Sensitivity of Simulated Hyporheic Exchange to River Bathymetry: The Steinlach River Test Site     

Reynold Chow  Hao Wu  Jeremy P. Bennett  Jürnjakob Dugge  Thomas Wöhling  Wolfgang Nowak 《Ground water》2019,57(3):378-391

This study determines the aspects of river bathymetry that have the greatest influence on the predictive biases when simulating hyporheic exchange. To investigate this, we build a highly parameterized HydroGeoSphere model of the Steinlach River Test Site in southwest Germany as a reference. This model is then modified with simpler bathymetries, evaluating the changes to hyporheic exchange fluxes and transit time distributions. Results indicate that simulating hyporheic exchange with a high-resolution detailed bathymetry using a three-dimensional fully coupled model leads to nested multiscale hyporheic exchange systems. A poorly resolved bathymetry will underestimate the small-scale hyporheic exchange, biasing the simulated hyporheic exchange towards larger scales, thus leading to overestimates of hyporheic exchange residence times. This can lead to gross biases in the estimation of a catchment's capacity to attenuate pollutants when extrapolated to account for all meanders along an entire river within a watershed. The detailed river slope alone is not enough to accurately simulate the locations and magnitudes of losing and gaining river reaches. Thus, local bedforms in terms of bathymetric highs and lows within the river are required. Bathymetry surveying campaigns can be more effective by prioritizing bathymetry measurements along the thalweg and gegenweg of a meandering channel. We define the gegenweg as the line that connects the shallowest points in successive cross-sections along a river opposite to the thalweg under average flow conditions. Incorporating local bedforms will likely capture the nested nature of hyporheic exchange, leading to more physically meaningful simulations of hyporheic exchange fluxes and transit times.  相似文献   

Integrated geophysical exploration in onshore frontier basins     

F. Martini  E. Rogers  S. Bennett  R. Davi  J.T. Doherty  J. Mongan 《Geophysical Prospecting》2019,67(6):1664-1675

Faced with the challenge of rapidly screening a huge expanse of frontier exploration acreage, often characterized by sparse vintage data, it is our experience that a combination of appropriate air- and ground-based geophysical techniques contributes positively to the exploration value chain. Airborne gravity gradiometry in conjunction with conventional gravity and magnetic data, as well as geological knowledge, add significant value to the screening process. This combination can subsequently assist in optimizing the location of the more time-consuming and expensive seismic programme. In addition, analysis and inversion of passive seismic data have also proven useful in providing depth to basement estimates, and results derived from all the techniques investigated have been consistent within several study areas. Following initial tests, where the data were independently analysed and cross-checked for consistency (including comparisons with active source seismic data and well data, when available), the company now routinely adopts the integration of these techniques in our frontier exploration acreage to support sedimentary basin delineation and mapping. This allows the optimal positioning and focussing of the higher spend and higher footprint programmes, such as active reflection seismic.  相似文献   

Reappraisal of the ‘Cullenstown Formation’: Implications for the Lower Palaeozoic tectonic history of SE Ireland     

M. C. Bennett  W. M. Dunne  S. P. Todd 《Geological Journal》1989,24(4):317-329

The structurally attenuated greenschist facies metasedimentary succession at Cullenstown Strand in south Co. Wexford comprises three formations which in stratigraphic order are (1) the Quartzite Formation, (2) the Greywacke/Quartzite Formation, and (3) the Greywacke Formation. The entire sequence is inverted and lies within the lower limb of a large scale overturned D1 anticlinal structure that closes towards the southeast. The three formations are lithologically and sedimentologically similar to the Shelmaliere Quartzite, the Cullentra Greywacke, and Newtown Greywacke Formations of the Bray Group in the Forth Mountain - Ferrycarrig area that probably lie on the normal limb of the D1 structure. The Cullenstown strata are therefore considered to be part of the Bray Group in southeast Leinster, and hence Cambrian in age. The rocks were affected by three major phases of deformation. D1 produced an overturned anticline containing an important tectonic slide. The D1 structures are modified by upright D2 and D3 structures, but from regional considerations it is argued that D1 is restricted to strata of Cambrian to Lower Ordovician age in southeast Leinster. A model for the tectonic evolution of the southeastern part of the Leinster Basin during Cambro-Ordovician times is presented and discussed. In this model, the southeast margin of the Leinster Basin was delineated by a mylonite zone along the northwest margin of the Precambrian Rosslare Complex. Bray and Ribband Group sediments close to the margin were deformed during the Llanvirn as a consequence of basin inversion which caused shortening and thrusting of the basin fill across the Rosslare block. The D1 compressional structures were subsequently modified during a period of extension, marked by the resumption of sedimentation and outbreak of voluminous volcanicity near the basin margin during the Llandeilo and Caradoc. The D2 and D3 structures in the Bray and Ribband Groups are an expression of later Caledonian deformation.  相似文献   

A provisional map of forest types for the British Isles 5000 years ago     

Keith David Bennett 《第四纪科学杂志》1989,4(2):141-144

The distributions of seven woodland types, plus unforested areas, are mapped for the British Isles at 5000 BP. The map was compiled using data of modern soil distribution, present-day ecological preferences of the tree taxa present, and the pollen record.  相似文献   

Instantaneous slip rates from geology and geodesy     

Richard A. Bennett 《Geophysical Journal International》2007,169(1):19-28

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The Gemini Multiobject Spectrographs     

J. Allington-Smith  P. Bettess  E. Chadwick  R. Content  R. Davies  G. Dodsworth  R. Haynes  D. Lee  I. Lewis  J. Webster  E. Atad  S. Beard  R. Bennett  J. Harris  P. Hastings  D. Kelly  T. Paul  M. Strachan  P. Williams  T. Bond  D. Crampton  T. Davidge  B. Leckie  C. Morbey  R. Murowinski  S. Roberts  L. Saddlemyer  J. Sebesta  J. Stilburn  K. Szeto 《Experimental Astronomy》1997,7(4):293-299

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SEDIMENT TRANSPORT PROCESSES IN AGRICULTURAL WATERSHEDS     

Roger A. Kuhnle  Sean J. Bennett  Carlos V. Alonso  Ronald L. Bingner  Eddy Langendoen 《国际泥沙研究》2000,(2)

lINTR0DUCTI0NTheerosion,transportanddep0siti0nofsedimentinawatershedarepallofthenaturalsystemofwatershedprocesses.InanundistUrbedwatershed,s0ilsinuplandareasaregraduallyeroded,transportCdforsomedistanceandeventuallydepositedatlowereIevations.WhenwatershedsaredistUrbedbyhumanactivitiessuchasclearingofvegetation,urbaniZati0n,orotherchangesthataffectthelandscaPe,unstablechannelswithlocallyhighratesoferosion,transport,0rdepositionofsedimentoftenaretheresult.Theimpact0fer0sionisespeciallyhigh…  相似文献   

Flux predictions of high-energy neutrinos from pulsars     

Bennett Link  Fiorella Burgio 《Monthly notices of the Royal Astronomical Society》2006,371(1):375-379

Young, rapidly rotating neutron stars could accelerate ions from their surfaces to energies of ∼1 PeV. If protons reach such energies, they will produce pions (with low probability) through resonant scattering with X-rays from the stellar surface. The pions subsequently decay to produce muon neutrinos. Here, we calculate the energy spectrum of muon neutrinos, and estimate the event rates at Earth. The spectrum consists of a sharp rise at ∼50 TeV, corresponding to the onset of the resonance, above which the flux drops with neutrino energy as  ε⁻²_ν  up to an upper energy cut-off that is determined by either kinematics or the maximum energy to which protons are accelerated. We estimate event rates as high as 10–100 km⁻² yr⁻¹ from some candidates, a flux that would be easily detected by IceCube. Lack of detection would allow constraints on the energetics of the poorly understood pulsar magnetosphere.  相似文献   

Agent-based modeling within a cyberinfrastructure environment: a service-oriented computing approach     

Wenwu Tang  Shaowen Wang  David A. Bennett  Yan Liu 《International journal of geographical information science》2013,27(9):1323-1346

Agent-based models (ABM) allow for the bottom-up simulation of dynamics in complex adaptive spatial systems through the explicit representation of pattern–process interactions. This bottom-up simulation, however, has been identified as both data- and computing-intensive. While cyberinfrastrucutre provides such support for intensive computation, the appropriate management and use of cyberinfrastructure (CI)-enabled computing resources for ABM raise a challenging and intriguing issue. To gain insight into this issue, in this article we present a service-oriented simulation framework that supports spatially explicit agent-based modeling within a CI environment. This framework is designed at three levels: intermodel, intrasimulation, and individual. Functionalities at these levels are encapsulated into services, each of which is an assembly of new or existing services. Services at the intermodel and intrasimulation levels are suitable for generic ABM; individual-level services are designed specifically for modeling intelligent agents. The service-oriented simulation framework enables the integration of domain-specific functionalities for ABM and allows access to high-performance and distributed computing resources to perform simulation tasks that are often computationally intensive. We used a case study to investigate the utility of the framework in enabling agent-based modeling within a CI environment. We conducted experiments using supercomputing resources on the TeraGrid – a key element of the US CI. It is indicated that the service-oriented framework facilitates the leverage of CI-enabled resources for computationally intensive agent-based modeling.  相似文献   

Multi-scale distribution and dynamics of bivalve larvae in a deep atoll lagoon (Ahe, French Polynesia)     

Thomas Y  Garen P  Bennett A  Le Pennec M  Clavier J 《Marine pollution bulletin》2012,65(10-12):453-462

Bivalve larvae and hydrographic parameters were sampled over a range of spatio-temporal scales in a deep atoll lagoon. Bivalve larvae abundances were very high throughout the year: 18,550 m(-3) in average. Larvae were (i) concentrated at mid-depth with nocturnal ascent and diurnal descent, (ii) heterogeneously dispersed at the lagoon scale, (iii) subject to day-to-day variation in abundance and (iv) transferred between different parts of the lagoon providing evidence of intra-lagoonal connectivity. The primacy of physical factors was seen on large spatial scale with the diluting effect of water renewal and transfers by hydrodynamics. On smaller spatial scale, the primacy of biological processes was recognised, with larval swimming activity leading to dial vertical migration correlated with food concentration. Variations in larval abundance were driven by bivalve reproductive activity correlated with meteorological conditions (i.e. windy periods). Finally, relationship between bivalve larvae patterns and pearl oyster (Pinctada margaritifera) settlement structuring is discussed.  相似文献