Use of a parsimonious rainfall–run‐off model for predicting hydrological response in ungauged basins          下载免费PDF全文

Thomas Skaugen  Ivar Olaf Peerebom  Anna Nilsson 《水文研究》2015,29(8):1999-2013

A new parameter parsimonious rainfall–run‐off model, the Distance Distribution Dynamics (DDD) model, is used to simulate hydrological time series at ungauged sites in the Lygne basin in Norway. The model parameters were estimated as functions of catchment characteristics determined by geographical information system. The multiple regression equations relating catchment characteristics and model parameters were trained from 84 calibrated catchments located all over Norway, and all model parameters showed significant correlations with catchment characteristics. The significant correlation coefficients (with p‐value < 0.05) ranged from 0.22 to 0.55. The suitability of DDD for predictions in ungauged basins was tested for 17 catchments not used to estimate the multiple regression equations. For ten of the 17 catchments, deviations in Nash–Sutcliffe efficiency (NSE) criteria between the calibrated and regionalised model were less than 0.1, and for two calibrated catchments within the Lygne basin, the deviations were less than 0.08. The median NSE for the regionalized DDD for the 17 catchments for two time series was 0.66 and 0.72. Deviations in NSE between calibrated and regionalised models are well explained by the deviations between calibrated and regressed parameters describing spatial snow distribution and snowmelt respectively. The quality of the simulated run‐off series for the ungauged sites in the Lygne basin was assessed by comparing flow indices describing high, medium and low flow estimated from observed run‐off at the 17 catchments and for the simulated run‐off series. The indices estimated for the simulated series were generally well within the ranges defined by the 17 observed series. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Errors in the upstream mobility scheme for countercurrent two-phase flow in heterogeneous porous media     

Svenn Tveit  Ivar Aavatsmark 《Computational Geosciences》2012,16(3):809-825

In reservoir simulation, the upstream mobility scheme is widely used for calculating fluid flow in porous media and has been shown feasible for flow when the porous medium is homogeneous. In the case of flow in heterogeneous porous media, the scheme has earlier been shown to give erroneous solutions in approximating pure gravity segregation. Here, we show that the scheme may exhibit larger errors when approximating flow in heterogeneous media for flux functions involving both advection and gravity segregation components. Errors have only been found in the case of countercurrent flow. The physically correct solution is approximated by an extension of the Godunov and Engquist–Osher flux. We also present a new finite volume scheme based on the local Lax–Friedrichs flux and test the performance of this scheme in the numerical experiments.  相似文献   

Efficient multiphysics modelling with adaptive grid refinement using a MPFA method     

Benjamin Faigle  Rainer Helmig  Ivar Aavatsmark  Bernd Flemisch 《Computational Geosciences》2014,18(5):625-636

A sequential solution procedure is used to simulate compositional two-phase flow in porous media. We employ a multiphysics concept that adapts the numerical complexity locally according to the underlying processes to increase efficiency. The framework is supplemented by a local refinement of the simulation grid. To calculate the fluxes on such grids, we employ a combination of the standard two-point flux approximation and a multipoint flux approximation where the grid is refined. This is then used to simulate a large-scale example related to underground CO₂ storage.  相似文献   

Plastic Pollution at a Sea Turtle Conservation Area in NE Brazil: Contrasting Developed and Undeveloped Beaches     

Juliana Assunção Ivar do Sul  Isaac R. Santos  Ana Cláudia Friedrich  Alexandre Matthiensen  Gilberto Fillmann 《Estuaries and Coasts》2011,34(4):814-823

Sea turtles are highly susceptible to plastic ingestion and entanglement. Beach debris were surveyed along the most important sea turtle nesting beaches in Brazil (Costa dos Coqueiros, Bahia State). No significant differences among developed and undeveloped beaches were observed in terms of total number of items. Local sources (tourism activities) represented 70% of debris on developed beaches, where cigarette butts, straws, paper fragments, soft plastic fragments, and food packaging were the most abundant items. Non-local sources (domestic and fishing activities) accounted for about 70% of debris on undeveloped beaches, where the most abundant items were rigid plastic fragments, ropes, soft plastic fragments, caps, and polystyrene. The projected surface area of beach debris did not vary among developed and undeveloped beaches. Overseas containers accounted for about 25% of regional plastic pollution, implying that international pollution prevention agreements are not being respected off the Brazilian coast.  相似文献   

Triassic platform-margin deltas in the western Barents Sea   总被引：1，自引：0，他引：1  

E. Glørstad-Clark  E.P. BirkelandJ.P. Nystuen  J.I. FaleideI. Midtkandal 《Marine and Petroleum Geology》2011,28(7):1294-1314

The Early to Middle Triassic in the Barents Sea was dominated by prograding transgressive-regressive sequences. Internal clinoform geometries indicate that sediments were derived from the Baltic Shield in the south and the Uralian Mountains in the east and southeast. These systems were formed in a large, relatively shallow epicontinental basin, where modest variations in relative sea-level relocated the shoreline significantly. This study shows the development of strike elongated depositional wedges that thicken just basinward of the platform-edge. Seismic facies and time-thickness maps show the position and development of platform-margin delta complexes within each sequence. Seismic clinoforms and trajectory analysis show significant lateral variation from the axis of the delta complex to areas adjacent to the main delivery system. Frequent toplap geometries are observed in proximity to coarse-grained deposits, while aggradation of seismic clinoforms characterizes areas laterally to the platform-margin deltas. Complex shifts in depocenters are revealed by large-scale compensational stacking pattern and relict platform breaks. Locally, relict breaks are created due to pre-existing paleo-topography. Platform-margin deltas can be identified by careful mapping of clinoform geometries, clinoform angles and trajectories. However, seismic analysis of prograding clinoform units indicate that the shoreline and delta complexes commonly are positioned landward of the platform-edge. Deposition of platform-margin deltas is sometimes caused by locally increased sediment supply during slightly rising relative sea-level, and occasionally caused by a regional drop in relative sea-level with significant shelf bypass.Development, position, thickness and facies distribution of platform deltas and platform-margin deltas of very broad low-relief basins, like the Triassic of the epicontinental Barents Sea basin, are strongly sensitive to changes in relative sea-level due to rapid emergence and submergence of wide areas, and to changes in position of major rivers supplying sand to the delta systems. In this respect, the depositional model of the present study deviates from models of clinoform successions obtained from small and narrow basins or siliciclastic platforms with high coarse-clastic sediment supply.  相似文献   

Plastic debris ingestion by marine catfish: an unexpected fisheries impact   总被引：1，自引：0，他引：1  

Possatto FE  Barletta M  Costa MF  do Sul JA  Dantas DV 《Marine pollution bulletin》2011,62(5):1098-1102

Plastic marine debris is a pervasive type of pollution. River basins and estuaries are a source of plastics pollution for coastal waters and oceans. Estuarine fauna is therefore exposed to chronic plastic pollution. Three important catfish species [Cathorops spixii (N = 60), Cathorops agassizii (N = 60) and Sciades herzbergii (N = 62)] from South Western Atlantic estuaries were investigated in a tropical estuary of the Brazilian Northeast in relation to their accidental ingestion of plastic marine debris. Individuals from all three species had ingested plastics. In C. spixii and C. agassizii, 18% and 33% of individuals had plastic debris in their stomachs, respectively. S. herzbergii showed 18% of individuals were contaminated. All ontogenetic phases (juveniles, sub-adults and adults) were contaminated. Nylon fragments from cables used in fishery activities (subsistence, artisanal and commercial) played a major role in this contamination. These catfish spend their entire life cycles within the estuary and are an important feeding resource for larger, economically important, species. It is not yet possible to quantify the scale and depth of the consequences of this type of pollution. However, plastics are well known threat to living resources in this and other estuaries. Conservation actions will need to from now onto take plastics pollution into consideration.  相似文献   

Impact of faulting in depocentres development,facies assemblages,drainage patterns,and provenance in continental half-graben basins: An example from the Fanja Basin of Oman     

Camilla L. Würtzen  Alvar Braathen  Miquel Poyatos-Moré  Mark J. Mulrooney  Lina H. Line  Ivar Midtkandal 《Basin Research》2023,35(2):705-743

Fault throw gradients create transverse folding, and this can influence accommodation creation and sedimentary routing and infill patterns in extensional half-graben basin. The Fanja half-graben basin (Oman) offers an excellent outcrop of an alluvial fan succession displaying cyclical stacking and basin-scale growth-fold patterns. These unique conditions allow for an investigation of fault-timing and accommodation development related to fault-transverse folding. Our study combines geological mapping, structural analysis, sedimentary logging and correlation, and bulk mineralogical compositions. Mapping reveals that the basin is bounded by a regional-scale fault, with local depocentres changing position in response to transverse syncline and anticline development ascribed to fault-displacement gradients. The alluvial Qahlah Formation (Late Cretaceous) is unconformably overlying the Semail Ophiolite, and is in turn overlain by the marine Jafnayn Formation (Late Palaeocene). Facies and stratigraphic analysis allows for subdivision of the Qahlah Formation into four informal units, from base to top: (i) laterite in topographic depressions of the ophiolite, (ii) greenish pebbly sandstones, deriving from axially draining braided streams deposited in the low-relief half-graben basin. This green Qahlah grades vertically into the red Qahlah, formed by alluvial fanglomerates and floodplain mudstones, with drainage patterns changing from fault-transverse to fault-parallel with increasing distance to the main fault. The red Qahlah can be divided into (iii) the Wadi al Theepa member, found in a western basin depocentre, with higher immaturity and sand: mud ratio, suggesting a more proximal source, and (iv) the Al Batah member, located in the eastern part of the basin. The latter shows better sorting, a lower sand: mud ratio, and more prominent graded sub-units. It also shows eastward expansion from an orthogonal monocline, ascribed to accommodation developed in a relay ramp. Changes in sedimentary facies and depositional patterns are consistent with differential mineralogical composition. The Green Qahlah is composed of quartz and lithic mafic rock fragments, sourced from the ophiolite and schists of the metamorphic basement. The Red Qahlah is composed of chert and kaolinite sourced from the Hawasina Nappe succession in the footwall of the master fault. These changes in source area are linked to unroofing of fault-footwalls and domal structures during the extensional collapse of the Semail Ophiolite. The novelty of this study resides in linking sedimentology and fault-displacement events controlling fault-perpendicular folding, and its influence on depocentre generation and stratigraphic architecture. This is an approach seldom considered in seismic analysis, and rarely analysed in outcrop studies, thus placing the results from this study among the key outcrop-based contributions to the field.  相似文献   

Benthonic foraminifera as indicators of the paleoposition of the Subarctic Convergence in the Norwegian-Greenland Sea     

Hans-Petter Sejrup  Hans Holtedahl  Olav Norvik  Ivar Miljeteig 《Boreas: An International Journal of Quaternary Research》1980,9(3):203-207

A method is presented for correlating benthonic foraminiferal communities in Late Quaternary marine sediments on continental shelves and in coastal areas with the planktonic foraminiferal stratigraphy of the North Atlantic and Norwegian Sea deep-sea sediments.  相似文献   

Effects of environmental stress on blue crab (<Emphasis Type="Italic">Callinectes sapidus</Emphasis>) harvests in Chesapeake Bay tributaries     

Johan?A.?Mistiaen  Ivar?E.?Strand  Douglas?LiptonEmail author 《Estuaries and Coasts》2003,26(2):316-322

Trotline blue crab (Callinectes sapidus) fishermen in the Patuxent, Chester, and Choptank tributaries of Chesapeake Bay set their gear in areas where the water quality, characterized by average mid-channel bottom dissolved oxygen, varies across the river systems and over the fishing season. Two harvest production models are developed to capture the potential effects of this source of environmental stress. One model treats the impact of water quality as influencing the availability of crabs to the gear, while the second treats the impact as another source of mortality. Both models are estimated assuming that dissolved oxygen has no effect on crab harvests above an upper threshold of 5 mg I⁻¹. Contrary to the mortality model, the availability model produces estimates that are consistent with our prior beliefs that productivity will be negatively impacted by poor water quality. To determine the percentage of the available crab stock in an area that will be harvested by a given amount of gear under different water quality conditions a simulation of the availability model is developed. The simulations show that a decline in average mid-channel bottom dissolved oxygen in the Patuxent River to 4 mg I⁻¹ may lead to a 48% decline in the percentage of the blue crab population in the area that will be harvested with the same amount of fishing effort.  相似文献   

The use of pump-out facilities by recreational boaters in Maryland     

Ivar E. Strand  George R. Gibson 《Estuaries and Coasts》1990,13(3):282-286

Because of the intense interest in the water quality of the Chesapeake Bay, the State of Maryland sponsored a survey of 500 Maryland boaters to determine their use of marina facilities to discharge sewage from portable toilets or holding tanks. We report results of that survey as well as examine some of the factors that contribute to the use of pump-out facilities. Presently, with under 10% of Maryland’s marinas having facilities available to pump out holding tanks or portable toilets, less than one in twenty boaters has ever used such a facility. Moreover, less than one in three boats equipped with holding tanks or portable toilets has ever used such a facility. Using a discrete choice behavioral model, we found that boaters with portable toilets were more likely to use facilities than ones with holding tanks, especially if the holding tanks were equipped with macerating devices. The price of using the pump-out facility negatively influenced pump-out use. We also found that vessels in transition were less likely to use marina facilities. Finally, the availability of a pump-out facility at a boater’s marina increased the likelihood of pumping by twofold. In Maryland reduction of boat-generated pollution will likely require a policy of both extensive pump-out services and low costs for the services.  相似文献