GRASS as Open Source Free Software GIS: Accomplishments and Perspectives     

Helena Mitasova  Markus Neteler 《Transactions in GIS》2004,8(2):145-154

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Geomorphological and pedological investigations on the glacial history of the Kali Gandaki (Nepal Himalaya)     

Markus Wagner 《GeoJournal》2005,63(1-4):91-113

In semi-arid orographic left tributaries of the Kali Gandaki at the northern and western flank of the Nilgiri Himal, glacio-geomorphological and pedological investigations were carried out on prehistoric moraines. Geomorphological relief analysis was derived from other literature and the own fieldwork of the author. The resulting glacial chronology was used as benchmark to explore the limits of different pedological dating methods regarding the degree of soil development. These methods are based on iron fractionation, total element contents and particle size distribution. In general the different glacial stages are mirrored correctly in the relative graduation of soil development. The ratio of well crystallised pedogenic iron-oxides to the total iron content and the ratio fine clay to total clay are most suitable, because they are almost independent from existing changes in the lithological composition. The total element based weathering indices are less suitable, because they react highly sensitive to the geology dependent shift to higher carbonate content. Most of the grain size based weathering indices are inapplicable because of the typically high textural variability within till deposits.  相似文献   

Is there a superior conceptual groundwater model structure for baseflow simulation?          下载免费PDF全文

Michael Stoelzle  Markus Weiler  Kerstin Stahl  Andreas Morhard  Tobias Schuetz 《水文研究》2015,29(6):1301-1313

Previous work has shown that streamflow response during baseflow conditions is a function of storage, but also that this functional relationship varies among seasons and catchments. Traditionally, hydrological models incorporate conceptual groundwater models consisting of linear or non‐linear storage–outflow functions. Identification of the right model structure and model parameterization however is challenging. The aim of this paper is to systematically test different model structures in a set of catchments where different aquifer types govern baseflow generation processes. Nine different two‐parameter conceptual groundwater models are applied with multi‐objective calibration to transform two different groundwater recharge series derived from a soil‐atmosphere‐vegetation transfer model into baseflow separated from streamflow data. The relative performance differences of the model structures allow to systematically improve the understanding of baseflow generation processes and to identify most appropriate model structures for different aquifer types. We found more versatile and more aquifer‐specific optimal model structures and elucidate the role of interflow, flow paths, recharge regimes and partially contributing storages. Aquifer‐specific recommendations of storage models were found for fractured and karstic aquifers, whereas large storage capacities blur the identification of superior model structures for complex and porous aquifers. A model performance matrix is presented, which highlights the joint effects of different recharge inputs, calibration criteria, model structures and aquifer types. The matrix is a guidance to improve groundwater model structures towards their representation of the dominant baseflow generation processes of specific aquifer types. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Exploration of remotely sensed forest structure and ultrasonic range sensor metrics to improve empirical snow models          下载免费PDF全文

Andrés Varhola  Nicholas C. Coops  Younes Alila  Markus Weiler 《水文研究》2014,28(15):4433-4448

Current methods to estimate snow accumulation and ablation at the plot and watershed levels can be improved as new technologies offer alternative approaches to more accurately monitor snow dynamics and their drivers. Here we conduct a meta‐analysis of snow and vegetation data collected in British Columbia to explore the relationships between a wide range of forest structure variables – obtained from Light Detection and Ranging (LiDAR), hemispherical photography (HP) and Landsat Thematic Mapper – and several indicators of snow accumulation and ablation estimated from manual snow surveys and ultrasonic range sensors. By merging and standardizing all the ground plot information available in the study area, we demonstrate how LiDAR‐derived forest cover above 0.5 m was the variable explaining the highest percentage of absolute peak snow water equivalent (SWE) (33%), while HP‐derived leaf area index and gap fraction (45° angle of view) were the best potential predictors of snow ablation rate (explaining 57% of variance). This study reveals how continuous SWE data from ultrasonic sensors are fundamental to obtain statistically significant relationships between snow indicators and structural metrics by increasing mean r² by 20% when compared to manual surveys. The relationships between vegetation and spectral indices from Landsat and snow indicators, not explored before, were almost as high as those shown by LiDAR or HP and thus point towards a new line of research with important practical implications. While the use of different data sources from two snow seasons prevented us from developing models with predictive capacity, a large sample size helped to identify outliers that weakened the relationships and suggest improvements for future research. A concise overview of the limitations of this and previous studies is provided along with propositions to consistently improve experimental designs to take advantage of remote sensing technologies, and better represent spatial and temporal variations of snow. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Dynamic Sliding Analysis of a Gravity Dam with Fluid-Structure-Foundation Interaction Using Finite Elements and Newmark’s Sliding Block Analysis     

Markus Goldgruber  Shervin Shahriari  Gerald Zenz 《Rock Mechanics and Rock Engineering》2015,48(6):2405-2419

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Lake sedimentary processes and vegetation changes over the last 45k cal a bp in the uplands of south-eastern Amazonia     

José Tasso Felix Guimarães  Prafulla Kumar Sahoo  Mariana Maha Jana Costa De Figueiredo  Karen da Silva Lopes  Markus Gastauer  Silvio Junio Ramos  Cecilio Frois Caldeira  Pedro Walfir M. Souza-Filho  Luiza Santos Reis  Marcio Sousa Da Silva  Paulo Rogenes Pontes  Renato Oliveira Da Silva Junior  Tarcísio Magevski Rodrigues 《第四纪科学杂志》2021,36(2):255-272

This study addresses paleoclimate influences in a southern Amazonia ecotone based on multiproxy records from lakes of the Carajás region during the last 45k cal a bp. Wet and cool environmental conditions marked the initial deposition in shallow depressions with detrital sediments and high weathering rates until 40k cal a bp. Concomitantly, forest and C3 canga plants, along with cool-adapted taxa, developed; however, short drier episodes enabled expansion of C4 plants and diagenetic formation of siderite. A massive event of siderite formation occurred approximately 30k cal a bp under strong drier conditions. Afterwards, wet and cool environmental conditions returned and persisted until the Last Glacial Maximum (LGM). The LGM was marked by lake-level lowstands and subaerial exposure. The transition from the LGM to the Holocene is marked by the onset of oscillations in temperature and humidity, with an expansion of forest and canga plants. Cool taxa were present for the last time in the Carajás region ~ 9.5–9k cal a bp. After 10k cal a bp , shallow lakes became upland swamps due to natural infilling processes, but the current vegetation types and structures of the plateaus were acquired only after 3k cal a bp under wetter climatic conditions.  相似文献   

Catchments of German surface water bodies     

Andreas Gericke  Judith Mahnkopf  Markus Venohr 《水文研究》2021,35(7):e14272

The European Water Framework Directive demands to assess and report the chemical and ecological status of water bodies (WB). Linking their status to drivers and pressures and deriving suitable mitigation measures require knowledge of the shape and area of WB catchments. We derived a network of 26 570 WB catchments in Germany using the hydrologically-defined drainage basins of the German federal states. We established a network of 338 149 drainage basins. This network underwent plausibility checks and a validation with the catchment areas of 348 monitoring stations across Germany. To this network, we assigned the longest intersecting or the next downstream WB code. To account for geometric inaccuracies we revised spurious intersections resulting in splittings and cycles in the WB network. As WB may be ecologically but not hydrologically well defined, we split them at confluences and intersections. The network of drainage basins matched the monitoring stations with a Nash-Sutcliffe efficiency of 1.00. The final WB network contained 11 005 out of the 11 586 original WBs longer than 1 m. The corresponding local catchment areas range from <<0.0001 to 446 km², with a median of 10 km². The dataset combines the requirements of hydrological and ecological modelling applications at basin or national scales with the needs of the EU reporting which can foster their acceptance by state authorities and river-basin management.  相似文献   

Shallow sediment deformation styles in north-western Campeche Knolls,Gulf of Mexico and their controls on the occurrence of hydrocarbon seepage     

Feng Ding  Volkhard Spiess  Ian R. MacDonald  Markus Brüning  Noemi Fekete  Gerhard Bohrmann 《Marine and Petroleum Geology》2010,27(4):959-972

During German R/V Meteor M67/2 expedition to Campeche Knolls, southern Gulf of Mexico, a set of 2D high resolution seismic data was acquired to study the near-surface sediment structure and its relationship with hydrocarbon seepages in this salt province. The comprehensive survey covered 20 individual bathymetric highs or ridges and identified three principle structural types: Passive Type, Chaopopte Type, and Asymmetric Flap Type. The first type is the result of passive diapirism, whereas the latter two were initialized by a regional compressional event in the Miocene, but are later differently modified by salt tectonism. Chapopote Type structures appear as symmetrical domes, with uplifted coarse-grained Miocene sediments in their cores and rather thin syn-kinematic sediments covering the crests. Asymmetric Flap Type structures are also first folded as domes or ridges, but one flap later subsided together with salt evacuation, resulting in single uplifted monoclines. With the coarse-grained pre-kinematic sediments as reservoir units, both structural types can focus and accumulate hydrocarbons. The geometries of the structures suggest that hydrocarbons are accumulated in the center of the Chapopote Type structures and in the subsided flaps of the Asymmetric Flap Type structures. Hydrocarbon leakage from these thinly sealed reservoirs is regarded as the principle mechanism for the seepage in the study area, and accordingly the most seepage-prone positions are above these reservoirs. The seep locations suggested by analysis of sea-surface oil slick images of SAR satellite data are also examined in this study. These independently derived seep locations confirm the seepage-prone positions to be above the shallow buried reservoirs. This study suggest that the shallow sediment structures control the distribution of the hydrocarbon seeps of the north-western Campeche Knolls, although the hydrocarbons are sourced from the greater depth.  相似文献   

Global warming-related tree growth decline and mortality on the north-eastern Tibetan plateau   总被引：1，自引：0，他引：1  

Eryuan Liang  Christoph Leuschner  Choimaa Dulamsuren  Bettina Wagner  Markus Hauck 《Climatic change》2016,134(1-2):163-176

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Attribution of extreme temperature changes during 1951–2010     

Yeon-Hee Kim  Seung-Ki Min  Xuebin Zhang  Francis Zwiers  Lisa V. Alexander  Markus G. Donat  Yu-Shiang Tung 《Climate Dynamics》2016,46(5-6):1769-1782

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