Modelling sediment transport as a moving wave — The transfer and deposition of mining waste     

G. Pickup  R. J. Higgins  I. Grant 《Journal of Hydrology》1983,60(1-4):281-301

The movement of slugs of bedload from a discrete input point down a river has proved difficult to model using conventional finite-difference formulations of equations of motion. A model is proposed which makes explicit allowance for the mean sediment velocity and, through a dispersion coefficient, the distribution of sediment velocity about the mean. A second comparative model uses the normal mass conservation or sediment transport continuity approach. The models have been tested over a 43-month period using data from seven monitored cross-sections of the Kawerong River on Bougainville Island, Papua New Guinea, a system which receives waste from a large copper mine. The dispersion model performs considerably better than the mass-conservation model.  相似文献   

Reply     

T. Grant Caldwell  Hugh M. Bibby  Colin Brown 《Geophysical Journal International》2007,171(2):567-567

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Hydrogeology of the Winnipeg Formation in Manitoba, Canada     

Grant A. G. Ferguson  Robert N. Betcher  Stephen E. Grasby 《Hydrogeology Journal》2007,15(3):573-587

The Winnipeg Formation is the basal sedimentary unit throughout much of southern and central Manitoba, Canada, where it forms a regional aquifer over most of its extent. This aquifer is an important source of water in southeastern Manitoba and in Manitoba’s Interlake area, but in most other areas, groundwater within the aquifer is saline. Chemical and isotopic evidence indicate the presence of groundwaters of three different origins: (1) basin brines; (2) modern meteoric recharge; and (3) subglacial recharge that occurred during the late Pleistocene. Hydraulic head and sedimentary facies distributions indicate that the flow system in parts of the area is not in a state of equilibrium and saline waters will encroach on areas currently occupied by freshwater in some areas, while in other areas, freshwater will replace saline water. These features must be considered in groundwater resource management, as groundwater withdrawals will likely hasten these processes.

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Resumen La Formación Winnipeg es la unidad sedimentaria basal en la mayor parte de Manitoba central, Canadá, donde forma un acuífero regional en la mayor parte de su extensión. Este acuífero es una fuente importante de agua en el Sureste de Manitoba y el área de entrelagos de Manitoba, pero en la mayoría de las otras zonas del acuífero, el agua es salina. Las evidencias químicas e isotópicas indican que existen aguas subterráneas de tres orígenes diferentes: (1) salmueras de cuenca; (2) recarga meteórica actual; y (3) recarga subglacial ocurrida durante el Pleistoceno Superior. Los niveles piezométricos y la distribución de las facies sedimentarias indican que el sistema de flujo no se encuentra en estado de equilibrio en parte del área y las aguas salinas irán invadiendo áreas actualmente ocupadas con aguas dulces, mientras que en otras zonas el agua dulce está reemplazando al agua salina. Estos hechos deben ser considerados en la gestión de las aguas subterráneas como recurso, ya que las extracciones de agua acelerarán probablemente estos procesos.

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Résumé La Formation de Winnipeg est l’unité sédimentaire de base sur la plus grande partie du Sud et du centre du Manitoba au Canada, où elle forme un aquifère régional sur pratiquement toute son extension. Cet aquifère représente une ressource en eau importante dans le Sud-Est du Manitoba et dans les zones d’entre les lacs, mais salée dans la plus part des autres zones. Les indications isotopiques et chimiques permettent de distinguer trois différentes origines des eaux souterraines: (1) les saumures de bassin; (2) la recharge météoritique moderne; (3) la recharge sub-glaciaire qui est apparue durant le Pléistocène récent. Les charges hydrauliques et la distribution des faciès sédimentaires indiquent que le système d’écoulement dans certaines zones n’est pas dans un état d’équilibre et que les eaux salées empièteront sur des zones d’eau douce, tandis que dans d’autres zones l’eau douce remplacera les eaux salées. Ces aspects doivent être considérés dans la gestion des ressources en eau souterraine, car le prélèvement des eaux souterraines pourrait accentuer ces processus.

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Transport and deposition of large woody debris in streams: a flume experiment   总被引：4，自引：0，他引：4  

Christian A. Braudrick  Gordon E. Grant 《Geomorphology》2001,41(4)

Large woody debris (LWD) is an integral component of forested streams of the Pacific Northwest and elsewhere, yet little is known about how far wood is transported and where it is deposited in streams. In this paper, we report the results of flume experiments that examine interactions among hydraulics, channel geometry, transport distance and deposition of floating wood. These experiments were carried out in a 1.22-m-wide×9.14-m-long gravel bed flume using wooden dowels of various sizes as surrogate logs. Channel planforms were either self-formed or created by hand, and ranged from meanders to alternate bars. Floating pieces tended to orient with long axes parallel to flow in the center of the channel. Pieces were deposited where channel depth was less than buoyant depth, typically at the head of mid-channel bars, in shallow zones where flow expanded, and on the outside of bends. We hypothesize that the distance logs travel may be a function of the channel's debris roughness, a dimensionless index incorporating ratios of piece length and diameter to channel width, depth and sinuosity. Travel distance decreased as the ratio of piece length to both channel width and radius of curvature increased, but the relative importance of these variables changed with channel planform. Large pieces can move further than our debris roughness models predict if greater than 50% of the active channel area is deeper than the buoyant depth of the piece, or if momentum is high enough to carry pieces across shallows. Our debris roughness model allows first-order prediction of the amount of wood transport under various channel geometries.  相似文献   

The beachwatch pollution monitoring programme: Changing priorities to recognize changed circumstances     

Ian Armstrong  Stephen Higham  Grant Hudson  Troy Colley 《Marine pollution bulletin》1996,33(7-12):249-259

Since the commissioning of the three major deepwater outfalls in Sydney, there has been a dramatic improvement in general beach water quality at Sydney's ocean beaches. This has required the NSW Environment Protection Authority's Beachwatch Programme to shift from assessing the impacts of gross sewage pollution due to nearshore outfalls to more diffuse pollution from stormwater and sewer overflows.

The visual indicators of gross sewage pollution originally used by Beachwatch for the daily assessment of bacterial water quality are now of limited value. General linear models (with multiple effects) were constructed to identify the secondary indicators which best describe the levels of bacterial contamination due to stormwater pollution. Data from four representative Sydney beaches were modelled separately due to the site-specific effects of pollution sources and hydrodynamics. Factors which were built into the models and were known on the day of prediction were rain amount, presence of stormwater material, the maximum daily stormwater rating, drain or lagoon flows at the time of sampling, and the drain/lagoon bacterial concentration two days before sampling.

Results indicate that there is a general linear relationship between visual indicators and bacterial density; however, the reliability of the prediction on a daily basis is poor and rainfall alone as a predictor is equivalent to or better than visual assessment alone. The primary source of information for the preparation of Beachwatch daily pollution bulletins now is rainfall reports from a telemetered network of rain gauges along the coast. This is a more cost-effective approach and has allowed the reallocation of resources to address more directly the problem of stormwater pollution at higher risk beaches.  相似文献   

The Holocene paleohydrology and climatic history of the northern great sandy desert - fitzroy trough: With special reference to the history of the northwest Australian monsoon     

Karl-Heinz Wyrwoll  Jennifer Hopwood  N. L. McKenzie 《Climatic change》1992,22(1):47-65

The Holocene history of the northwest Australian monsoon is considered in the light of new stratigraphic findings from the southern margin of the monsoon regime. A discussion of the present-day climatology of northwestern Australia and synoptic controls on precipitation in the areas at the southern margin of the monsoon regime is given as background information for the interpretation of stratigraphic findings from swamp and alluvial sequences. The stratigraphic findings point to little change in the intensity of the northwest Australian monsoon since ca. 6.5 ka. A more tentative inference drawn from the field evidence is that the monsoon activity may well have been reduced in this region during the Early Holocene; during this time insolation levels were also reduced. The possible relationship of the northwest Australian monsoon to insolation levels is explored. It is clear that monsoon behavior cannot be accounted for as a simple linear response of monsoon intensity to variations in insolation. Possible controls are discussed with particular emphasis on the plausibility of changes in the damping of convective motions providing the mechanism. Gill's model of heat-induced circulation is used to provide some evidence in favour of this conjecture.  相似文献   

Climate change in Yellowstone National Park: Is the drought-related risk of wildfires increasing?     

Robert C. Balling Jr.  Grant A. Meyer  Stephen G. Wells 《Climatic change》1992,22(1):35-45

The increased frequency of wildfires in the United States has become a common prediction associated with the build-up of greenhouse gases. In this investigation, variations in annual wildfire data in Yellowstone National Park are compared to variations in historical climate conditions for the area. Univariate and multivariate analytical techniques reveal that (a) summer temperatures in the Park are increasing, (b) January-June precipitation levels are decreasing, and (c) variations in burn area within the Park are significantly related to the observed variations in climate. Outputs from four different general circulation model simulations for 2 × CO₂ are included in the analyses; model predictions for increasing aridity in the Yellowstone Park area are generally in agreement with observed trends in the historical climate records.  相似文献   

Reply to the comment by R. Westaway on 'Active tectonics of the north and central Aegean Sea' by T. Taymaz, J. Jackson and D. McKenzie     

T. Taymaz  J. Jackson  D. McKenzie 《Geophysical Journal International》1992,110(3):623-623

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Evidence for the trapped liquid shift effect in the Mount Ayliff Intrusion,South Africa   总被引：1，自引：2，他引：1  

R. Grant Cawthorn  Bernhard K. Sander  Ian M. Jones 《Contributions to Mineralogy and Petrology》1992,111(2):194-202

Postcumulus trapped liquid shift in layered complexes produces cumulate minerals with more fractionated compositions than the original primary phases. This effect is shown by olivine compositions from the base of the Mount Ayliff Intrusion, where varying proportions of olivine to interstitial liquid produce a suite of rocks which define a tight linear trend on a binary whole-rock plot of MgO versus FeO. Extrapolation of this trend constrains the composition of the primary cumulus olivine to the range Fo_84–86, whereas olivine actually present have compositions Fo_77–83. The magnitude of the discrepancy between the theoretical and observed olivine compositions correlates directly with the weight fraction of interstitial liquid. These observations are quantitatively predicted by the trapped liquid shift model. They also argue against significant migration of residual liquid. Trapped liquid shift is documented over a vertical interval of 60 m. It occurred in rocks lying only 1 m above the basal contact of the intrusion and hence must be a comparatively rapid process.  相似文献   

Soviet sea otters increase     

M. Grant Gross 《Marine pollution bulletin》1973,4(9):131

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