Stream-aquifer interactions in the Maules Creek catchment, Namoi Valley, New South Wales, Australia   总被引：1，自引：1，他引：0  

Martin S. Andersen  R. I. Acworth 《Hydrogeology Journal》2009,17(8):2005-2021

The interaction between surface-water streams and groundwater in the Maules Creek catchment of northern New South Wales, Australia has been investigated using a wide range of techniques. Zones of groundwater discharge were mapped by measuring the temperature and fluid electrical-conductivity distribution in bores and surface water. Zones where surface water appears to be recharging the aquifer were investigated by measuring the vertical head gradient between the stream and adjacent bores and by estimates of the decreasing surface flow. Geological heterogeneity appears to be the most significant factor in controlling exchange. Lithological information was assembled using geophysical logging of existing bores, supplemented by the results of electrical resistivity imaging. A preliminary water balance was assembled from the available State records of groundwater abstraction for irrigation, rainfall, evapotranspiration and flow gauging in Maules Creek and the adjacent Namoi River. The analysis has demonstrated the complexity of these coupled systems and gives an indication of the most efficient techniques to be deployed in the field to investigate these complex but important systems.  相似文献   

A Compilation of Radiocarbon Dates from Disko Bugt,Central West Greenland/Meteorological Observations in 1996 at the Arctic Station,Qeqertarsuaq (Godhavn), Central West Greenland/A Discussion on Pingos in Mellemfjord,Disko, Central West Greenland/Open System Pingos in Mellemfjord,Disko, Central West Greenland: A Reply to Gurney and Worsley     

Morten Rasch  Birger Hansen  Ole Humlum  Niels Nielsen  Peter Funch  Stephen D. Gurney 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):143-159

188 new and previously published radiocarbon dates on Holocene material from Disko Bugt, central West Greenland, are presented together with relevant informations (laboratory number, place name, dated material, geografic coordinates, altitude and δ¹³C-value) about the dates.

In October 1990 an automatic weather station was established at the Arctic station (65 °15′N,53 °31′W), Qeqertarsuaq (Godhavn), Central West Greenland. The Station register parameters each 20 min., and the parameters have been described in an earlier paper in this journal by Nielsen et al. (1995). The present paper summarises main points of the climate during 1996.

Open system, or more correctly, hydraulic pingos, are genetically poorly understood. A continuing problem concerns their need for a perennial groundwater supply (intra- or sub-permafrost). This has to be maintained despite the existence of continuous permafrost in many areas where they are located. Recent work on Disko Island has suggested a new type of hydraulic pingo developing only in a “marsh environment”. It is argued that the marsh setting is not relevant to the formation of these features and that they are simply hydraulic pingos.

Abstract

A group of marsh initiated open system pingo remnants from the Iterdlagssûp kûgssua valley mouth, in Mellemfjord, Disko Island, Central West Greenland was described in Christiansen (1995). Gurney and Worsley (1997) state that the location of this group of pingo remnants in the Iterdlagssûp kûgssua valley mouth is of no relevance to their genesis, and that they presumably were the result of an assumed late Holocene sea level regression, causing permafrost to be established in the valley bottom. In this reply the arguments by Gurney and Worsley (1997) on the Iterdlagssûp kûgssua valley pingos are commented, and it is argued by way of sea level information, frost penetration and water supply that the special setting must indeed have caused pingo initiation and growth. Furthermore, the area has experienced a relative sea level rise during the late Holocene.  相似文献   

Understanding groundwater processes by representing aquifer heterogeneity in the Maules Creek Catchment, Namoi Valley (New South Wales, Australia)     

B. M. S. Giambastiani  A. M. McCallum  M. S. Andersen  B. F. J. Kelly  R. I. Acworth 《Hydrogeology Journal》2012,20(6):1027-1044

A FEFLOW three-dimensional (3D) groundwater model is developed to enhance the understanding of groundwater processes in the complex alluvial stratigraphy of Maules Creek Catchment (New South Wales, Australia). The aquifer vertical heterogeneity is replicated by indexing 204 lithological logs into units of high or low hydraulic conductivity, and by developing a 3D geological conceptual model with a vertical resolution based on the average lithological unit thickness for the region. The model mesh is populated with the indexed geology using nearest neighbour gridding. The calibrated model is successful in simulating the observed flow dynamics and in quantifying the important water-budget components. This indicates that the lateral groundwater flow from the mountainous region is the main inflow component of the system. Under natural conditions, the Namoi River acts as a sink of water, but groundwater abstraction increasingly removes a large amount of water each year causing dewatering of the system. The pumping condition affects the river–aquifer interaction by reversing the flow, from gaining to losing river conditions during the simulation period. The procedure is relevant for the development of groundwater models of heterogeneous systems in order to improve the understanding of the interplay between aquifer architecture and groundwater processes.  相似文献   

From Fish to Jellyfish in the Eutrophicated Limfjorden (Denmark)     

Hans Ulrik Riisgård  Per Andersen  Erik Hoffmann 《Estuaries and Coasts》2012,35(3):701-713

The heavily eutrophicated Limfjorden (Denmark) provides a good illustration of the value of long-term monitoring, especially if this is combined with an experimental, interdisciplinary research approach. Here, we first give a short overview of the environmental status of Limfjorden, including the historical development of nutrient overloading and subsequent oxygen depletion in near-bottom water, and how the annual landings of edible bottom-dwelling fish species (plaice, flounder, eel and others) caught in Limfjorden have decreased from about 2,500 t in the early 1920s to only about 20 t in recent years where the fish have been replaced by an increasing number of especially the moon jellyfish, Aurelia aurita, which mainly preys on zooplankton. Next, we evaluate the ecological consequences of the present high number of jellyfish, based on data from recent years’ research on the abundance of jellyfish, their population dynamics and predation impact. In Limfjorden, the benthic polyp stage of A. aurita ensures a large number of small ephyrae in the early spring and subsequently a large population of adult medusae that control the zooplankton during summer and autumn. The holopelagic invasive ctenophore Mnemiopsis leidyi, which was observed in Limfjorden for the first time in 2007, is a second carnivore adding additional predation pressure of the indigenous A. aurita so that copepods and other mesozooplankton organisms may be virtually absent, as observed in 2008 and 2009 where ciliates made up a substantial part of the zooplankton biomass. Marine environmental management programmes should be aware of the increasing importance of both indigenous and new invasive jellyfish species that may show mass occurrence in especially eutrophicated and over-fished areas.  相似文献   

Assessment of Erythemal UV Level in Nepal Based on Solar UV Estimates from Total Ozone Mapping Spectrometer     

Binod Kumar BHATTARAI  Berit KJELDSTAD  Trond Morten THORSETH 《大气科学进展》2011,28(4):789-796

Nepal lies on the southern slope of Himalaya in Asia. In a width ranging between 150 and 250 km, the altitude varies greatly from about 100 m at its southern border to a maximum of 8848 min the northern part. Like the variation in altitude, climatic condition varies quite a lot. Long-term monthly mean erythemal UV daily dose values for Nepal are evaluated using Total Ozone Mapping Spectrometer (TOMS) estimation from the time of its overpass between 1996 and 2003. The results are presented as summer and winter maps of mean UV levels in each satellite grid. The mean winter erythemal UV daily dose ranges between 2.1 and 3.6 kJ m-2 whereas summer values are found to lie between 4.6 and 9.7 kJ m-2. The altitude variation increases the UV levels by about 0.2 kJ km-1 in winter months, and 0.9 kJ km-1 in summer. A multiyear monthly average erythemal daily dose in most of the areas shows that the summer value is about three times higher than that in winter. Although year-to-year variation is not pronounced in high- and mid-elevation regions, UV levels seemed to decrease from 1997 to 2002 in the southern part of the country in the low elevation region by about 5.35%. Due to the combined effects of the altitude, low ozone concentration in the troposphere, and thin air, surface UV radiation at higher altitudes is found to be higher than in the surrounding regions.  相似文献   

Seismic characterization of reservoirs with multiple fracture sets using velocity and attenuation anisotropy data     

Aamir Ali  Morten Jakobsen 《Journal of Applied Geophysics》2011,75(3):590-602

Knowledge about the spatial distribution of the fracture density and the azimuthal fracture orientation can greatly help in optimizing production from fractured reservoirs. Frequency-dependent seismic velocity and attenuation anisotropy data contain information about the fractures present in the reservoir. In this study, we use the measurements of velocity and attenuation anisotropy data corresponding to different seismic frequencies and azimuths to infer information about the multiple fracture sets present in the reservoir. We consider a reservoir model with two sets of vertical fractures characterized by unknown azimuthal fracture orientations and fracture densities. Frequency-dependent seismic velocity and attenuation anisotropy data is computed using the effective viscoelastic stiffness tensor and solving the Christoffel equation. A Bayesian inversion method is then applied to measurements of velocity and attenuation anisotropy data corresponding to different seismic frequencies and azimuth to estimate the azimuthal fracture orientations and the fracture densities, as well as their uncertainties. Our numerical examples suggest that velocity anisotropy data alone cannot recover the unknown fracture parameters. However, an improved estimation of the unknown fracture parameters can be obtained by joint inversion of velocity and attenuation anisotropy data.  相似文献   

The Zn abundance and isotopic composition of diatom frustules,a proxy for Zn availability in ocean surface seawater     

Morten B. Andersen  Derek Vance  Corey Archer  Robert F. Anderson  Michael J. Ellwood  Claire S. Allen 《Earth and Planetary Science Letters》2011,301(1-2):137-145

We have developed cleaning methods for extracting diatomopal from bulk marine sediment samples, for measurement of both zinc (Zn) abundance and isotope composition. This cleaning technique was then applied to a set of Holocene core-top samples from the Southern Ocean. The measured δ⁶⁶Zn (reported relative to the JMC_Lyon standard) and Zn/Si ratios from the Southern Ocean diatom_opal samples range from 0.7 to 1.5‰, and from 14 to 0.9 μmol/mol, respectively. The Zn abundance and isotope composition data show a clear correlation with opal burial rates and other oceanographic parameters. In common with previous work, we interpret the systematic changes in the Zn/Si ratio to be linked to the variability in the concentrations of bioavailable Zn in the ambient surface seawater where the diatom opal is formed. This variability is likely to be primarily controlled by the degree to which Zn is taken up into phytoplankton biomass. The observed systematic pattern in the δ⁶⁶Zn compositions of the diatom_opal core-top samples is, similarly, likely to reflect changes in the δ⁶⁶Zn composition of the ambient Zn in the surface waters above the core-top sites, which is progressively driven towards isotopically heavier values by preferential incorporation of the lighter isotopes into phytoplankton organic material. Thus, the systematic relationship between Zn isotopes and abundance observed in the core-top diatom_opal samples suggests a potential tool for investigating the biogeochemical cycling of Zn in the past surface ocean for down-core diatom_opal material. In this respect, it may be possible to test hypotheses that attribute variations in atmospheric CO₂ on glacial–interglacial timescales to the degree to which trace metals limited primary productivity in HNLC zones.  相似文献   

The Middle Miocene to Recent Davis Strait Drift Complex: implications for Arctic�CAtlantic water exchange     

Tove Nielsen  Claus Andersen  Paul C. Knutz  Antoon Kuijpers 《Geo-Marine Letters》2011,31(5-6):419-426

A large-scale contourite drift complex has been recognised on multi-channel 2D reflection seismic data acquired in the south-eastern Davis Strait and adjacent Labrador Sea slope offshore West Greenland between 63°?C66°N. Based on well-tie data, the drift complex developed from the Middle Miocene to the Recent. It has been mapped in a wide variety of water depths ranging from about 700?m, at a NNW-ESE-elongated crest located above structural highs in the Davis Strait, to more than 2,000?m beyond the slope to the Labrador Sea. The overall drift geometry has been described by subdivision into two first-order seismic units, enabling the generation of time-isochore maps. The reflection patterns demonstrating current-related deposition are illustrated by seismic examples. The time-isochores of the two first-order seismic units show lateral changes in their depocentres: the lower unit is absent in a zone slightly displaced south-westwards of the present-day crest, indicating changes in the prevailing deepwater current system during the Early Pliocene. The observations can be explained by two alternative palaeoceanographic scenarios: (1) either the present-day oceanographic setting with Arctic?CAtlantic water exchange across the Davis Strait was largely established by the mid-Miocene, with only minor adjustments during the Early Pliocene caused by tectonic movements, or (2) it became established during the Early Pliocene as a consequence of enhanced northward flow across the Davis Strait due to lowering of the sill depth.  相似文献   

An assessment of an oil spill in Gladstone, Australia - impacts on intertidal areas at one month post-spill     

Andersen LE  Melville F  Jolley D 《Marine pollution bulletin》2008,57(6-12):607-615

In January 2006, 25 tonnes of heavy fuel oil spilled into the Port of Gladstone in Queensland, Australia, from the breached hull of a bulk carrier ship. Over the following days, approximately 18 tonnes of the oil was recovered, however a certain amount of oil was deposited in the intertidal areas of Port Curtis leaving a highly visible, viscous residue. The objectives of this research were to assess the immediate impacts on the intertidal habitat and to gain baseline information for future comparative assessments. Sediment PAH and metal concentrations, mangrove communities and intertidal macroinvertebrates were assessed within one month post-spill at oil-impacted sites; adjacent sites which were not visibly impacted; and reference sites which were located outside the recorded distribution of the oil spill. Highest PAH concentrations were found at the impacted sites, with concentrations of some PAHs exceeding Australian and New Zealand Sediment Quality Guidelines (ANZECC/ARMCANZ, 2000). These sites contained very few or no crab holes in the high intertidal area, indicating a low crab density in comparison to reference sites. Little immediate impact was evident on the mangrove and macrobenthic communities, however future surveys may show evidence of longer-term impacts on these communities.  相似文献   

Deriving effects of pressure depletion on elastic framework moduli from sonic logs     

Anne-Kari Furre  Mona Andersen  Anita Smalø Moen  Randi Kristin Tønnessen 《Geophysical Prospecting》2009,57(3):427-437

We have developed a method to determine the effect of pore pressure depletion on elastic framework moduli, by utilizing sonic logs from wells drilled at different locations through a reservoir at varying depletion stages. This is done by first inverting the sonic logs for elastic framework bulk and shear moduli, thus carefully removing pressure dependent fluid effects. By crossplotting these elastic framework moduli against an increase in net stress (which is directly related to depletion), we derive the stress sensitivity of the elastic framework moduli. We found that the observed stress sensitivity was consistent with time-lapse seismic results and that the sensitivity derived from the sonic logs was much smaller than predicted by hydrostatic measurements on core samples. This method is applicable to depletion scenarios in mature fields and can be used both for modelling and inverting time-lapse seismic data for effects of pore pressure depletion on seismic data.  相似文献