bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characteristics of seston in a regulated Appalachian Mountain river, U.S.A
Authors: Kazmierczak R. F. , Webster J. R. , Benfield E. F. 
Published: February 2007

AbstractSix size classes of seston were collected seasonally from the New River, Virginia, U.S.A., during three flow regimes: low flow, discharge changes resulting from daily cycles of hydroelectric power generation, and naturally occurring storm discharge cycles. Seston concentration and particle shape, density, and settling velocity were measured for all size classes, seasons, and flow regimes. Seston concentration, density, and settling velocity varied significantly with size class, season, and flow regime. Total concentrations ranged from a low of 0.47 mg litre−1 during autumn base‐flow to a high of 92.6 mg litre−1 during a winter storm. Mean seston densities ranged between 1.60 and 2.02 g cm−1, which is much lower than previously published measurements for rivers, suggesting that seston in the New River may be mainly organic‐inorganic aggregates. Mean seston settling velocity was lowest during low‐flow and hydroelectric discharges (0.10 cms−1) and highest during storms (0.19 cms−1). Seston particle shape varied significantly only with size class. The inability of a commonly used transport equation to predict transport during most discharge conditions suggests that, in some systems, seston concentration and transport may be less a function of discharge and power than of long‐term seasonal and short‐term discharge cycle effects on the density and size characteristics of seston.
Modification of temperature behaviour through regulation of a British river system
Authors: Webb B. W. , Walling D. E. 
Published: February 2007

AbstractThe effects of flow regulation on temperature behaviour in the River Exe, Devon, U.K. have been studied, and attention is given to the local impact of impoundment and its downstream persistence. Temperature levels and seasonal thermal regime are considered as well as diel temperature fluctuations and temperatures during extreme weather conditions. Variations in temperature during individual reservoir releases have also been monitored. The impact of impoundment has been to make the stream environment immediately below the dam more homothermous so that temperatures rearely rise above 17·5°C or fall below 2·0°C, and monthyl average diel ranges are < 3 and < 1°C in summer and winter months respectively. In contrast to other reservoirs in Britain and abroad, this effect has been largely caused by increased groundwater flow downstream from the reservoir following impoundment. Regulation has also affected downstream temperature behaviour and has moderated the thermal regime of the Exe mainstream. This influence is generally restricted to a distance of up to 20 km from the dam, but in conditions of hot weather and low flows it may extend to almost 40 km from the impoundment.
River regulation by seasonal groundwater abstraction: The case of the River Itchen
Authors: Giles D. M. , Lowings V. A. , Midgley P. 
Published: February 2007

AbstractThis paper describes the development of groundwater to regulate the flows of the River Itchen in Southern England. The permeable chalk geology of the river catchment makes the use of natural groundwater storage more cost effective than conventional surface reservoirs. The principles of groundwater regulation and the construction and testing of the first two schemes are described. Flow extension and mathematical modelling have been used to assess yields and assist with operational decisions. The paper concludes that groundwater regulation is a viable alternative to reservoirs in permeable catchments and further schemes are planned.
Channel change and sediment transport in regulated U.K. rivers
Authors: Carling P. A. 
Published: February 2007

AbstractThe history of investigations of channel change consequent upon river regulation is traced from the late 1960s until the present. The associated sediment transport and depositional processes are also reviewed. Conveniently the approaches adopted historically have fallen into three basic groups, these are: (1) analyses of the changes in channel networks as evident in adjustments to hydraulic geometry related to catchment area; (2) analyses concerned with sediment transport processes and channel adjustments at the reach scale (typically utilizing regime‐type concepts), and finally; (3) more recent attempts at an integrated approach utilizing holistic concepts of channel change over extended time periods.A major conclusion drawn from this review is that each reservoir‐catchment system is unique, producing singular responses that cannot easily be integrated into a basic general model except at a facile level. The continuing lack of complete theoretical models of channel adjustment is a hindrance in predicting regulation effects and may be related to limited understanding of such factors as sediment supply dynamics and bank collapse mechanisms. Emphasis is placed on: the importance of the aggregational as well as the well‐known degradational response of channels below dams; the recognition of suitable temporal frameworks; the potentially destabilizing effect of rare large floods; and the local effects of unregulated tributary inflows. In addition more sophisticated theory and analysis needs applying to the transport and subsequent deposition of suspended sediments in gravel‐beds whilst the three‐dimensional facies relationships of regulated river alluvial suites need clarification in the light of recent initiatives concerning the sedimentary architecture of other alluvial systems.
Compensation flows in the UK: A hydrological review
Authors: Gustard Alan 
Published: February 2007

AbstractA survey of United Kingdom reservoirs identified the development of compensation flow policy from the early 19th Century to the present day. Details on the level and pattern of releases below 261 impounding reservoirs provided the basis for assessing the spatial and temporal variation in compensation flows and the impact of impoundment on downstream flow regimes. By standardizing compensation releases by the natural pre‐impoundment mean discharge, release patterns from reservoirs with a wide range of both catchment area and climate could be compared. Analysis of the change in flood and low flow frequency following impoundment enabled the impact of reservoir regulation to be evaluated at the regional scale. For individual reservoirs the natural downstream increase in river flow provides a basis for determining the length of river reach which is sensitive to regime changes. The majority of present day compensation discharges were set to satisfy river interests which no longer apply or were based on inadequate hydrological or biological information. This has led to a wide range of release patterns and it is therefore recommended that the re‐evaluation of existing water resource schemes should include an assessment of the suitability of current release patterns for present day downstream demands and water resource requirements.
Prediction of regulation effects on natural biological rhythms in south‐central African freshwater fish
Authors: Jackson P. B. N. 
Published: February 2007

AbstractFish in south‐central African freshwaters are governed by biological rhythms. First, these are associated with the markedly seasonal summer annual rainfall when breeding takes place with an initially high mortality among newspawned juveniles. Second, a longer term rhythm of annual rainfall variability occurs in cycles up to or more than a decade. These cause water levels to vary from exceptionally high levels to near desiccation in endorheic systems.Studies of the shallow endorheic lakes Mweru Wa'Ntipa (Zambia), Ngami (Botswana), and Chilwa (Malawi) are cited showing that species diversity rapidly increases by colonization from adjacent ‘inocula’ (relict communities surviving in more permanent nearby water bodies, e.g. deep pools in perennial streams) when filling starts. During the drydown phase of the cycle, diversity decreases through lack of annual breeding environment and diminution of water quantity and quality. A few, usually three, species remain longer which, being physiologically hardy or showing phenotypic plasticity, are tolerant of higher salinity, temperature, etc., conditions associated with dry‐out. Despite the lakes' wide geographical separation these taxa in every case are a single species of the tilapia, genus Oreochromis, the catfish Clarias gariepinus, and the minnow Barbus paludinosus, which build up large populations valuable to local fisheries.Evidence from the Pongolo River, Zululand, regulated by a large dam, shows that fish of downstream endorheic lakes react similarly to artificial water deprivation, with mainly the same taxa persisting. Managed water releases timed to coincide with breeding rhythms largely restore the conditions which previously prevailed. Data from Zambezi impoundments indicate conversely that reaction of previously riverine fish to large man‐made lakes is for previously sparse lentic taxa like Oreochromis to proliferate greatly while lotic forms like Labeo are reduced in number.Since fish stocks are a valuable natural resource, such basic scientific results may be applied with great advantage. The collaboration between engineer, biologist, and management authority can minimize adverse environmental effects and predict better opportunity cost assessments of a projected river manipulation.
Determination of hydraulic parameters for instream flow assessments
Authors: Courot A. 
Published: February 2007

AbstractDetermination of the hydraulic parameters of a stream is the first stage in the instream flow incremental method (IFIM). Two different modellings have been applied to simulate the hydraulic conditions (i.e. depth and velocity) of the Orne river at Rabodanges in order to assess the changes in fish habitat with the flow. One process consists of representing the reach examined by a few sections (the pilot sections), the other is a conventional flow model. The accuracy of both types of model has been calculated by comparison with depth and velocity data available for four different rates of flow. As regards the flow model, the accuracy of depth calculations is average (16 per cent) but decreases for low rates of flow. Velocity values are less accurate (24 per cent). Concerning the pilot sections method, the degree of accuracy of velocities should be improved (80 per cent) but the accuracy of depths is interesting (7 per cent). The representation of the flow conditions the accuracy of per cent usable area (PUA). For brown trout juveniles and fry the accuracy on PUA is of the same order of magnitude as the degree of accuracy of depth. The inaccuracy on velocities due to the method is not totally reflected in the PUA values, the probability‐of‐use curves of the species considered can act as a filter for errors linked to the method followed for assessing hydraulic parameters.
The Orinoco river: A review of hydrobiological research
Authors: Vásquez Enrique 
Published: February 2007

AbstractThe Orinoco River is one of the world's longest rivers (2060 km) and in terms of average water discharge (36000 m3 s−1) it ranks third. Seventy per cent of its basin (1.1 × 106km2) is found in Venezuela and the rest in Colombia. Due to the uneven distribution of the population toward the northern coastal areas (97 per cent of the population inhabits 55 per cent of the country with only 16 per cent of the surface waters) plans have been carried out to develop resources in the Orinoco Basin. So far these programs include mining (mainly iron and bauxite), oil exploration and extraction from the Orinoco Oil Belt, industry, river transport, and hydroelectric exploitation. Development of the latter has involved the construction of two dams on the Caroní River (the most important blackwater tributary of the Orinoco) and two more are planned on this same river. Hydroelectric projects are also being considered for the Orinoco River. Physicochemical and biological characterization has been regarded as of major importance to establish base‐line information to detect and quantify possible alterations in this river which is considered to be in a pristine state. Systematic hydrobiological research has recently been carried out in the river, some of its major tributaries, and floodplain lakes, and a fair amount of knowledge has emerged mainly from its lower section.Phytoplankton studies have revealed the presence of over 400 species of algae. Zooplankton research has identified 116 taxa of rotifers and 58 taxa of cladocerans. In general plankton densities negatively correlate with water level. Diatoms were observed to predominate in the Orinoco River while Cyanophyta predominate in the studied floodplain lakes. Seventeen aquatic macrophyte species have been recorded in the lakes of the Orinoco with high densities of Eichhornia crassipes, Oxycarium cubense, and Paspalum repens. Rooted emergent and floating‐plant cover tends to increase rapidly during high water.Some 318 species and subspecies of fish have been reported for the Orinoco Basin, even though this number is far from complete. Preliminary data have revealed different species associations among relatively close lakes with biomasses ranging between 30 to 900kg ha−1 displaying considerable variations in diversity and species richness. Fisheries along the Orinoco are mainly of a multispecific nature and their overall potential has been estimated as being in the order of 45 000t yr−1.In general, management plans have taken into consideration the multispecific potential of the Orinoco Basin but indicate a lack of sufficient knowledge of the physical, biological, and social aspects involved. Furthermore development plans tend to precede the generation of this basic knowledge, thereby increasing the risks of conflict among the various users of the resources involved.
River fisheries in Brazil: A review
Authors: Jr. Miguel Petrere 
Published: February 2007

AbstractRiverine fisheries in Brazil are reviewed. There is a broad description of the environment and the fish, and arguments for the high diversity of fish fauna diversity are examined. The country is divided into five large river basins and the fisheries are described in relation to the main fish species caught, the main gear employed, and the fishing strategies. Exotic species introduction is discussed along with strategies for fish stock management. Effects of dams on resident fish stocks and consequences for the small scale fisheries are discussed and compared with the effects of pollution.
Long‐term nitrate trends in the river trent and four major tributaries
Authors: Josæ P. 
Published: February 2007

AbstractNitrate levels which have been rising in many British rivers for at least thirty years have become of particular interest since Britain adopted the EC Drinking Water Directive. The literature examining nitrate trends in the rivers of the U.K. and Eire is reviewed. Long‐term nitrate concentration trends are derived for eight sites in the River Trent drainage system. These include sites on two rural tributaries, two urbanized tributaries, and the main river. Currently, mean annual concentrations for these sites range from about 4.0 mg1−1N in the rural catchments, to 12.4 mg 1−1 N in the urbanized tributaries, and to between 8.7 mg 1−1N and 11.0 mg 1−1 N along the mainstream. Moreover rates of increase of nitrate concentration of approximately 0.06 mg 1−1 N yr −1 in the rural catchments, contrast with values up to 0.20 mg 1−1 N yr −1 in the two urbanized tributaries and River Trent. Long term nitrate loads have been calculated for the River Trent at Nottingham using a discharge weighted mean interval method. This method probably provides the best available estimate of nitrate loads calculable from irregular data of variable sampling frequency for lowland rivers. Annual nitrate loads varied between 10700t yr −1 and 29 800t yr −1 over the period of record. A rate of increase in nitrate load of 455 t yr −1 was obtained. The increases in nitrate concentrations and loads within the Trent basin are matched by similar rates of increase in other European catchments.
Long‐term effects of navigation dams on a segment of the upper Mississippi River
Authors: Grubaugh J. W. , Anderson R. V. 
Published: February 2007

AbstractNavigation dams on the upper Mississippi River have altered the long‐term relationship of river stage to river discharge. Analysis of the 34‐year pre‐dam and 74‐year post‐dam data sets indicated that the completion of Lock and Dam 19 in 1913 increased river width and volume behind the dam. The immediate impact was a higher mean river stage less influenced by changes in river discharge. The dam's long‐term impact was to increase sedimentation causing a steady loss of both river width and volume that resulted in stage/discharge relationships approaching those of the pre‐dam era. The present condition of higher mean river stage coupled with greater stage fluctuation is a major factor in the increased recurrence and duration of floods on the upper Mississippi River in recent decades.
Aquatic invertebrate surveys as a water quality management tool in the Anglian Water region
Authors: Extence C. A. , Ferguson A. J. D. 
Published: February 2007

AbstractThe benefits of utilizing biological data in managing water quality are discussed, and the drawbacks and restrictions of traditional methods used to summarize and present biological results, are briefly outlined. Recent work in the Anglian Water region has led to the development of the Lincoln Quality Index, and this method overcomes some of these problems, enabling biological data to be usefully incorporated into environmental management programmes. Examples are given to show how the technique can assist in detecting and determining the significance of intermittent and shock pollution loads. The impact of deteriorating sewage effluent quality is also considered in some detail. The adoption of the Lincoln Quality Index method offers the opportunity for substantial cost savings, as well as allowing water quality surveillance programmes to be undertaken with increased flexibility. Areas where further work would be beneficial are finally identified.
Prediction of invertebrate communities using stream measurements
Authors: Wright J. F. , Armitage P. D. , Furse M. T. , Moss D. 
Published: February 2007

AbstractAn account is given of the development of a computer‐based system for prediction of the invertebrate fauna to be expected at unpolluted sites using environmental features. The variables for use in prediction and the flexibility of the output, with respect to taxonomic level, are demonstrated using an early version of the system which has been tested within the water industry. The practical value for river management of predictions of species, families, and biological indices is elaborated. In addition, the relevance of the system throughout Great Britain for setting target values of a biological index is demonstrated.A new version of the prediction system has recently been developed. It has application over a wider range of river systems and incorporates additional options for prediction, as requested by the Water Industry. Further developments of the system to make it more efficient for operational use are now under active consideration.
Assessment of the value of rivers for Otters (Lutra lutra)
Authors: Andrews Elizabeth 
Published: February 2007

AbstractThe British otter Lutra lutra L. requires good water quality, an adequate supply of fish and certain types of vegetation or cavities (holts) adjacent to water bodies for resting and breeding sites. In the U.K. otters and their holts are legally protected.Trained surveyors are needed to confirm the presence of otters on a river as the animals are rarely seen, but their tracks and droppings (spraints) may be detected. To evaluate a river for otters, information is required on water quality, fish species and biomass, as well as available habitat. Pioneer evaluation work based on the River Corridor Survey techniques has been done on Welsh rivers with good otter populations. Riparian vegetation, especially trees, is shown to be particularly important. This work is now being extended to areas on the margins of otter distribution such as the lower river Wye in England and Wales. Such surveys provide important management information for water authorities and give opportunities for enhancement work to benefit this animal.
Modelling water quality of a reregulated stream below a peaking hydropower dam
Authors: Zimmerman Marc J. , Dortch Mark S. 
Published: February 2007

AbstractThis paper describes CE‐QUAL‐R1V1, a dynamic, one‐dimensional, stream water quality model capable of simulating branched riverine systems with multiple hydraulic control structures, such as weirs, reregulation dams, and navigation locks and dams. We provide examples of potential water quality impacts associated with operations alternatives for a reregulation dam proposed for construction downstream from Buford Dam on the Chattahoochee River near Atlanta, Georgia, in the southeastern United States. Model calibration, confirmation, and application are examined. The model is calibrated for stage, transport, temperature, dissolved oxygen, carbonaceous biochemical oxygen demand, ammonium‐N, and nitrate‐N. Results indicate that release operations which maintain cool temperatures in summer may cause undesirable decreases in dissolved oxygen and increases in dissolved iron in autumn. Flexibility in release scheduling is recommended to avoid unnecessary problems.
Comparison of macrobenthos in braided and channelized sectors of the Drôme River, France
Authors: Peeters E. T. H. M. , Tachet H. 
Published: February 2007

AbstractThe influence of braided pattern on macrobenthic communities was studied in the Lower Drǒme River (France). The qualitative differences between embanked and braided sections are weak. The sessile species (for example Psychomyia pusilla) are more frequent in the embanked section whereas the drifting species (for example Baetis fuscatus) are more frequent in the braided section. The density of macroinvertebrates in the latter, especially in the secondary channels, is higher than in the embanked section, but the diversity remains low because the location of the channels changes at each extreme flood.
Sediment deposition in cutoff meander bends and implications for effective management
Authors: Douglas Shields F. , Abt Steven R. 
Published: February 2007

AbstractCutoff bends along modified, stabilized streams often constitute a valuable recreational, ecological, and aesthetic resource. However, their resource value rapidly declines as they fill with sediment, and new cutoff bends do not form to replace them in highly managed rivers.Data from repetitive hydrographic surveys of 20 cutoff bends along four rivers in the southeastern United States were examined using conceptual and analytical models in order to provide a more objective basis for bend management. Bend volume was found to be a log‐decay function of cumulative water discharge through the cutoff reach. Regression analyses were used to generate functions to predict the log‐decay constant. The log‐decay constant varied directly with master stream suspended bed‐material concentration and inversely with variables describing the geometry of the upstream entrance of the old bend. Management of cutoff bends should focus on sequencing construction activities and modification of the upstream bend entrance geometry to reduce the quantity of bed material diverted into the bend. Construction of blockage structures to top‐bank elevation in upstream entrances of cutoff bends is recommended for systems with average suspended bed‐material concentrations greater than about 50ppm. Blockage or modification of entrance geometry of longer bends preserves more aquatic habitat longer than similar levels of effort directed toward shorter bends. Maintenance of a hydraulic connection between the river and at least one end of the cutoff bend is recommended.