Integrating process‐based flow and temperature models to assess riparian forests and temperature amelioration in salmon streams          下载免费PDF全文

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   

Report on the Twelfth United Nations/European Space Agency Workshop on Basic Space Science (Beijing, P.R. China, 24–28 May 2004)     

Willem Wamsteker  Hans J. Haubold 《Astrophysics and Space Science》2006,305(3):325-330

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Reply to the comment by Stephenson “Discussion of de Lange, W.P. and Moon, V.G. 2005. Estimating long-term cliff recession rates from shore platform widths. Engineering Geology 80, 292–301”     

Vicki Moon  Willem de Lange 《Engineering Geology》2008,101(3-4):292-294

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Distribution of trace and major elements in sediment and pore waters of the Lena Delta and Laptev Sea   总被引：1，自引：0，他引：1  

Rob F. Nolting  Maarten van Dalen  Willem Helder 《Marine Chemistry》1996,53(3-4)

Sediment cores collected during the SPASIBA expedition in 1991 were analysed for their trace- and major element concentrations. Leachable (0.1 N HCl) as well as residual concentrations were determined. Fe and Mn were measured in the interstitial waters to characterize redox conditions. Lateral distribution patterns of solid phase Cu, Cd, Ni, Pb and Zn show a small increase in concentration from the Lena Delta in seaward direction. In general concentrations of these metals are very low and similar to natural background values. With some exceptions, solid phase profiles with depth of all investigated elements do not show strong variations. No enrichment of Pb and Zn in surface layers was found. Remobilization processes and transport of particles enriched in Mn are responsible for Mn accumulation in a particular area. Pore-water concentrations of dissolved Mn in the latter sediments are very high (> 700 μM) and suggest strong Mn reduction directly below the sediment-water interface. In contrast to Mn, the depth profiles of Cd show a surface layer with lower concentrations and an increase deeper down the sediment. The C/N ratio in the sediment decreases from 13 in the Lena mouth to 9 in the more marine part of the Laptev Sea. Surface sediments in the Laptev Sea are very uniform and homogeneous and show only small concentration gradients.  相似文献   

When will the eel recover? A full life-cycle model     

Astrom  Marten; Dekker  Willem 《ICES Journal of Marine Science》2007,64(7):1491-1498

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Late Holocene linkages between decade–century scale climate variability and productivity at Lake Tanganyika, Africa     

Andrew S. Cohen  Kiram E. Lezzar  Julia Cole  David Dettman  Geoffrey S. Ellis  Meagan Eagle Gonneea  Pierre-Denis Plisnier  Victor Langenberg  Maarten Blaauw  Derrick Zilifi 《Journal of Paleolimnology》2006,36(2):189-209

Microlaminated sediment cores from the Kalya slope region of Lake Tanganyika provide a near-annually resolved paleoclimate record between ∼∼2,840 and 1,420 cal. yr B.P. demonstrating strong linkages between climate variability and lacustrine productivity. Laminae couplets comprise dark, terrigenous-dominated half couplets, interpreted as low density underflows deposited from riverine sources during the rainy season, alternating with light, planktonic diatomaceous ooze, with little terrigenous component, interpreted as windy/dry season deposits. Laminated portions of the studied cores consist of conspicuous dark and light colored bundles of laminae couplets. Light and dark bundles alternate at decadal time scales. Within dark bundles, both light and dark half couplets are significantly thinner than within light bundles, implying slower sediment accumulation rates during both seasons over those intervals.Time series analyses of laminae thickness patterns demonstrate significant periodicities at interannual–centennial time scales. Longer time scale periodicities (multidecadal to centennial scale) of light and dark half couplet thicknesses are coherent and in some cases are similar to solar cycle periods on these time scales. Although laminae thickness cycles do not strongly covary with the actual Δ¹⁴C record for this same time period, two large Δ¹⁴C anomalies are associated with substantial decreases in both light and dark laminae thickness. In contrast to the multidecadal– centennial time scale, significant annual to decadal periodicities, which are broadly consistent with ENSO/PDO forcing and their impact on East African climate, are not coherent between light and dark half couplets. The coherency of light–dark couplets at decadal–centennial time scales, but not at shorter time scales, is consistent with a model of a long-term relationship between precipitation (recorded in wet season dark laminae thickness) and productivity (light laminae thickness), which is not manifest at shorter time scales. We hypothesize that this coupling results from long-term recharging of internal nutrient loading during wet periods (higher erosion of soil P) and reduced loading during drought intervals. The relationship is not expressed on short time scales during which the dominant control on productivity is wind-driven, dry season upwelling, which is uncorrelated with wet-season precipitation. Our record greatly extends the temporal record of this quasi-periodic behavior throughout the late Holocene and provides the first evidence linking decade- to century-scale episodes of enhanced productivity to enhanced precipitation levels and nutrient recharge in a productive tropical lake.  相似文献   

Metrics to assess how longitudinal channel network connectivity and in‐stream Atlantic salmon habitats are impacted by hydropower regulation          下载免费PDF全文

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   

A synoptic decomposition of rainfall over the Cape south coast of South Africa     

Christien J. Engelbrecht  Willem A. Landman  Francois A. Engelbrecht  Johan Malherbe 《Climate Dynamics》2015,44(9-10):2589-2607

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Variability of rainfall over Lake Kariba catchment area in the Zambezi river basin,Zimbabwe     

Shepherd Muchuru  Joel O. Botai  Christina M. Botai  Willem A. Landman  Abiodun M. Adeola 《Theoretical and Applied Climatology》2016,124(1-2):325-338

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Convection at the melting point: A thermal history of the earth's core     

Willem V. R. Malkus 《地球物理与天体物理流体动力学》2013,107(1):267-278

Abstract

Higgins 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