Evaluating soil water routing approaches in watershed-scale,ecohydrologic modelling     

Garett Pignotti  Indrajeet Chaubey  Keith Cherkauer  Mark Williams  Melba Crawford 《水文研究》2021,35(3):e14034

Soil water dynamics are central in linking and regulating natural cycles in ecohydrology, however, mathematical representation of soil water processes in models is challenging given the complexity of these interactions. To assess the impacts of soil water simulation approaches on various model outputs, the Soil and Water Assessment Tool was modified to accommodate an alternative soil water percolation method and tested at two geographically and climatically distinct, instrumented watersheds in the United States. Soil water was evaluated at the site scale via measured observations, and hydrologic and biophysical outputs were analysed at the watershed scale. Results demonstrated an improved Kling–Gupta Efficiency of up to 0.3 and a reduction in percent bias from 5 to 25% at the site scale, when soil water percolation was changed from a threshold, bucket-based approach to an alternative approach based on variable hydraulic conductivity. The primary difference between the approaches was attributed to the ability to simulate soil water content above field capacity for successive days; however, regardless of the approach, a lack of site-specific characterization of soil properties by the soils database at the site scale was found to severely limit the analysis. Differences in approach led to a regime shift in percolation from a few, high magnitude events to frequent, low magnitude events. At the watershed scale, the variable hydraulic conductivity-based approach reduced average annual percolation by 20–50 mm, directly impacting the water balance and subsequently biophysical predictions. For instance, annual denitrification increased by 14–24 kg/ha for the new approach. Overall, the study demonstrates the need for continued efforts to enhance soil water model representation for improving biophysical process simulations.  相似文献   

Perceptual models of uncertainty for socio-hydrological systems: a flood risk change example     

Ida K. Westerberg  Keith J. Beven  Gemma Coxon  Tobias Krueger 《水文科学杂志》2020,65(Z2):1705-1713

ABSTRACT

Characterizing, understanding and better estimating uncertainties are key concerns for drawing robust conclusions when analyzing changing socio-hydrological systems. Here we suggest developing a perceptual model of uncertainty that is complementary to the perceptual model of the socio-hydrological system and we provide an example application to flood risk change analysis. Such a perceptual model aims to make all relevant uncertainty sources – and different perceptions thereof – explicit in a structured way. It is a first step to assessing uncertainty in system outcomes that can help to prioritize research efforts and to structure dialogue and communication about uncertainty in interdisciplinary work.  相似文献   

Multibeam sonar backscatter data processing     

Alexandre C. G. Schimel  Jonathan Beaudoin  Iain M. Parnum  Tim Le Bas  Val Schmidt  Gordon Keith  Daniel Ierodiaconou 《Marine Geophysical Researches》2018,39(1-2):121-137

Multibeam sonar systems now routinely record seafloor backscatter data, which are processed into backscatter mosaics and angular responses, both of which can assist in identifying seafloor types and morphology. Those data products are obtained from the multibeam sonar raw data files through a sequence of data processing stages that follows a basic plan, but the implementation of which varies greatly between sonar systems and software. In this article, we provide a comprehensive review of this backscatter data processing chain, with a focus on the variability in the possible implementation of each processing stage. Our objective for undertaking this task is twofold: (1) to provide an overview of backscatter data processing for the consideration of the general user and (2) to provide suggestions to multibeam sonar manufacturers, software providers and the operators of these systems and software for eventually reducing the lack of control, uncertainty and variability associated with current data processing implementations and the resulting backscatter data products. One such suggestion is the adoption of a nomenclature for increasingly refined levels of processing, akin to the nomenclature adopted for satellite remote-sensing data deliverables.  相似文献   

Recharge and Groundwater Flow Within an Intracratonic Basin,Midwestern United States          下载免费PDF全文

Samuel V. Panno  Zohreh Askari  Walton R. Kelly  Thomas M. Parris  Keith C. Hackley 《Ground water》2018,56(1):32-45

The conservative nature of chloride (Cl^?) in groundwater and the abundance of geochemical data from various sources (both published and unpublished) provided a means of developing, for the first time, a representation of the hydrogeology of the Illinois Basin on a basin‐wide scale. The creation of Cl^? isocons superimposed on plan view maps of selected formations and on cross sections across the Illinois Basin yielded a conceptual model on a basin‐wide scale of recharge into, groundwater flow within and through the Illinois Basin. The maps and cross sections reveal the infiltration and movement of freshwater into the basin and dilution of brines within various geologic strata occurring at basin margins and along geologic structures. Cross‐formational movement of brines is also seen in the northern part of the basin. The maps and cross sections also show barriers to groundwater movement created by aquitards resulting in areas of apparent isolation/stagnation of concentrated brines within the basin. The distribution of Cl^? within the Illinois Basin suggests that the current chemical composition of groundwater and distribution of brines within the basin is dependent on five parameters: (1) presence of bedrock exposures along basin margins; (2) permeability of geologic strata and their distribution relative to one another; (3) presence or absence of major geologic structures; (4) intersection of major waterways with geologic structures, basin margins, and permeable bedrock exposures; and (5) isolation of brines within the basin due to aquitards, inhomogeneous permeability, and, in the case of the deepest part of the basin, brine density effects.  相似文献   

A method for uncertainty constraint of catchment discharge and phosphorus load estimates          下载免费PDF全文

Michael J. Hollaway  Keith J. Beven  Clare Mc W. H. Benskin  Adrian L. Collins  Robert Evans  Peter D. Falloon  Kirsty J. Forber  Kevin M. Hiscock  Ron Kahana  Christopher J. A. Macleod  Mary C. Ockenden  Martha L. Villamizar  Catherine Wearing  Paul J. A. Withers  Jian G. Zhou  Nicholas J. Barber  Philip M. Haygarth 《水文研究》2018,32(17):2779-2787

River discharge and nutrient measurements are subject to aleatory and epistemic uncertainties. In this study, we present a novel method for estimating these uncertainties in colocated discharge and phosphorus (P) measurements. The “voting point”‐based method constrains the derived stage‐discharge rating curve both on the fit to available gaugings and to the catchment water balance. This helps reduce the uncertainty beyond the range of available gaugings and during out of bank situations. In the example presented here, for the top 5% of flows, uncertainties are shown to be 139% using a traditional power law fit, compared with 40% when using our updated “voting point” method. Furthermore, the method is extended to in situ and lab analysed nutrient concentration data pairings, with lower uncertainties (81%) shown for high concentrations (top 5%) than when a traditional regression is applied (102%). Overall, for both discharge and nutrient data, the method presented goes some way to accounting for epistemic uncertainties associated with nonstationary physical characteristics of the monitoring site.  相似文献   

A New Wavelet Method for Identification of Eddies and Assessment of Incidents on Islands of the Eastern Caribbean     

Jason D. Tambie  Madiha Farag-Miller  Keith Miller  Bheshem Ramlal  Michael Sutherland 《Marine Geodesy》2019,42(3):227-245

Using two dimensional continuous wavelet transforms, a novel method for identification of mesoscale eddies is presented to facilitate extraction of characteristics for area, amplitude, type, and location from maps of sea level anomalies. In comparison with the previously established growing method for eddy identification, it is found that the wavelet method identifies more than twice the number of eddies and is particularly better at resolving small eddies down to the 0.25 degree resolution of the data. Such research into eddy identification and tracking is significant to the assessment of eddies with potential to impact on coastlines of small islands. The method is applied to the identification of eddies on tracks towards islands of the Eastern Caribbean over 23?years. Spatial and temporal variation in rate of occurrence and magnitude is established. For Barbados there is an average of 9 anticyclonic incidents a year with maximum amplitude of typically 0.22?m in the dry seasons and 0.16?m in the wet seasons. Seasonal variation is reversed for the other islands with twice the number of anticyclonic incidents having maximum amplitudes of about 0.20?m annually.  相似文献   

Changes in monthly baseflow across the U.S. Midwest   总被引：1，自引：0，他引：1  

Jessica R. Ayers  Gabriele Villarini  Christopher Jones  Keith Schilling 《水文研究》2019,33(5):748-758

Characterizing streamflow changes in the agricultural U.S. Midwest is critical for effective planning and management of water resources throughout the region. The objective of this study is to determine if and how baseflow has responded to land alteration and climate changes across the study area during the 50‐year study period by exploring hydrologic variations based on long‐term stream gage data. This study evaluates monthly contributions to annual baseflow along with possible trends over the 1966–2016 period for 458 U.S. Geological Survey streamflow gages within 12 different Midwestern states. It also examines the influence of climate and land use factors on the observed baseflow trends. Monthly contribution breakdowns demonstrate how the majority of baseflow is discharged into streams during the spring months (March, April, and May) and is overall more substantial throughout the spring (especially in April) and summer (June, July, and August). Baseflow has not remained constant over the study period, and the results of the trend detection from the Mann–Kendall test reveal that baseflows have increased and are the strongest from May to September. This analysis is confirmed by quantile regression, which suggests that for most of the year, the largest changes are detected in the central part of the distribution. Although increasing baseflow trends are widespread throughout the region, decreasing trends are few and limited to Kansas and Nebraska. Further analysis reveals that baseflow changes are being driven by both climate and land use change across the region. Increasing trends in baseflow are linked to increases in precipitation throughout the year and are most prominent during May and June. Changes in agricultural intensity (in terms of harvested corn and soybean acreage) are linked to increasing trends in the central and western Midwest, whereas increasing temperatures may lead to decreasing baseflow trends in spring and summer in northern Wisconsin, Kansas, and Nebraska.  相似文献   

Changes in the Geometry and Volume of Rabots glaciär,Sweden, 2003–2011: Recent Accelerated Volume Loss Linked to More Negative Summer Balances          下载免费PDF全文

Keith A. Brugger  Latysha Pankratz 《Geografiska Annaler: Series A, Physical Geography》2015,97(2):265-278

Terminus geometry, ice margins, and surface elevations on Rabots glaciär were measured using differential GPS during summer 2011 and compared with those similarly measured in 2003. Glacier length over the eight years decreased by ～105 m corresponding to 13 m a^?1, a rate consistent with ice recession over the last several decades. Measured changes in surface elevations show that between 2003 and 2011 the glacier's volume decreased by ～27.6 ± 2.6 × 10⁶ m³, or 3.5 ± 0.3 × 10⁶ m³ a^?1. This compares favorably with an estimate of ?28.1 ± 2.6 × 10⁶ m³ based on a mass‐balance approach. The rate of volume loss appears, however, to have significantly increased after 2003, being substantially greater than rates determined for the intervals 1959–80, 1980–89, and 1989–2003. This increase corresponds to a sustained interval of more negative summer balances. Previous work suggests that as of 2003 Rabots glaciär had not yet completed its response to a ～1°C warming that occurred c. 1900, and thus the current marked increase rate of ice loss might reflect the effect of recent, or accelerated regional warming that occurred during the last decade superimposed on its continued response to that earlier warming.  相似文献   

On the use of IPCC-class models to assess the impact of climate on Living Marine Resources     

Charles A. Stock  Michael A. Alexander  Nicholas A. Bond  Keith M. Brander  William W.L. Cheung  Enrique N. Curchitser  Thomas L. Delworth  John P. Dunne  Stephen M. Griffies  Melissa A. Haltuch  Jonathan A. Hare  Anne B. Hollowed  Patrick Lehodey  Simon A. Levin  Jason S. Link  Kenneth A. Rose  Ryan R. Rykaczewski  Jorge L. Sarmiento  Ronald J. Stouffer  Franklin B. Schwing  Francisco E. Werner 《Progress in Oceanography》2011,88(1-4):1-27

The study of climate impacts on Living Marine Resources (LMRs) has increased rapidly in recent years with the availability of climate model simulations contributed to the assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Collaboration between climate and LMR scientists and shared understanding of critical challenges for such applications are essential for developing robust projections of climate impacts on LMRs. This paper assesses present approaches for generating projections of climate impacts on LMRs using IPCC-class climate models, recommends practices that should be followed for these applications, and identifies priority developments that could improve current projections. Understanding of the climate system and its representation within climate models has progressed to a point where many climate model outputs can now be used effectively to make LMR projections. However, uncertainty in climate model projections (particularly biases and inter-model spread at regional to local scales), coarse climate model resolution, and the uncertainty and potential complexity of the mechanisms underlying the response of LMRs to climate limit the robustness and precision of LMR projections. A variety of techniques including the analysis of multi-model ensembles, bias corrections, and statistical and dynamical downscaling can ameliorate some limitations, though the assumptions underlying these approaches and the sensitivity of results to their application must be assessed for each application. Developments in LMR science that could improve current projections of climate impacts on LMRs include improved understanding of the multi-scale mechanisms that link climate and LMRs and better representations of these mechanisms within more holistic LMR models. These developments require a strong baseline of field and laboratory observations including long time series and measurements over the broad range of spatial and temporal scales over which LMRs and climate interact. Priority developments for IPCC-class climate models include improved model accuracy (particularly at regional and local scales), inter-annual to decadal-scale predictions, and the continued development of earth system models capable of simulating the evolution of both the physical climate system and biosphere. Efforts to address these issues should occur in parallel and be informed by the continued application of existing climate and LMR models.  相似文献   

Modelling of elastic damping in nonlinear time-history analyses of cantilever RC walls     

Eleni Smyrou  M. J. Nigel Priestley  Athol J. Carr 《Bulletin of Earthquake Engineering》2011,9(5):1559-1578

Damping constitutes a major source of uncertainty in dynamic analysis and an open issue to experimental and analytical research. After a thorough review of the current views and approaches existing in literature on damping and its appropriate modelling, this paper focuses on the implications of the available modelling options on analysis. As result of a series of considerations, a damping modelling solution for nonlinear dynamic analyses of cantilever RC walls is suggested within the frame of Direct Displacement-Based Design, supported by comparative analyses on wall structures.  相似文献