bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessing options for stream regulation using hydrologic simulations and cumulative impact analysis: Flathead River Basin, U.S.A.
Authors: Jourdonnais J. H. , Stanford J. A. , Hauer F. R. , Hall C. A. S.
Published: February 2007

This study attempted to resolve regulation problems up‐ and downstream of Flathead Lake and on the lake proper. Members of a technical working group, representing eight water and wildlife management agencies, contributed 75 regulation scenarios they deemed necessary to conserve or enhance ecological (fish and wildlife) and societal (hydropower production, flood control, and recreation) resources for which they had management authority. The hydrology model simulated the effect of each scenario on system water balance; scenarios that were within the physical and legal constraints of the system were accepted for determination of cumulative impacts on resources. A multiattribute tradeoff analysis was used to assess cumulative impacts to key resources as a consequence of each regulation scenario (simulation) accepted for evaluation. Impacts were subjectively and independently quantified by each member of the working group following a point and importance weighting system agreed to a priori. Valuation of impacts was done on the basis of 36 technical studies of the effects of regulation on system resources. Impact valuations were summed to yield a variable referred to as weighted cumulative impact (WCI), where the highest, positive WCI indicated least cumulative impact on resources. Scenarios were then ranked in terms of WCI. When ecological resources only were evaluated, the preregulation Flathead Lake scenario generated the highest WCI. However, when all resources were considered, scenarios ranked very differently but a preferred alternative was identified by virtue of its highest WCI. This interactive process of hydrology simulation and computation of cumulative impacts mediated resource conflicts and served as an important tool in deriving water management recommendations in the Flathead River Basin. The process may be useful elsewhere.
Effect of decreased temperature on growth and smoltification of juvenile atlantic salmon (salmo salar) and brown trout (salmo trutta) in a norwegian regulated river
Authors: Saltveit Svein Jakob
Published: February 2007

The lowermost 20 km of the River Surna, northwestern Norway receives cool water during summer from a hypolimnetic release mountain reservoir. In this part of the river, yearlings of both Atlantic salmon and brown trout are significantly smaller compared with those in the upper section of the river, which is unaffected by the cold water release. The slower growth below the power station causes both Atlantic salmon and anadromous brown trout to smoltify one year later compared with fish in the upper section of the river. This leads to higher mortality and therefore lower production of both adult salmon and trout.
Macroinvertebrate responses along a complex regulated stream environmental gradient
Authors: Voelz Neal J. , Ward J. V.
Published: February 2007

Samples were collected year‐round over a one‐year period at sites located downstream from a hypolimnetic‐release reservoir on the Blue River, Colorado, to examine macroinvertebrate responses along a complex environmental gradient induced by river regulation. Six sampling sites were established in riffles downstream of the dam using approximately a geometric progression starting at 0.25 km. Ordination techniques were used to elucidate macroinvertebrate distributional patterns along the complex environmental gradient. The detrended correspondence analysis (DCA) showed a sequential faunal gradient with the most rapid change occurring within the first 2.0 km below the impoundment. Detrended canonical correspondence analysis (DCCA) was used to relate faunal distributions to downstream changes in environmental variables. Downstream decreases in periphyton standing crop and minimum temperatures, and downstream increases in food resources and maximum temperatures, were identified as the major variables structuring faunal assemblages. The combined use of different gradient analysis techniques proved useful for identifying distinct macroinvertebrate distributional patterns and the environmental variables that may be responsible for these patterns.
The Rhine rift valley ground water—river interactions: Evolution of their susceptibility to pollution
Authors: Carbiener R. , Tremolieres M.
Published: February 2007

The exchange processes between the Rhine river and the alluvial aquifer were analysed in the upper part of the rift valley (upstream of Strasbourg). Hydraulic works, and the consequent suppression of flooding, along the Alsace Rhine floodplain greatly modified these processes. The transfer of persistent toxic micropollutants (organochlorine compounds, mercury), and non‐persistent pollutants (organophosphorous compounds: Sandoz spill) from the Rhine to the groundwater‐fed streams was exhibited by pollutant bioaccumulation in fish (particularly in the eel) and eutrophication of these streams near the canalized river.

Comparison of the hydrological functioning of the two main river floodplains (the Rhine and its tributary, the Ill in the Alsace Rhine plain) shows two completely different exchange processes: in the case of the canalized Rhine, the groundwater is affected by direct transfer of pollutants through the channel bed. In the other case, that of the river Ill, where the floodplain is still widely flooded each year, the self‐purification of the floodwaters transferred to the groundwater is very effective: the soil‐root system of alluvial forest and meadow apparently having a high purification capacity.
Transferability of water entitlements in Australia
Authors: Pigram John J. , Musgrave Warren F.
Published: February 2007

Until recently, entitlements to water in Australia have been tied to a specific area of land. Several State water management agencies have now adopted more flexible arrangements for the transfer of water rights between users on regulated streams. The case for freer transfers is linked to the perceived need for greater efficiency in water use. Transferability also has potential in facilitating the movement of water between different sectors of the water industry and in achieving more rational and environmentally acceptable use of resources. Justification for breaking the nexus between water rights and land needs to be assessed against a number of physical, social, economic, and environmental issues some of which have only become apparent with accelerated resource development, and expansion and concentration of Australia's urban‐industrial base. These trends are reflected in competing claims on water resources to supply the increasing demand from city‐based populations; to maintain the viability of industrial systems; to sustain more intensive high technology forms of irrigation agriculture; and to satisfy the water needs of often remote mining and tourist developments. No longer can such claims easily be met by harnessing further water resources. Transfers of water rights, on a much larger scale, within and between water‐using regions and sectors, and across State borders, are likely to be an important element in Australia's water industry in coming decades.
Benthic macroinvertebrate communities in nonregulated and regulated waters of the clearwater river, Idaho, U.S.A.
Authors: Munn Mark D. , Brusven Merlyn A.
Published: February 2007

Benthic macroinvertebrates were examined over a two‐year period in nonregulated, regulated, and semiregulated reaches of the Clearwater River in northern Idaho. Macroinvertebrate communities in the nonregulated reach above Dworshak Reservoir were taxonomically diverse at all stations. In contrast, the macroinvertebrate community in the regulated reach of the North Fork of the Clearwater River (NFCR) was severely altered with high macroinvertebrate abundance and low taxa richness (2 to 8 taxa). Orthoclad chironomids dominated this reach composing between 68 and 99 per cent of total benthic invertebrate numbers. The mayfly Ephemerella infrequens was the only other macroinvertebrate to be abundant in the regulated reach. The major factors contributing to the simplified macroinvertebrate community are reduced habitat diversity, fluctuating water levels, altered thermal regime, and possibly an altered food supply. The effects of the dam were mitigated in the semiregulated Mainstem of the Clearwater River (MSCR) due to the merger of a nonregulated fork entering 2.5 km downstream from the dam. The macroinvertebrate community in the semiregulated MSCR was more complex than the regulated reach with a community structure resembling that found above the reservoir.
Complex response of a sand‐bed stream to upstream impoundment
Authors: Sherrard J. J. , Erskine Wayne D.
Published: February 2007

Mangrove Creek Dam, the eighth highest dam in NSW, Australia has induced a complex response of the downstream, sand‐bed channel. Since dam closure on 1 October 1981, mean daily flows and the peak instantaneous discharge of floods have been reduced greatly (up to 94 per cent) and nearly 100 per cent of the incoming sediment load has been trapped behind the Dam. The magnitude of the hydrologic effects decreases with distance downstream. River response varies in direct proportion to the magnitude of the altered hydrologic regime and includes alternating but localized bed aggradation and degradation as well as channel contraction. Contraction has occurred by a combination of in‐channel bench construction, the formation and bank attachment of longitudinal bars and bank deposition. Leptospermum polygalifolium has rapidly colonized these in‐channel deposits and will result in the stabilization of benches. Armouring has not been a significant feedback process to date because of the limited degradation and low gravel supply. It is postulated that the above trends will continue, thus converting the former large, straight, active sand‐bed channel into a small, sinuous, well‐ vegetated sand‐bed stream.
Turbidity control and fisheries enhancement in a bottomland hardwood backwater system in Louisiana (U.S.A.)
Authors: Ewing Michael S.
Published: February 2007

In response to a noticeable decline in recreational fishing in the formerly productive Larto—Saline backwater complex of east central Louisiana, a study was begun to identify causative factors for the decline and to determine effective methods to remedy the problem. To this end, water quality and fisheries surveys were conducted in the system for the study period 1 July, 1981 to 30 June, 1989.

Data collected during the early years of the study indicated chronically high turbidity (> 100 FTU) to be the major factor limiting game fish production. The high turbidity can be related to man‐made alterations of natural flood patterns that had changed the major source of backwater flooding from Black River to the highly turbid Red River.

In September, 1986, a construction project was undertaken to restore flood patterns to approximate natural conditions. Sampling subsequent to this construction has shown a significant decrease in turbidity and an increase in game fish production.
Development of water level regulation strategies for fish and wildlife, upper Mississippi river system
Authors: Lubinski K. S. , Carmody G. , Wilcox D. , Drazkowski B.
Published: February 2007

Water level regulation has been proposed as a tool for maintaining or enhancing fish and wildlife resources in navigation pools and associated flood plains of the Upper Mississippi River System. Research related to the development of water level management plans is being conducted under the Long Term Resource Monitoring Program. Research strategies include investigations of cause and effect relationships, spatial and temporal patterns of resource components, and alternative problem solutions. The principal hypothesis being tested states that water level fluctuations resulting from navigation dam operation create less than optimal conditions for the reproduction and growth of target aquatic macrophyte and fish species. Representative navigation pools have been selected to describe hydrologic, engineering, and legal constraints within which fish and wildlife objectives can be established. Spatial analyses are underway to predict the magnitude and location of habitat changes that will result from controlled changes in water elevation.
Flume study of the hydraulic effects of large woody debris in lowland rivers
Authors: Young W. J.
Published: February 2007

As a part of a study investigating the hydraulic effects of large woody debris (LWD) in lowland rivers, a series of small‐scale experiments were conducted in a rectangular glass‐walled recirculating flume. These experiments were undertaken to determine the order of magnitude of the increase in flood levels caused by LWD at different positions within a channel cross‐section. Position variables that were considered in these experiments were height above bed, angle to flow direction, and separation distance in the direction of flow. This study was undertaken to quantify the hydraulic benefits (primarily reduced flood levels) gained by the removal of LWD from lowland rivers, which is a common practice in several countries. From an integrated river management perspective it is necessary to weigh any hydraulic benefits of LWD removal up against the environmental costs of loss of faunal habitat, and possible geomorphic instability.

The results of these experiments indicate that the levels of LWD commonly occurring in the lowland rivers of southeastern Australia seldom cause any significant effect on flood levels. However, where LWD occur at channel constrictions, or where unusually high densities of LWD are present, the effect on flood levels will be significant.
Recovery of aquatic macroinvertebrate assemblages downstream of the Canning Dam, Western Australia
Authors: Storey A. W. , Edward D. H. , Gazey P.
Published: February 2007

Macroinvertebrate assemblages downstream from the Canning Dam, on the Canning River, Western Australia, were sampled to assess the impact of long‐term impoundment and the role of a major tributary in community recovery.

Kick samples and associated physical measurements were taken from riffle zones in three reaches in March and July 1989. The lower reach was located immediately downstream of the confluence with Stinton Creek, the first major tributary below the dam, with the middle and upper reaches positioned between the tributary and the dam.

Reduced concentrations of dissolved oxygen in the upper and middle reaches in March, compared to the lower reach were attributed to significantly higher levels of organics, high summer water temperatures, and a proposed increase in microbial activity. The build‐up of organics was probably related to reduced flushing, as a result of impoundment. Stinton Creek increased the discharge of the Canning River below the confluence, particularly in winter, which presumably prevented the build‐up of organics in the lower reach.

Significant differences in the aquatic macroinvertebrate fauna between reaches were detected. A total of 68 taxa was recorded from the lower reach, 88 per cent of which were also present in the middle and upper reaches. However, the middle and upper reaches contained a greater number of taxa (112 and 90 respectively), approximately 50 per cent of which were not recorded from the lower reach. The additional taxa were more typical of lowland rivers or lentic (standing water) systems, suggesting that physical conditions in the middle and upper reaches were more like a lowland river than an upland stream.

More collectors and shredders occurred in the upper and middle reaches, associated with the accumulation of particulate organic matter. Ordination and classification procedures based on macroinvertebrate assemblages clearly separated samples from the upper and middle reaches from the lower reach. There was also a distinct seasonal separation.

These observations support a hypothesis that while the reduced flow below Canning Dam had an impact on the macroinvertebrate fauna, confluence with a major tributary (Stinton Creek) allowed recovery of the macroinvertebrate community, through the tributary acting as a source of increased discharge. The implications for the management of impounded rivers in southwestern Australia are discussed.
Cross‐channel distribution patterns of zoobenthos in a regulated reach of the tennessee river
Authors: Haag Kim H. , Thorp James H.
Published: February 2007

The importance of substrate type and water depth was investigated in a regulated reach of a large, navigable river in the U.S.A. Benthic grab samples were collected in June and August, 1989, along two shore‐to‐shore transects in the lower Tennessee River, approximately 1.5 km downstream from Kentucky Lock and Dam. Diversity, averaged over all samples, was not significantly different from June to August. River depth of our samples, which ranged from 3.1 m to 6.5 m, significantly influenced macroinvertebrate density but had no detectable effect on the total number of taxa collected. Densities of flatworms, Asiatic clams, snails, isopods, and mayflies increased significantly with increasing depth, whereas the abundance of native mussels (Unionidae) and caddisflies decreased with depth. Substrate type (sand through cobble) influenced both the total number of taxa and the total number of organisms collected. Sample areas dominated by cobble contained significantly fewer individuals than areas composed predominantly of gravel substrate. Asiatic clams, the single most abundant species collected, were consistently more numerous on intermediate substrate sizes. In contrast, densities of native mussels, snails, and mayflies were not correlated with bottom type. Sample areas included relatively little mud and sand, resulting in relatively low numbers of oligochaetes and midges in our collections.
Development and habitat selection of chironomid communities
Authors: Grzybkowska Maria
Published: February 2007

The macrobenthos (especially Chironomidae) along channel margins has been compared for two 5th‐order rivers, the River Grabia, which has not changed its morphology for many years, and the River Widawka, which experienced an increase of channel width (by over 5 m) about eight years before the present study due to human impact. Also, the effect of frequent short‐term high water levels on the macrobenthos near the bank was investigated in the 7th order section of the Warta River downstream of a dam.

The macrobenthos distribution was found to be similar in the ‘impacted’ Warta and Widawka Rivers, with the highest abundance near the bank, decreasing towards the mid‐channel. In the marginal zone of the Widawka River, abundant detritivorous invertebrates having low oxygen tolerance (mainly Prodiamesinae and Chironomini) were observed. The percentage of Chironomini in this zone of the Warta River was even higher than that in the Widawka River. A different pattern was observed in the ‘natural’ Grabia River—the lowest species number and density were at the banks: Orthocladiinae dominated especially in the mid‐river.

A high abundance fluctuation of one of two dominant species in the margin of the Warta River—Glyptotendipes gripekoveni K. is remarkable. The larvae temporarily reached high densities on snags, which were periodically exposed and submerged by water, although over a year their density was lower (399 ind m−2) than that of those inhabiting the bottom (543 ind m−2).
Macrozoobenthos of floodplain waters of the rivers rhine and meuse in the Netherlands: A structural and functional analysis in relation to hydrology
Authors: Van Brink F. W. B. Den , Van Velde G. Der
Published: February 2007

The river systems of the Rhine and Meuse include a large number of floodplain waters showing differences in hydrology and geomorphology. A classification of 100 water bodies based on their macroinvertebrate communities has been worked out as a tool for ecological management. Analyses were performed on structural (species composition) and functional (trophic relations) aspects of macrozoobenthos in relation to hydrological, vegetational, and physicochemical parameters. Based on the classification of macroinvertebrate communities, three major groups of water bodies can be distinguished, which are related to the frequency of inundation. The flood frequency constitutes the major environmental gradient which structures the zoobenthos communities in the Dutch floodplain waters. Faunal composition is mediated by substrate availability, water chemistry, and the availability of nutritional resources. This typology serves as a basis for the prediction of the impact of hydrology changes on the macrozoobenthic communities of floodplain waters of highly eutrophic and polluted rivers.
Surface water connection and the macrozoobenthos of two types of floodplains on the upper rhine
Authors: Obrdlik Petr , Fuchs Ulrike
Published: February 2007

Macrozoobenthos (especially gastropods) abundance data have been used to ordinate sampling stations on two floodplains of the Upper Rhine with different hydraulic regimes: 30 species of gastropods were recorded in the area actively inundated by the Rhine, while backwaters that have not been flooded for over 50 years housed only 19 species.

Potamopyrgus antipodarum is a characteristic species of the permanent aquatic biotopes fed by groundwater and connected with other floodplain waters. Small, isolated, and drying‐up former lateral channels and pools, slowly inundated during a flood, are characterized by Planorbis planorbis with Bathyomphalus contortus. Gyralus albus and Valvata cristata are characteristic of small, partly isolated, and partly drying‐up water bodies of the active floodplain, which are inundated rapidly and very turbulently during the flood. Due to restricted hydrological dynamics the waterbodies of the former floodplain were mainly inhabited by ubiquitous species.
Aquatic macroinvertebrate assemblages of two contrasting floodplains: The rhǒne and ain rivers, France
Authors: Castella E. , Richardot‐Coulet M. , Roux C. , Richoux P.
Published: February 2007

The study examines the relationship between floodplain aquatic macroinvertebrates and sector‐scale parameters such as geomorphology and history of regulation. The assemblages of six groups of invertebrates (Molluscs, Crustaceans, Ephemeroptera, Odonata, Trichoptera, and Coleoptera) were compared in various types of former channels from two contrasting but adjacent floodplain sectors: (1) the Jons sector of the Rhǒne River where successive meandering and braiding phases has left diversified fluvial forms in the landscape but where the main river is now embanked, and (2) the unregulated Ain River sector where the river is still actively meandering, although this process is being slowed by incision. The results demonstrate little difference in faunal composition between the two sectors but a significant difference in faunal structure. In the Rhǒne floodplain, there was a clear distinction between the faunal assemblages together with a high taxa richness at the scale of the sector (dominance of the beta diversity). In the Ain floodplain, the faunal assemblages were overlapping and the taxa richness was high at the sample scale (alpha diversity). Sector‐scale spatial patterns of the faunal assemblages along former channels were also distinct: between‐channel heterogeneity dominated in the Rhǒne, whereas within‐channel heterogeneity dominated on the Ain. These results stress the influence of geomorphological and historical determinants on the floodplain communities and, conversely, the relevance of macroinvertebrate assemblages for the assessment, at the landscape scale, of aquatic systems within the floodplains.
Composition and distribution of carabid communities along rivers and ponds in the region of upper weser (NW/NDS/FRG) with respect to protection and management of a floodplain ecosystem
Authors: Gerken B. , Dörfer K. , Buschmann M. , Kamps‐Schwob S. , Berthelmann J. , Gertenbach D.
Published: February 2007

On the basis of investigations on carabids along the Weser and some tributaries, ponds, and secondary habitats in gravel‐pits, the composition and spatial distribution of carabid communities are described: 132 carabid species were found in riverine habitats of the Weser floodplains near Höxter/Holzminden (FRG) and the relationship of selected species to grain‐size and coverage of vegetation are documented. Some typical carabid communities of mid‐European river ecosystems are present along the Weser, but the species and their few, mostly relic, habitats as well as secondary habitats in gravel‐pits are endangered. A long‐term and area‐oriented habitat management is necessary to protect and to develop the autochthonous carabid fauna.
The use of coleoptera (arthropoda:insecta) for floodplain characterization on the River Trent, U.K.
Authors: Greenwood M. T. , Bickerton M. A. , Castella E. , Large A. R. G. , Petts G. E.
Published: February 2007

Following a long history of floodplain degradation, directly or indirectly as a result of river regulation, international attention is turning to the restoration of these ecologically important ecotones. One immediate problem is to assess the ecological value of different floodplain habitats. With reference to two floodplain sectors—one non‐regulated and one regulated—on the River Trent, U.K., this paper characterizes the dominant floodplain units using two families of beetles (Coleoptera: Carabidae and Staphylinidae). Five dominant habitat units, riparian, wetland, woodland, pasture, and arable, are clearly differentiated by both families using ordination analyses. Although the faunal assemblages of specific units within the two sectors have many similarities, the units within the regulated sector are more clearly differentiated, having larger assemblages of ‘describer’ species. It is suggested that the enhanced environmental gradients between units within this sector may be responsible for stronger faunal contrasts.
Differentiation between epigeic and hypogeic fauna in gravel streams
Authors: Bretschko G.
Published: February 2007

The ‘hyporheic zone’ is described. According to the classical definition, water below the sediment surface is groundwater and the hyporheic interstitial zone is part of the phreatic system. This ignores the vertical distribution of the epigeic benthic fauna. The uppermost layer of the sediment (bed sediments) of the hyporheic zone is dominated by epigeic faunal elements and is therefore part of the surface system. In contrast to hypogeic species, the depth penetration of epigeic species is limited. Possible explanations are discussed.
Structure of interstitial assemblages in a regulated channel of the river rhine (France)
Authors: Des Chǎtelliers M. Creuzé , Marmonier P. , Dole‐Olivier M. J. , Castella E.
Published: February 2007

The interstitial assemblages of the River Rhine were studied in the Rhinau sector (France). The studied area is located in aVegulated channel of the river, controlled by a hydroelectric dam. Twenty stations were sampled in September 1988. Ten litres of interstitial water were pumped at 50 cm depth in each station using the Bou‐Rouch technique. Interstitial waters were poorly oxygenated and the hyporheic fauna had three major characteristics: (1) microcrustaceans were dominant, (2) the insects were rare and (3) the stygofauna was absent. The richest stations were well oxygenated and did not correspond to any particular geomorphological features. These findings contrast with the situation observed on other large European rivers (Rhǒne, Danube) where the interstitial assemblages appear to be locally more diversified and rich in stygofauna.
Flooding frequency and invertebrate emergence from dry floodplain sediments of the river murray, Australia
Authors: Boulton A. J. , Lloyd L. N.
Published: February 2007

Regulation of lowland rivers often alienates large areas of the floodplain, altering the natural regime of flooding frequency, duration, and magnitude. The extent to which such changes alter the productivity of river‐floodplain ecosystems and the contribution of aquatic invertebrates emerging from dry floodplain sediments is unknown. To examine this in a section of the River Murray in South Australia, fourteen replicate sods of dry sediment collected from four areas of the floodplain that had experienced different average flood recurrence frequencies (annually, 1 in 7, 1 in 11, and 1 in 22 years) were inundated in the laboratory, simulating flooding. Invertebrates emerging from the dry sediments were sampled with replacement 1, 2, 3, 7, 10, 14, 21, and 28 days after inundation, enabling comparisons of temporal changes in faunal composition and biomass. The greatest biomass and numbers of invertebrates emerged from annually‐flooded sods whereas sediments usually flooded once in 22 years yielded only protozoans. Large numbers of cladocerans and rotifers were recorded within two days of inundation whereas ostracods were not numerous until two weeks later. Heterogeneity in faunal composition and biomass among replicates probably reflected patchiness in microtopography and resting stage settlement, and variable hatching ‘strategies’. Although experimental conditions rapidly diverged from the natural situation over time because of the unrealistic constraints of enclosure, results suggest a potentially significant contribution by emergent invertebrates to the newly‐inundated floodplain foodweb. Reducing floodplain inundation frequency through regulation and flood mitigation probably severely reduces this reserve, removing a food resource for young fish and other predators.
Invertebrate communities of former southern moravian floodplains (Czechoslovakia) and impacts of regulation
Authors: Adamek Zdenek , Sukop Ivo
Published: February 2007

The natural hydrobiological conditions of southern Moravian floodplains have been drastically altered by regulation of the lower Dyje river and its tributaries. Natural floodplains were characterized by temporary pools and swamps, each inhabited by a typical community of aquatic invertebrates, and permanent water bodies (rivers and abandoned channels). Some aquatic taxa migrated onto ‘terrestrial’ localities during flood periods. Following regulation, floods were eliminated and most of the wet floodplain habitats disappeared, together with their typical species. The results of faunistic studies carried out in different permanent and temporary water bodies of the floodplains are reviewed. Altogether 188 taxa of planktonic and 206 taxa of benthic and semiplanktonic animals have been recorded. Of the planktonic community, rotifers (96 taxa) and copepods (41 taxa) have very favourable conditions for their development, especially in the spring. The main season for cladocera (53 taxa) development (summer) is less favourable due to the short duration of flooding (in flooded meadows) or poor oxygen conditions (in temporary pools with a high content of decaying organic matter). Among the zoobenthos, mainly facultative aquatic macroinvertebrates (larvae of insects) appear in these localities.
Impact of channelization on the mimmshall brook, Hertfordshire, Uk
Authors: Darby Stephen E. , Thorne Colin R.
Published: February 2007

Water End, Hertfordshire, has been designated as a Site of Special Scientific Interest due to the presence of some of the most important swallow holes in southern England. However, the swallow holes are being infilled by sediment and rubbish, resulting in severe environmental deterioration. Sedimentation appears to have been accelerated by human disruption of the Mimmshall Brook catchment, within which the swallow holes are located. A study of the sediment dynamics within the Mimmshall catchment was undertaken to identify instabilities and sediment transfer dynamics in the fluvial system. Channelization is shown to be the primary cause of the sedimentation problem. It was found that channelization triggers sediment flux divergences which in turn necessitate channel changes to restore equilibrium. As nickpoints migrate upstream of channelized reaches, bed degradation increases bank height. This decreases the stability of the bank with respect to mass failure. Bank failures occur under ‘worst case’ conditions once the threshold of bank instability is crossed. Bank erosion and mass failures were found to be the major sources of sediment to Water End and it was concluded that bank retreat must be controlled if environmental deterioration at Water End is to be slowed or reversed.
Sediment transport and channel characteristics of a sand‐bed portion of the green river below flaming gorge dam, Utah, USA
Authors: Lyons Joseph K. , Pucherelli Michael J. , Clark Richard C.
Published: February 2007

The Green River is a major tributary of the Colorado River with a drainage area of 115 770 km2 in Colorado, Utah and Wyoming. The influence of Flaming Gorge Dam on sediment transport and the potential for future channel change were studied using comparative analysis of historical aerial photographs from 1952 to 1987 and geographical information systems, published sediment (1951‐86) and discharge (1965‐87) records, and sediment data collected during 1986‐8. Since the closure of the dam in 1964, new equilibrium channel widths were apparently achieved by 1974 in the reach 161‐279 km below Flaming Gorge Reservoir and by 1981 in the reach 465‐509 km below the reservoir. Recent high flows have resulted in an increase in average channel width in both reaches as measured on aerial photographs taken in 1986 and 1987. Sediment data from US Geological Survey gauges on the Green River and its primary tributaries and three sites established on the Green River for this study suggest that bed material sediment transport in the Green River has now attained a quasi‐equilibrium, with the river transporting just the load supplied to it. The potential for future channel changes exists, as evidenced by the response of the channel (i.e. channel widening) to the increased flows during 1983, 1984 and 1986. Future adjustments in channel characteristics should be limited to responses to changes in discharge and sediment supply and transport in the basin.
Ecology of the lower rhône after 200 years of human influence: A review
Authors: Fruget J. F.
Published: February 2007

Embankments of the last century and contemporary channelization and development of urban and industrial areas along the Rhone Valley have greatly changed the river. The impacts of these on three biological descriptors of the hydrosystem (benthic invertebrates, fish communities and aquatic birds) have been studied. A reduction in the morphological diversity of the regulated hydrosystem has caused a reduction in biological diversity. This system has become a slow potamic system as a consequence of the more uniform environmental conditions: the benthic macroinvertebrate fauna has become eurytopic and pollution tolerant, with very localized potamic species; fish communities are dominated by limnophilic cyprinids; and water bird communities are limited by the absence of typical species of fluvial areas, such as terns.
Channel change and flood events since 1783 on the regulated river tay, Scotland: Implications for flood hazard management
Authors: Gilvear D. J. , Winterbottom S. J.
Published: February 2007

An analysis of old maps and documentary sources reveals that major changes in river channel planform have occurred over the last 200 years on the River Tay system, Scotland, UK. Reaches showing natural river channel planform change, however, are relatively small and a stable planform is characteristic of many sections of the river. River planform instability appears to be controlled by channel bed slope, sediment load and the enhanced vulnerability of former river channel courses to erosion. Flood protection embankments built in the 19th and 20th centuries modified unstable multichannel wandering gravel bed river sections to narrower single‐channel reaches, with limited lateral migration. On the River Tummel, 20th century impoundment has caused further geomorphological change in response to clearwater erosion close to the dam and aggradation processes within the regulated river downstream, but isolation of the effects of impoundment from those of channelization are problematic. An examination of the geomorphic effects of a high magnitude flood event in 1990 and historical accounts of earlier large floods reveal that the 1990 flood was the third largest since 1800 in the study area. Despite river regulation and bank protection the zones naturally characterized by instability are still susceptible to planform changes causing flood embankments to be breached, channel shifts and development of gravel bars.
Channel response to large‐scale river training works: hunter river, Australia
Authors: Erskine Wayne D.
Published: February 2007

Extensive river training works were undertaken on the upper Hunter River, Australia between 1956 and 1978 in response to rapid lateral migration and channel widening caused by a series of large floods between 1949 and 1955. River training involved artificial cutoffs, extensive realignment, structural bank protection works and tree planting. Channel length and hence sinuosity (ratio of channel length to valley length) decreased throughout each of six reaches located in the 78.9 km long study area as a direct result of the artificial cutoffs and realignment. Although the overall length reduction was less than 5%, one section experienced a 17% reduction. Localized channel straightening directly increased slope, decreased roughness and consequently increased flow velocity. The structural works have generally succeeded, converting an actively migrating stream into a laterally stable channel. Largely because of channel straightening and reduced sediment supply by floodplain reworking, the river has responded by eroding its bed by up to 1.1 m since the 1950s. Bed erosion preferentially removed the sand and fine gravel fraction producing an armour layer of coarse gravel. This armour layer halted further erosion by protecting the underlying fine material and is now only episodically mobilized by floods with return periods greater than 5.6 years on the annual maximum series. Unfortunately degradation was not predicted before the river training works were undertaken and it was only the fortuitous formation of the bed armour layer which prevented the degradation from becoming a major problem.
Vegetation, river management and land use in the dutch rhine floodplains
Authors: Jongman Rob H. G.
Published: February 2007

The floodplains of the lower Rhine are situated in a densely populated area of the Netherlands. Although they are used intensively the floodplains still fulfill important ecological functions. The lower Rhine is the downstream sedimentation zone of the River Rhine and its floodplains are characterized by river‐transported vascular flora originating from southern and eastern Europe. Using multivariate methods data from previously published work and field data on grasslands and former river beds have been analysed to determine trends in ecological changes. The consequence of continued sedimentation and decreased erosion is an increased drying out of the floodplains. Excavation and recultivation of formerly excavated land does not reverse the losses in flora and vegetation. Statistically there is a negative relationship between the characteristic flora and recultivated land. The natural transversal river gradient also disappears, together with its characteristic ecological diversity. Aquatic environments in the floodplains have been changed completely since regulation work started in the 19th century. Most former river beds have disappeared due to silting up. Data on short‐term vegetation succession confirm the long term analysis of map data.
Effects of diversion on the chemistry of a stream in Japan
Authors: Kagawa H.
Published: February 2007

On the upper reaches of the Ishite River, Japan the stream water is diverted completely at about 3 km above the Ishitegawa Reservoir, except under flood conditions. The chemical composition of the regenerated streamflow 2.4 km downstream from the diversion was determined 70 times during two years (1986‐7) to investigate the effects of the diversion on water chemistry. Factor analysis suggested that two main factors controlled the water chemistry. Factor 1 explained 45.7% of the total variance and was correlated positively with the concentrations of Ca2+, Mg2+, Na+, HCO− 3, SO2− 4 and Cl−, which seemed to reflect the leaching of dominant ions from the catchment soil. The factor 1 score was correlated negatively with the ecological ‘Ca‐Mg index’ (r2 = 0.912), a low value of which is necessary to avoid phosphorus enrichment by phytoplankton in the downstream reservoir. The diversion seemed to contribute to this purpose because the log flow‐rate value was correlated positively with the index (r2 = 0.730). On the other hand, factor 2 explained 10.2% of the total variance and was correlated positively with NO− 3 concentration and negatively with pH. Factor 2 was considered in relation to the partial pressure of dissolved CO2 gas in the stream water and appeared to be a complex biological factor that reflected CO2 production in the catchment soil and consumption in the stream.
Effects of dams and reservoirs on the hydrological characteristics of the lower drava river
Authors: Bonacci Ognjen , Tadic Zdenko , Trninic Dusan
Published: February 2007

During the last 20 years numerous water supply, hydroelectric and other large structures have been built along the Drava River and in its catchment area in Slovenia, Croatia, Hungary and Austria. Their construction has greatly influenced the water regime of the Drava River, especially during low water periods. The changes in the low flow regime along the stretch from Varazdin (285 km) to its confluence with the Danube (0 km) are examined. The analysis includes changes in the water levels, discharges and the amounts of suspended sediment and bed load. The intensity of changes, the time of their occurrence and their trends are examined.
Dynamic stability in hydropsychid guilds along a regulated stream: The role of competitive interactions versus environmental perturbations
Authors: Camargo Julio A.
Published: February 2007

Temporal alterations in the structure of hydropsychid guilds were studied along a regulated stream (Río Duratón, northern Spain) to examine the role of interspecific competitive interactions and environmental perturbations in determining species persistence. Discharge fluctuations of hypolimnial waters with a significant oxygen deficit were produced daily by Burgomillodo Dam. Under unregulated conditions (upstream sampling site), it is assumed that the coexistence of competing hydropsychid species is a function of species dominance (d') and resource limitation (R), as major causes of interaction strength among competitors, and the niche overlap (O) as a major cause of connectance among competitors, d' tends to increase with the number of subordinate species. Thus, and according to May's model of stability, a hydropsychid guild will tend to be unstable (by competitive displacement) if d'R(SO)0.5 > 1, where S is the number of competing species in the guild. The product d'R(SO)0.5 is used as a competition coefficient (β′). To facilitate the calculation of β′, the values of R and 0 are assumed to be 1 and 0.5, respectively. Riffle macrobenthic surveys were undertaken in June and December 1987, and in June 1988. Upstream from the dam, values of β′ were 0.599, 1080 and 0.656, and values of S were 7, 7 and 6. Downstream from the dam, β′ was less than unity during all sampling surveys, but S decreased at all downstream sampling sites (mainly just below the dam). Total density and total biomass were significantly higher downstream than upstream (except just below the dam). Hydropsyche pellucidula was dominant upstream, whereas H. siltalai became dominant downstream. Temporal variations in individual weights of H. bulbifera and H. exocellata downstream were different from those upstream. This fact is interpreted as a phenomenon of character displacement. It is concluded that interspecific competitive interactions upstream and environmental perturbations downstream determined species persistence in hydropsychid guilds.
Life cycle and production of Baetis rhodani in a regulated river in Western Norway: Comparison of pre‐ and post‐regulation conditions
Authors: Raddum Gannur G. , Fjellheim Arne
Published: February 2007

The benthic invertebrate fauna of the lowland part of the Aurland River was investigated in 1966–7 over a full year cycle. The watershed was built out for hydropower production during 1979–83. In this study the life cycle and production of Baetis rhodani from pre‐regulated conditions (1966–7) was compared with two types of post‐regulation streams (1988–9). Before regulation the water flow was high during May‐June and in autumn, combined with heavy rainfall. The lowest flow was in winter and early spring. The pre‐regulated temperature was low in winter, increasing from April to a maximum in August (10–14°). After regulation one part of the river received reduced flow and increased summer temperatures (upper part) and one received hypolimnion release and reduced summer temperatures (lower part). In the upper part the density of B. rhodani increased between 10 and 20 times. The reason for this seems to be increased temperature, reduced accidental drift of larvae and increased amount of stored organic material on the bottom. In the lower part the density increase was two to five times and the production two times higher after regulation. The lower increase in production than density was due to a much higher proportion of small larvae. B. rhodani had mainly an univoltine life cycle before regulation, but a small part of the population was bivoltine. After regulation the species was univoltine in the lower part. In the upper part the life cycle was about one month faster, but no clear indication of bivoltinism was seen. The absence of the second generation is due to low temperatures and probably a lack of signals connected with temperature.
Impact of combined sewer overflows on the water quality of an urban watercourse
Authors: Rees Adrian , White Keith N.
Published: February 2007

The lower Irwell/upper Manchester Ship Canal is a canalized waterway in the north‐west of England with a catchment area of 700 km2. A 12 month study established a baseline of key chemical and physical parameters (dissolved oxygen, biological oxygen demand, temperature, pH, conductivity, NO−3, NO−2, PO3‐4, NH+4, suspended solids) with which episodic deteriorations in water quality along the river could be compared. The relative importance of changes in flow, and the impact of the tributaries on water quality in the Irwell, was assessed by mass balance calculations and multivariant analysis. Particular attention has been given to the interactions between sediments and the chemistry of the water column. The main conclusions to emerge are that: (i) the lower Irwell/Ship Canal is subject to significant organic pollution from storm water overflows discharging directly to the river above the study area and via its major tributaries, the Irk and Medlock; (ii) the Irk and, to a lesser extent, the Medlock have an adverse effect on water quality in the Irwell‐increases in mass flux below the confluences above that attributable to direct loading suggest that sediment interactions with the water column are partly responsible; (iii) high flow per se, rather than combined sewer overflows in storm events, may be causing deteriorations in water quality due to the release of pollutants from resuspended sediments; and (iv) limited storm data appear to show a readily‐soluble ‘first flush’ of pollution to be followed by a delayed impact caused by degradation of newly introduced material. The feasibility of short‐term restorative measures such as the installation of oxygen/air injection systems and the provision of weirs are examined in the context of river management; weirs do not appear to be promising solutions.