ISSN:0886-9375    

DOI:10.1002/rrr.3450030102

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractPursuant to the Northwest Power Planning Council's Fish and Wildlife Program for the Columbia River system, we estimated losses in fish populations and developed mitigation, compensation, and protection alternatives for reservoirs and downstream river reaches affected by hydropower development in the Flathead and Kootenai River systems in northwest Montana, U.S.A. The construction of Hungry Horse Dam has resulted in estimated annual losses of 65500 migratory juvenile westslope cutthroat and 1965 adult migratory bull trout from the Flathead Lake and River system. In addition, operations of Hungry Horse and Kerr dams caused annual losses conservatively estimated at 96300 river‐spawning and 131000 lakeshore‐spawning kokanee adults. Water level fluctuations caused by dam operations at Libby and Hungry Horse reservoirs result in: (1) altered thermal stratification, (2) indirect losses in phytoplankton and zooplankton production, (3) direct washout of phytoplankton and zooplankton through dam penstocks, (4) reductions in standing crop of benthic organisms and of insects on the water surface, and (5) reduced fish growth in the late summer and fall. Mitigative measures include: (1) 99.2 and 113.3 m3s−1minimum flows in the Flathead and Kootenai rivers respectively, to protect salmonid eggs and juveniles, (2) improvement of fish passage to restore migrations between the Flathead and Swan systems, and (3) biological rule curves for operations at Libby and Hungry Horse reservoirs. To compensate for fisheries losses, we recommend enhancement of spawning and rearing habitat, introductions of hatchery juveniles, and spawning channels. We recommend protection from further hydropower development for 100 stream reaches (1386 km) for fish species of special concern, and for outstanding sport fisheries. These and other measures will be considered by various agencies in developing an overall fisheries restoration plan which should be flexible, and employ principles of adaptive management. Effectiveness of the plan may be limited by heavy reliance on hatchery fish. Although mitigation efforts may not restore fish populations to pre‐dam levels, substantial benefits should be r

ISSN:0886-9375    

DOI:10.1002/rrr.3450030103

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA multitude of Norwegian rivers are managed for generating hydroelectric power (HEP). The hydrology of these hydrorivers changes in various ways which reflect the implemented HEP schemes. Increased winter flows and a concomitant lack of ice‐cover are features found downstream of power installations on many Norwegian hydrorivers.Our study objectives were (1) to assess the changes in aquatic macrophyte abundance subsequent to HEP development; and (2) to evaluate the environmental conditions under which nuisance growths of macrophytes are likely to occur. Towards these ends, Norwegian literature data were compiled and assessed. Some case studies are outlined showing the variety of situations under which prolific growths of macrophytes might result. Unfortunately, available data on macrophyte‐associated problems proved deficient in many respects. This occurred chiefly because most macrophyte studies are conducted either before, or after, an HEP scheme is completed. Evidently, no concerted efforts are made for assessing the likelihood of macrophyte‐dominated nuisance growth in the planning stage of a Norwegian HEP s

ISSN:0886-9375    

DOI:10.1002/rrr.3450030104

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractWe used 0.5 m diameter nets to sample the drift downstream from a peaking hydroelectric project on the Caney Fork River, Tennessee. The relative contribution of the terrestrial, lentic, and lotic environments to stream drift varied seasonally. Stream benthos (primarily Chironomidae andLirceus fontinalis) occurred in the drift throughout the year; however, their relative importance varied seasonally.Daphniasp. from the reservoir also occurred in the drift year round with the highest densities in fall and spring when they were the predominant species in the drift. In summer, terrestrial insects apparently utilized exposed portions of the river bed during periods of no power generation. In June as the river stage increased following initiation of generation, adult terrestrial insects became a major component of the drift. Threadfin shad (Dorosoma petenense) dominated the biomass in the drift during December. Although the importance of stream benthos to fish populations is generally recognized, the contribution of the terrestrial and upstream reservoir environments to the forage base in the tailwater may also be important and should be considered in developing management strategies for tailwater fisheries.

ISSN:0886-9375    

DOI:10.1002/rrr.3450030105

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractRecent studies on the impact of peaking hydropower have indicated that impacts directly associated with peaking releases can be categorized as those which result from the hydraulic surge during start‐up of generation and the chronic effects of frequent flow fluctuations to biota occupying the fluctuation zones. The instream flow incremental methodology (IFIM) was not designed for application to dynamic flows. In order to determine if such an application was appropriate, we chose to conduct exacting habitat descriptions at the unique zones associated with peaking hydropower (degradation, aggradation, and recovery) and combine this information with suitability criteria for the banded sculpin (Cottus carolinae) and stage/discharge records to obtain weighted usable habitat estimates under typical peaking releases. The results demonstrate that habitat declines as the peaking surge passes an area and rises during low flow periods. However, the difficulties in interpretation of the results remain. That is, the biological response (lateral or longitudinal movement or entrainment) as well as the refuge value of certain hydraulic conditions remain to be investigated. This suggests that the present management value of IFIM applied to peaking hydropower is in examining minimum habitat values that occur during the generation cycle and a comparison of gains or losses in the minimum (greatest amount of hydraulic refuge available) WUA estimates under various proposed release scenario

ISSN:0886-9375    

DOI:10.1002/rrr.3450030106

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

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 requireme

ISSN:0886-9375    

DOI:10.1002/rrr.3450030107

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

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

ISSN:0886-9375    

DOI:10.1002/rrr.3450030108

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

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

ISSN:0886-9375    

DOI:10.1002/rrr.3450030109

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractIn March 1985 engineering tests of scour valves at the base of the Llyn Clywedog regulating reservoir resulted in a controlled peak release discharge of 53m3s−1into regulated reaches of the upper Severn. To exploit this unusual opportunity, simple monitoring systems were set up within the first 50 km downstream to assess the morphological effects on bed and banks and the movement of bed and suspended sediments. The interpretation of suspended sediment transport patterns became the major analytical task following the release, since bedload and morphological impacts were minimal. In comparison with natural floods, the scour valve release exhibited suspended sediment concentrations usually associated with a five‐year event, but with a complex time and space pattern resulting from the release strategy. Wet antecedent conditions and the short duration of the scour valve release help to explain why impacts on the downstream channel were, otherwise, much more restricted than those of a water resource test release in 1975. Since scour releases can be planned with greater flexibility than major water resource releases, indications are that they should be made ‘on the back of’ natural high flows, although sensitive sites may require pro

ISSN:0886-9375    

DOI:10.1002/rrr.3450030110

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe effect of regulation, by multiple impoundment, on ‘discontinuity’ (recovery) ‘distances’ (sensuWard and Stanford, 1983) for various physico‐chemical attributes of the Palmiet River (a short, steep gradient, cool temperate, acid, low‐nutrient system) was investigated. Physico‐chemical features were measured monthly, from February 1986 to August 1987, at 11 sites along the river, but concentrating on two zones: one below an upper‐reach impoundment, Nuweberg Dam, and one below a middle‐reach impoundment, Arieskraal Dam. Median total suspended solids, nitrates, nitrites and ammonium all increased below both dams with varying levels of ‘recovery’. Median spot temperatures, pH and alkalinity increased below Nuweberg, but decreased below Arieskraal Dam, whereas the converse was true for soluble reactive phosphate. Nuweberg had no effect on conductivity and total dissolved solids, while Arieskraal caused a slight decrease. The river remained well oxygenated down its length.Distinct seasonal variations were recorded for: flow rate, with flow reversal below Nuweberg and flow constancy below Arieskraal; temperature, with seasonal shifts and dampening of annual temperature range below both dams; alkalinity, with seasonal shifts below Arieskraal, and nitrites and nitrates, but not for any other attributes. At least partial recovery was noted in all cases, but in some instances, recovery was incomplete to the estuary. The implications of such alterations, for invertebrates, in terms of reduction in habitat diversity as well as for food supply must be considerable and studies are currently under way to determine community st

ISSN:0886-9375    

DOI:10.1002/rrr.3450030111

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY