Morphological Investigations in the River Odra

Since 1992, the Federal Institute of Hydrology (Bundesanstalt für Gewässerkunde – BfG) performs morphological investigations in the river Odra downstream from the confluence of the river Neiße (Nysa Luzycka). The results of these investigations give a clear insight into the morphodynamic behaviour of this part of the river and indicate that on average 380 000 t of suspended solids and 130 000 t of bed load are transported by the river Odra at Hohensaaten per year, with a distinct seasonal variability in the case of suspended solids. Detailed studies on type and composition of the bed substrates have revealed that the river bottom is composed of very fine material: at Ratzdorf already 75 % of the bed material is finer than 2 mm, at Widuchowa almost all of the river bed material consists of sand finer than 0.63 mm. Because of the high sensitivity of the river bottom to discharge increases and the corresponding increases of bottom shear stress sand was found to be the dominating fraction of the suspended load in case of extreme flood events.     

Utility of high-resolution climate model simulations for water resources prediction over the Korean Peninsula: a sensitivity study / Utilité de simulations de modèle climatique à haute résolution pour la prévision des ressources en eau dans la Péninsule Coréenne: étude de sensibilité

Abstract

Abstract The utility of simulations of Global Climate Models (GCMs) for regional water resources prediction and management on the Korean Peninsula was assessed by a probabilistic measure. Global Climate Model simulations of an indicator variable (e.g. surface precipitation or temperature) were used for discriminating high vs low regional observations of a target variable (e.g. watershed precipitation or reservoir inflow). The formulation uses the significance probability of the Kolmogorov-Smirnov test for detecting differences between two distributions. High resolution Atmospheric Model Intercomparison Project-II (AMIP-II) type GCM simulations performed by the European Centre for Medium-Range Weather Forecasts (ECMWF) and AMIP-I type GCM simulations performed by the Korean Meteorological Research Institute (METRI) were used to obtain information for the indicator variables. Observed mean areal precipitation and temperature, and watershed-outlet discharge values for seven major river basins in Korea were used as the target variables. The results suggest that the use of the climate model nodal output from both climate models in the vicinity of the target basin with monthly resolution will be beneficial for water resources planning and management analysis that depends on watershed mean areal precipitation and temperature, and outlet discharge.     

Les flux de matières dissoutes et particulaires exportés des Andes par le Rio Béni (Amazonie Bolivienne), en période de crue

Résumén

Le Rio Béni est l’un des principaux formateurs andins du Rio Madeira, le plus important des affluents méridionaux de l’Amazone. La station hydrométrique de “Angosto del Bala” sur le Rio Béni contrôle un bassin andin de 67500 km², aux caractéristiques géomorpho-climatiques très contrastées.

Afin de connaître l’évolution temporelle des teneurs relatives des éléments des phases dissoutes et particulaires, un suivi hydrologique et hydrogéochimique a été réalisé à cette station en mars 1988, période de hautes eaux où une crue de fréquence annuelle a été observée. Les résultats obtenus montrent l’existence d’une grande variabilité temporelle des concentrations, mais présentant un cortège hydrogéochimique stable au cours de la crue.

Enfin, l’importance quantitative de cette période de hautes eaux sur le bilan moyen annuel des flux exportés est souligné.     

Structures et cinématique liées á la mise en place des péridotites de Ronda (Cordilléres Bétiques,Espagne)

The interaction of the Mid-Atlantic Ridge with the North Atlantic Mantle Plume has produced a magmatic plateau centred about Iceland. The crust of this plateau is 30 km thick on average. This abnormal thickness implies that, unlike other slow-spreading ridges, addition of magmatic material to the crust is not balanced by crustal stretching. The thermal effect of the plume also reduces the strength of the lithosphere. Both mechanisms affect the rifting process in Iceland. A structural review, including new field observations, demonstrates that the structure of the Iceland plateau differs from that of other slow-spreading oceanic ridges. Lithospheric spreading is currently accommodated in a 200 km wide deformation strip, by the development of a system of half-grabens controlled by growth faults. Similar extinct structures, with various polarities, are preserved in the lava pile of the Iceland plateau. These structures are identified as lithospheric rollover anticlines that developed in hanging walls of listric faults. We introduce a new tectonic model of accretion, whereby the development of the magmatic plateau involved activation, growth and decay of a system of growth fault/rollover systems underlain by shallow magma chambers. Deactivation of a given extensional system, after a lifetime of a few My, was at the expense of the activation of a new, laterally offset, one. Correspondingly, such systems formed successively at different places within a 200 km wide diffuse plate boundary. Unlike previous ones, this new model explains the lack of an axial valley in Iceland, the dip pattern of the lava pile, the complex geographical distribution of ages of extinct volcanic systems and the outcrops of extinct magma chambers.     

Variabilité interannuelle et intra-annuelle des transports solides de l’Oued Bouhamdane, à l’amont du barrage Hammam Debagh (Algérie orientale)

Résumé

Dans la région du Maghreb au climat semi-aride méditerranéen, l’agressivité des pluies et leur forte variabilité contribuent à l’érosion des sols qui alimente la charge solide des oueds, facteur d’envasement rapide des barrages hydrauliques. Aspect important caractérisant les écoulements liquides et solides dans le contexte méditerranéen, le thème de la variabilité temporelle est privilégié dans ce travail, focalisé sur le bassin de l’Oued Bouhamdane (Algérie orientale). Depuis décembre 1987, les débits de l’oued, contrôlés depuis septembre 1969 par une station hydrométrique (1105 km²), sont régularisés par le barrage Hammam Debagh, situé à l’amont immédiat de la section de jaugeage (1070 km²). L’étude a nécessité le traitement d’une longue chronique de mesures directes de la concentration en matières en suspension (MES) et des écoulements liquides, complétée par les données d’apport journalier disponibles au barrage. A l’aide d’une fonction de type puissance liant les débits solides instantanés et les débits liquides instantanés, deux séries—1969–1987 et 1995–2010—de débits solides journaliers ont été générées, respectivement au droit de la station hydrométrique et au site du barrage. L’apport solide spécifique, modéré en valeur moyenne (257 t km^?2 an^?1), est marqué par une très forte variabilité interannuelle (0,5 et 1396 t km^?2 an^?1 respectivement en 1996/97 et 2004/05), qui augmente sensiblement pendant la saison des hautes eaux. La charge solide apportée par le cours d’eau pendant les évènements de crue contribue de façon considérable aux totaux annuels et mensuels de la dégradation spécifique calculée à l’échelle du bassin. L’approche comparative montre que le flux sédimentaire estimé par la méthode des mesures des concentrations de l’oued à la station hydrométrique (0,22–0,29 hm³ an^?1) ne rend pas compte de la totalité du volume d’envasement du barrage (0,98 hm³ an^?1 en moyenne), mise en évidence à l’aide de levés bathymétriques et incluant les transports de fond et d’autres apports de sédiments, très difficiles à mesurer.

Editeur Z.W. Kundzewicz; Editeur associé G. Mahé

Citation Louamri, A., Mebarki, A., et Laignel, B., 2013. Variabilité interannuelle et intra-annuelle des transports solides de l’Oued Bouhamdane, à l’amont du barrage Hammam Debagh (Algérie orientale). Hydrological Sciences Journal, 58 (7), 1559–1572.     

Identifying and Analyzing the Dominant Languages in Small Island Developing States

Despite their small size, in both area and population, many different languages are spoken by residents of the small island developing states (SIDS). Most of these languages are used by very few people. With one exception, the remaining forty-nine SIDS have one or more official languages. Slightly over 62 percent of the eighty official languages are those of former colonial rulers. Of the total of 1,500 languages, the Weaver’s minimum positive deviation method identified only 106 as dominant languages. These languages are spoken by more than 96 percent of the population in the SIDS. The data further show that twenty-eight of the fifty SIDS are monolingual and the remaining twenty-two are either bilingual or multilingual. Surprisingly, in many monolingual SIDS, the official language is not the dominant language. The dominant languages of these nations were first categorized as monolingual, bilingual, and multilingual and then were analyzed by their location, area, and population size. No statistically significant variation was found between them. Reasons for these conditions are explained, and future research direction is provided. Key Words: bilingual, dominant languages, monolingual, multilingual, small island developing countries.     

A ~4500 yr record of river floods obtained from a sediment core in Lake Atnsjøen, eastern Norway

To extend the historical record of river floods in southern Norway, a 572-cm long sediment core was retrieved from 42 m water depth in Atnsjøen, eastern Norway. The sediment core contains 30 light gray clastic sediment layers interpreted to have been deposited during river floods in the snow/ice free season. In the upper 123 cm of the core, four prominent flood layers occur. The youngest of these overlap with the historical record. The thickest (flood layer 5) possibly reflects a general increase in river-flood activity as a result of the post-Medieval climate deterioration (lower air temperatures, thicker and more long-lasting snow cover, and more frequent rain/snow storms) associated with the ent/r144384j0266l5p8/xxlarge8216.gif" alt="lsquo" align="BASELINE" BORDER="0">Little Ice Ageent/r144384j0266l5p8/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">. The most pronounced pre-historic flood layers in the core were, according to an age model based on linear regression between eleven bulk AMS radiocarbon dates, deposited around 4135, 3770, 3635, 3470, 3345, 2690, 2595, 2455, 2415, 2255, 2230, 2150, 2120, 1870, 1815, 1665, 1640, 1480, 1400, 1380, 1290, 935, 885, 670, 655 and 435 cal. BP (BP = AD 1950). The mean return period of the river flood layers is, according to the linear regression age model, ~ 150 ± 30 cal. yr (mean ± 1 S.E.).     

识别断层活动和失稳的热场标志——实验室的证据

利用一套双向伺服系统对含压性和张性雁列断层的标本进行变形实验,实验中应用红外热像仪和接触式测温仪同步记录岩石变形过程中热红外辐射的亮度温度场和温度场的变化;使用数字CCD相机同步采集标本表面的数字图像,并利用数字散斑方法对采集到的图像进行分析得到位移场和应变场的演化过程。实验结果表明:1)在断层贯通前压性雁列岩桥区温度最高,而张性雁列岩桥区温度最低;数字散斑结果显示压性岩桥区平均应变最高,而张性岩桥区平均应变最低。温度场对两类雁列断层在岩桥区相反的受力状态有清晰的响应,可以为判断断层应力状态提供标志。2)雁列断层经历了从岩桥区应力积累、破坏到断层失稳错动两个变形阶段,升温机制也由应变升温变为摩擦升温;伴随升温机制的转变,在岩桥区观测到断层失稳错动前的破坏降温、温度快速起伏以及升温脉冲等现象,是观测失稳前兆的最佳部位。3)在雁列岩桥区裂纹端点附近观测到升温脉冲,表现为温度快升快降,随后即出现断层带的快速升温。升温脉冲现象可能与裂纹端部的应力奇异集中和破裂扩展引起的应力释放有关。裂纹端部的扩展是断层失稳错动的条件,随后断层带的升温正是断层失稳错动造成的。断层带开始升温发生在失稳前2～3s内,岩桥区的降温发生在失稳     

Simulated long-term changes in river discharge and soil moisture due to global warming / Simulations à long terme de changements d’écoulement fluvial et d’humidité du sol causés par le réchauffement global

Abstract

Abstract By use of a coupled ocean–atmosphere–land model, this study explores the changes of water availability, as measured by river discharge and soil moisture, that could occur by the middle of the 21st century in response to combined increases of greenhouse gases and sulphate aerosols based upon the ?IS92a? scenario. In addition, it presents the simulated change in water availability that might be realized in a few centuries in response to a quadrupling of CO₂ concentration in the atmosphere. Averaging the results over extended periods, the radiatively forced changes, which are very similar between the two sets of experiments, were successfully extracted. The analysis indicates that the discharges from Arctic rivers such as the Mackenzie and Ob’ increase by up to 20% (of the pre-Industrial Period level) by the middle of the 21st century and by up to 40% or more in a few centuries. In the tropics, the discharges from the Amazonas and Ganga-Brahmaputra rivers increase substantially. However, the percentage changes in runoff from other tropical and many mid-latitude rivers are smaller, with both positive and negative signs. For soil moisture, the results of this study indicate reductions during much of the year in many semiarid regions of the world, such as the southwestern region of North America, the northeastern region of China, the Mediterranean coast of Europe, and the grasslands of Australia and Africa. As a percentage, the reduction is particularly large during the dry season. From middle to high latitudes of the Northern Hemisphere, soil moisture decreases in summer but increases in winter.