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1.
Integrating process‐based flow and temperature models to assess riparian forests and temperature amelioration in salmon streams
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Luca Fabris Iain Archibald Malcolm Willem Bastiaan Buddendorf Chris Soulsby 《水文研究》2018,32(6):776-791
The importance of riparian tree cover in reducing energy inputs to streams is increasingly recognized in schemes to mitigate climate change effects and protect freshwater ecosystems. Assessing different riparian management strategies requires catchment‐scale understanding of how different planting scenarios would affect the stream energy balance, coupled with a quantitative assessment of spatial patterns of streamflow generation. Here, we use the physically based MIKE SHE model to integrate simulations of catchment‐scale run‐off generation and in‐stream hydraulics with a heat transfer model. This was calibrated to model the spatio‐temporal distribution of hourly stream water temperature during warm low flow periods in a Scottish salmon stream. The model was explored as a “proof of concept” for a tool to investigate the effects of riparian management on high stream water temperatures that could affect juvenile Atlantic salmon. Uncertainty was incorporated into the assessment using the generalized likelihood uncertainty estimation approach. Results showed that by decreasing both the warming (daylight hours) and the cooling (night‐time hours) rates, forest cover leads to a reduction of the temperature range (with a delay of the time to peak by up to 2 hr) and can therefore be effectively used to moderate projected climate change effects. The modelling presented here facilitated the quantification of potential mitigating effects of alternative riparian management strategies and provided a valuable tool that has potential to be utilized as an evidence base for catchment management guidance. 相似文献
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Metrics to assess how longitudinal channel network connectivity and in‐stream Atlantic salmon habitats are impacted by hydropower regulation
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Willem B. Buddendorf Iain A. Malcolm Josie Geris Mark E. Wilkinson Chris Soulsby 《水文研究》2017,31(12):2132-2142
Habitat fragmentation in channel networks and riverine ecosystems is increasing globally due to the construction of barriers and river regulation. The resulting divergence from the natural state poses a threat to ecosystem integrity. Consequently, a trade‐off is required between the conservation of biodiversity in channel networks and socio‐economic factors including power generation, potable water supplies, fisheries, and tourism. Many of Scotland's rivers are regulated for hydropower generation but also support populations of Atlantic salmon (Salmo salar L.) that have high economic and conservation value. This paper investigates the use of connectivity metrics and weightings to assess the impact of river barriers (impoundments) associated with hydropower regulation on natural longitudinal channel connectivity for Atlantic salmon. We applied 2 different weighting approaches in the connectivity models that accounted for spatial variability in habitat quality for spawning and fry production and contrasted these models with a more traditional approach using wetted area. Assessments of habitat loss using the habitat quality weighted models contrasted with those using the less biologically relevant wetted area. This highlights the importance of including relevant ecological and hydrogeomorphic information in assessing regulation impacts on natural channel connectivity. Specifically, we highlight scenarios where losing a smaller area of productive habitat can have a larger impact on Atlantic salmon than losing a greater area of less suitable habitat. It is recommended that future channel connectivity assessments should attempt to include biologically relevant weightings, rather than relying on simpler metrics like wetted area which can produce misleading assessments of barrier impacts. 相似文献
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Kastelein RA Verboom WC Jennings N de Haan D van der Heul S 《Marine environmental research》2008,66(3):319-326
Two harbor porpoises in a floating pen were subjected to five pure tone underwater signals of 70 or 120kHz with different signal durations, amplitudes and duty cycles (% of time sound is produced). Some signals were continuous, others were intermittent (duty cycles varied between 8% and 100%). The effect of each signal was judged by comparing the animals' surfacing locations and number of surfacings (i.e. number of respirations) during test periods with those during baseline periods. In all cases, both porpoises moved away from the sound source, but the effect of the signals on respiration rates was negligible. Pulsed 70kHz signals with a source level (SL) of 137dB had a similar effect as a continuous 70kHz signal with an SL of 148dB (re 1muPa, rms). Also, a pulsed 70kHz signal with an SL of 147dB had a much stronger deterring effect than a continuous 70kHz signal with a similar SL. For pulsed 70kHz signals (2s pulse duration, 4s pulse interval, SL 147dB re 1muPa, rms), the avoidance threshold sound pressure level (SPL), in the context of the present study, was estimated to be around 130dB (re 1muPa, rms) for porpoise 064 and around 124dB (re 1muPa, rms) for porpoise 047. This study shows that ultrasonic pingers (70kHz) can deter harbor porpoises. Such ultrasonic pingers have the advantage that they do not have a "dinner bell" effect on pinnipeds, and probably have no, or less, effect on other marine fauna, which are often sensitive to low frequency sounds. 相似文献
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Willem V. R. Malkus 《地球物理与天体物理流体动力学》2013,107(1):267-278
AbstractHiggins and Kennedy (1971) concluded that the Earth's fluid core has a stable stratification if it is at its melting point. Busse (1972) and Elsasser suggested as an alternative that a hydrostatic-isentropic distribution of particulate solid can produce neutral stability in a partially molten core. Here this suggestion is quantified and a determination is made of the efficiency of the production of fluid motion from the heat flux. This is used to establish that macroscopic convection can exist only if the particulate solid is of sufficiently small size. A thermal history of the core compatible with upper mantle heat flux is advanced in which it is suggested that the inner core is a fairly recent feature. The implication of these results for convection-driven and precession-driven dynamos is that both can function for a small enough suspended particulate, that the convection-dynamo will fail for particles greater than one micron in diameter, and that the precession-driven dynamo probably cannot survive particles greater than ten microns in diameter. 相似文献
7.
Hydrophobic and electrostatic parameters in bacterial adhesion 总被引:5,自引:0,他引:5
Mark C. M. van Loosdrecht Willem Norde Johannes Lyklema Alexander J. B. Zehnder 《Aquatic Sciences - Research Across Boundaries》1990,52(1):103-114
Recently it has been shown that the initial stages of bacterial adhesion to a model-surface of sulphated polystyrene can best be described using hydrophobic and electrostatic parameters. In the present study it is tested whether these parameters can generally be applied to predict bacterial adhesion by using (i) glass, as a model for hydrophilic and natural surfaces of silicates and oxides, (ii) polystyrene coated with proteins, as a model for a surface coated with an organic layer, and (iii) river Rhine sediment, as an example of a natural surface. Adhesion to glass was dominated by electrostatic interaction, whereas adhesion to polystyrene coated with various types of proteins depended on the surface characteristics of the bacteria and the type of protein. By relating Van der Waals interactions to hydrophobicity of the interacting species, the adhesion of bacteria to the various surfaces including the river Rhine sediments could be interpreted in terms of the DLVO-theory. It is therefore concluded that the conceptual principles of the DLVO-theory (interplay of Van der Waals and electrostatic interactions) are suitable to describe, at least qualitatively, the initial processes of bacterial adhesion to a wide range of surfaces. 相似文献
8.
The Jewel seam of the Cadomin area is complexly folded and cut by several thrust faults. Vitrinite reflectance anisotropy was determined from twenty oriented coal blocks, collected from various structural positions. Five of the blocks have uniaxial anisotropies, five have biaxial positive anisotropies, the remaining ten are biaxial negative. The biaxial coals display maximum reflectance axes parallel to nearby fold axes, which suggests a relationship between vitrinite anisotropy and deformation. The biaxial vitrinite reflectance ellipsoids result from superposition of tectonic strains on a primary, sedimentary burial related, uniaxial anisotropy. A tectonic stress field was probably present during the later stages of sedimentary burial and subsequent deformation.Coalification resulted largely from pre-deformational, sedimentary burial, but the final coalification stage was syn-deformational, as illustrated by the intersection of isorank surfaces and the Jewel seam and the biaxial vitrinite reflectance anisotropy. 相似文献
9.
The groups of nitrogen components that contribute most to the eutrophication of the sea are ammonia, nitrogen oxides and their respective reaction products. The emission of ammonia is mainly from animal husbandry, whereas the emission of nitrogen oxides is mainly from combustion processes. Ammonia reacts in the atmosphere to form particulate ammonium. Nitrogen oxides react to form nitric acid, nitrous acid, particulate nitrate and peroxyacetyl nitrate. The various nitrogen components have different physical and chemical properties. Therefore, their dry and wet deposition velocities differ. The dry deposition velocity of gas to the sea depends on its solubility, reactivity, concentration in seawater and the wind speed. The dry deposition velocity of a particle depends on its size and the wind speed. The wet removal rate is a function of meteorological conditions. For a gas it further depends on the solubility and reactivity of the gas. For a particle, it further depends on the particle's ability to act as a condensation nucleus for particles. The total deposition of ammonia and its reaction products to the North Sea is about 140 kt N a−1. The total deposition of nitrogen oxides and their reaction products is about 200 kt N a−1. 相似文献
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