Evolution of cutoffs across meander necks in Powder River,Montana, USA     

Glenn R. Gay  Hubert H. Gay  William H. Gay  Holly A. Martinson  Robert H. Meade  John A. Moody 《地球表面变化过程与地形》1998,23(7):651-662

Over a period of several decades, gullies have been observed in various stages of forming, growing and completing the cutoff of meander necks in Powder River. During one episode of overbank flow, water flowing over the down-stream bank of the neck forms a headcut. The headcut migrates up-valley, forming a gully in its wake, until it has traversed the entire neck, cutting off the meander. The river then follows the course of the gully, which is subsequently enlarged as the river develops its new channel. The complete process usually requires several episodes of high water: in only one of the five cases described herein was a meander cutoff initiated and completed during a single large flood. © 1998 John Wiley & Sons, Ltd.  相似文献   

Field observations in a small subtropical estuary during and after a rainstorm event     

Hubert Chanson 《Estuarine, Coastal and Shelf Science》2008

In Australia, a large majority of small subtropical estuaries are narrow, elongated and meandering channels with large width to depth ratio and cross-sections which deepen and widen towards the mouth. Up to date, episodic rainstorm events in such small systems were rarely documented, and this study presents a field data set collected during and immediately after a rainstorm. A number of hydrodynamic and physio-chemical parameters were recorded simultaneously at several longitudinal locations for 12 h. The field measurements demonstrated a significant flushing of the estuarine zone, caused primarily by the rainfall runoff from the nearby shopping malls and roadways. Some strong vertical stratification of the water column was observed at all sampling locations, and the depth-averaged salinity data exhibited a dome-shaped intrusion curve. A solution of the salt dispersion equation provided some agreement with the freshwater flushing conditions during the wet weather.  相似文献   

Turbulence characteristics of a small subtropical estuary during and after some moderate rainfall   总被引：1，自引：0，他引：1  

Mark Trevethan  Hubert Chanson  Richard Brown 《Estuarine, Coastal and Shelf Science》2008,79(4):661-670

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The segmentation procedure as a tool for discrete modeling of hydrometeorological regimes   总被引：1，自引：1，他引：0  

P. Hubert 《Stochastic Environmental Research and Risk Assessment (SERRA)》2000,14(4-5):297-304

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Ecohydrological modelling with EcH2O‐iso to quantify forest and grassland effects on water partitioning and flux ages     

Audrey Douinot  Doerthe Tetzlaff  Marco Maneta  Sylvain Kuppel  Hubert Schulte‐Bisping  Chris Soulsby 《水文研究》2019,33(16):2174-2191

We used the new process‐based, tracer‐aided ecohydrological model EcH₂O‐iso to assess the effects of vegetation cover on water balance partitioning and associated flux ages under temperate deciduous beech forest (F) and grassland (G) at an intensively monitored site in Northern Germany. Unique, multicriteria calibration, based on measured components of energy balance, hydrological function and biomass accumulation, resulted in good simulations reproducing measured soil surface temperatures, soil water content, transpiration, and biomass production. Model results showed the forest “used” more water than the grassland; of 620 mm average annual precipitation, losses were higher through interception (29% under F, 16% for G) and combined soil evaporation and transpiration (59% F, 47% G). Consequently, groundwater (GW) recharge was enhanced under grassland at 37% (~225 mm) of precipitation compared with 12% (~73 mm) for forest. The model tracked the ages of water in different storage compartments and associated fluxes. In shallow soil horizons, the average ages of soil water fluxes and evaporation were similar in both plots (~1.5 months), though transpiration and GW recharge were older under forest (~6 months compared with ~3 months for transpiration, and ~12 months compared with ~10 months for GW). Flux tracking using measured chloride data as a conservative tracer provided independent support for the modelling results, though highlighted effects of uncertainties in forest partitioning of evaporation and transpiration. By tracking storage—flux—age interactions under different land covers, EcH₂O‐iso could quantify the effects of vegetation on water partitioning and age distributions. Given the likelihood of drier, warmer summers, such models can help assess the implications of land use for water resource availability to inform debates over building landscape resilience to climate change. Better conceptualization of soil water mixing processes and improved calibration data on leaf area index and root distribution appear obvious respective modelling and data needs for improved simulations.  相似文献   

The effect of forcing and landscape distribution on performance and consistency of model structures          下载免费PDF全文

Tanja Euser  Markus Hrachowitz  Hessel C. Winsemius  Hubert H.G. Savenije 《水文研究》2015,29(17):3727-3743

It is often challenging to determine the appropriate level of spatial model forcing and model distribution in conceptual rainfall‐runoff modelling. This paper compares the value of incorporating both spatially distributed forcing data and spatially distributed model conceptualisations based on landscape heterogeneity, applied to the Ourthe catchment in Belgium. Distributed forcing data were used to create a spatial distribution of model states. Eight different configurations were tested: a lumped and distributed model structure, each with four levels of model state distribution. The results show that in the study catchment the distributed model structure can in general better reproduce the dynamics of the hydrograph, and furthermore, that the differences in performance and consistency between calibration and validation are smallest for the distributed model structure with distributed model states. For the Ourthe catchment, it can be concluded that the positive effect of incorporating a distributed model structure is larger than that of incorporating distributed model states. Distribution of model structure increases both model performance and consistency. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

A Three-Dimensional Analytical Solution for the Study of Air Pollutant Dispersion in a Finite Layer     

Ema’a Ema’a Jean Marie  Ben-Bolie Germain Hubert  Ele Abiama Patrice  Ali Zarma  Owono Ateba Pierre 《Boundary-Layer Meteorology》2015,155(2):289-300

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Sulfur-rich monazite with high common Pb in ore-bearing schists from the Schellgaden mining district (Tauern Window, Eastern Alps)     

Erwin Krenn  Hubert Putz  Fritz Finger  Werner H. Paar 《Mineralogy and Petrology》2011,102(1-4):51-62

The compositional variation of accessory monazite in ore bearing micaschists from the Schellgaden mining district, Tauern Window, Eastern Alps, was studied by means of the electron microprobe. In ore-rich domains monazite yields unusually high sulfur contents (up to 2.5?wt.% SO₃), which enter the monazite structure together with Ca and Sr as ??anhydrite-celestine?? component replacing P and REEs. The exchange reaction is S⁶⁺+ (Ca, Sr)²⁺ = REE³⁺+ P⁵⁺. Sulfur-rich monazite is intergrown with anglesite, pyromorphite or galena and shows oscillatory zoning indicating growth from S-bearing fluids. This type of S-enriched monazite yields very high common lead contents (up to 0.5?wt.% PbO) and unrealistic high apparent Th-U-total Pb single dates (> 1?Ga). However, S-enriched monazite grains provide a flat trendline in the Th* vs. Pb isochron diagram similar to the trendline defined through low-S, and low-Pb monazite crystals (0.1?C1?wt.% SO₃, < 0.05?wt.% PbO), which were observed in ore-poor parts of micaschists. Results from this study imply an Alpine rather than a pre-Alpine formation age for monazite and a strong S-rich fluid activity during the Alpine orogeny. Apart from this geological aspect, the current study also shows that the detection of sulfur in monazite may serve as a warning for a possible presence of common Pb.  相似文献   

Evolution of exhumation and erosion in western West Gondwanaland as recorded by detrital zircons of late Neoproterozoic and Cambrian sedimentary rocks of NW and Central Argentina     

Hubert Miller  Christopher Adams  Florencio G. Aceñolaza  Alejandro J. Toselli 《International Journal of Earth Sciences》2011,100(2-3):619-629

The evolution of the provenance areas for Late Neoproterozoic, Cambrian and Early Ordovician sedimentary and meta-sedimentary rocks of north central and northwest Argentina is discussed using 123 maximum ages of detrital zircons from 42 samples from this and previously published studies. Most detrital zircon ages fall into two groups: 1,200–900 Ma and 670–545 Ma. These ages are essentially identical for the non- to very low grade metamorphic late Neoproterozoic to Early Cambrian Puncoviscana Formation and the low to high grade metamorphic rocks of Eastern Sierras Pampeanas. Hence, both units are related to similar provenance areas at the same time of sedimentation. The time span from zircon crystallization in the Earth’s crust to exhumation and erosion may be very long. This is important when determining maximum ages of sedimentary rocks. Variation of zircon maxima may also be influenced by concurrent sedimentary cover of proposed provenance areas. For the late Mesoproterozoic to early Neoproterozoic zircon age group, an active mountain range of the southwest Brazilian Sunsás orogen is the most probable provenance area. The younger, late Neoproterozoic zircons are related to the continuously developing mountains of the Brasiliano orogen of southwest and south central Brazil. Young zircons, up to 514 Ma, from fossil-bearing Puncoviscana and Suncho Formation outcrops are related to late Early Cambrian volcanism contemporaneous with sedimentation. This situation continues through the Late Cambrian to the Early Ordovician, but the Sunsás orogen provenance diminishes as possible Río de la Plata craton origins become important.  相似文献   

Can shells of freshwater mussels (Unionidae) be used to estimate low summer discharge of rivers and associated droughts?     

Emma A. A. Versteegh  Hubert B. Vonhof  Simon R. Troelstra  Dick Kroon 《International Journal of Earth Sciences》2011,100(6):1423-1432

This paper examines if shell oxygen isotope ratios (δ¹⁸O_ar) of Unio sp. can be used as a proxy of past discharge of the river Meuse. The proxy was developed from a modern dataset for the reference time interval 1997–2007, which showed a logarithmic relationship between discharge and measured water oxygen isotope ratios (δ¹⁸O_w). To test this relationship for past time intervals, δ¹⁸O_ar values were measured in the aragonite of the growth increments of four Unio sp. shells; two from a relatively wet period and two from a very dry time interval (1910–1918 and 1969–1977, respectively). Shell δ¹⁸O_ar records were converted into δ¹⁸O_w values using existing water temperature records. Summer δ¹⁸O_w values, reconstructed from δ¹⁸O_ar of 1910–1918, showed a similar range as the summer δ¹⁸O_w values for the reference time interval 1997–2007, whilst summer reconstructed δ¹⁸O_w values for the time interval 1969–1977 were anomalously high. These high δ¹⁸O_w values suggest that the river Meuse experienced severe summer droughts during the latter time interval. δ¹⁸O_w values were then applied to calculate discharge values. It was attempted to estimate discharge from the reconstructed δ¹⁸O_w values using the logarithmic relationship between δ¹⁸O_w and discharge. A comparison of the calculated summer discharge results with observed discharge data showed that Meuse low-discharge events below a threshold value of 6 m³/s can be detected in the reconstructed δ¹⁸O_w records, but true quantification remains problematic.  相似文献