Within-storm variations in runoff and sediment export from a rapidly eroding coal-refuse deposit     

Laurence C. Smith  Greg A. Olyphant 《地球表面变化过程与地形》1994,19(4):369-375

Measurements of rainfall, runoff and sediment export from a barren deposit of coal mine refuse in south-western Indiana were collected during three storms in the summer and autumn of 1990. Interfluve sheetwash, sediment mass flux, sediment concentration and, to a lesser extent, trunk gully discharge all responded quickly to changes in rainfall intensity. Grain-size distributions varied considerably during storms, containing exclusively fine-grained sediment at low sediment discharges but very large quantities of coarse (> 2mm) sediment at peak sediment discharges. Although data from a fairly long, multipulsed storm indicate that sediment production is limited by supply, the imbricated layer of flat chips that exists at the surface of the deposit is apparently mobilized during most high-intensity pulses of rainfall, thereby producing large volumes of coarse sediment during summer thunderstorms.  相似文献   

Contemporary global horizontal crustal motion     

D. E. Smith  R. Kolenkiewicz  R. S. Nerem  P. J. Dunn  M. H. Torrence  J. W. Robbins  S. M. Klosko  R. G. Williamson  E. C. Pavlis 《Geophysical Journal International》1994,119(2):511-520

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Nutrient enrichments and phytoplankton growth in the surface waters of the Louisiana Bight   总被引：1，自引：0，他引：1  

Stephen M. Smith  Gary L. Hitchcock 《Estuaries and Coasts》1994,17(4):740-753

Nitrate concentrations have increased twofold in the Mississippi River during the past three decades. The increased nitrogen loading to the Louisiana shelf has been postulated as a factor leading to eutrophication and the subsequent development of hypoxia west of the Mississippi River delta. While ratios of nitrogen:phosphorus and nitrogen:silica are relatively high in surface waters on the western Louisiana shelf, nitrogen has been posed as the ‘limiting’ nutrient in this region. Bioassays were performed with nutrient additions to surface waters collected from the Louisiana shelf to examine the potential for specific nutrient limitation. Experiments were conducted in March and September 1991, and May 1992. The growth responses of natural and cultured phytoplankton populations were determined by measuring the time course of in vivo and 3-(3,4 dichlorophenyl)-1, 1-dimethylurea (DCMU)-induced fluorescence, as well as initial and final chlorophylla concentrations. The results suggest that phosphate and silicate potentially limit phytoplankton growth during the winter-spring, particularly at low salinities. In late summer, in contrast, nitrogen limitation may be prominent at higher salinities.  相似文献   

Differences in the crab fauna of mangrove areas at a southwest Florida and a northeast Australia location: Implications for leaf litter processing     

Carole C. McIvor  T. J. Smith 《Estuaries and Coasts》1995,18(4):591-597

Existing paradigms suggest that mangrove leaf litter is processed primarily via the detrital pathway in forests in the Caribbean biogeographic realm whereas herbivorous crabs are relatively more important litter processors in the Indo-West Pacific. To test this hypothesis, we used pitfall traps to collect intertidal crabs to characterize the crab fauna in a mangrove estuary in southwest Florida. We also tethered mangrove leaves to determine if herbivorous crabs are major leaf consumers there. We compared the results with previously published data collected in an analogous manner from forests in northeastern Australia. The crab fauna in Rookery Bay, Florida, is dominated by carnivorous xanthid and deposit-feeding ocypodid crabs whereas that of the Murray River in northeastern Australia is dominated by herbivorous grapsid crabs. No leaves tethered at five sites in the forests in Southwest Florida were taken by crabs. This contrasts greatly with reported values of leaf removal by crabs in Australian forests of 28–79% of the leaves reaching the forest floor. These differences in the faunal assemblages and in the fate of marked or tethered leaves provide preliminary support for the hypothesis that leaf litter is in fact processed in fundamentally different ways in the two biogeographic realms.  相似文献   

Understanding telluric distortion matrices   总被引：9，自引：1，他引：9  

J. Torquil Smith 《Geophysical Journal International》1995,122(1):219-226

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A comparison of the reactions to government taxation measures of twentieth century mining companies and nineteenth century pastoralists     

Derek L Smith 《The Australian geographer》1995,26(1):61-70

This paper compares pastoralists in South Australia in the nineteenth century with Australian mining companies in the twentieth century as they resist the efforts of government to extract a greater proportion of the wealth created in the exploitation of natural resources. In effect, in both cases the struggle relates to the allocation of economic rent between private and corporate capital on the one hand, and the owners of the resources, the people of Australia, on the other. It is difficult not to be impressed by the similarities in the ideologies, objectives and strategies of these two groups of resource exploiters, separated though they are by over one hundred years.  相似文献   

Agricultural policy reforms and sustainable land management: a New Zealand case study     

William Smith  Lindsay Saunders 《The Australian geographer》1995,26(2):112-118

This paper examines the link between poverty and land management within the context of New Zealand's almost total removal of subsidies to agriculture since 1984. The impact of these policy changes is explored through the findings from a detailed study of sixteen farms in the North Island hill country. Stress is identified as a primary link between social damage and environmental degradation. This link reinforces the impact of other linkages expressed in reduced production, lower stocking rates, and reduced capital inputs. Deregulation is claimed to be good. This paper shows that in certain circumstances this is not so.  相似文献   

Greenhouse climatic change and flood damages,the implications     

D. I. Smith 《Climatic change》1993,25(3-4):319-333

Most scenarios of greenhouse climate change are obtained from general circulation models. These provide poor information on changes to extreme events. It is therefore, difficult to convert changes of flood frequency into their impact on flood damages. The procedures for estimating urban flood losses are outlined. Australian case studies illustrate the possible effects of greenhouse-induced changes in comparison to the variability under current climate; changes in urban flood losses for small and large catchments; and the implications for dam design. In all cases, relatively small increases in flood frequency would cause significant increases in loss. The policy implications are outlined, it must not be assumed that the availability of more precise data on future flood frequencies will be matched by policy response in the field of flood plain management.  相似文献   

Mineralized and unmineralized calderas in Spain; Part II, evolution of the Rodalquilar caldera complex and associated gold-alunite deposits   总被引：1，自引：0，他引：1  

J. J. Rytuba  A. Arribas Jr.  C. G. Cunningham  E. H. McKee  M. H. Podwysocki  J. G. Smith  W. C. Kelly  A. Arribas 《Mineralium Deposita》1990,25(1):S29-S35

The Rodalquilar caldera complex is located in the western part of the Cabo de Gata volcanic field in southeastern Spain and is the first documented example of epithermal gold-alunite mineralization within a caldera in Europe. The Rodalquilar caldera is an oval collapse structure having a maximum diameter of 8 km and formed at 11 Ma from eruption of the Cinto ash-flow tuff. The oval Lomilla caldera, with a diameter of 2 km, is nested within the central resurgent dome of the older Rodalquilar caldera. The Lomilla caldera resulted from the eruption of the Lazaras ash-flow tuff which was ponded within the moat of the Rodalquilar caldera. The last phase of volcanic activity in the caldera complex was the emplacement of hornblende andesite flows and intrusions. This magmatic event resulted in structural doming of the caldera, opening of fractures and faults, and provided the heat source for the large hydrothermal systems which deposited quartz-alunite type gold deposits and base metal vein systems. The gold-alunite deposits are enclosed in areas of intense acid sulfate alteration and localized in ring and radial faults and fractures present in the east wall of the Lomilla caldera. Like other acid-sulfate type deposits, the Rodalquilar gold-alunite deposits are closely related in time and space to porphyritic, intermediate composition magma emplaced along caldera structures but unrelated to the caldera forming magmatic system.  相似文献   

A revised estimate of the life span for Lake Nasser     

Scot E. Smith 《Environmental Geology》1990,15(2):123-129

A number of estimates of the potential life span of Lake Nasser located in Egypt and Sudan have been made in the past several years. Published estimates range from as little as 20 years (Sterling 1970) to over 1500 years (Makary 1982). The wide range of differing values is a function of many variables, including computation method, input data, and theoretical assumptions underlying the mathematical approach taken. Such a broad range of values is typical of sedimentation studies performed for areas that lack an adequate historic data base.One of the chief constraints to development of a reliable estimate the Lake Nasser's case has been lack of sufficient historical data on which to construct a useful data base. Enough information of this type has been collected since the reservoir's formation in 1964 to permit a realistic assessment of its life span. Granted the obvious need to determine the useful lifetime of this or any other reservoir, it is now possible to assess the reliability of the current official estimate for Lake Nasser. By applying appropriate modifications and additional data to the official estimate, an improved estimate was made.The time forecasted for filling of the reservoir by the official estimate is 362 years, somewhat less than the original design life of 500 years. By taking into account changes in the hydrological regime of the Nile after 1964 and another compaction factor, an estimate of 535 years was made. The additional time before filling estimated in the revision is significant for decision rules governing operation of the Aswan High Dam.  相似文献