Lithospheric structure north of Scotland—I. P-wave modelling, deep reflection profiles and gravity     

R. Peter LL. Morgan  Penny J. Barton  Mike Warner  Joanna Morgan  Claire Price †  Kevin Jones 《Geophysical Journal International》2000,142(3):716-736

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Contrasting Approaches to the Management of Common Property Resources: An institutional analysis of fisheries development strategies in Shetland and the Solomon Islands     

Kevin Crean 《The Australian geographer》2000,31(3):367-382

The paper compares and contrasts the development experiences of two fisheries-dependent archipelagos: the Shetland Islands, located in the temperate seas of the North-east Atlantic, and the Lau community of the island of Malaita, in the Solomon Islands of the tropical Pacific Ocean. Whilst the coastal communities of both island groups have always depended upon the sea for their livelihood, their indigenous peoples are distinct in origins, culture, historic tradition, economy, and social imperatives. However, a closer examination of the recent development of the two archipelagos reveals that, whilst they are contrasting in the fisheries sector specifics, they have, over different time scales, adopted similar management strategies in the pursuit of sustainable fishing. In both instances, the island communities have sought to support the local fisheries economy by tempering the external forces of the centre. This has been achieved, with varying degrees of success, by adopting management control and resource 'ownership' strategies in response to social and economic turbulence in the environment. The experiences of the two archipelagos have demonstrated that to maintain a coherent fisheries management strategy over time and a sustainable resources base requires a pro-active approach, the input of resources, and moderation of the pressures created by the market. The future is uncertain as the fisheries organisations of the archipelagos seek to stabilise the access and ownership arrangements applied to the common-property fisheries resources of coastal waters.  相似文献   

A metamodel based on MAGIC to predict the pre-industrial acidity status of surface waters     

Martin Erlandsson  Jens Fölster  Anders Wilander  Kevin Bishop 《Aquatic Sciences - Research Across Boundaries》2008,70(3):238-247

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NAPL Hydraulic Conductivity and Velocity Estimates Based on Laboratory Test Results          下载免费PDF全文

Michael J. Gefell  Kevin Russell  Mark Mahoney 《Ground water》2018,56(5):690-693

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PPAPI: A Program for Groundwater Modeling Tasks in Distributed Parallel Computing Environments          下载免费PDF全文

Jens Schumacher  Kevin Hayley  Louis‐Charles Boutin  Emma White 《Ground water》2018,56(2):248-250

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Unraveling the roles of asymmetric uplift,normal faulting and groundwater flow to drainage rearrangement in an emerging karstic landscape          下载免费PDF全文

Christine Authemayou  Gilles Brocard  Bernard Delcaillau  Stéphane Molliex  Kevin Pedoja  Laurent Husson  Sonny Aribowo  Sri Yudawati Cahyarini 《地球表面变化过程与地形》2018,43(9):1885-1898

Landscape adjustment to tectonic, lithologic and climatic forcing leads to drainage reorganization and migration of divides. The respective contribution of these forcings, especially on carbonate landscapes is not well defined. Here, we have addressed this issue by combining field observations, satellite image interpretation and digital elevation model (DEM) quantitative analysis to assess drainage response to spatially heterogeneous rainfall, asymmetric uplift, and normal faulting on an emerging carbonated platform (Sumba Island, Indonesia). We map geomorphic markers of fluvial dynamics and drainage rearrangement and compute a χ parameter that incorporates the contributions of unevenly distributed precipitation and asymmetric uplift to estimate erosional disequilibrium across drainage divides. We find that asymmetric emergence of Sumba Island created an initial parallel drainage, asymmetric across a divide that propagates landwards. Soon after establishing itself on the emerging slopes this drainage was disturbed by normal faulting, which has become the main force driving drainage rearrangement. Vertical offsets across normal fault scarps first triggered aggradation within valleys over the hanging walls, and then disconnected upstream reaches from downstream reaches, leading to the formation of wind gaps atop the fault scarps and upstream perched sedimentary basins. The defeat of rivers by growing fault scarps was catalysed by the possibility for surface water to be rerouted near the fault scarps into underground water networks inside the underlying carbonates. At the end of the process, the opposite drainage across the main water divide captured the struggling drainage. Capture mechanisms include initial groundwater capture of the perched alluvial aquifers, followed by ground sapping at the head of the opposite drainage and surface stream diversion by avulsion. Finally, normal faulting is the main driving force of drainage rearrangement allowing avulsion and karstic rerouting whereas asymmetric uplift and climate forcings have shown a low efficiency. The role of karstification is more ambiguous, catalysing or inhibiting drainage rearrangement. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

Using wind run to predict sand drift     

Andreas C.W. Baas  Derek W.T. Jackson  Irene Delgado-Fernandez  Kevin Lynch  J. Andrew G. Cooper 《地球表面变化过程与地形》2020,45(8):1817-1827

Conventional aeolian sand transport models relate mass transport rate to wind speed or shear velocity, usually expressed and empirically tested on a 1-s time scale. Projections of total sand delivery over long time scales based on these models are highly sensitive to any small bias arising from statistical fitting on empirical data. We analysed time series of wind speed and sand transport rate collected at 14 independent measurement stations on a beach during a prior field experiment. The results show that relating total sand drift to cumulative above-threshold wind run yields models which are more statistically robust when fitted on empirical data, generating smaller prediction errors when projected to longer time scales. Testing of different power exponents indicates that a linear relationship between sand drift and above-threshold wind run yields the best results. These findings inspire a speculative novel phenomenological model relating the mass flow of air in the boundary layer to the mass transport of sand over the surface. © 2020 John Wiley & Sons, Ltd.  相似文献   

An Approach for Passive Removal of Residual LNAPL from Groundwater     

Kevin Svitana  Jacob South 《Ground Water Monitoring & Remediation》2019,39(2):64-70

Light nonaqueous phase liquids (LNAPLs) are a problematic challenge for obtaining site closure or no further action remediation sites. The source of the LNAPLs varies from leaking underground petroleum storage tanks, to manufacturing facilities where oil leaks create LNAPL accumulations beneath factory floors. Active recovery using pumping or periodic vacuum recovery from wells or sumps is used for remediation, but usually has disappointing results when LNAPL reaccumulates to thicknesses exceeding the 0.01-foot action level recognized by many states. This paper presents a simple passive approach for recovering persistent LNAPL using nonwoven hydrophobic oil absorbing cloth. The method used laboratory trials to assess physical properties of the cloth. Parameters observed and assessed included sorptive capacity and rate, buoyancy, and LNAPL wicking. It was determined that the cloth could be rolled and secured with cable ties for placement in the wells/sumps. Two placement designs were developed, one where rolled sorbent freely floated on the well/sump fluid surface and a second where the sorbent roll was placed in the fluid column at a fixed depth. Sorbents were then used at two manufacturing facilities where LNAPLs persisted for decades. In both instances, many wells/sumps were reduced to thicknesses below the action level in less than 2 months. In most wells, LNAPL did not reaccumulate. Where it did reaccumulate, it was less than 50% of the original thickness. Using laboratory-derived recovery rates, cloth sorbents could be sized to minimize placement/recovery frequency while effectively recovering LNAPL.  相似文献   

Long-term perspective on the relationship between phytoplankton and nutrient concentrations in a southeastern Australian estuary     

Michaela E. Larsson  Penelope A. Ajani  Ana M. Rubio  Kristy Guise  Ross G. McPherson  Steven J. Brett  Kevin P. Davies  Martina A. Doblin 《Marine pollution bulletin》2017,114(1):227-238

Sixteen years (1997–2013) of physicochemical, nutrient and phytoplankton biomass (Chlorophyll-a (Chl-a)) data and a decade (2003-2013) of phytoplankton composition and abundance data were analyzed to assess how the algal community in a temperate southeastern Australian estuary has responded to decreased chronic point source nitrogen loading following effluent treatment upgrade works in 2003. Nitrogen concentrations were significantly lower (P < 0.05) following enhanced effluent treatment and Chl-a levels decreased (P < 0.05) during the warmer months. Temperature and nutrient concentrations significantly influenced temporal changes of Chl-a (explaining 55% of variability), while salinity, temperature, pH and nutrient concentrations influenced phytoplankton abundance and composition (25% explained). Harmful Algal Bloom (HAB) dynamics differed between sites likely influenced by physical attributes of the estuary. This study demonstrates that enhanced effluent treatment can significantly decrease chronic point source nitrogen loading and that Chl-a concentrations can be lowered during the warmer months when the risk of blooms and HABs is greatest.  相似文献   

On the Importance of Gravity in DNAPL Invasion of Saturated Horizontal Fractures          下载免费PDF全文

Sean P. L. Cianflone  Sarah E. Dickson  Kevin G. Mumford 《Ground water》2017,55(1):27-37

Invasion percolation (IP) models of dense non‐aqueous phase liquid (DNAPL) invasion into saturated horizontal fractures typically neglect viscous and gravity forces, as it is assumed that capillarity dominates in many situations. An IP model simulating DNAPL invasion into saturated horizontal fractures was modified to include gravity as a local effect. The model was optimized using a genetic algorithm, and demonstrated that the inclusion of gravity is important for replicating the architecture of the DNAPL invasion pattern. The optimized gravity‐included simulation showed the DNAPL invasion pattern to be significantly more representative of the experimentally observed pattern (80% accuracy) than did the optimized gravity‐neglected simulation (70% accuracy). Additional simulations of DNAPL invasion in 360 randomly generated fractures were compared with and without gravity forces. These simulations showed that with increasing fracture roughness, the minimum difference between simulations with and without gravity increases to 35% for a standard deviation of the mid‐aperture elevation field (SD_z) of 10 mm. Even for low roughness (SD_z = 0.1 mm), the difference was as high as 30%. Furthermore, a scaled Bond Number is defined which includes data regarding DNAPL type, media type and statistical characteristics of the fracture. The value of this scaled Bond Number can be used to determine the conditions under which gravity should be considered when simulating DNAPL invasion in a macroscopically horizontal fracture. Finally, a set of equations defining the minimum and maximum absolute percentage difference between gravity‐included and gravity‐neglected simulations is presented based on the fracture and DNAPL characteristics.  相似文献