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1.
2.
Vasileios Diamantis Ioannis Papaspyrou Parasxos Melidis Alexander Aivasidis 《Bioprocess and biosystems engineering》2010,33(2):293-298
Aerated channel reactors with a uniform field of aeration may display flow stratification and short-circuit phenomena in wastewater
treatment systems. In this study, we present data suggesting that flow stratification is closely related to the aeration rate
and the arrangement of aerators. A full-scale oxidation ditch, with a total volume of 6,500 m3 and a membrane-diffused aerated zone of 60 × 7 × 5 m (length–width–depth), was selected for water velocity measurements.
Two profiles of the oxidation ditch were studied in detail: the first one was at the end of the aerated zone and the second
one at the end of the anoxic zone. The results of this work demonstrate that the horizontal water velocity at the end of the
aerated zone displayed significant stratification, with maximum velocity near the water surface (0.5–0.7 m/s) and almost zero
velocity at a depth of 2.5 m. At the end of the anoxic zone, water velocity was uniform and equal to 0.27–0.31 m/s. Increasing
the aeration rate from 1,800 to 4,300 m3/h, almost 90% of the water flow was found to discharge through the upper-half of the channel reactor profile. Different options
to mitigate flow stratification of the oxidation ditch are discussed in this paper. 相似文献
3.
Fluvial geomorphology proposes the methodology of cognition and assessment of the riverine landscape and points to the possibilities
of exploitation of its results in hydrobiological research. Habitat structure of two reaches of the Drietomica brook (Biele
Karpaty Mts, Slovakia) was assesed at level of morphological and morphohydraulic units in the sense of the River Morphology
Hierarchical Classification (RMHC)). Physical habitats were described by flow hydraulics and substrate properties as directly
measured variables (current velocity, depth, substrate size) and related variables (flow type, Froude and Reynolds numbers).
According to the shear stress (expressed by Fr and Re), the morphological units were divided into two main groups — with low
shear stress — pools, glides, edgewaters, bar nooks and bars; with high shear stress — riffles, runs, rapids and scours; characterized
also by different Ephemeroptera, Plecoptera and Trichoptera (EPT) communities. The EPT communities were analyzed in relation
to the morphological, hydraulic and substrate characteristics of the stream channel. The main environmental gradient responsible
for the variation in EPT fauna was found using Principal Component Analysis and was related to gradient of flow in term of
current velocity and other hydraulic attributes covered by Fr and Re numbers. The EPT communities (by means of abundance,
feeding types, current, microhabitat and zonation preferences) showed preferences for different morphological units, flow
type and current velocity. Depth and substrate grain size showed only weak relation to EPT communities. 相似文献
4.
The objective of this study was to estimate the hydraulic conductivity of sandy soil under different plant cover at the locality
Mláky II at Sekule (southwest Slovakia). Two sites were demarcated at the locality, with mainly moss species at glade site,
and pine forest at forest site. The estimation of unsaturated hydraulic conductivity was conducted by (a) minidisk infiltrometer
and (b) the analysis of a dye tracer total resident concentration. The latter approach assumed the applicability of the stochastic—convective
flow theory in the sandy soil. In the dye tracer experiment, two plots (1 × 1 m each) were established in both sites, and
100 mm of dye tracer (Brilliant Blue FCF) solution was applied on the soil surface. Similar results were obtained in both
plots, with more than 70 % area of horizons stained in the depth of 30–50 cm. In some cases, the predicted and measured hydraulic
conductivity were found within an order of magnitude, thus revealing similar impact of different plant cover on hydraulic
properties of sandy soil studied. In contrast to sandy soils used for agriculture, the influence of the plant/surface humus
and topsoil interface extended in the form of a highly heterogeneous matrix flow to the depth of 50–60 cm, where it was dampened
by horizontal layering. 相似文献
5.
Marko Miliša Ivan Habdija Biserka Primc-Habdija Ines Radanović Renata Matoničkin Kepčija 《Hydrobiologia》2006,553(1):231-243
We investigated the distribution patterns of particulate organic matter (POM) on travertine barriers in respect to flow velocity.
Research was conducted on the barrage-lake system of the Plitvice Lakes, Croatia. Four layers were distinguished within the
substrate (moss mat + three travertine layers) in three hydraulic habitats at three sites. Substrate samples were collected
monthly with a core sampler. The aim of the study was to explore the ability of moss mats and travertine substrate to accumulate
POM; to ascertain the role of flow velocity and to produce a model of POM distribution pattern. The average of POM deposited
in the 10 cm deep zone decreased significantly in the three sites along longitudinal profile of the system. Most POM was deposited
in the moss mats, and the amounts decreased exponentially with depth. This was observed for coarse particulate organic matter
(CPOM), ultra-fine particulate organic matter (UPOM) and total organic matter (TPOM) while fine organic matter (FPOM) deposition
appeared unaffected by depth. More POM was accumulated in hydraulic habitats of low flow velocity. Correlation between flow
velocity and POM accumulation was generally negative. Positive correlations between flow velocity and deposition rates were
noted for CPOM in moss mats and top travertine layers; the deposition of other POM fractions was negatively influenced by
the flow velocity. The influence of flow velocity decreased with increasing depth. In the deepest layers (7–10 cm) flow velocity
influenced only the deposition of the smallest particles (UPOM). 相似文献
6.
Marko Miliša Renata Matoničkin Kepčija Ines Radanović Ana Ostojić Ivan Habdija 《Hydrobiologia》2006,573(1):183-197
The effects of aquatic macrophyte (willows and sawgrass) removal on flow velocity, tufa deposition, POM dynamics, and macroinvertebrate
community structure were studied in the tufa barrier habitats of the barrage system of Plitvice Lakes, Croatia. Samples were
collected from two hydraulic habitats (fast > 100 cm s−1 and slow < 100 cm s−1) at both a control (no macrophytes removed) and impact (macrophytes removed) site. Samples were collected with a core sampler
(four layers in vertical profile of barrier bed) monthly on 6 dates before and 7 dates after the removal of macrophytes. Macrophytes
were removed in May 2002 at the impact site. After the macrophyte removal flow velocity decreased significantly at both hydraulic
habitats. Retarded flow resulted in: (a) a decrease in macroinvertebrate density and diversity since most of the taxa were
rheophilic (preferring habitats with higher flow velocity) and (b) an increase in POM concentrations (FPOM and UPOM) since
decreases in flow velocity facilitate particle deposition in lotic habitats. The effects of macrophyte removal were present,
and diminish along the vertical sediment profile of the barrier bed. Tufa deposition was not influenced by the macrophyte
removal.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. 相似文献
7.
Stream thalweg depth profiles (along path of greatest channel depth) and woody debris tallies have recently become components
of routine field procedures for quantifying physical habitat in national stream monitoring efforts. Mean residual depth, standard
deviation of thalweg depth, and large woody debris (LWD) volumes are potential metrics of habitat complexity calculated from
these survey data. We used 42 intensive dye-transit studies to demonstrate the relevance of these easily measured channel
habitat complexity metrics to transient hydraulic (“dead zone”) storage, a channel process important for biotic habitat as
well as retention and “spiraling” of dissolved and particulate nutrients. We examined transient storage and channel morphology
in small gravel and cobble-bedded upland streams (wetted width 2–5 m; slopes 2.6–8.3%) representing a wide range of flow stages,
LWD loading, and channel complexity, including measurements before and after LWD was added to enhance fish habitat. While
transient storage volume fraction decreased as flow stage increased in simple channels, those with complex morphology and
well-developed riparian vegetation maintained high transient storage fractions even during storm flows. LWD additions increased
transient storage and channel complexity over the 2 years of post-treatment measurements. We predict with considerable precision
two different formulations of transient hydraulic storage fraction using single-variable linear regressions on residual depth
(R
2 = 0.61–0.89), thalweg depth variance (R
2 = 0.64–0.91), or large woody debris volume (R
2 = 0.48–0.74). Demonstration of these likely causal associations contributes to understanding the process of transient storage
and redefines the use of thalweg profile metrics as a new approach to quantifying morphologic and hydraulic complexity in
streams. 相似文献
8.
This study investigated the interactions of submersed plants with environmental factors using structural equation modeling
(SEM) and evaluated the effect strength of respective factors in an aquatic ecosystem using a data set collected at a fourth
order stream in Japan. A model that simultaneously examines the relative importance of factors of the system has developed.
The investigated factors included plant biomass (Biomass) of submersed macrophytes (Potamogeton malaianus and Potamogeton oxyphyllus) and other environmental factors, i.e. water velocity and water depth (Hydraulic), pore water nitrogen (TNL), pore water
phosphorus (TPL), sediment organic matter (Organic) and sediment particle size (Texture). The estimated model showed that
the Biomass was negatively correlated with Hydraulic but positively correlated with Organic whilst TNL and TPL affected the
Biomass with almost equal strength. The effects caused by Hydraulic to Texture were greater than the ones caused by Biomass.
At the narrow ranges of water velocity (0–7 cm s−1) and shallow depth (0–35 cm), the effect of wash-away of Organic by Hydraulic were smaller than the retention effect of Organic
by Biomass. These results provide more insights into interactions of the submersed macrophytes with environmental factors.
Handling editor: K. Martens 相似文献
9.
K. Bunzl 《Radiation and environmental biophysics》2001,40(3):237-241
Experimentally observed activity–depth profiles of fallout radionuclides in the soil frequently exhibit a comparatively fast
moving tail in soil layers below the peak concentration (tailing). Monte Carlo calculations on the basis of the convection-dispersion
model show that this phenomenon can be explained by assuming that either the hydraulic properties of the soil (characterised
by the diffusion/dispersion coefficient and pore water velocity) or the sorption properties of the soil (characterised by
the distribution coefficient K
d
), or both, exhibit a horizontal variability according to a log-normal distribution. Modifications of the activity–depth profile
due to a K
d
value which decreases linearly with depth were examined by using a random walk approach, based also on the convection-dispersion
model. In this case, however, a pronounced tailing effect of the activity–depth profile did not result. Interpretation and
realistic modelling of an experimentally observed activity–depth profile which exhibits a tailing effect is thus not unambiguously
possible without any additional information on the spatial variability of the hydraulic parameters and, independently, also
for the sorption properties.
Received: 5 January 2001 / Accepted: 1 May 2001 相似文献
10.
Field measurement of soil water repellency and its impact on water flow under different vegetation 总被引:1,自引:0,他引:1
L’ubomír Lichner Paul D. Hallett Debbie S. Feeney Olívia Ďugová Miloslav Šír Miroslav Tesař 《Biologia》2007,62(5):537-541
Numerous recent laboratory studies have shown that vegetation can influence soil water flow by inducing very low levels of
water repellency. In this study we extended on this previous research by developing a field-based test using a miniature infiltrometer
to assess low levels of water repellency from physically based measurements of liquid flow in soil. The field-based test was
verified through a simple laboratory experiment and then applied to determine the impact of vegetation and antecedent soil
water content. The soil hydraulic properties determined were hydraulic conductivity, sorptivity, as well as the persistence
and index of water repellency. Tests were conducted following a dry spell and wet spell on (1) forest soil (0 cm depth), (2)
glade soil (0 cm depth) and (3) glade soil (50 cm depth). It was found that both the persistence and index of water repellency,
R, decreased in the order as follows: forest soil > glade soil (0 cm) > glade soil (50 cm) for both dry and wet spell. The
range of values of R was 0.28 (wettable) to 360 (highly water repellent), which affected hydraulic conductivity k
r(−2 cm). R increased and hence k
r(−2 cm) decreased in the order: forest soil < glade soil (0 cm) < glade soil (50 cm) for both the dry and wet spell. There
were clear interactions between vegetation and changes to water flow caused by presence of repellency.
Presented at the International Conference on Biohydrology, Prague, Czech Republic, 20–22 September 2006. 相似文献
11.
Seasonal oscillations in the carbon (δ13C) and nitrogen (δ15N) isotope signatures of aquatic algae can cause seasonal enrichment–depletion cycles in the isotopic composition of planktonic
invertebrates (e.g., copepods). Yet, there is growing evidence that seasonal enrichment–depletion cycles also occur in the
isotope signatures of larger invertebrate consumers, taxa used to define reference points in isotope-based trophic models
(e.g., trophic baselines). To evaluate the general assumption of temporal stability in non-zooplankton aquatic invertebrates,
δ13C and δ15N time series data from the literature were analyzed for seasonality and the influence of biotic (feeding group) and abiotic
(trophic state, climate regime) factors on isotope temporal patterns. The amplitude of δ13C and δ15N enrichment–depletion cycles was negatively related to body size, although all size-classes of invertebrates displayed a
winter-to-summer enrichment in δ13C and depletion in δ15N. Among feeding groups, periphytic grazers were more variable and displayed larger temporal changes in δ13C than detritivores. For nitrogen, temporal variability and magnitude of directional change of δ15N was most strongly related to ecosystem trophic state (eutrophic > mesotrophic, oligotrophic). This study provides evidence
of seasonality in the isotopic composition of aquatic invertebrates across very broad geographical and ecological gradients
as well as identifying factors that are likely to modulate the strength and variability of seasonality. These results emphasize
the need for researchers to recognize the likelihood of temporal changes in non-zooplankton aquatic invertebrate consumers
at time scales relevant to seasonal studies and, if present, to account for temporal dynamics in isotope trophic models. 相似文献
12.
A.-W. Pan J. He Y. Kinouchi Hisao Yamaguchi Hiroshi Miyamoto 《European journal of applied physiology and occupational physiology》1997,75(5):388-395
The present study investigated the mechanism of diving bradycardia. A group of 14 healthy untrained male subjects were examined
during breath-holding either out of the water (30–33°C), in head-out immersion, or in whole-body submersion (27–29°C) in a
diving pool. Blood velocity, blood volume flow in the carotid artery, diastolic blood pressure and electrocardiogram were
measured and recorded during the experiments. The peak blood velocity increased by 13.6% (P < 0.01) and R-wave amplitude increased by 57.1% (P < 0.005) when the subjects entered water from air. End-diastolic blood velocity in the carotid artery increased significantly during breath-holding, e.g. increased from 0.20 (SD 0.02) m · s−1 at rest to 0.33 (SD 0.04) m · s−1 (P < 0.001) at 50.0 s in breath-hold submersion to a 2.0-m depth. Blood volume flow in the carotid artery increased by 26.6%
(P < 0.05) at 30 s and 36.6% (P < 0.001) at 40 s in breath-hold submersion to a 2.0-m depth. Diastolic blood pressure increased by 15.4% (P < 0.01) at 60 s during breath-holding in head-out immersion. Blood volume flow, and diastolic blood pressure increased significantly more and faster during breath-holding in submersion than out of the
water. There was a good negative correlation with the heart rate: the root mean square correlation coefficient r was 0.73 (P < 0.001). It was concluded that an increased accumulation of blood in the aorta and arteries at end-diastole and decreased
venous return, caused by an increase in systemic peripheral resistance during breath-holding, underlies diving bradycardia.
Accepted: 22 November 1996 相似文献
13.
Hilde Eggermont James M. Russell Georg Schettler Kay Van Damme Ilse Bessems Dirk Verschuren 《Hydrobiologia》2007,592(1):151-173
This study describes the physical and chemical properties of 17 Afroalpine lakes (>2 m deep) and 11 pools (<2 m deep) in the
Rwenzori mountains, Uganda-DR Congo, with the aim to establish the baseline conditions against which to evaluate future environmental
and biological changes in these unique tropical ecosystems, and to provide the foundation for lake-based paleoenvironmental
studies. Most Rwenzori lakes are located above 3,500 m elevation, and dilute (5–52 μS/cm specific conductance at 25°C) open
systems with surface in- and outflow. Multivariate ordination and pairwise correlations between environmental variables mainly
differentiate between (1) lakes located near or above 4,000 m (3,890–4,487 m), with at least some direct input of glacial
meltwater and surrounded by rocky catchments or alpine vegetation; and (2) lakes located mostly below 4,000 m (2,990–4,054
m), remote from glaciers and surrounded by Ericaceous vegetation and/or bogs. The former group are mildly acidic to neutral
clear-water lakes (surface pH: 5.80–7.82; Secchi depth: 120–280 cm) with often above-average dissolved ion concentrations
(18–52 μS/cm). These lakes are (ultra-) oligotrophic to mesotrophic (TP: 3.1–12.4 μg/l; Chl-a: 0.3–10.9 μg/l) and phosphorus-limited (mass TN/TP: 22.9–81.4). The latter group are mildly to strongly acidic (pH: 4.30–6.69)
waters stained by dissolved organic carbon (DOC: 6.8–13.6 mg/l) and more modest transparency (Secchi-disk depth: 60–132 cm).
Ratios of particulate carbon, particulate nitrogen and chlorophyll a in these lakes indicate that organic matter in suspension is primarily derived from the lakes’ catchments rather than aquatic
primary productivity. Since key features in the Rwenzori lakes’ abiotic environment are strongly tied to temperature and catchment
hydrology, these Afroalpine lake ecosystems can be expected to respond sensitively to climate change and glacier melting.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. 相似文献
14.
Background
Intercostal muscles are richly innervated by mechanoreceptors. In vivo studies of cat intercostal muscle have shown that there are 3 populations of intercostal muscle mechanoreceptors: primary muscle spindles (1°), secondary muscle spindles (2°) and Golgi tendon organs (GTO). The purpose of this study was to determine the mechanical transduction properties of intercostal muscle mechanoreceptors in response to controlled length and velocity displacements of the intercostal space. Mechanoreceptors, recorded from dorsal root fibers, were localized within an isolated intercostal muscle space (ICS). Changes in ICS displacement and the velocity of ICS displacement were independently controlled with an electromagnetic motor. ICS velocity (0.5 – 100 μm/msec to a displacement of 2,000 μm) and displacement (50–2,000 μm at a constant velocity of 10 μm/msec) parameters encompassed the full range of rib motion. 相似文献15.
Baoshan Cui Xinsheng Zhao Zhifeng Yang Bin Chen Na Tang Xuejie Tan 《Frontiers of Biology in China》2008,3(2):194-202
We investigated and monitored a reed community in the fields. Data on the bio-ecological characteristics and β-diversity of reed communities in different environmental gradients (mainly based on water depth) of the Yellow River Delta
were collected through multianalysis, extremum analysis and β-diversity index analysis. In accordance with the square sum of deviations (Ward) cluster analysis, 10 sampling plots were
divided into six types with the dominant plants in different plots varying according to the change in environmental gradients.
The dominant plants in these plots varied from aquatic plants to xerophytes and salt tolerant plants as water depth decreased.
The average height and diameter of the reeds at breast level were significantly correlated with the average water depth. The
fitness curves of average density and coverage with average water depth were nonlinear. When the average water depth was 0.3
m, the average density and coverage of reeds reached the apex value, while the height and diameter of the reeds at breast
level increased with the water depth. There were obvious changes to the environmental gradient in the Yellow River Delta.
The transitional communities were also found to exist in the Yellow River Delta by β-diversity analysis. Vicarious species appeared with the change in water depth. The occurrence of substitute species is determined
by the function of common species between adjacent belts. The different functions of common species led to differences in
community structure and function and differences in dominant plants. The result reflects the variations of species present
in different habitats and directly reflects environmental heterogeneity. The values of β-diversity indices of adjacent plots were higher than those of nonadjacent plots. There are transition zones between the xerophytes
and aquatic plants in the Yellow River Delta. In an aquatic environment, the similarity of reed community is higher than that
of xeromorphic plants. The β-diversity index can reflect plant succession trends caused by the change in environmental gradients in the Yellow River Delta.
The β-diversity index reveals plant responses to changes in environmental gradient and is helpful in observing changes in patterns
of species diversity in relation to environmental gradient change and evolving trends in the future, which in turn plays a
prominent role when environmental water requirements of wetland are discussed.
__________
Translated from Acta Ecologica Sinica, 2006, 26(5): 1533–1541 [译自: 生态学报] 相似文献
16.
The impact of four environmental parameters (water depth, type of substratum, current velocity and light intensity), on Ranunculus peltatus morphology and reproduction was tested in four 1 month semi- controlled experiments. Four development stages were underlined
from April to August 2001 in R. peltatus: an elongation stage (April–June), a flowering stage (May–June), a fragmentation stage (June–July) and a potential regenerative
stage (July–August). Water depth was therefore tested on R. peltatus elongation, type of substratum on R. peltatus elongation and flowering, current velocity on R. peltatus fragmentation and light intensity on its possible regeneration. The maximum development was measured for a 32 cm water depth.
Current velocity did not have a significant effect on R. peltatus fragmentation. Regeneration depended strongly on light availability. This stage occurred only for unshaded or 50% shaded
plants. Darkness prevented plants from regrowing. 相似文献
17.
Ikuko Fujisaki Kenneth G. Rice Leonard G. Pearlstine Frank J. Mazzotti 《Hydrobiologia》2009,635(1):329-338
Feeding opportunities of American alligators (Alligator mississippiensis) in freshwater wetlands in south Florida are closely linked to hydrologic conditions. In the Everglades, seasonally and annually
fluctuating surface water levels affect populations of aquatic organisms that alligators consume. Since prey becomes more
concentrated when water depth decreases, we hypothesized an inverse relationship between body condition and water depth in
the Everglades. On average, condition of adult alligators in the dry season was significantly higher than in the wet season,
but this was not the case for juveniles/subadults. The correlation between body condition and measured water depth at capture
locations was weak; however, there was a significant negative correlation between the condition and predicted water depth
prior to capture for all animals except for spring juveniles/subadults which had a weak positive condition–water depth relationship.
Overall, a relatively strong inverse correlation occurred at 10–49 days prior to the capture day, suggesting that current
body condition of alligators may depend on feeding opportunities during that period. Fitted regression of body condition on
water depth (mean depth of 10 days when condition-water depth correlation was greatest) resulted in a significantly negative
slope, except for spring adult females and spring juveniles/subadults for which slopes were not significantly different from
zero. Our results imply that water management practices may be critical for alligators in the Everglades since water depth
can affect animal condition in a relatively short period of time. 相似文献
18.
Plant water relations of nine woody species were studied in a lower montane rain forest in Panama. These data provide a partial
test of the hypothesis that hydraulic architecture of lower montane species might limit transpiration and thus leaf size or
nutrient transport (as suggested by J. Cavelier and E. G. Leigh, respectively). Diurnal variation in leaf transpiration was
closely correlated with changes in net radiation. Peak transpiration rates (7 × 10–5 kg s–1 m–2) were as high as peak transpiration rates from tropical lowland forests but mean daily water use [0.39 ± 0.08 (SEM) kg m–2 day–1] were mostly lower than comparable data from tropical lowland forests. Thus transpiration rates are sufficiently high for
sufficiently long periods to make it unlikely that nutrient transport is limited by transpiration. Another objective of this
study was a comparison of two different methods to measure hydraulic conductance (Kh = flow rate per unit pressure gradient) and leaf specific conductance of stem segments (KL = Kh/leaf area distal to the segment). The results obtained with the traditional conductivity apparatus and the high pressure
flow meter method, yielded similar results in six out of seven cases.
Received: 20 March / Accepted: 21 October 1997 相似文献
19.
Diego Tonolla Vicenç Acuña Urs Uehlinger Thomas Frank Klement Tockner 《Ecosystems》2010,13(5):727-740
River floodplains are composed of a shifting mosaic of aquatic and terrestrial habitats. Each habitat type exhibits distinct
environmental and ecological properties. Temperature is a key property driving ecological processes and controlling the composition
and distribution of biota. However, given the size and complexity of floodplains, ground surveys based on point measurements
are spatially limited. In this study, we applied thermal infrared (IR) imagery to quantify surface temperature patterns at
12–15 min intervals over 24 h cycles in two near-natural Alpine river floodplains (Roseg, Tagliamento). Furthermore, vertical
temperature distribution was measured at 3–5 min intervals in unsaturated gravel sediment deposits (at 1 cm distances; 0–29 cm
depth). Each habitat type exhibited a distinct thermal signature creating a complex thermal mosaic. The diel temperature pulse
and maximum daily temperature were the main thermal components that differentiated habitat types. In both floodplains, exposed
gravel sediments exhibited the highest diel pulse (up to 23°C), whereas in aquatic habitats the pulse was as low as 11°C (main
channel in the Roseg floodplain). In the unsaturated gravel sediment deposits, the maximum diel kinetic temperature pulse
ranged from 40.4°C (sediment surface) to 2.7°C (29 cm sediment depth). Vertically, the spatiotemporal variation of temperature
was about as high as horizontally across the entire floodplain surface. This study emphasized that remotely sensed thermal
IR imagery provides a powerful non-invasive method to quantitatively assess thermal heterogeneity of complex aquatic and terrestrial
ecosystems at a resolution required to understand ecosystem processes and the distribution of biota. 相似文献
20.
Numerical fish-habitat modelling on various scales is considered to be state of the art in river management. However, most
of the concepts applied use steady-state hydraulic parameters such as flow velocity and water depth. Herein we present analysis
and discussion of the possibility of including a drift-feeding parameter (SIF) into habitat evaluations based on multiplying suitability indices. “Sources” and “sinks” of benthic drift were identified
according to both the zero-crossing and hydraulic-threshold methods in an alpine gravel-bed river. Minor differences could
be determined between the two methods in a well-developed riffle–pool section. Macroinvertebrates, used for simulating benthic
drift, were collected by multi-habitat sampling and appraised according to their critical threshold (τ
cr) for motion on the bed surface and sinking velocity (v
s). The findings of the calculation of drift rates using one- (1D) and two-dimensional (2D) hydrodynamic numerical models highlight
a specification of best feeding position for drift-feeding fish (i.e. brown trout, grayling) considering the SIF parameter. Riffle–pool sequences are characteristic of pristine alpine streams; our findings underline their importance as
production (riffles) and consumption areas (pools) in terms of holistic river function. Moreover, the results indicate that
(artificial) lateral obstruction (e.g. dams) may lead to a reduced transport rate of benthic organisms due to low bottom shear
stress (<0.25 N m−2). Thus, deposition of drifting macroinvertebrates occurs in backwaters, with downstream impacts on benthic and fish communities. 相似文献