摘要:

AbstractFollowing turbine installation at the Kielder dam, the River North Tyne downstream is now characterized by large daily fluctuations in flow. A survey of trichopteran populations (Hydropsychidae, Rhyacophilidae and Polycentropodidae) was carried out to assess the impact of hydroelectric power generation (Phase III), and to compare the results with similar pre‐impoundment (Phase I) and post‐impoundment (Phase II) surveys. Benthic samples were collected quarterly upstream from the reservoir and at four stations downstream. Although the same three species (Hydropsyche siltalai, Hydropsyche pellucidula and Rhyacophila dorsalis) continue to dominate, there were some notable differences found between sampling sites. Species diversity was drastically reduced at the station nearest the dam, where 99% of all larvae collected wereR. dorsalis. At the next station 5 km downstream, where previouslyH. siltalaihad been dominant,R. dorsalisnow constitutes 65% of collections. At the two stations farthest away from the dam the former prevalence ofH. siltalaiwas re‐established. It is suggested that the unstable, high flows at the reservoir outlet are likely to favour the predatoryR. dorsalisrather than the filter feeding hydropsychids whose nets may be susceptible to damage. Upstream from Kielder Water,R. dorsaliswas prominent in benthic samples, whereas numbers ofH. siltalaiwere 10 times lower than in Phase II and 60 times lower than in Phase I. The extent to which such upstream changes may be related to altered patterns of community structure below the dam is not known, but these observations may warrant a more cautious approach when considering upstream areas as unaffected ‘reference sites’. Instar analyses suggested that winter‐warm, summer‐cool discharges were continuing to modify larval growth rates, as noted in Phase II. The results of this study are discussed in relation to present trends in water resource development in Britain, especially with regard to future needs in monitoring

ISSN:0886-9375    

DOI:10.1002/rrr.3450080302

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractEmpirical evidence from a semiarid watershed of the southwestern United States (Verde River basin, Arizona) indicated that abundance and species richness of mixed deciduous riparian forests varied in a curvilinear and quantifiable fashion as a function of stream flow parameters. Three indicators of riparian abundance—foliage area, stem basal area and stand width—increased most significantly with growing season flow volume, a surrogate indicator of riparian water availability. Tree species richness varied in a bell curve fashion with flood size, with the greatest richness occurring at streams with intermediate flood magnitudes. These instream flow models have management implications for riparian habitats. They suggest that flow volume (and the related attributes of water‐table recharge and floodplain soil wetting) is the primary factor regulating riparian vegetation abundance in the Verde River watershed, and provide a first approximation of the extent of riparian loss expected from flow diversion or other types of flow redu

ISSN:0886-9375    

DOI:10.1002/rrr.3450080303

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe influences of the Samarra impoundment on the ecology of the downstream sector of the river Tigris are investigated. Zooplankton were collected monthly from July 1987 to July 1988. It was found that zooplankton were most abundant during high river discharges in March. During the month of low river discharge, September, the zooplankton population was greatly reduced immediately below the barrage and remained so to the last downstream station. Several factors seem to explain such differences. The high discharge from the impoundment was found to be the dominating factor and may flush the small backwaters in which zooplankton were abundant, thus increasing the population in the river. Zooplankton species vary in their ability to sustain populations in the river, variations which are due mainly to species‐specific characteristic

ISSN:0886-9375    

DOI:10.1002/rrr.3450080304

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe δ13C and δ15N of seston, organic matter sources (riparian vegetation, algae, macrophytes, plankton) and an invertebrate detritivore were examined in a regulated Rocky Mountain river (fourth order). The isotopic composition of seston varied among sites and seasons for all size fractions; among‐site variation was weakest for ultra‐fine particulate organic matter (53 μm) from 0.5 km below the dam was relatively13C‐depleted (−30 to −28°), reflecting the contribution of reservoir‐derived plankton; seston from the site 8.7 km downstream was relatively13C‐enriched (−18 to −23°), reflecting autochthonous inputs. Tributary seston had an intermediate δ13C value (−22 to −26°), reflecting allochthonous inputs (conifer litter) and macrophyte (Elodea) detrital inputs. δ15N values of seston were generally similar among sites (4–8°) but were more depleted for the tributary (1–4°). Depleted δ15N values (0–2.5°) for seston from below the dam in late summer corresponded to a blue‐green algae bloom in the reservoir. Isotopic shifts of organic matter incubated for 60–90 daysin situwere small (<2°) and varied in direction depending on isotope and litter type. The isotopic composition of stonefly larvae,Pteronarcys californica, varied among sites, and closely matched that of the local seston (especially FPOM), suggesting that with respect to detritus origin, larvae were opportunistic foragers. The origin of organic matter is influenced by flow regulat

ISSN:0886-9375    

DOI:10.1002/rrr.3450080305

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractSurvey data from 1906 and 1988 for the lower River Murray, Australia, reveal changes in channel morphology associated with the construction of Locks 2 and 3 (1925–8), which form contiguous pools in the Valley and Gorge sections, respectively. Regulated annual flows are less than half the volume of natural flows, and the frequency of maximum flows has decreased. Upstream weirs have reduced the sediment supply to the study reach by 1.05 × 106tonnes per annum. The trap efficiencies of Pools 2 and 3 from 1906 to 1988 were 8 and 13% respectively, with retention channel of 80723 and 267470 tonnes. Responses over the past 60–70 years have differed between the pools‐some channel characteristics have attained a new dynamic equilibrium and others have not. In Pool 3 the average bed slope has been reduced by 000004 (44%) and has attained equilibrium, but in Pool 2 the supply and redistribution of sediment have not been sufficient to reduce the bed slope. There are continuous areas of degradation and aggradation in Pool 3 but discontinuous areas in Pool 2, reflecting different stages in slope adjustment. Cross‐sections have become wider and shallower in Pool 3 but narrower and deeper in Pool 2. These adjustments are influenced by local boundary conditions, floodplain morphology and the position of the study reach in the sequence of weirs. In general, the situation in the lower Murray does not conform to conventional models of the impact of regulation, which are based on data from upland dams. The Murray's gross morphology remains as a relict of the natural, semi‐arid regime. Low contemporary stream energies and cohesive bank materials restrict the initiation of channel metamorphosis and prolong the time required for the completion of channel

ISSN:0886-9375    

DOI:10.1002/rrr.3450080306

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA procedure designed to test the transferability of habitat suitability criteria was evaluated in the Cache la Poudre River, Colorado. Habitat suitability criteria were developed for active adult and juvenile rainbow trout in the South Platte River, Colorado. These criteria were tested by comparing microhabitat use predicted from the criteria with observed microhabitat use by adult rainbow trout in the Cache la Poudre River. A one‐sidedX2test, using counts of occupied and unoccupied cells in each suitability classification, was used to test for non‐random selection for optimum habitat use over usable habitat and for suitable over unsuitable habitat. Criteria for adult rainbow trout were judged to be transferable to the Cache la Poudre River, but juvenile criteria (applied to adults) were not transferable. Random subsampling of occupied and unoccupied cells was conducted to determine the effect of sample size on the reliability of the test procedure. The incidence of type I and type II errors increased rapidly as the sample size was reduced below 55 occupied and 200 unoccupied cells. Recommended modifications to the procedure included the adoption of a systematic or randomized sampling design and direct measurement of microhabitat variables. With these modifications, the procedure is economical, simple and reliable. Use of the procedure as a quality assurance device in routine applications of the instream flow incremental methodology was encoura

ISSN:0886-9375    

DOI:10.1002/rrr.3450080307

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractIn the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylidFerrissia petterdiremains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparidNotopalawas thought to be extinct. The introduced physidPhysa acutais widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion ofNotopala hanleyiin a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment.

ISSN:0886-9375    

DOI:10.1002/rrr.3450080308

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0886-9375    

DOI:10.1002/rrr.3450080309

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0886-9375    

DOI:10.1002/rrr.3450080310

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0886-9375    

DOI:10.1002/rrr.3450080311

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY