Sichttiefen im Überlinger See (Bodensee) 1953–1962     

Dr. Hubert Lehn 《Aquatic Sciences - Research Across Boundaries》1968,30(1):67-74

Zusammenfassung Die monatlichen Sichttiefenmessungen (meist 3) mit der SECCHI-Scheibe im überlinger See (Bodensee) von 1953–1962 werden miteinander verglichen. Sie liefern Hinweise auf die planktische Prim?rproduktion. Die kurzfristige Streuung der Sichttiefen ist teilweise gross. Das Sichttiefenmittel liegt bei 7,4 m, die Extreme bei 1,9 m und 15,0 m. Das produktionsbedingte Sichttiefenminimum vom Frühjahr bis Herbst jeden Jahres wird durch ein Frühsommermaximum (Produktionszusammenbruch) unterteilt. Zwischen 1953 und 1962 besteht, trotz grosser Schwankungsbreite, eine Sichttiefenregression von j?hrlich 2 cm, eine von 6 cm jedoch zwischen dem Mittelwert von 1920–1924 (9,5 m) und dem von 1953–1962 (7,4 m). Der Sichttiefenrückgang verl?uft seit 1900 sigmoid. Dabei ist der geringere Anstieg der Kurve von 1953–1962 nicht mehr mit dem progressiv steigenden Phosphatphosphor korrelierbar. Dieser kann heute im Bodensee nur noch selten ein produktionsbegrenzender Faktor sein.

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Summary In the überlinger See (Lake of Constance) the Secchi-disk transparencies are usually recorded three times a month; the results obtained from 1963–1962 have been compared with each other. They give an indication of planktic primary production. The divergence of transparencies is partly very considerable within short periods. The average transparency lies at about 7,4 m, the extreme transparencies at 1,9 m and 15,0 m. Every year, from spring to autumn, there is a minimum of transparency induced by planktic production; it is interrupted by a maximum occurring in early summer (production collapse). From 1953–1962, in spite of considerable fluctuation scope, a yearly regression of transparency of 2 cm was observed. However, between the average transparencies from 1920–1924 (9,5 m) and from 1953–1962 (7,4 m), the yearly regression amounts to 6 cm. From 1900, the regression of transparency represents a sigmoid curve. However, the slighter rise of the curve from 1953–1962 can no longer be correlated with the progressive rising of phosphate-phosphorus, which now very seldom is to be considered as a limiting factor of planktic production in the Lake of Constance.

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Résumé L'auteur compare les résultats des mesures de transparence effectuées à l'aide du disque Secchi en général trois fois par mois dans le überlinger See (Lac de Constance) de 1953–1962. Ces mesures fournissent des indications sur la production primaire du phytoplancton. La transparence varie parfois considérablement en de courts intervalles. La moyenne des transparences est à 7,4 m, alors que les valeurs extrêmes se situent à 1,9 m et 15,0 m. Chaque année, du printemps à l'automne, il y a un minimum de transparence d? à la production du plancton; il est interrompu par un maximum au début de l'été (effondrement de la production). On a constaté entre 1953 et 1962 une régression annuelle de la transparence de 2 cm; toutefois, si l'on compare la moyenne de 1920–1924 (9,5 m) avec celle de 1953–1962 (7,4 m), cette régression annuelle est de 6 cm. Depuis 1900, la régression de la transparence dessine une courbe sigmo?de. Cependant il n'existe plus de corrélation entre la montée plus douce de la courbe de 1953–1962 et l'augmentation progressive du phosphate-phosphore; ce dernier ne peut en effet plus guère être considéré comme un facteur de limitation de la production planctique dans le lac de Constance.

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Graphical characterisation of probability distribution tails     

K. Chaouche  P. Hubert  G. Lang 《Stochastic Environmental Research and Risk Assessment (SERRA)》2002,16(5):342-357

 The purpose of this paper is to present a graphical method to characterise the nature of a distribution (exponential or algebraic). In the algebraic case, this statistical tool provides an estimation procedure of the parameter characterising the decrease of the survival function. The realizations of the random variable under study being available in the form of time series, this method is based on the relationship between the duration of exceeding an intensity threshold and the accumulation of the realizations of the random variable during this length of time. The behaviour of the duration-accumulation graphs (when the threshold of reference increases indefinitely) results in a function, the limit of which only depends on the parameter characterising the algebraic decrease of the probability distribution. The estimate of this parameter is biased but can be corrected effectively by numerical methods. We applied this method to two rainfall series differing by their geographical origin (Dédougou in Burkina Faso and a station on the Island of La Réunion) and their time step (respectively 1 day and 76 seconds). For both of them, the behaviour of tail distributions is shown to be algebraic and the values of the parameter characterizing the algebraic decrease of the probability distribution of the two series are very close. This would tend to justify the assumption of a multifractal nature for these series. This work was achieved as part of the National Programme of Research in Hydrology of the INSU (project 99 PNRH 27). The authors are grateful to A. Barcello for providing them the data of the Island of La Réunion Island.  相似文献   

Seismic Microzonation: A Comparison between Geotechnical and Seismological Approaches in Pointe-à-Pitre (French West Indies)   总被引：1，自引：0，他引：1  

Benoit LeBrun  Anne-Marie Duval  Pierre-Yves Bard  Olivier Monge  Myriam Bour  Sylvain Vidal  Hubert Fabriol 《Bulletin of Earthquake Engineering》2004,2(1):27-50

Pointe-à-Pitre, the main city of Guadeloupe in the French West Indies, has on several occasions been partially destroyed by major historical earthquakes. Moreover, a post-seismic assessment of the damage from the 1985 Montserrat earthquake indicates that the town is prone to site effects. Consequently, from 1996 to 1998, BRGM conducted a seismic microzonation study based on geotechnical and geological data. At the same time, three seismological studies were being conducted – two based on earthquake recordings using a time-series analysis and the classical spectral ratio (CSR) method (CETE/LCPC and BRGM), and the third based on noise measurement at 400 points using the horizontal-to-vertical noise ratio (HVNR) method (CETE/LCPC). The objective of this paper is not to carry out a new microzonation study by taking into account all the results, but rather to show in what respects the results of these different methods are in agreement or not. A comparison of the results of the seismological studies with the geotechnical microzonation shows that they are in fairly good agreement, albeit with some discrepancies. The results indicate that the seismological methods and the geotechnical data are highly complementary and should be used together in compiling seismic transfer-function microzonation maps. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Policies related to agriculture and environment in the European Community     

Hubert Tunney   《Marine pollution bulletin》1994,29(6-12):508-514

This paper summarizes recent EC policy relating to agriculture and the environment. The important changes in the reform of the Common Agricultural Policy are outlined and in particular the agri-environmental measures that provide for Member States to aid farmers that take measures to reduce pollution from intensive agriculture and improve the rural environment. The Nitrate Directive, which is the first EC Directive relating to agriculture and the environment, is summarized. Other water directives relevant to agriculture and the aquatic environment as they relate to nutrients (nitrogen and phosphorus) in water are also outlined. The EC Fifth Action Programme on the Environment as it relates to agriculture is also considered. Finally, an attempt is made to assess the likely impact of these policies on agriculture and the aquatic environment.  相似文献   

Algorithm for Surface/Ground-Water Allocation under Appropriation Doctrine     

Tissa H. Lllangasekare  Hubert J. Morel-Seytoux 《Ground water》1986,24(2):199-206

A stream-aquifer simulation model was developed to evaluate different conjunctive use management strategies in the South Platte River in Colorado. A component of this model simulates the allocation of surface and ground water for agricultural use. The water law based on the doctrine of prior appropriation provides the basic framework for water allocation in the study area. The physical sequence in which the river diversions are located along the river is different from the sequence in which the water has to be allocated according to the priority of rights. An algorithm is designed to allocate the river flows computed by the physical simulation component of the model to the appropriators according to the water rights and other imposed criteria as specified by the conjunctive management scheme under study. The algorithm is demonstrated on a management problem involving the evaluation of a streamflow augmentation scheme in the study reach.  相似文献   

Transport of radionuclides in an unconfined chalk aquifer inferred from U-series disequilibria     

Amélie Hubert  Bernard Bourdon  Eric Pili 《Geochimica et cosmochimica acta》2006,70(22):5437-5454

U-series disequilibria measured in waters and rocks from a chalk aquifer in France have been used as an analog for long-term radionuclide migration. Drill core samples from a range of depths in the vadose zone and in the saturated zone, as well as groundwater samples were analyzed for ²³⁸U, ²³⁴U, ²³²Th and ²³⁰Th to determine transport mechanisms at the water/rock interface and to quantify parameters controlling the migration of radionuclides. Isotope measurements in rocks were done by TIMS, whereas (²³⁴U/²³⁸U) and (²³⁰Th/²³²Th) activity ratios in water samples were measured by multi-collector-ICP-MS. Both depletion and enrichment in ²³⁴U relative to ²³⁸U were observed in carbonate rock samples resulting from chemical weathering in the unsaturated zone and calcite precipitation in the zone of water-table oscillation, respectively. The correlation between (²³⁰Th/²³²Th) activity ratios and ⁸⁷Sr/⁸⁶Sr ratios found in the chalk samples indicates that thorium is mainly contained in a minor silicate phase whose abundance is variable in chalk samples. Water samples are all characterized by (²³⁴U/²³⁸U) > 1 resulting from α-recoil effect of ²³⁴Th. Groundwaters are characterized by a more radiogenic signature in ⁸⁷Sr/⁸⁶Sr than the rocks. Moreover, (²³⁰Th/²³²Th) activity ratios in the waters are lower than in the rocks, and increase with distance from the water divide, which suggests that Th transport is controlled by colloids formed during water infiltration in the soil. A 1-D transport model has been developed in order to constrain the U-series nuclide transport considering a transient behavior of radionuclides in the aquifer and a time-dependent composition for the solid phase. This model permits a prediction of the time scale of equilibration of the system, and an estimation of parameters such as weathering rate, distribution coefficients and α-recoil fractions. Retardation factors of 10-35 and from 1 × 10⁴ to 2 × 10⁵ were predicted for U and Th, respectively, and can be used to predict the migration of radionuclides released as contaminants in the environment. At the scale of our watershed (∼32 km²), a characteristic migration time from recharge to riverine discharge of 200-600 yr for U and 0.2-3.7 Myr for Th was obtained.  相似文献   

Fischökologische Leitbilder fünf ausgewählter Salzkammergutseen     

Hubert Gassner  Josef Wanzenbck 《Limnologica》1999,29(4):436-448

Ecological base line states for fish communities are necessary for the evaluation of ecological integrity. In Austria the fish communities of all the larger lakes are strongly influenced by human activities, like commercial fisheries, fish stocking, eutrophication or shore line degradation, and therefore these baseline states can not be developed by comparison with a natural, undisturbed lake. We developed ecological baseline states for the fish communities of the lakes Hallstättersee, Traunsee, Mondsee, Irrsee and Wallersee by reconstructing the native fish communities of these lakes from historical documents (from between 1500 to 1940). Then we classified the potential fish species of these lakes according to their ecological requirements. Finally we developed the base line states with 16 different ecological factors similar to the factors used for the ecological integrity assessment procedure for streams.

The process of reconstructing the fish communities and some advantages and disadvantages of the base line states for fish communities are discussed.  相似文献   

Primordial Nucleosynthesis     

Hubert Reeves 《Astrophysics and Space Science》1999,265(1-4):17-21

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Shape-induced pseudo-single-domain remanence     

Karl Fabian  & Alex Hubert 《Geophysical Journal International》1999,138(3):717-726

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Using salt intrusion measurements to determine the freshwater discharge distribution over the branches of a multi-channel estuary: The Mekong Delta case     

Anh Duc Nguyen  Hubert H.G. Savenije  Duc Nghia Pham  Duc Thang Tang 《Estuarine, Coastal and Shelf Science》2008

The fresh water discharge is an important parameter for modelling salt intrusion in an estuary. In alluvial converging estuaries during periods of low flow, when salinity is highest, the river discharge is generally small compared to the tidal flow. This makes the determination of the fresh water discharge a challenging task. Even if discharge observations are available during a full tidal cycle, the fresh water discharge is seldom much larger than the measurement error in the tidal discharge. Observations further upstream, outside the tidal region, do not always reflect the actual flow in the saline area due to withdrawals or additional drainage. Discharge computation is even more difficult in a complex system such as the Mekong Delta, which is a multi-channel estuary consisting of many branches, over which the freshwater discharge distribution cannot be measured directly. This paper presents a new approach to determine the freshwater discharge distribution over the branches of the Mekong Delta by means of an analytical salt intrusion model, based on measurements made during the dry season of 2005 and 2006. It appears that the analytical model agrees well with observations and with a hydraulic model. This paper demonstrates that with relatively simple and appropriate salinity measurements and making use of the analytical salt intrusion model, it is possible to obtain an accurate discharge distribution over the branches of a complex estuary system. This makes the analytical model a powerful tool to analyze the water resources in tidal regions.  相似文献