental impact values for the macrobenthic community living just below the dam were higher than those for the fish community.

It is concluded that the main physiochemical factors involved in environmental impacts were dissolved oxygen deficit and short‐term flow fluctuations for the macrobenthic community, and oxygen deficit for the fish fauna. Benthic macroinvertebrates appear to be the best aquatic organisms for detecting changes and for reflecting the spatial recovery of environmental conditions.
Habitat utilization and preferences in juvenile atlantic salmon (salmo salar) in streams
Authors: Heggenes Jan
Published: February 2007

Young Atlantic salmon appear to occupy similar suitable stream habitats year round. The salmon is stationary, often associated with “home stones”. At low water temperatures in winter, the fish seek shelter in the substrate, which has to be coarse enough to provide interstices for the fish to hide in. In summer, salmon select habitats within tolerable ranges of habitat variables, rather than narrow optima. It is suggested that a genetic basis to habitat evaluation allows incorporation of the full range of behavioural responses. This is important as partially different habitats may be selected in diverse streams. Habitat availability influences both habitat use and habitat preferences. Suitable summer habitats have depths in the range 5–90 cm; mean water velocities 10–80 cm s−1, and gravel‐to‐boulder substratum. Fish size affects habitat use, as young of the year are found in the more shallow habitats closer to the stream banks, whereas the older parr use a wider range of habitats. In the absence of brown trout, the Atlantic salmon parr, and especially young of the year, use habitats otherwise inhabited by brown trout. Water velocities are in many cases the principal physical habitat variable determining the distribution of Atlantic salmon in streams, but other variables are also important. Depth is more important in small streams than in large streams.
Response of montane meadow vegetation after two years of streamflow augmentation
Authors: Henszey Robert J. , Skinner Quentin D. , Wesche Thomas A.
Published: February 2007

Changes in montane meadow vegetation were examined in a previously ephemeral drainage that received flow augmentation as a mitigation measure for a transbasin diversion in southeastern Wyoming. After two years of elevated surface and groundwater levels, the herbaceous vegetation shifted toward more water‐tolerant species. Dry meadows became like moist meadows, moist meadows became more like moist‐wet meadows, and moist‐wet meadows became more like wet meadows. Sedge (Carex spp.) biomass increased from 337 to 456 g m−2 in the wet meadows, while tufted hairgrass (Deschampsia cespitosa) biomass decreased from 18 to 3 g m−2 in the moist‐wet meadows. Slimstem reedgrass (Calamagrostis neglecta) remained unchanged in the meadows with shallow standing water, but increased from 17 to 88 stems m−2 in the dry meadows with an elevated water table. Bare ground also increased as much as 31 per cent in the meadows without a defined drainage channel.
The effects on fish spawning and management implications of impoundment water releases in an intermittent South African river
Authors: Cambray J. A.
Published: February 2007

The potamodromous smallscale redfin minnow (Pseudobarbus asper) spawned in the riffle areas of the regulated Groot River, the major tributary of the Gamtoos River system, during controlled releases of water from Beervlei Dam. Water had been released at irregular intervals from this flood control dam solely for irrigating agricultural lands. Flushing flows removed accumulated salts from riverine pools and were followed by reduced flows which initiated spawning of the minnow species. Developing embryos of P. asper were found in the riffle zone of the main river channel during the water releases. Ripe‐running males were located under the boulders in the riffles. Several developing embryos of Labeo umbratus were found with the P. asper eggs. Very little is known about the effects of man‐made alterations to the river flow regime on the reproductive activity of fishes in the majority of South African river systems. The agriculturally based flooding regime at Beervlei may have increased the recruitment of the redfin minnow species. Water management must give cognizance to the biological and environmental requirements within the regulated river systems. Water release strategies from Beervlei Dam should include instream flow decisions based on the requirements of the aquatic environment as well as for agriculture.
The flood pulse advantage and the restoration of river‐floodplain systems
Authors: Bayley Peter B.
Published: February 2007

The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river‐floodplain system, this restoration would provide a large, self‐sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.
Physicochemical factors affecting larval fish densities in mississippi river floodplain ponds, Louisiana (U.S.A.)
Authors: Sabo Matthew J. , Kelso William E. , Bryan C. Frederick , Rutherford D. Allen
Published: February 2007

We collected water‐quality data from 15 artificial floodplain ponds along the Mississippi River during May 1988 and quantified shoreline length, shoreline sinuousity, volume, and depth variation. Ponds regarded as high‐quality nurseries (based upon larval fish densities) contained higher dissolved oxygen concentrations and lower total organic carbon concentrations than ponds of lower nursery quality (p < 0.02). High‐quality nurseries also maintained higher conductivity and turbidity than low‐quality nurseries (p < 0.05). Results indicated that dissolved oxygen and pH probably fluctuated less in high quality nurseries and therefore provided better conditions for survival and growth of larval fishes. Total organic carbon and conductivity were directly related to pond morphometry (p < 0.004) and affected dissolved oxygen and pH in ponds. Large, high‐volume ponds with sinuous shorelines and variable depths tended to contain both high conductivities and low total organic carbon concentrations. Pond morphometry may have affected water quality and subsequently determined the nursery value of artificial floodplain ponds.