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1.
This study examined the influence of flow hydraulics and coarse particle mobility on bed scour adjacent to coho salmon (Oncorhynchus kisutch) redds in a coastal California watershed for a bankfull flood. It was theorized that coarse particle mobility (i.e., mobility of particles larger than the median bed particle size, D50) exerts a strong control on bed scour depth. Maximum scour depth at the study sites was found to be negatively correlated with flow shear stress, which is dissimilar to findings from previous scour studies in spawning reaches. This resulted from a relatively similar coarse particle size (D84) for all study sites and a negative relationship between shear stress and coarse particle exposure to flow (or the D84/D50 ratio), which together caused sites with low shear stress to have a high degree of localized coarse particle mobility and an associated high maximum scour depth. This study provides new insights into the vulnerability of spawning reaches with low flow energy to redd scour and highlights the need to consider the mobility of coarse particle sizes explicitly when examining the dominant controls on redd scour. 相似文献
2.
In‐stream chinook salmon (Oncorhynchus tschawytscha) spawning habitat in California's Central Valley has been degraded by minimal gravel recruitment due to river impoundment and historic gravel extraction. In a recent project marking a new direction for spawning habitat rehabilitation, 2450 m3 of gravel and several boulders were used to craft bars and chutes. To improve the design of future projects, a test was carried out in which a commercial modelling package was used to design and evaluate alternative gravel configurations in relation to the actual pre‐ and post‐project configurations. Tested scenarios included alternate bars, central braid, a combination of alternate bars and a braid, and a flat riffle with uniformly spaced boulders. All runs were compared for their spawning habitat value and for susceptibility to erosion. The flat riffle scenario produced the most total, high, and medium quality habitat, but would yield little habitat under flows deviating from the design discharge. Bar and braid scenarios were highly gravel efficient, with nearly 1 m2 of habitat per 1 m3 of gravel added, and yielded large contiguous high quality habitat patches that were superior to the actual design. At near bankfull flow, negligible sediment entrainment was predicted for any scenario. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
3.
Extensive hydroelectric development in the Columbia River system has eliminated most mainstem riverine habitat available for spawning by fall chinook salmon (Oncorhynchus tshawytscha). The two remaining populations, Hanford Reach, Columbia River and Hells Canyon Reach, Snake River, are separated geographically and their status is markedly different. Annual escapements to Hanford Reach have averaged approximately 80 000 adults, while the Snake River run size has declined to <1500 adults over the past 10 years. We compared their spawning habitat characteristics over a range of measurement scales, as a means to identify strategies for rebuilding the weak Snake River population. Physical habitat characteristics of redds were similar for both study areas. Redd locations were correlated with channel characteristics, such as braiding and sinuosity. Several differences between the two spawning areas were identified at the watershed scale: the Hells Canyon Reach had a much steeper longitudinal gradient, was largely confined by bedrock, and had a more variable flow regime. These features are controlling variables that operate at the reach‐scale to limit the availability and size of substrate and other conditions that influence egg deposition and incubation survival. Geomorphological characteristics of the two study sites are sufficiently different to indicate that the production potential of the Hells Canyon Reach population is markedly lower than that of the Hanford Reach population. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
4.
We conducted a regional classification and analysis of riverine floodplain physical features that represent key attributes of salmon rearing habitats. Riverine habitat classifications, including floodplain area and river channel complexity, were derived at moderate (30 m) spatial resolution using multispectral Landsat imagery and global terrain data (90 m) encompassing over 3 400 000 km2 and most North Pacific Rim (NPR) salmon rivers. Similar classifications were derived using finer scale (i.e. ≤ 2.4‐m resolution) remote sensing data over a smaller set of 31 regionally representative flood plains. A suite of physical habitat metrics (e.g. channel sinuosity, nodes, floodplain width) were derived from each dataset and used to assess the congruence between similar habitat features at the different spatial scales and to evaluate the utility of moderate scale geospatial data for determining abundance of selected juvenile salmon habitats relative to fine scale remote sensing measurements. The resulting habitat metrics corresponded favorably (p < 0.0001) between the moderate scale and the fine scale floodplain classifications; a subset of these metrics (channel nodes and maximum floodplain width) also were strong indicators (R2 > 0.5, p < 0.0001) of floodplain habitats defined from the finer scale analysis. These relationships were used to estimate the abundance and distribution of three critical shallow water floodplain habitats for juvenile salmon (parafluvial and orthofluvial springs, and shallow shore) across the entire NPR domain. The resulting database provides a potential tool to evaluate and prioritize salmon conservation efforts both within individual river systems and across major catchments on the basis of physical habitat distribution and abundance. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
5.
Two morphologically distinct moss communities were found in the River Suldalslågen. The liver moss community consists of species which form a dense mat on the bottom, while the river moss (Fontinalis) community forms long tufts. Moss growth has increased since hydropower regulations due to reduced floods and increased winter flows. Increased moss cover affects the bottom structure, as well as intra‐gravel and near‐bottom hydraulics. We studied densities of juvenile Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) by electrofishing and habitat selection by direct underwater observation, in areas with natural moss cover compared with areas where mosses were experimentally removed. Areas with dense mats of liver mosses held lower densities of young of year (YoY) and older salmon parr than areas where liver moss had been removed. No differences in densities of YoY salmon were found between areas with and without Fontinalis. For older salmon, parr results were inconclusive. In some samples more and in others fewer fish were found in areas with Fontinalis moss removed. For trout, densities were higher in areas with Fontinalis, while results for liver moss were inconclusive. No major differences were found with regard to microhabitat selection between areas with and without river moss, suggesting that habitat quality in these areas was similar during summer, except with respect to substrate. Salmon held more exposed positions in areas without liver moss, but this is mainly attributed to different habitat availabilities. It is concluded that the relative increase in liver mosses in the River Suldalslågen has a negative impact on juvenile Atlantic salmon fish density. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
6.
S. C. Zeug K. Sellheim C. Watry B. Rook J. Hannon J. Zimmerman D. Cox J. Merz 《河流研究与利用》2014,30(6):707-718
Anadromous salmonid diversity and abundance worldwide have been adversely impacted by anthropogenic forces, and millions of dollars are spent each year on stream habitat restoration and enhancement. However, there is a paucity of data comparing site use by salmonids before and after enhancement implementation, and few studies examine the specific environmental conditions that determine whether salmonids utilize an enhanced site. This study examines the use of gravel augmentation to improve spawning site utilization by Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus mykiss) on the Lower American River, California, USA. Spawning increased across all augmentation sites for both species, although there were species‐specific and year‐specific differences in the degree to which a site was utilized and in the spatial distribution of redds in relation to substrate size, habitat features and other redds. There were also differences in redd architecture across sites that were related to differences in gravel size. This study illustrates that gravel augmentation projects can enhance spawning habitat for salmonids where spawning beds have degraded but that species‐specific and site‐specific attributes and gravel size can influence the relative effectiveness of a project. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
7.
Peter M. Kiffney George R. Pess Joseph H. Anderson P. Faulds K. Burton Stephen C. Riley 《河流研究与利用》2009,25(4):438-452
Migration barriers are a major reason for species loss and population decline of freshwater organisms. Significant efforts have been made to remove or provide passage around these barriers; however, our understanding of the ecological effects of these efforts is minimal. Installation of a fish passage facility at the Landsburg Dam, WA, USA provided migratory fish access to habitat from which they had been excluded for over 100 years. Relying on voluntary recruitment, we examined the effectiveness of this facility in restoring coho (Oncorhynchus kisutch) salmon populations above the diversion, and whether reintroduction of native anadromous species affected the distribution and abundance of resident trout (O. mykiss and O. clarki). Before the ladder, late summer total salmonid (trout only) density increased with distance from the dam. This pattern was reversed after the ladder was opened, as total salmonid density (salmon + trout) approximately doubled in the three reaches closest to the dam. These changes were primarily due to the addition of coho, but small trout density also increased in lower reaches and decreased in upper reaches. A nearby source population, dispersal by adults and juveniles, low density of resident trout and high quality habitat above the barrier likely promoted rapid colonization of targeted species. Our results suggest that barrier removal creates an opportunity for migratory species to re‐establish populations leading to range expansion and potentially to increased population size. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
8.
The River2D two‐dimensional hydraulic and habitat model was used to simulate fall‐run Chinook salmon (Oncorhynchus tschawytscha) spawning and fry and juvenile rearing habitat of the first phase of a stream channel restoration project on Clear Creek, California. Habitat was simulated for a range of stream flows: (1) before restoration; (2) based on the restoration design; (3) immediately after restoration; and (4) after one and two large flow events. Hydraulic and structural data were collected for three sites before restoration, and prerestoration habitat was simulated. Habitat simulated for these sites was extrapolated to the prerestoration area based on habitat mapping. The topographical plan for the restoration was used to simulate the anticipated habitat after restoration. Although the restoration increased spawning habitat, it was less successful for rearing habitat. Channel changes associated with high‐flow events did not entirely negate the benefits of the restoration project. The results of this study point out the need for models that can simulate the changes in channel topography associated with high‐flow events, which could then be used to simulate habitat over time. Published 2013. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
9.
K. L. Sellheim C. B. Watry B. Rook S. C. Zeug J. Hannon J. Zimmerman K. Dove J. E. Merz 《河流研究与利用》2016,32(4):610-621
Gravel augmentation is used in sediment‐starved streams to improve salmonid spawning habitat. As gravel is added to river channels, water surface elevations may rise in adjacent areas, activating floodplain habitat at lower flows, and floodplains inundate more frequently, potentially affecting the quantity and quality of juvenile salmonid rearing habitat. We analysed 5 years of juvenile Chinook salmon Oncorhynchus tschawytscha and steelhead Oncorhynchus mykiss data from snorkel surveys before and after gravel augmentation in the Lower American River, a low‐gradient, highly regulated alluvial river in California's Central Valley. We measured the quality and quantity of rearing habitat (current velocity and areal extent of inundated riparian vegetation) following gravel placement and tested whether these factors affected juvenile abundance. Gravel augmentation increased floodplain extent by 3.7–19.8%, decreased average flow velocity from 1.6 to 0.3 m s?1 and increased the amount of vegetative cover from 0.3% to 22.6%. Juvenile abundances increased significantly for both species following augmentation. However, the strength of the relationship between abundance and habitat variables was greater for smaller salmonids. These results suggest that, in addition to enhancing salmonid spawning habitat, gravel augmentation can improve rearing habitat where channel incision and/or regulated hydrographs disconnect floodplains from main river channels. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
10.
Enhancement projects within anadromous salmonid rivers of California have increased in recent years. Much of this work is intended as mitigation in regulated streams where salmon and steelhead spawning habitat is inaccessible or degraded due to dams, water diversions and channelization. Little research has been done to assess the benefits of spawning habitat enhancement to stream organisms other than salmon. We monitored benthic macroinvertebrates at seven spawning gravel augmentation sites in the lower Mokelumne River, a regulated stream in the Central Valley of California. Placement of cleaned floodplain gravel decreased depths and increased stream velocities. Benthic organisms colonized new gravels quickly, equalling densities and biomass of unenhanced spawning sites within 4 weeks. Macroinvertebrate species richness equalled that of unenhanced sites within 4 weeks and diversity within 2 weeks. Standing crop, as indicated by densities and dry biomass, was significantly higher in enhancement sites after 12 weeks than in unenhanced sites and remained so over the following 10 weeks. Although mobile collector/browsers initially dominated new gravels, sedentary collectors were the most common feeding category after 4 weeks, similar to unenhanced sites. These data suggest that cleaned gravels from adjacent floodplain materials, used to enhance salmonid spawning sites, are quickly incorporated into the stream ecosystem, benefiting benthic macroinvertebrate densities and dry biomass. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
11.
In the Central United States, the Arkansas darter (Etheostoma cragini) is listed as a threatened fish species by the State of Kansas. Survival of the darter is threatened by loss of habitat caused by changing streamflow conditions, in particular flow depletion. Future management of darter populations and habitats requires an understanding of streamflow conditions and how those conditions may have changed over time in response to natural and anthropogenic factors. In Kansas, streamflow alteration was assessed at 9 U.S. Geological Survey streamgages in 6 priority basins with no pronounced long‐term trends in precipitation. The assessment was based on a comparison of observed (O) and predicted expected (E) reference conditions for 29 flow metrics. The O/E results indicated a likely or possible diminished flow condition in 2 basins; the primary cause of which is groundwater‐level declines resulting from groundwater pumping for irrigated agriculture. In these 2 basins, habitat characteristics adversely affected by flow depletion may include stream connectivity, pools, and water temperature. The other 4 basins were minimally affected, or unaffected, by flow depletion and therefore may provide the best opportunity for preservation of darter habitat. Through the O/E analysis, anthropogenic streamflow alteration was quantified and the results will enable better‐informed decisions pertaining to the future management of darters in Kansas. 相似文献
12.
In water resource studies, long-term measurements of river streamflow are essential. They allow us to observe trends and natural cycles and are prerequisites for hydraulic and hydrology models. This paper presents a new application of the stage-discharge rating curve model introduced by Maghrebi et al. (2016) to estimate continuous streamflow along the Gono River, Japan. The proposed method, named single stage-discharge (SSD) method, needs only one observed data to estimate the continuous streamflow. However, other similar methods require more than one observational data to fit the curve. The results of the discharge estimation by the SSD are compared with the improved fluvial acoustic tomography system (FATS), conventional rating curve (RC), and flow-area rating curve (FARC). Some statistical indicators, such as the coefficient of determination (R2), root mean square error (RMSE), percent bias (PBAIS), mean absolute error (MAE), and Kling-Gupta efficiency (KGE), are used to assess the performance of the proposed model. ADCP data are used as a benchmark for comparing four studied models. As a result of the comparison, the SSD method outperformed of FATS method. Also, the three studied RC methods were highly accurate at estimating streamflow if all observed data were used in calibration. However, if the observed data in calibration was reduced, the SSD method by R2 = 0.99, RMSE = 2.83 (m3/s), PBIAS = 0.715(%), MAE = 2.30 (m3/s), and KGE = 0.972 showed the best performance compared to other methods. It can be summarized that the SSD method is the feasible method in the data-scarce region and delivers a strong potential for streamflow estimation. 相似文献
13.
Fluvial processes of erosion, sediment transport and deposition determine the changing form and sedimentary structure of naturally adjusting riparian zones. Riparian sediment storage has both scientific and management importance in relation to: (i) the quantities of sediment that are involved; (ii) the quality of the sediment; and (iii) the dispersal of biological materials, notably the vegetation propagules that are transported and deposited in association with the sediment. After discussing the significance of riparian sedimentation processes, this paper reviews methods for quantifying contemporary sediment deposition within water bodies and their margins. Methods for investigating contemporary riparian sedimentation are given particular emphasis, and the extent to which different methods provide comparable estimates and have been used to support the analysis of different physical and chemical properties of the sediment are outlined. The importance of the following are stressed: (i) selecting a sampling method that is suited to the sedimentation environment; (ii) incorporating careful cross‐calibration if measurements from different methods are to be combined; and (iii) replicating measurements to give more robust estimates if small traps are employed. It is concluded that artificial turf mats provide a useful design of sediment trap across a range of environmental conditions because: (i) their surface roughness reduces problems of sediment removal by flood waters or rainfall; (ii) their pliability permits installation on irregular surfaces; (iii) they can be securely attached to the ground with metal pins to resist high shear stresses from river flows; (iv) they are robust and light and so easily manipulated in the field and laboratory; (v) it is possible to fully recover the deposited sediment to accurately determine the amount of sediment deposited and to support a range of other analyses. Results are presented to illustrate how artificial turf mats can be used to estimate the quantity and quality of deposited sediment and to explore the associated deposition of viable seeds. This provides one example of the important hydroecological role of riparian sedimentation processes and of the potential for the development of innovative, interdisciplinary research on riparian sediment dynamics. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
14.
Nicole L. Hill Jessamine R. Trueman Ashlee D. Prévost Dylan J. Fraser William R. Ardren James W.A. Grant 《Journal of Great Lakes research》2019,45(2):394-399
By impeding migration and degrading habitat downstream, dam construction has caused population declines in many migratory fish populations. As part of the landlocked Atlantic salmon (Salmo salar) restoration program in Lake Champlain, the Willsboro Dam was removed from the Boquet River, NY in 2015 providing an opportunity to study the effects of dam removal on spawning habitat quality and availability. Spawning habitat surveys were conducted downstream of the dam site in 2014, 2016 and 2017, and in historical spawning grounds upstream in 2016 and 2017. The habitat used was characterized by measuring depth, water velocity, and substrate size at each redd. Mean habitat use did not differ between upstream and downstream sites for any variables in 2016 and only differed for depth in 2017. However, the variance in depth and substrate used for spawning were lower at the upstream site in 2016, likely due to an abundance of habitat. In the downstream site, the mean and variance in depth at redds decreased after dam removal as did the variance in substrate size, increasing the habitat suitability of redds. When compared to literature data, habitat used upstream of the former dam was of medium quality in both 2016 and 2017, and improved downstream from low to medium quality in both column velocity and substrate size after dam removal. This study illustrates that positive shifts in the quality of habitat used can occur rapidly following dam removal by allowing access to suitable spawning habitat upstream and improving habitat downstream. 相似文献
15.
Stream substratum plays a key role for many riverine species and has become a focus topic in the context of structural habitat improvements. There is a lack of studies that compare the effectiveness of different substratum restoration measures. Herein, we compare four restoration techniques (two different gravel introductions, substratum raking and sickle‐formed constrictor) that were carried out in six replicate rivers. Each measure was monitored for changes in physicochemical substratum quality and the effects of the construction work on downstream sites. Generally, the effects on physicochemical substratum quality were highly variable between restoration types and rivers and strongly decreased within 1 year. Most pronounced changes of substratum quality were detected for the gravel introductions. Substratum raking and the sickle‐formed constrictor had the smallest effects, which were dependent on the original substratum composition of the restored sites. At the same time, substratum raking caused an average fine sediment deposition of 17 kg m?2 on downstream sites, being sixfold higher than for the other measures. Consequently, all of the investigated substratum restoration techniques are confined to short‐term improvement of substratum quality. This finding, together with the observed damage on downstream sites, suggests that a rethinking of the currently applied restoration techniques is required, better considering catchment and natural substratum dynamics in river restoration. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
16.
17.
Pacific salmon (Oncorhynchus) use a variety of rearing environments prior to seaward migration, yet large river habitats and their use have not been well defined, particularly at the southernmost salmon range where major landscape‐level alterations have occurred. We explored juvenile Chinook salmon (Oncorhynchus tshawytscha) and steelhead (Oncorhynchus mykiss) presence along the river continuum and in main‐channel and off‐channel habitats of a regulated California Mediterranean‐climate river. Over an 8‐year period, off‐channels of the lower Mokelumne River exhibited slower and warmer water than the main‐channel. Probability of salmonid presence varied by stream reach and habitat types. Steelhead and Chinook salmon both demonstrated transitional responses to the dry season, with juveniles leaving off‐channels by midsummer. This corresponded to flow recession, increasing water temperatures, salmonid growth and end of emigration period. Main‐channel steelhead observations continued until the following storm season, which brought cool flood flows to reconnect off‐channels and the next juvenile cohort of both species to the river. Within arid climates, low‐gradient off‐channels appear more transiently used than in cooler and more northern humid climate systems. Within a highly regulated Mediterranean‐climate river, off‐channel habitats become increasingly scarce, disconnected or temperature limiting in low‐gradient reaches both seasonally and due to anthropogenic modifications. These observations may provide guidance for future management within large salmon streams. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
18.
森林植被改善对鄱阳湖流域径流和输沙过程的影响 总被引：1，自引：0，他引：1
以河流基流为切入点,研究流域植被调节径流、水土保持等微观作用影响大中型河流湖泊径流过程和水沙过程宏观效应的机理。鄱阳湖流域60年来天然降水没有发生趋势性变化。流域森林覆盖率由34.73%上升到63.00%,植被质量改善,赣江等入湖河流基流增加83 m~3/s,河流输沙量减少。2000年以后和2000年以前相比较,枯水期降水径流系数增大,年流量过程平坦化,一定程度上减小洪灾风险,有利于水资源利用和生态环境保护。2001年以后进入鄱阳湖泥沙平均每年减少1 007×10~4t;出湖泥沙增加314×10~4t。因此,鄱阳湖入江水道由淤积转变为冲刷,但出湖流量过程没有趋势性变化。 相似文献
19.
Precipitation in fall and winter is important to recharge aquifers in Northern California and the Pacific Northwestern United States, causing the baseflow in rivers ascend during the time when Chinook salmon (Oncorhynchus tshawytscha) construct redds. Herein, we evaluate the availability of spawning habitats under a constant streamflow common in regulated rivers against ascending baseflows patterned from free‐flowing rivers. A binomial logistic regression model was applied to predict the suitability of redd locations based on physical characteristics. Next, two‐dimensional hydrodynamic habitat models were developed at two locations representing a broad range of channel forms common in large rivers. Hydrodynamic and habitat models were leveraged together to simulate the quality, amount, and spatial distribution of spawning habitat at a series of individual flow rates, as well as the combined effect of those flow rates through a spawning season with ascending baseflows. Ascending baseflows increased the abundance of spawning habitat over individual streamflows at a site where the river channel is confined by levee‐like features. However, improvements were greater at an unconfined site that facilitated lateral connectivity and greater expansion of wetted channel area as streamflows increased. Ascending baseflows provided spatial separation in preferred habitats over a spawning season, which may reduce the risk of superimposition among runs or among species. Ascending baseflows provided a benefit across the range of hydrologic regimes in a 100‐year gauge record ranging from 20% to 122% improvements in habitat area over low streamflows that are currently used to manage for spawning habitat. Although replicating natural flow regimes in managed systems can be impossible or impractical, these results demonstrate that incorporating elements of the natural flow regime like ascending baseflows can benefit the restoration and conservation of riverine species. 相似文献
20.
B. Ahmadi‐Nedushan A. St‐Hilaire M. Bérubé T. B. M. J. Ouarda É. Robichaud 《河流研究与利用》2008,24(3):279-292
The attempts made to manage water to meet human requirements should also consider the needs of freshwater species and ecosystems. There are many tools available to assess instream flow needs, one of which is the use of habitat preference models. In this study, a fuzzy approach was used for modelling habitat preferences for two life stages of Atlantic salmon (Salmo salar). Experienced fish biologists and technicians contributed to the development of fuzzy sets and fuzzy preference rules for spawning and parr habitat. Fuzzy sets were defined for water depth, velocity and substrate composition. Fuzzy preference rules for the two life stages were then defined as sets of IF–THEN rules relating the physical attributes to habitat suitability. The fuzzy suitability indices are then used to obtain weighted usable area (WUA) at different discharges and to estimate the ecologic flow required to preserve habitat. Different methods are applied to combine the membership function and rules defined by the experts. A sensitivity analysis of rules of the combined system indicated that a limited number of rules are determinant and results are highly dependent on the consequences of these rules. A modification in the consequence of these rules can significantly alter WUA estimations. It is therefore recommended to combine the knowledge of many experts in the elicitation process and to quantify the uncertainty associated with the combination of expert knowledge. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献