Current status,distribution, life cycle and ecology ofRhithrogena germanica Eaton, 1885 in Switzerland: Preliminary results (Ephemeroptera,Heptageniidae)     

Verena Lubini  Michel Sartori 《Aquatic Sciences - Research Across Boundaries》1994,56(4):388-397

Rh. germanica is a European species that, due to human impacts, has progressively disappeared from its original territories and is now considered rare. In SwitzerlandRh. germanica has disappeared from the Aare, Broye and Kleine Emme rivers and is actually found in a limited reach of the River Rhine and some of its tributaries (Limmat, Sihl, Thur and Töss rivers).Rh. germanica is a univoltine species, hatching probably in summer. The emergence occurs from February to the beginning of April. It takes place on the water surface. Laboratory observations have shown that the subimaginal stage lasts four days.Rh. germanica occurs on different substrate types, ranging from stones and cobbles to pebbles and gravel. The larvae are more abundant in zones of erosion with coarse and porous sediments than in depositional zones with fine sediments and silts. They are most abundant in riffles with water velocities from 20 to 150 cm/sec. The species tolerates moderately organic-polluted waters.The particular strategy concerning growth and emergence ofRh. germanica is also discussed.  相似文献   

Landsliding and sediment flux in the Central Swiss Alps: A photogrammetric study of the Schimbrig landslide, Entlebuch   总被引：2，自引：0，他引：2  

Marco Schwab  Dirk Rieke-Zapp  Heinz Schneider  Markus Liniger  Fritz Schlunegger   《Geomorphology》2008,97(3-4):392-406

This study explores the effects of hillslope mass failure on the sediment flux in the Waldemme drainage basin, Central Swiss Alps, over decadal time scales. This area is characterized by abundant landslides affecting principally flysch units and is therefore an important sediment source. The analysis concentrates on the Schimbrig landslide that potentially contributes up to 15% to the sediment budget of the Waldemme drainage basin. Volumetric changes are quantified using high-resolution elevation models that were extracted using digital photogrammetric techniques. Sediment discharge data were used to constrain the significance of the landslide for sediment flux in the channel network. The temporal extent of the photogrammetric analysis ranges from 1962 to 1998, including an earth slide event in 1994. The analyses reveal that during periods of low slip rates of the landslide, nearly all of the displaced sediments were eroded and supplied to the channel network. In contrast, during active periods, only a fraction of the displaced landslide mass was exported to the trunk stream. Interestingly, the 1994 earth slide event did not disturb the long-term sediment discharge pattern of the channel network, nor did it influence the sediment flux at a weekly scale. However, suspended sediment pulses correlate with higher-than-average precipitation events. This was especially the case in August 2005 when a storm event (> 100 years return period) triggered several debris flows and earth flows in the whole drainage basin and in the Schimbrig area. This storm did not result in a significant increase in the slip rates of the entire landslide's main body. It is therefore proposed that debris flows and earth flows perform the connectivity between hillslope processes (e.g. landsliding) and the trunk stream during and between phases of landslide activity in this particular setting.  相似文献   

Seismic source zone characterization for the seismic hazard assessment project PEGASOS by the Expert Group 2 (EG1b)   总被引：4，自引：0，他引：4  

Martin Burkhard  Gottfried Grünthal 《Swiss Journal of Geoscience》2009,102(1):149-188

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Water quality in rivers of western Switzerland: Application of an adaptable index based on benthic invertebrates   总被引：1，自引：0，他引：1  

Claude Lang  Geneviève l'Eplattenier  Olivier Reymond 《Aquatic Sciences - Research Across Boundaries》1989,51(3):224-234

Water quality was estimated from 205 samples of benthic invertebrates collected between 1982 and 1986 in 51 rivers of western Switzerland (canton of Vaud). Each sample consisted of the combined list of taxa resulting from one spring sample pooled with one summer sample. Water quality was indicated by total number of taxa and number of taxa intolerant of pollution: i. e. Heptageniidae, Plecoptera, and Trichoptera with a case. Six classes of values were delimited for each of these two variables by cluster analysis. Values from zero to five were attributed to each class. The index of water quality was computed by adding these two values in each sample. According to this index, good water quality was indicated by 42% of samples. This index can be adapted to other rivers because its components are easily modified.  相似文献   

Evidence for coelacanths in the Late Triassic (Rhaetian) of England     

Luke M. Hauser  David M. Martill 《Proceedings of the Geologists' Association. Geologists' Association》2013

The right gular plate of an indeterminate coelacanth from the Westbury Formation (Upper Triassic, Rhaetian) of Blue Anchor Point, Somerset, southwest England is reported. This occurrence represents the first convincing evidence of coelacanths from the Triassic of the United Kingdom. The new specimen suggests a fish of approximately 0.61 m length.  相似文献   

Distinguishing between debris flows and hyperconcentrated flows: an example from the eastern Swiss Alps          下载免费PDF全文

Nancy C. Calhoun  John J. Clague 《地球表面变化过程与地形》2018,43(6):1280-1294

Much research has been done on water‐rich mass flows, but the distinction between hyperconcentrated flows and debris flows, and whether the two are indeed different processes, continue to be debated. Here, we contribute to the ongoing discussion of these phenomena by describing and interpreting the deposit of a large landslide‐induced mass flow in the eastern Swiss Alps. About 9400 years ago, 10‐12 km³ of limestone detached from the wall of the Vorderrhein River valley and rapidly fragmented while sliding towards the valley bottom. The rock mass struck the valley floor with enormous force and liquefied at least 1 km³ of valley‐fill sediments. A slurry of liquefied sediment – the ‘Bonaduz gravel’ – traveled tens of kilometres down the Vorderrhein valley from the impact site, carrying huge fragments of rockslide debris that became stranded on the valley floor, forming hills termed ‘tomas’. Part of the flow was deflected by a cross‐valley barrier and traveled 14 km up a tributary of the Vorderrhein valley. The Bonaduz gravel is >65 m thick and fines upward from massive sandy cobble gravel at its base to silty sand at its top. Sedimentologic and geomorphic evidence indicates that Bonaduz gravel was transported as a hyperconcentated flow, likely above a basal carpet of coarse diamictic sediment that behaved as a debris flow. The large amount of water involved in the flow indicates that at least part of the Flims rockslide entered a lake. The Bonaduz deposit shares many properties with sediments left by hyperconcentrated flows generated in flumes, including normal grading and elutriation pipes produced by the rapid escape of fluids when the flow comes to rest. These properties are characteristic of non‐Newtonian laminar flows with high sediment concentrations. Our study reinforces laboratory and theoretical studies showing that debris flows and hyperconcentrated flows are different processes. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

Evaluation and generalization of radiation‐based methods for calculating evaporation     

C.‐Y. Xu  V. P. Singh 《水文研究》2000,14(2):339-349

Eight radiation‐based equations for determining evaporation were evaluated and expressed in five generalized forms. Five evaporation equations (Abtew, Hargreaves, Makkink, Priestley and Taylor and Turc), where each represents one generalized form, were then compared with pan evaporation measured at Changins station in Switzerland. The comparison was first made using the original constant values involved in each equation, and then using the recalibrated constant values. Evaluation of the Priestley and Taylor equation requires net radiation data as input, in this study, net radiation was estimated using Equation (16) owing to the lack of observation data. The results showed that when the original constant values were used, large errors resulted for most of the equations. When recalibrated constant values were substituted for the original constant values, four of the five equations improved greatly, and all five equations performed well for determining mean annual evaporation. For seasonal and monthly evaporation, the Hargreaves and Turc equations showed a significant bias, especially for cold months. With properly determined constant values, the Makkink and modified Priestley and Taylor equations resulted in monthly evaporation values that agreed most closely with pan evaporation in the study region. The simple Abtew equation can also be used when other meteorological data except radiation are not available. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Groundwater components in the alluvial aquifer of the alpine Rhone River valley, Bois de Finges area, Wallis Canton, Switzerland     

Marc Schürch  François-D. Vuataz 《Hydrogeology Journal》2000,8(5):549-563

Source, type, and quantity of various components of groundwater, as well as their spatial and temporal variations were determined by different hydrochemical methods in the alluvial aquifer of the upper Rhone River valley, Bois de Finges, Wallis Canton, Switzerland. The methods used are hydrochemical modeling, stable-isotope analysis, and chemical analysis of surface water and groundwater. Sampling during high- and low-water periods determined the spatial distribution of the water chemistry, whereas monthly sampling over three years provided a basis for understanding seasonal variability. The physico-chemical parameters of the groundwater have spatial and seasonal variations. The groundwater chemical composition of the Rhone alluvial aquifer indicates a mixing of weakly mineralized Rhone River water and SO₄-rich water entering from the south side of the valley. Temporal changes in groundwater chemistry and in groundwater levels reflect the seasonal variations of the different contributors to groundwater recharge. The Rhone River recharges the alluvial aquifer only during the summer high-water period. Electronic Publication  相似文献   

The earthquake of 250 a.d. in Augusta Raurica, A real event with a 3D site-effect?     

Donat Fäh  Sibylle Steimen  Ivo Oprsal  Johannes Ripperger  Jochen Wössner  Regula Schatzmann  Philipp Kästli  Ina Spottke  Peter Huggenberger 《Journal of Seismology》2006,10(4):459-477

The Roman city Augusta Raurica is located East of Basel, Switzerland. One important topic of the city’s history concerns the hypothesis of an earthquake striking the city in the middle of the third century a.d. This idea had been formulated according to archaeological features and findings, but had not been tested so far. A selection of the archaeological features were reviewed and dated in order to test the hypothesis of a single event. However, archaeological investigations do not draw a conclusive picture; it could not be proven that all features of possible destruction date to the same event. Detailed seismological investigations were performed. These included geological and geotechnical mapping of the unconsolidated sediments. Important parameters such as the thickness and composition of the unconsolidated sediments, the terrain topography and the topography of the bedrock surface were mapped. Ambient vibration H/V measurements provided the fundamental frequency of resonance for the unconsolidated sediments. The velocity of shear waves traveling through sediments is the controlling parameter for amplification of seismic waves. This material property is estimated using the relation between the ellipticity of the fundamental mode Rayleigh wave and the H/V curve. From all information we compiled a three-dimensional model of the surface geology. This model is used to simulate earthquake ground motion and amplification effects in the city, and to map the variability of the amplification. In the part of the city where possible earthquake damage was recognized, amplification occurs in the frequency band of building resonance (2–8 Hz). In the other part of the city amplification occurs much above the building’s resonance. From 1D modelling we estimate a difference in spectral amplification of about a factor of 2.5 to 3 between the two parts of the city. This corresponds approximately to a difference in macroseismic intensity of one unit. 3D modelling showed a large variability of ground motion within very close distance in the part of the city where possible earthquake damage was recognized. The maximum amplification reaches values up to a factor of nine, which is due to 3D effects and the choice of using vertically incident waves. Finally, all paleoseismological findings in the area of Basel were reviewed in order to find indications of a large event in the time-period of interest. Paleoseismological findings provide no hints to a large earthquake in the third century. If we assume that an earthquake caused at least part of the identified damage in Augusta Raurica, we have to assign to this event a magnitude Mw of about 6.0 or even lower, that is much smaller than the value of 6.9 that is actually in the Swiss earthquake catalogue. The earthquake source of this event must then be very close to the site of Augusta Raurica and a strong site-effect occurred in one part of the city.  相似文献   

Climate Risks and Their Impact on Agriculture and Forests in Switzerland   总被引：4，自引：1，他引：4  

J. Fuhrer  M. Beniston  A. Fischlin  Ch. Frei  S. Goyette  K. Jasper  Ch. Pfister 《Climatic change》2006,79(1-2):79-102

There is growing evidence that, as a result of global climate change, some of the most severe weather events could become more frequent in Europe over the next 50 to 100 years. The paper aims to (i) describe observed trends and scenarios for summer heat waves, windstorms and heavy precipitation, based on results from simulations with global circulation models, regional climate models, and other downscaling procedures, and (ii) discuss potential impacts on agricultural systems and forests in Switzerland. Trends and scenarios project more frequent heavy precipitation during winter corresponding, for example, to a three-fold increase in the exceedance of today's 15-year extreme values by the end of the 21st century. This increases the risk of large-scale flooding and loss of topsoil due to erosion. In contrast, constraints in agricultural practice due to waterlogged soils may become less in a warmer climate. In summer, the most remarkable trend is a decrease in the frequency of wet days, and shorter return times of heat waves and droughts. This increases the risk of losses of crop yield and forage quality. In forests, the more frequent occurrence of dry years may accelerate the replacement of sensitive tree species and reduce carbon stocks, and the projected slight increase in the frequency of extreme storms by the end of the century could increase the risk of windthrow. Some possible measures to maintain goods and services of agricultural and forest ecosystems are mentioned, but it is suggested that more frequent extremes may have more severe consequences than progressive changes in means. In order to effectively decrease the risk for social and economic impacts, long-term adaptive strategies in agriculture and silviculture, investments for prevention, and new insurance concepts seem necessary.  相似文献