Benchmarking observational uncertainties for hydrology: rainfall,river discharge and water quality   总被引：2，自引：0，他引：2  

Hilary McMillan  Tobias Krueger  Jim Freer 《水文研究》2012,26(26):4078-4111

This review and commentary sets out the need for authoritative and concise information on the expected error distributions and magnitudes in observational data. We discuss the necessary components of a benchmark of dominant data uncertainties and the recent developments in hydrology which increase the need for such guidance. We initiate the creation of a catalogue of accessible information on characteristics of data uncertainty for the key hydrological variables of rainfall, river discharge and water quality (suspended solids, phosphorus and nitrogen). This includes demonstration of how uncertainties can be quantified, summarizing current knowledge and the standard quantitative results available. In particular, synthesis of results from multiple studies allows conclusions to be drawn on factors which control the magnitude of data uncertainty and hence improves provision of prior guidance on those uncertainties. Rainfall uncertainties were found to be driven by spatial scale, whereas river discharge uncertainty was dominated by flow condition and gauging method. Water quality variables presented a more complex picture with many component errors. For all variables, it was easy to find examples where relative error magnitudes exceeded 40%. We consider how data uncertainties impact on the interpretation of catchment dynamics, model regionalization and model evaluation. In closing the review, we make recommendations for future research priorities in quantifying data uncertainty and highlight the need for an improved ‘culture of engagement’ with observational uncertainties. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Species loss in the brown world: are heterotrophic systems inherently stable?     

Michael J. Rubbo  Lisa K. Belden  Sara I. Storrs-Mendez  Jonathan J. Cole  Joseph M. Kiesecker 《Aquatic Sciences - Research Across Boundaries》2012,74(3):397-404

Determining the effects of species loss on ecosystems has received considerable attention given the current threats many ecosystems are facing. A significant body of research has yielded many insights to this question, but this work has been limited by a focus on ecosystems where primary production plays a significant role in energy transfer. As many ecosystems rely on energy sources that are not derived from in situ production, there is a need to better understand how species loss will affect ecosystems of varying trophic states. To examine the effects of species loss on an ecosystem that is not reliant on in situ primary production, we manipulated the larval amphibian community of temporary forest ponds. These ponds are heterotrophic systems that rely on allochthonous inputs of detritus as a basal energy source. The larvae of two amphibian species that are prone to local extinction, wood frogs (Lithobates sylvatica) and spotted salamanders (Ambystoma maculatum), were removed from ponds and net ecosystem production was monitored. We found no effects of the removal of these top consumers on ecosystem functioning or on lower trophic groups (i.e., zooplankton, algae, bacteria). While amphibians can influence food web dynamics in other systems, their influence on system processes in temporary forest ponds appears to be limited. We hypothesize that the lack of any effects is due to the microbial degradation of detritus ??swamping?? the system, providing more than enough energy to maintain the food web, and/or due to omnivory dampening species interactions. These data indicate that the functioning of heterotrophic systems may be inherently stable due to internal dynamics that minimize interaction strengths among trophic groups.  相似文献   

The influence of dunes on mixing in a migrating salt‐wedge: Fraser River estuary,Canada     

Ray Kostaschuk  Jim Best  Paul V. Villard 《地球表面变化过程与地形》2010,35(4):460-465

Dune bedforms and salt‐wedge intrusions are common features in many estuaries with sand beds, and yet little is known about the interactions between the two. Flow visualization with an echosounder and velocity measurements with an acoustic Doppler current profiler over areas of flat‐bed and sand dunes in the highly‐stratified Fraser River estuary, Canada, were used to examine the effect of dunes on interfacial mixing. As the salt‐wedge migrates upstream over the flat‐bed, mixing is restricted to the lower portion of the water column. However, as the salt‐wedge migrates into the dune field from the flat bed, there is a dramatic change in the flow, and large internal in‐phase waves develop over each of the larger dunes, with water from the salt‐wedge reaching the surface of the estuary. The friction Richardson number shows that bed friction is more important in interfacial mixing over the dunes than over the flat‐bed, and a plot of internal Froude Number versus obstacle (dune) height shows that the salt‐wedge flow over the dunes is mainly supercritical. Such bedforms can be expected to cause similar effects in interfacial mixing in other estuaries and sediment‐laden density currents, and may thus be influential in fluid mixing and sediment transport. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

震后快速钻探:历史、现状与未来     

Emily E.Brodsky  Kuo-Fong Ma  Jim Mori  Demian M.Saffer  李丽 《国际地震动态》2010,(4):9-18

大地震发生后立即在断层带上进行钻探可以帮助我们获取更多的地震信息,尤其是可获得决定断层动态破裂的摩擦水平和强度,观测断层的愈合过程及可能触发余震的应力变化,并可获取控制破裂过程的重要的物理和化学属性。在2008年11月由国际大陆科学钻探项目（ICDP）和南加州地震中心（SCEC）联合在日本东京举办的为期3天的“震后快速钻探：历史、现状与未来”研讨会上,  相似文献   

The coalescence and organization of lahars at Semeru volcano, Indonesia     

E. E. Doyle  S. J. Cronin  S. E. Cole  J.-C. Thouret 《Bulletin of Volcanology》2010,72(8):961-970

We present multi-parameter geophysical measurements of rainfall-induced lahars at Semeru Volcano, East Java, using two observation sites 510 m apart, 11.5 km from the summit. Our study site in the Curah Lengkong channel is composed of a 30-m wide box-valley, with a base of gravel and lava bedrock, representing an ideal geometry for high density measurements of active lahars. Instrumentation included pore-pressure sensors (stage), a broad-band seismograph (arrival times, vibrational energy, and turbulence), video footage, and direct bucket sampling. A total of 8 rainfall-induced lahars were recorded, with durations of 1–3 h, heights 0.5–2 m, and peak velocities 3–6 m/s. Flow types ranged from dilute to dense hyperconcentrated flows. These recorded flows were commonly composed of partly coalesced, discrete and unsteady gravity current packets, represented by multiple peaks within each lahar. These packets most likely originate from multiple lahar sources, and can be traced between instrument sites. Those with the highest concentrations and greatest wetted areas were often located mid-lahar at our measured reach, accelerating towards the flow front. As these lahars travel downstream, the individual packets thus coalesce and the flow develops a more organised structure. Observations of different degrees of coalescence between these discrete flow packets illustrate that a single mature debris flow may have formed from multiple dynamically independent lahars, each with different origins.  相似文献   

Flood-tide Delta Morphological Change at the Gippsland Lakes Artificial Entrance,Australia (1889–2009)     

Peter Wheeler  Jim Peterson  Lee Gordon-Brown 《The Australian geographer》2010,41(2):183-216

Analysis of historical survey and navigation charts, aerial imagery, and digital hydro-data (representing a time-series of 1889–2009) allows the morphological evolution of a flood-tide delta at the artificial entrance to the Gippsland Lakes (Victoria, Australia) to be visualised and quantified. Analysis shows that flood-tide delta growth has imposed progressively greater demands upon port managers for publicly funded maintenance dredging. This flood-tide delta growth corresponds with a progressive diminution of Gippsland Lakes catchment river discharge volumes, and dampening of flow variability, due to both regional precipitation pattern changes and changes in catchment water resource allocation. Future climate change predictions for the Gippsland Lakes catchment and coastal area suggest both further decreases in catchment river discharge, and changing sediment flux along this sector of the Ninety Mile Beach. Thus, scope for flood-tide delta nourishment will probably increase, as will the demand for mitigation of the inevitable effects upon entrance channel navigability. Information derived from the analysis of time-series bathymetry used for this study offers baseline information in support of stakeholder consensus building regarding options for maintaining navigability. Analysis points to the merit of considering (and testing via morphological modelling) alternative options for navigation channel maintenance than those in present practice. We argue that the circumstances prevailing at the artificial entrance call for consideration of engineered configuration changes practised elsewhere by entrance managers faced with similar issues.  相似文献   

Impact of climate change on floodplain inundation and hydrological connectivity between wetlands and rivers in a tropical river catchment   总被引：1，自引：0，他引：1       下载免费PDF全文

Fazlul Karim  Cuan Petheram  Steve Marvanek  Catherine Ticehurst  Jim Wallace  Masud Hasan 《水文研究》2016,30(10):1574-1593

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Spatial characteristics of ocean surface waves   总被引：2，自引：2，他引：0  

Johannes Gemmrich  Jim Thomson  W. Erick Rogers  Andrey Pleskachevsky  Susanne Lehner 《Ocean Dynamics》2016,66(8):1025-1035

The spatial variability of open ocean wave fields on scales of O (10km) is assessed from four different data sources: TerraSAR-X SAR imagery, four drifting SWIFT buoys, a moored waverider buoy, and WAVEWATCH III^? model runs. Two examples from the open north-east Pacific, comprising of a pure wind sea and a mixed sea with swell, are given. Wave parameters attained from observations have a natural variability, which decreases with increasing record length or acquisition area. The retrieval of dominant wave scales from point observations and model output are inherently different to dominant scales retrieved from spatial observations. This can lead to significant differences in the dominant steepness associated with a given wave field. These uncertainties have to be taken into account when models are assessed against observations or when new wave retrieval algorithms from spatial or temporal data are tested. However, there is evidence of abrupt changes in wave field characteristics that are larger than the expected methodological uncertainties.  相似文献   

Application of sugar foam to red soils in a semiarid Mediterranean environment     

F. J. García Navarro  J. A. Amorós Ortiz-Villajos  C. J. Sánchez Jiménez  S. Bravo Martín-Consuegra  E. Márquez Cubero  Raimundo Jiménez Ballesta 《Environmental Earth Sciences》2009,59(3):603-611

The study described here involved evaluating the effects that the application of one by-product (sugar foam waste) has upon red soils in the region of La Mancha (Central Spain). In view of the fact that this is a location where this type of soil abounds, this technique has been a common practice for many years. The principal goal was to investigate the impact of this approach on some of the soil properties and, secondly, on its level of fertility. As a result, this represents an investigation into the effects that this type of waste has on some soil quality parameters. The results showed that, after the addition of by-products over 25 years, sugar foam waste is of agricultural interest mainly due to the increase in organic matter concentration (about 2%) and, to a lesser extent, by increases in calcium carbonate (more than 30%) and P (four times more). The soil pH was also found to increase slightly (1.4), while the electrical conductivity almost did not change. The properties associated with these pedological qualities therefore had a positive effect by improving nutrient availability. As a result, foams arising from sugar industries have a positive effect on soil quality and the application of such foams to soils is beneficial since the need to dispose this residue is also removed.  相似文献   

Gypsy Architecture: Houses of the Roma in Eastern Europe     

David “Jim” Nemeth 《The Professional geographer》2013,65(4):583-586

Why is Ortley Beach, New Jersey, known as Superstorm Sandy's ground zero? This article employs qualitative vulnerability analysis to understand why vulnerability of second homes in Ortley Beach resulted in dune failure and slow rebuilding after Sandy. The second-home owners who largely make up the community in Ortley Beach are identified as the key vulnerable group. This group's lack of political representation and financial compensation after Sandy increased house damage and slowed rebuilding. Identifying the level of vulnerability of the majority group in a location is paramount to understanding how the community recovers from a disaster. Such identification can also aid in preparing communities, especially for types of disasters they have not yet encountered.  相似文献