摘要:

AbstractA previously ephemeral stream is being used to convey water and create fish habitat as part of mitigation for impacts of a transbasin water diversion project. This stream, the South Fork of Middle Crow Creek, is located in the Medicine Bow National Forest, Wyoming. After two years of increased flow to the 8.8 km study reach, the amount of stream channel had increased 32 per cent and the total area of beaver ponds had more than doubled. Brook trout (Salvelinus fontinalis) stocked into the beaver ponds are surviving and growing. Factors limiting fishery development in the augmented stream include interrupted flow, discontinuous channels, and summer water temperatures exceeding 25°C. Analysis using the Physical Habitat Simulation System indicated that a flow of 0.07m3s−1would maximize the amount of weighted usable area for brook trout under the channel conditions present in 19

ISSN:0886-9375    

DOI:10.1002/rrr.3450040302

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

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

ISSN:0886-9375    

DOI:10.1002/rrr.3450040303

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractSystematic light trapping was carried out in Lyon on the banks of the Rhǒne river from 1958 to 1982, mainly in the months of June and July. The changes in the type and abundance of the adult Trichoptera and Ephemeroptera species captured over the last 25 years were studied in relation to the perturbations sustained by the river‐and thus by the larval instars.A Correspondence Analysis carried out on the monthly samples defined a first factorial axis which could represent a ‘biological time’ scale characterized by phases of rapid (1959‐1974) or slower (1974‐1982) change of the faunal communities.Five ‘successive’ faunal groups were defined according to the length of historical presence of each of the 88 species along this axis. The most stenoecic species (faunal groups 1, 2 and then 3) seem to disappear and gradually only a small number of species whose ecological requirements are less demanding (faunal groups 4 and 5) subsist.This faunal impoverishment is a consequence of the increasing uniformity of the biotope caused by continuous environmental changes mainly in flow regulation. This has led to reduction in diversity of the substratum and possible food sources. Regular flush‐outs of upstream reservoirs release sediments which clog interstitial spaces over long periods and this effect has been aggravated since 1966 by the bringing into service of a dam situated just downstream from the station.It seems that a new but delicate equilibrium has been reached since 1974; this situation probably corresponds to a less stenoecic

ISSN:0886-9375    

DOI:10.1002/rrr.3450040304

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractInvestigations were conducted into the causes of a decline in the abundance of rooted aquatic plants in the River Nene. These were formerly troublesome to navigation and obstructed summer storm flows and were regularly cut by Anglian Water until 1976. After 1977 plant growth caused only localized problems so cutting ceased. An investigation into the causes of the plant decline was initiated in order to provide predictions for management decisions about the future use of machinery and personnel. It was concluded that there was a natural loss of plants by scouring in the abnormally high flows of 1976/7 winter. The regular pattern of maintenance dredging, which had been implemented following water industry reorganization in 1974, was shown to suppress abundance for at least five years after dredging. These two sequential events had lowered abundance over the navigable Nene to levels which no longer warrant weedcutting.

ISSN:0886-9375    

DOI:10.1002/rrr.3450040305

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe Cernadilla reservoir, located on the River Tera (northwest Spain, Duero Basin) is an oligotrophic reservoir with a capacity of more than 250 × 106m3and a depth of 70 m. The regulated flow pattern is characterized by higher summer flows, higher day flows than night ones, and lower weekend flows. The effects of this artificial flow regime on the stream ecosystem were evaluated by comparing the aquatic communities of an upstream station with those of three downstream stations, located at 1, 8, and 24 km from the dam. Physiocochemical characteristics of the water, fish and macrobenthic communities, and macrophytes were studied at each station.Summer water temperatures were significantly lower downstream of the reservoir. Macrophyte biomass, macrobenthic diversity, and richness were reduced below the dam. The trophic structure was changed by an increase of shredders and grazers.Fishery total biomass greatly fluctuated seasonally, but was higher above the reservoir than below it. However, in spring the trout populations were higher upstream because large numbers of spawning cyprinids from the reservoir invaded upstream reaches of the River Tera and displayed resident trout populations

ISSN:0886-9375    

DOI:10.1002/rrr.3450040306

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe watershed of California's Central Valley drains into San Francisco Bay, the largest estuary on the Pacific Coast. The water resources of the Valley have been intensively exploited, particularly in the last 50 years, with the construction of large‐scale irrigation systems. About half the 35 km3average annual freshwater inflow to the estuary is now diverted, with up to 85 per cent in dry years. These diversions are now having significant adverse effects on the estuarine ecosystem including substantial declines in the economically significant anadromous fishery.At the time the large dam projects in the watershed were designed, no consideration was given to impacts on the estuary. Growing recognition of this error has led the California state agency that governs water allocation to consider applying operating conditions on the upstream reservoirs in order to provide sufficient freshwater inflows in the estuary to maintain the estuarine ecosystem.A set of freshwater flow and salinity standards has been proposed and is described in this paper. These flow requirements are based on extensive research on the role of freshwater inflow on estuarine hydrodynamics and on the estuarine ecosystem. These requirements have three overlapping goals:.1Maximizing phytoplankton production ‐ the base of the estuarine foodchain.2Protecting spawning and migration of anadromous fishery.1Protecting brackish wetlan

ISSN:0886-9375    

DOI:10.1002/rrr.3450040307

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractConstruction of the La Grande Complex in Eastern Canada called for complete or partial diversion of six rivers, the mean annual discharge of which varied from 60 to 1600 m3s−1, and the transfer of water from two adjoining watersheds (1586m3s−1) into La Grande Rivière. Three of these rivers with reduced flow, Eastmain (from 700 to 95m3s−1), Opinaca (from 260 to 35m3s−1), and Caniapiscau (from 1708 to 960m3s−1) and the waterways with increased flows, Boyd‐Sakami (from 1 to 811m3s−1) and La Grande Rivière (from 1760 to 3400m3s−1) were intensively monitored from 1978 to 1988, while the others were surveyed sporadically. Very few modifications were observed, compared to previous conditions, in banks stability, water quality, and aquatic fauna of the affected rivers: those which appeared can be explained by the water level fluctuations, the water quality of the tributaries of the residual drainage basin, and/or by the direct influence of the reservoirs. In James Bay, the areal extent of the Eastmain River and La Grand Rivière plumes varied with discharge in an exponential relation, mostly under ice cover; resources from the coastal environment had not yet undergone any major changes. Because of the very small population dwelling in the area, less than 3000 inhabitants, modifications in the hydrological regime of these rivers did cause relatively few impacts, the main being greater banks instability in specific locations, reduction of the thickness and ice cover on La Grande Rivière, enhancement of navigation constraints on Eastmain River, and higher mercury levels in fish related to operatio

ISSN:0886-9375    

DOI:10.1002/rrr.3450040308

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

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 examplePsychomyia pusilla) are more frequent in the embanked section whereas the drifting species (for exampleBaetis 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

ISSN:0886-9375    

DOI:10.1002/rrr.3450040309

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

ISSN:0886-9375    

DOI:10.1002/rrr.3450040310

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

ISSN:0886-9375    

DOI:10.1002/rrr.3450040311

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY