bluuebunny/crossref_metadata_2025 huggingface dataset:
The environmental impacts of the tucuri dam on the middle and lower tocantins river basin, Brazil
Authors: Barrow C. J.
Published: February 2007

An attempt is made to appraise the present and likely future environmental impacts of the Tucuruí Dam upon the mid and lower Araguaia‐Tocantins Basin (Brazilian Amazonia). Information has been obtained by literature review and from field visits made by the author in 1981, 1983, and 1985. The problems of impoundment‐related environmental impact assessment in tropical developing countries are also discussed.

Tucuruí is the world's fourth largest hydroelectric project and is the first large dam to be completed in an Amazonian rainforest environment. It is also the first of a number of large dams which Brazil plans to construct in the Araguaia‐Tocantins Basin and on other tributaries of the Amazon. The appraisal of problems associated with Tucuruí Dam should help planners minimize difficulties with future Amazonian hydroprojects.

Like many developing country environmental impact assessments, that carried out at Tucuruí was begun after the construction site had been selected and construction had begun. Tucuruí impact studies have tended to concentrate on the environmental and socioeconomic impacts generated in the vicinity of the dam and reservoir; downstream impacts have received less attention but are already apparent. Major impacts identified include reservoir siltation, disruption of fisheries and agriculture (especially floodland cultivation) downstream, and human disease problems.
Changes in benthic sediment in the thomson river, Southeastern Australia, during construction of the thomson dam
Authors: Davey G. W. , Doeg T. J. , Blyth J. D.
Published: February 2007

The particle‐composition (0.15 to >64 mm) of the stream‐bed was monitored by Surber sampling at sites above and below the site of the Thomson Dam during the two years of most active construction. Levels of particles between 0.5−2 mm were highest 9.5 km below the dam site, and increased throughout the study. Levels of these grades at sites above and well below the dam site were variable, but showed no consistent trends. Material greater than 2 mm showed no substantial variation either over time or between sites spanning approximately 70 km of river length and 250 m of elevation.

Artificial substratum samplers were used to estimate the rate of sediment input (0‐2 mm) between sampling dates. Sediment input was clearly highest 1 km and 9.5 km below the dam site. Input was seasonal, with maxima in winter and spring of each year. Size classes 1‐2 mm and <0.063 mm contributed over 60 per cent of the total deposited sediment. Over the second year of the study, high levels of sediment <0.063 mm were deposited at a site 33 km below the dam site, indicating the progressive movement of material down the river.

Some fine sediment was found to penetrate unconsolidated bed material to depths down to 60 cm. It is suggested that such material, resulting from land disturbance, is capable of filling interstitial spaces in the stream‐bed, and that major disturbance of the bed may be necessary to dislodge it.
Thermal characteristics of two regulated rivers in mid‐wales, U.K.
Authors: Cowx I. G. , Young W. O. , Booth J. P.
Published: February 2007

Data for three rivers in the upper Severn catchment are examined to assess the influence of regulation strategies on the thermal characteristics. Seasonal and diel temperature variations are markedly influence by the release discharge and the depth of withdrawal from the reservoir. The downstream influence of river regulation is confined to a relatively short reach (ca. 30 km) below the dams. Nevertheless, the control of water temperature during hot, dry summers could benefit salmon populations.
Classification and succession of former channels of the french upper rhone alluvial plain using mollusca
Authors: Richardot‐Coulet M. , Castella E. , Castella C.
Published: February 2007

This paper deals with the results of an extensive sampling of eight former channels of the Rhǒne and eight of its tributary, the Ain River, France, designed to assess the value of molluscs as ‚describers’︁ of ecosystem dynamics.

The sampling was stratified on the distribution of aquatic macrophytes. The distribution of molluscs species is shown to provide information on the rate of eutrophication, the groundwater supply and the succession of the abandonned river channels toward semi‐aquatic and terrestrial conditions. Molluscs, together with other macroinvertebrates, not only describe the present stage of these ecosystems but also provide some predictive information on their successional pattern for assistance in the management of the alluvial plain.
Stream regulation in Argentina, including the superior Paraná and Paraguay rivers
Authors: Bonetto Argentino A. , Castello Hugo P. , Wais Irene R.
Published: February 2007

Argentine water resources are located in three hydrologically contrasting regions: the so‐called Del Plata basin, the Arid Central Andean area, and Patagonia. About 150 dams and impounding reservoirs that exceed a capacity of 150 × 103 m3, have been built. Most limnological studies of regulated rivers have been conducted recently. In the Del Plata basin, Argentine dams are scarce, although many have been built or are projected upstream, mainly in Brazil. The ecological problems of the reservoirs are related to decomposition of inundated terrestrial vegetation; algae blooms, dissolved oxygen depletion phenomena, eutrophication, impaired fish migrations, overproduction of water hyacinth Eichhornia spp., and schistosomiasis. The importance of examining the influence of the projected middle Paraná dams on downstream sediment regimes, especially as it affects the delta, is emphasized. In the Arid or Central Andean region, the main development of the Grande‐Tercero rivers includes dams, reservoirs, and the operation of a nuclear power plant. One of the most important effects will be a slight increase in the water temperature of the Rio Tercero reservoir as a consequence of water use in the cooling system of the nuclear power plant. In the Patagonian region, the main dams are those built and projected for the Colorado and Negro basins. In the Negro basin studies are being carried out mainly in the Ramos Mexia Reservoir, on different aspects of zooplankton and phytoplankton, benthos, and fishes. Commercial fishing is not permitted and fishing is based mainly on the introduced salmonids which show symptoms of undernourishment because of a lack of forage fishes. Indigenous fishes have been decimated by the introduced salmonids.

Although studies have been conducted in several areas, much work remains to be done in relation to the environmental effects of dams on streams in Argentina. Results from ecological studies are still insufficient to solve the multiple problems associated with them, such as climatic influences, retention of suspended solids, deforestation, schistosomiasis and other aquatic diseases, pollution, eutrophication, fish‐ways and fish migrations, accumulations of the water‐hyacinth, salt and nutrient regimes, and siltation. Even partial solutions to these problems will require an ensemble of urgent measures to assure the maximum benefits with minor risks and ecological costs.
Ecological considerations in the development and application of instream flow‐habitat models
Authors: Orth Donald J.
Published: February 2007

Methodologies for recommending instream flows for protecting lotic ecosystems are evolving amid constructive criticism. During this period of change it is important that all concerned parties are aware of the ecological factors that control stream ecosystems and fish populations. Ecological factors relating to stream ecology, population dynamics, energetics, predation, and competition are reviewed to explain why indices of microhabitat availability are not expected to be consistent predictors of fish population density. Implications of these concepts for development and application of instream flow‐habitat models for recommending instream flow regimes are discussed. Current ecological theory and empirical studies support the hypothesis that microhabitat availability may limit fish populations but not continuously. Therefore, assessments must consider the limiting habitat events as well as temperature and water quality constraints. Also, invertebrates and non‐game fishes must be considered in instream flow assessments because of their importance in stream ecosystems.
Hydraulic effects of aquatic weeds in U.K. rivers
Authors: Watson David
Published: February 2007

The effects of large aquatic plants (aquatic macrophytes) have been given limited attention in literature dealing with open channel flow. This is despite a large number of river channels in the U.K. being affected by profuse growths of these plants. This paper contributes to three major areas in relation to aquatic macrophytes and river channels.

First, a literature review examines four areas of vegetated channel research. Early work on vegetated channels concentrated upon grass‐lined farm drainage channels in the U.S.A. This was complemented by flume studies of predominantly artificial vegetative roughness elements. The review discusses research into large aquatic plants in stream channels, and the discussion draws together a number of disparate areas of research into vegetated channels including theoretical considerations.

Secondly, the paper discusses results obtained from laboratory flume experiments, using real plants, and field monitoring on the River Ebble, Wiltshire, U.K. The relationship between discharge and Manning's roughness coefficient (n) is examined. Field monitoring results are presented as generalizations in the relationship between Manning's n when the monitoring sites were vegetated and unvegetated. The relationship between plant cover in the channel and Manning's n is also examined. Two measurements of plant cover are employed: the percentage cross‐sectional area of channel vegetated, and biomass per unit area. The field data for Manning's n and discharge are then discussed in detail in a case study of one site on the River Ebble.

Finally, the results obtained from field monitoring are compared to previous research. In the light of these comparisons and detailed examination of the field and flume data, a conceptual model of the effects of aquatic plant growth on channel roughness, mean flow depth, and flow stage is represented. Using this model, an estimate can be made of the likely effect of changing plant cover and discharge on flow stage in an open channel.
The importance for birds of the riparian woodlands within the alluvial corridor of the river garonne, S.W. France
Authors: Decamps H. , Joachim J. , Lauga J.
Published: February 2007

Communities of nesting birds were studied in four distinct biotopes within the alluvial corridor of the River Garonne: 50 terrace woodlands, 17 riparian woodlands, one poplar plantation, and one slope woodland. A total of 400 stations were investigated, consisting of eight distinct classes of forest size for the terrace woodlands and four for the riparian woodlands. The distribution of 64 species of birds, observed by means of 20 minute listening point surveys, was related to three main factors: forest size, site wetness, and the wooded space marginality (forests, woods, copses, hedges, trees).

Indices of mean richness and of mean abundance show that the riparian woodlands were the richest and the most densely populated. The surface area of woodlands has a strong effect on the structure of the bird community on terraces but less in the riparian environment.

Multivariate analysis contrasted the species from the open islands within closed environments with the species from the closed islands within an open environment. The effect upon the nesting bird communities of the fragmentation of the original forest within the alluvial corridor of the River Garonne is demonstrated by a grouping of two characteristics: the connectivity of the riparian woodlands and the insularity of the terrace woodlands. The conservation of a continuous ribbon of riparian woodlands is shown to be an important condition for maintaining a rich community of nesting birds.
Water development and associated hydrologic changes in the Platte river, Nebraska, U.S.A
Authors: Hadley R. F. , Karlinger M. R. , Burns A. W. , Eschner T. R.
Published: February 2007

Major changes in hydrologic regime and morphology of channels of the Platte River and its major tributaries, the South Platte River and North Platte River in Colorado, Wyoming, and Nebraska have occurred since about 1860, when the water resources of the basin began to be developed for agriculture, municipal, and industrial uses. The extent of this water development, which continues to increase with growth in population and land use, has affected the timing of streamflow and transport of fluvial sediment in the Platte River through diversions, reservoir storage, and increased use of groundwater. Changes in flow regime, such as increase in low‐flow magnitudes and abatement of peak‐flow magnitudes, have made the riverine environment conducive to vegetative growth while reducing channel scour. These factors, in turn, contribute to morphologic changes of decreased channel width and channel area and increased island formation. This paper will focus on these trends over the last several decades in the study area on the Platte River in Nebraska.
Aquatic weed problems in a hydroelectric river: The R. Otra, Norway
Authors: Rørslett Bjørn
Published: February 2007

Excessive abundance of submerged macrophytes is a less well‐known but highly undesirable effect resulting from hydropower development. An example is the acidic River Otra, which is an extensively exploited hydroelectric river located in a region of infertile soils in southern Norway. The operating schemes annually generate some 4·1 TWh of hydropower. Many stretches of the River Otra support massive infestations of a submerged phenotype of Juncus bulbosus L. Evidence from a multidisciplinary study demonstrates that proliferation of J. bulbosus is achieved under an altered flow regime typical of Norwegian hydrorivers. The main features are augmented winter flows, concomitant lack of ice‐cover, and intermediate ranges and frequencies of water‐level fluctuation. These hydrological conditions prevail in tailwaters and intermediate‐type hydrolakes on the Otra. By contrast with the Otra River, an adjacent water‐course, the acidified Tovdal River, supported only scattered J. bulbosus in its upper, non‐regulated sections, whereas a hydrolake on the lower Tovdal River had locally abundant growth of J. bulbosus. Acidification per se is an unlikely determinant of profuse growth for this species: non‐natural habitats created by hydropower operation provide vacant space for an opportunistic species such as J. bulbosus.
Deforestation of large reservoir basins
Authors: Paiva Melquíades Pinto
Published: February 2007

This paper deals with the possible alternatives regarding deforestation of large reservoir basins, concluding in favour of the convenience of adopting zoned deforestation, in accordance with the uses for which they are planned. At the same time, a methodology is developed to estimate the quantity of vegetal biomass to be removed from flooding basins of such reservoirs before closing the respective barrages. To this end, recommendations are made regarding plans for the filling phase which must be elaborated together with the plans of deforestation, so that mutual adjustments are allowed, attaining maximum reductions in costs and duration of clearing services. Finally, it is recommended that the occurrence of trunks emerging from the water should be reduced to a minimum in order to avoid the development of floating acquatic macrophytes.
Channel response to grade‐control structures on Muddy Creek, Mississippi
Authors: Harvey Michael D. , Watson Chester C.
Published: February 2007

Grade‐control structures are commonly employed to prevent bed degradation and concomitant bank instability of channelized reaches of rivers. A study of a 20 km reach of a coastal plains stream was conducted in 1985 to determine the effects of 12 rock‐lined grade‐control structures that were installed between 1977 and 1983 prior to channel excavation. An Allowable Tractive Stress Method (TR.25) was used to determine the placement of grade‐control structures, and the gradients between them, for a trapezoidal‐shaped channel designed to convey the 1 year recurrence interval peak flow. The design was successful in preventing bed degradation and bank erosion over the period of observation. However, unpredicted channel responses have occurred. Aggradation is apparent between control structures, and a two‐stage compound channel has formed as a consequence of berm development, especially in the lower, older subreach. In the lower subreach, the vegetated berms have constricted the cross‐sectional area at the design discharge (99 m3 s−1), and as a result, water‐surface slope, shear stress, and unit‐stream power have incresed. Bed material has become coarser and better sorted, which has increased shear intensity values. These unexpected changes are attributed to the lack of adequate consideration of the requirement for balance between sediment supply and transport in the TR.25 procedure; seven tributaries contribute sediment to the main channel of the study reach. It appears that the increased energy is utilized in bedload transport rather than channel erosion. This study demonstrates that the TR.25 method is too conservative if significant amounts of sediment are being supplied to the design channel. In such cases, adjustments in channel morphology will increase the energy to accommodate bedload transport.
Suspended solids transport in the regulated River Blithe, Staffordshire, U.K.
Authors: Gilvear David. J.
Published: February 2007

Suspended solids concentrations and turbidity were monitored on the regulated River Blithe at two sites downstream of the reservoir for a period of 18 months. Changes in the suspended solids loads transported and the nature of the material in suspension are related to dam overspill and tributary flood events. A hysteretic relationship between suspended solids concentrations and discharge is characteristic of both sites, sediment supply being limited within the regulated river. Downstream of the dam, rapid bank erosion occurred on meander bends but the suspended solids loads transported by the regulated river relate more to the resuspension and transport of tributary injected sediments and scouring of a dense periphyton. Close to the dam, fine biogenic matter dominated the seston, which scanning electron microscopy revealed to contain algal fragments and inorganic diatom frustules, but downstream, tributary‐derived minerogenic particles were dominant.
Historical aspects of irrigation agriculture and river regulation in the Murraay‐Darling Basin, Australia
Authors: Davidson B. R.
Published: February 2007

River regulation in Australia is a feature of the last on hundred years. Irrigation farms were established along the River Murray in the 1880's and on the Murrumbidgee in the first quarter of the twentieth century. These demonstrated that such labour‐intensive types of farming were unprofitable in Australia. The additional profits obtained by irrigation farmers were not sufficient to pay for the reservoirs and distributary works required and these had to be paid for by the State. Water was sold to farmers at a price which was only sufficient to maintain the projects.

Political pressure led to a further increase in the consturction of reservoirs and the area irrigated in the Murray‐Darling basin expanded from 0·6 million hectaers in 1945 to 1·6 million hectares in 1979. As irrigation practices improved, farm profits increased, but the price of water continued to be based on the cost of maintaining the projects. This led to increased profits being built into the price of irrigated land. Low water prices encouraged farmers to over‐irrigate and aggravated the problem of rising water tables and salination.

It is argued herein, that the efficiency of water usage in irrigation could be improved by transferring the existing water rights from the state of irrigators, and making them transferable from one irrigator to another or from irrigators to other users at prices negotiated in a free market. Such a system would ensure that water was put to its optimum use, reducing wastage and minimizing detrimental effects of over‐use. The water price established in such a market could be used to calculate whether the marginal returns from irrigation and other uses were high enough to justify the construction of new projects.
A flood alleviation of the Kakehashi Basin, Japan
Authors: Nakagawa Takeo
Published: February 2007

A flood alleviation scheme is proposed for the Kakehashi basin, Japan. The scheme consists of one diversion channel, four retarding basins and one dam. The region between the diversion channel and the Kakehashi river is protected from floods. The measures proposed make it possible to achieve flood alleviation whilst minimising changes of the Kakehashi river, and impacts on historical environments and cultural properties. It is emphasized that preservation of the sinuous channel of the Kakehashi river must play a key role in future management because of the physical, biological and aesthetic advantages when compared with a straight stream channel.
Regulated rivers in the United Kingdom
Authors: Petts Geoffrey E.
Published: February 2007

This paper identifies the principal regulated rivers in Britain and summarizes their physical and ecological characteristics. Virtually all major rivers in the United Kingdom are shown to be regulated directly or indirectly by mainstream impoundments, interbasin transfers, pumped storage reservoirs, or groundwater abstractions. Flow records for sixty per cent of all gauging stations are significantly affected by flow manipulations. Three phases in the development of river regulation are identified: firstly, the development of direct supply and compensation reservoirs from 1840; secondly, the development of large dams and large‐scale interbasin water transfers from 1890; and thirdly, the modern era of multipurpose river regulation that began in 1965.

Any assessment of the environmental effects of river regulation must consider the spatial variation of natural river systems throughout the U.K., climatic changes, and the cumulative effect of river regulation and other impacts over an historic timescale. Today, the rivers of the U.K. are shown to have an underlying character that reflects the marked climatic, geologic, and topographic differences between the upland north and west, and lowland south and east; differences in part that relate to their different histories during the Pleistocene. However, many rivers show the effects of human impacts that began about 5000 years ago. Most rivers have experienced changes since about 1930 consequent upon afforestaton, land drainage, and channelization. These, together with short‐term climatic changes, make defining ecological impacts of river regulation problematic. Pollution has had the most dramatic effects. Nevertheless, it is suggested that new concepts of environmentally sound river regulation could lead to the restoration and even enhancement of rivers in the United Kingdom.
River regulation in the United Kingdom: An historical perspective
Authors: Sheail John
Published: February 2007

The beginnings of direct river modification in the U.K. are traced back to the 1st century A.D. when works were undertaken for land drainage and transportation. After the Roman period river works were widespread, there being more than 5,000 water‐mills by 1086, but of small scale until the 17th century. Impressive drainage schemes were supplemented from the end of the 18th century by the construction of numerous small dams for water supply and to provide compensation water. Severe pollution during the mid‐19th century led eventually to an organized system of river management. By 1900 the era of large dam buildings and large (> 1000 km) inter‐basin transfers had begun. The regulation of rivers in the U.K. has been subjected to much public scrutiny and debate, more so than the development of any other resource. However, the problems being encountered in river management today are shown to be embedded in the history of water resource development.
River regulation: A regional perspective—Northumbrian water authority
Authors: Johnson P.
Published: February 2007

In the past three decades, river regulation has become a key component of integrated water management in the U.K. water industry. This paper reviews the concept and operation of river regulation with reference to the Northumbrian Water Authority region. The role of regulating the Rivers Tyne and Tees is considered within a regional perspective. Regulation began on the River Tees in 1965 and the regulation potential of the region was completed with the Kielder Scheme on the River Tyne in 1981. During the year, regulation in Teesdale is largely determined by abstraction demands. Hydropower releases from Kielder have an important effect on the River Tyne. The control patterns and priorities are discussed in general and specifically with regard to statutory and other requirements. These include minimum maintained flows, drought orders, riparian and amenity interests, water‐quality, and ecology. Flexibility and cooperation are key concepts; the management of water‐quality remains arguably the major problem.
Regulation of the River Thames. A case study on the teddington flow proposal
Authors: Sexton J. R.
Published: February 2007

This paper discusses the inception, development and assessment of one specific scheme: the Teddington Flow Proposal. The Proposal modifies existing flow regulation policy to provide an additional 170 Ml d−1 for supply. After extensive studies concerning water quality, water levels, and the potential effects on ecology, navigation, recreation and amenity, no significant detrimental effects have been identified.

The overall effect of the Teddington Flow Proposal would be beneficial. The river environment would be improved in major drought years, when the most serious effects on the river would otherwise occur. This more than offsets a small deterioration in certain factors in some non‐drought years. The biggest benefit will be to the five million people living and the even greater number working in London who will have less frequent and less severe restrictions on their water supply with virtually no consequential increase in their water charges.
Fish and fisheries of regulated rivers in the UK
Authors: Mann R. H. K.
Published: February 2007

This paper examines the historical and recent influences of river regulation on fish populations and fisheries in Britain. The construction of a series of canals and interconnecting waters during the 18th and 19th centuries facilitated the spread of some species between catchments. These slow‐flowing habitats allowed many lowland species to thrive and this is reflected today in the fish community structure in some rivers.

The problems of barriers to the movement of migratory species imposed by dams and weirs and the efficacy of compensation measures are discussed. The latter embrace fish passes, adult fish and smolt transport, and stocking. Potential problems for the future include the disruption of the homing of salmon to their natal rivers caused by transfers of water between catchments.

River basin management in Britain attempts to reconcile the water resource requirements of fisheries with those of other water users. This can be seen in the practice of Regional Water Authorities to include ameliorative measures in many of their land drainage and flood prevention designs. However, more research is required on the long‐term problems and benefits of these and other river regulation schemes on resident fish populations.
Fish populations of a small lowland channelized river in England subject to long‐term river maintenance and management works
Authors: Swales Stephen
Published: February 2007

Fish populations in the River Perry, a small lowland channelized river in England, were affected by long‐term river maintenance and improvement works. Habitat diversity at two ‘old channelized’ sites was low compared with a downstream ‘partially channelized’ site and an unmodified site, where natural river features such as the pool‐riffle pattern were more apparent. The fish community was low in diversity at all sites, with two running‐water cyprinids, dace Leuciscus leuciscus (L.) and chub Leuciscus cephalus (L.), being the dominant fish species. Relative species composition varied between sites, with dace predominating at the ‘old channelized’ sites and chub increasingly dominant at the ‘partially channelized’ and unmodified sites. Population density and biomass estimates of dace were similar at all sites, but chub were up three times more abundant at the ‘partially channelized’ and unmodified sites than at the ‘old channelized’ sites. Populations of dace and chub at the ‘old channelized’ sites contained a higher proportion of small fish than populations at the downstream sites, which exhibited a more balanced population structure. The growth rates of both dace and chub varied between sites. Low recaptures of marked dace suggested a highly mobile movement pattern while higher recapture rates of chub, particularly at the ‘partially channelized’ and unmodified sites, seemed to indicate a more sedentary activity pattern. The conclusion of the study is that long‐term river maintenance and management works may delay the morphological and biological recovery of lowland channelized rivers.
The role of riparian woods in regulating nitrogen fluxes between the alluvial aquifer and surface water: A conceptual model
Authors: Pinay G. , Decamps H.
Published: February 2007

Conceptual models are proposed to explain nitrogen fluxes in the soils of riparian zones in relation to the different modalities of water logging and nitrate inputs. Non‐submerged, temporarily submerged, and always submerged, sites are considered in both winter and summer. It is shown that capacities for epuration are elevated for nitrate loads from the alluvial aquifer during the lateral transfer of water from agricultural land to the river through the riparian zone. About 30 m of groundwater flow under the riparian wood studied is sufficient to remove all nitrate. Denitrification rates up to 50 mg N2 per m2 per day were observed in the field, but a potential for more denitrification exists. The efficiency of the riparian woods as natural filters regulating nutrient transfers to the river deserves more consideration in river management.
A mathematical hydraulic model of the River Nene ‐ A canalized, and heavily controlled river
Authors: Williams J. J. R. , Fawthrop N. P.
Published: February 2007

The paper describes a mathematical hydraulic model of the River Nene in East Anglia, England. This river, which is typical of many in that predominantly flat region, is canalized and subsequently heavily controlled. The routing model has been developed in order to investigate the effect of improvements that could be made to the river to reduce the frequency of flooding. The model is in its final stage of development and results are presented of a flood that was monitored in March 1982.
Radial stem growth of coniferous trees near Swedish reservoirs
Authors: Grelsson Gunnel
Published: February 2007

Tree ring data are presented for two species of coniferous trees growing close to the margins of two contrasting types of reservoir, an annually regulated one (bordered by Picea abies) and a daily and weekly regulated one (Pinns sylvestris). The radial growth‐ring data for the periods before and after damming and regulation were compared utilizing a mathematical growth model. The basic hypothesis was that changed water‐level conditions due to hydroelectric development would change the groundwater levels and associated factors and thus affect tree growth. For spruce trees growing along the long‐term (annually) regulated reservoir, no significant differences in growth between the pre‐damming and post‐damming periods were found; nor was any correlation found between tree growth and the duration of the period of high‐water level in this reservoir. For pine trees growing along the short‐term (daily and weekly) regulated reservoir a significant increase in the variation in growth was found following regulation, but only at the lowest levels. No other significant differences in tree growth between the periods before and after regulation were found.
An attempt to facilitate water management issues in the Zambezi river basin using decision support systems
Authors: Pinay G. , Salewicz K. A. , Kovacs G.
Published: February 2007

This paper reviews the Decision Support Systems for Managing Large International Rivers Project at IIASA, and its application in the Zambezi river case study.
The benefits and costs of allocating space in an existing reservoir to river regulation
Authors: Higgins Roger J.
Published: February 2007

Subsequent to the selection of design capacity and the construction of a storage reservoir, water demands, valley land‐use, and economic constraints may change and the reallocation of storage space in an existing reservoir may become desirable. The benefits of reallocating space to flood mitigation are the equivalent annual flood damages averted, while the costs arise from water shortages which would not have occurred if space had not been reallocated. These benefits and costs can be quantified for a particular region and the optimal airspace provision calculated. In a case study area, reallocation of part of the storage volume was justified, while excessive reallocation would result in significant net costs to the region. The optimum airspace allocation was not sensitive to the value assigned to water. The procedure used here could be applied to other river valleys, where the solution would be dependent on the intensity of land‐use, as it influences both potential flood damages and the costs of water shortages.
Deterministic modelling of vertical circulation in shallow lakes and reservoirs
Authors: Falconer R. A. , Cox I. C. S.
Published: February 2007

The paper describes the development and application of a two‐dimensional breadth averaged deterministic mathematical model to determine the wind induced vertical circulation and mixing in shallow lakes or impoundments. Such models are increasingly being used by water engineers and scientists so that water supply lakes and reservoirs can be managed and operated more efficiently, particularly in connection with environmental and ecological considerations. The model includes the solution of the two‐dimensional form of the mass and momentum conservation equations, with particular emphasis being placed on the inclusion and representation of the bed friction, wind shear stress, and the turbulent mixing process. The pressure field was determined from the depth averaged form of the governing differential equations, with the complete set of equations being expressed in an implicit finite difference form for solution. Results from the model were compared with analytical solutions for two idealized flow fields, with good agreement being obtained between both sets of results. Simulations of wind‐induced circulation were then performed for two U.K. reservoirs, with the results obtained being in keeping with the published results of other researchers.
Influence of regulation on environmental conditions and the macroinvertebrate community in the upper Colorado river
Authors: Rader Russell B. , Ward James V.
Published: February 2007

The influence of stream regulation on environmental conditions and concomitant alterations of macroinvertebrate community structure was determined from field studies conducted from September 1981‐June 1983 at three sites on the upper Colorado River. Site 1 (reference site) was located above Granby and Shadow Mountain Reservoirs, a deep‐release storage impoundment, whereas sites 2 (regulated site) and 3 (recovery site) were located 0·4 and 4·0 km, respectively, below the dam.

Although macroinvertebrate diversity was reduced at the regulated site compared to both the reference and recovery sites, the number of taxa (43) was considerably higher than values reported from studies of other regulated streams in the Rocky Mountains. Macroinvertebrate mean annual density in the regulated site was twenty times higher than at the reference site and slightly higher than the recovery site. The regulated site was characterized by the absence of heptageniid mayflies, reductions in stoneflies, caddisflies, shredders, and predators, and high densities of Baetis spp., Ephemerella infrequens, chironomids, and non‐insect taxa. Many of these faunal changes are attributed to alterations in the temperature regime induced by regulation and to changes in the source and temporal sequencing of organic detritus. Although the number of annual degree days was actually greater below the dam than above the reservoir, other components of the thermal regime was severely altered by regulation. At the regulated site the primary source of coarse organic detritus was autochthonous (decaying algae) with a vernal pulse, in contrast to the typical autumnal pulse of allochthonous leaf litter. There was no evidence that the greater substrate permeability and flow predictability below the dam directly influenced the reduction of species.
Seasonal variation in the composition of the drift below a peaking hydroelectric project
Authors: Layzer James B. , Nehus Timothy J. , Pennington Wendell , Gore James A. , Nestler John M.
Published: February 2007

We used 0.5 m diameter nets to sample the drift downstream from a peaking hydroelectric project on the Caney Fork River, Tennessee. The relative contribution of the terrestrial, lentic, and lotic environments to stream drift varied seasonally. Stream benthos (primarily Chironomidae and Lirceus fontinalis) occurred in the drift throughout the year; however, their relative importance varied seasonally. Daphnia sp. from the reservoir also occurred in the drift year round with the highest densities in fall and spring when they were the predominant species in the drift. In summer, terrestrial insects apparently utilized exposed portions of the river bed during periods of no power generation. In June as the river stage increased following initiation of generation, adult terrestrial insects became a major component of the drift. Threadfin shad (Dorosoma petenense) dominated the biomass in the drift during December. Although the importance of stream benthos to fish populations is generally recognized, the contribution of the terrestrial and upstream reservoir environments to the forage base in the tailwater may also be important and should be considered in developing management strategies for tailwater fisheries.
Assessing the impacts of stream regulation in the flathead river Basin, Montana, U.S.A. I. Simulation modelling of system water balance
Authors: Hall Charles A. S. , Jourdonnais Jon H. , Stanford Jack A.
Published: February 2007

A Fortran‐based simulation model was written to predict water movement into and out of Flathead Lake. Since tributaries, the lake proper and downstream flows were either freeflowing or regulated by hydroelectric dams, it was necessary for the model to adjust simulated, regulated flows to account for predicted natural flows. Empirical input to the model consisted of daily discharge data or statistical summaries of data sets for an 80+ year period of record for gauging sites on major tributaries, the lake and its outlet river. The model produces graphical output of empirical observations or simulates lake levels and riverine flows on the basis of any selected period of the record. The model was successfully used to evaluate the feasibility of various water management scenarios to enhance or protect fish and wildlife and also permit various hydropower production quotas.
Framework for control of dynamic ice breakup by river regulation
Authors: Ferrick M. G. , Mulherin N. D.
Published: February 2007

In this paper, we describe and classify the entire range of ice breakup behaviour, from thermal to dynamic, to provide order to this complex process. The theory and model of Ferrick et al. (1986b) are refined, building on the concept of an intrinsic relationship between river waves and dynamic ice breakup. A force balance is developed for a common dynamic breakup behaviour. Empirical criteria that quantify the resistance to breakup of an ice cover are obtained from a case study and compared with published values. Sensitivity studies of ice breakup with the completed model demonstrate insights that follow from the theory presented, and the intuitive nature of the results. This framework for understanding river ice processes provides the option for ice management by river regulation, and we focus on the potential for control of ice breakup. The concept of controlled breakup involves a release of water from a dam that moves the ice downstream of locations with a high potential for damages during breakup. The abrupt, short‐duration characteristics of the controlled release, patterned after those of unregulated river breakup, minimize both the volume of water required to cause breakup and the water levels at breakup. The open water created by the breakup collects heat that increases the rate of melting of the ice. The benefits of successful regulation include the prevention of flooding, minimum erosion and decreased potential for ice damage to structures during breakup without adverse affects on the environment.
The effect of stream regulation on the physico‐chemical properties of the palmiet river, South Africa
Authors: Byren Barbara A. , Davies Bryan R.
Published: February 2007

The effect of regulation, by multiple impoundment, on ‘discontinuity’ (recovery) ‘distances’ (sensu Ward and Stanford, 1983) for various physico‐chemical attributes of the Palmiet River (a short, steep gradient, cool temperate, acid, low‐nutrient system) was investigated. Physico‐chemical features were measured monthly, from February 1986 to August 1987, at 11 sites along the river, but concentrating on two zones: one below an upper‐reach impoundment, Nuweberg Dam, and one below a middle‐reach impoundment, Arieskraal Dam. Median total suspended solids, nitrates, nitrites and ammonium all increased below both dams with varying levels of ‘recovery’. Median spot temperatures, pH and alkalinity increased below Nuweberg, but decreased below Arieskraal Dam, whereas the converse was true for soluble reactive phosphate. Nuweberg had no effect on conductivity and total dissolved solids, while Arieskraal caused a slight decrease. The river remained well oxygenated down its length.

Distinct seasonal variations were recorded for: flow rate, with flow reversal below Nuweberg and flow constancy below Arieskraal; temperature, with seasonal shifts and dampening of annual temperature range below both dams; alkalinity, with seasonal shifts below Arieskraal, and nitrites and nitrates, but not for any other attributes. At least partial recovery was noted in all cases, but in some instances, recovery was incomplete to the estuary. The implications of such alterations, for invertebrates, in terms of reduction in habitat diversity as well as for food supply must be considerable and studies are currently under way to determine community structure and diversity.
Effects of an upland impoundment on structural and functional properties of a small stream in a basaltic plateau (golan heights, Israel)
Authors: Tuch Koby , Gasith Avital
Published: February 2007

The aim of the study was to evaluate the impact of an upland storage reservoir, typical of the series of reservoirs in the Golan Heights basaltic plateau, on structural and functional properties of the downstream ecosystem, in the vicinity of the reservoir, shortly after damming.

The effect of impoundment on water quality conditions may be divided into winter‐spring, and summer periods. In the former, the impoundment seems to lengthen the period of flow of runoff quality water. This is evident by the elevated winter and spring turbidities and the higher concentrations of suspended solids below the reservoir. In summer, water quality below the reservoir is controlled by the consequences of stratification in the reservoir. The hypolimnial release results in depression of the maximal temperature and narrowing of the daily and seasonal temperature variations. It supplies water enriched in nutrients and low in oxygen, suspended solids and turbidity. The macroinvertebrate community responds to impoundment in density changes and shifting of dominance. We hypothesize that the thermal effect of hypolimnial release from warm monomictic reservoirs on the invertebrate community of warm streams will differ from an equivalent thermal change caused by cold dimictic reservoirs in cold, temperate zone, streams.

The effect of impoundment on functional properties of the ecosystem are most pronounced. The rate of production of benthic algae biomass below the reservoir increased by more than two orders of magnitude, but the effect diminished downstream. The rate of processing of plant material below the reservoir was lower than above the reservoir. Further investigation is needed to clarify this effect. Changes in reservoir operation are recommended to diminish the effects of impoundment.
Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera
Authors: Stanford Jack A. , Ward James V.
Published: February 2007

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.
Changes in benthic animal production of a weir basin after eight years of succession
Authors: Fjellheim Arne , Raddum Gunnar G. , Schnell Øyvind A.
Published: February 2007

Benthic animal production was studied in a weir basin area of western Norway in 1984, eleven years after construction of the basin and eight years after the first benthic study. Compared to estimates from 1976, a marked change in production and species composition had occurred. Benthic animal production at two stations inside the basin was 199 and 169 KJ m−2 yr−1, an increase of 440 and 270 per cent respectively compared to 1976. In a riffle upstream of the basin, the production estimate was 50 KJ m−2 yr−1, a decrease of 40 per cent since 1976. Chironomids formed the main contribution to the increased production in the weir basin, mainly through increased abundance of larger species like Stictochironomus pictulus and Micropsectra spp. Also other species more adapted to lentic water, like the ephemeropterans Siphlonurus aestivalis and Ameletus inopinatus, showed increased density. The fauna succession and increased production in the weir basin was mainly due to improved habitats and food conditions, as the amount of organic sediments had increased since the first production study.