Monthly streamflow forecasting using neuro-wavelet techniques and input analysis     

André Gustavo da Silva Melo Honorato  Gustavo Barbosa Lima da Silva  Celso Augusto Guimarães Santos 《水文科学杂志》2013,58(15-16):2060-2075

ABSTRACT

Combinations of low-frequency components (also known as approximations) resulting from the wavelet decomposition are tested as inputs to an artificial neural network (ANN) in a hybrid approach, and compared to classical ANN models for flow forecasting for 1, 3, 6 and 12 months ahead. In addition, the inputs are rewritten in terms of the flow, revealing what type of information was being provided to the network, in order to understand the effect of the approximations on the forecasting performance. The results show that the hybrid approach improved the accuracy of all tested models, especially for 1, 3 and 6 months ahead. The input analyses show that high-frequency components are more important for shorter forecast horizons, while for longer horizons, they may worsen the model accuracy.  相似文献   

Improvement of streams hydro‐geomorphological assessment using LiDAR DEMs     

Pascale M. Biron  Guénolé Choné  Thomas Buffin‐Bélanger  Sylvio Demers  Taylor Olsen 《地球表面变化过程与地形》2013,38(15):1808-1821

Hydro‐geomorphological assessments are an essential component for riverine management plans. They usually require costly and time‐consuming field surveys to characterize the spatial variability of key variables such as flow depth, width, discharge, water surface slope, grain size and unit stream power throughout the river corridor. The objective of this research is to develop automated tools for hydro‐geomorphological assessments using high‐resolution LiDAR digital elevation models (DEMs). More specifically, this paper aims at developing geographic information system (GIS) tools to extract channel slope, width and discharge from 1 m‐resolution LiDAR DEMs to estimate the spatial distribution of unit stream power in two contrasted watersheds in Quebec: a small agricultural stream (Des Fèves River) and a large gravel‐bed river (Matane River). For slope, the centreline extracted from the raw LiDAR DEM was resampled at a coarser resolution using the minimum elevation value. The channel width extraction algorithm progressively increased the centerline from the raw DEM until thresholds of elevation differences and slopes were reached. Based on the comparison with over 4000 differential global positioning system (GPS) measurements of the water surface collected in a 50 km reach of the Matane River, the longitudinal profile and slope estimates extracted from the raw and resampled LiDAR DEMs were in very good agreement with the field measurements (correlation coefficients ranging from 0 · 83 to 0 · 87) and can thus be used to compute stream power. The extracted width also corresponded very well to the channel as seen from ortho‐photos, although the presence of bars in the Matane River increased the level of error in width estimates. The estimated maximum unit stream power spatial patterns corresponded well with field evidence of bank erosion, indicating that LiDAR DEMs can be used with confidence for initial hydro‐geomorphological assessments. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Isolation parameters for improving the seismic performance of irregular bridges     

José M. Jara  Dorian Villanueva  Manuel Jara  Bertha A. Olmos 《Bulletin of Earthquake Engineering》2013,11(2):663-686

Bridge structures are usually built on irregular topographical surfaces which create substructures with different pier heights and non uniform stiffness distribution. Three irregularity types of typical reinforced concrete (RC) medium length bridges located in a high seismicity zone of Mexico, were analyzed aimed at determining the best strength and stiffness parameters of an isolation system. The isolation system is composed by lead rubber bearings (LRB) located on each pile and abutment. The variation of the bridge characteristics and the isolation parameters produced 169 models that were subjected to ten seismic records representative of the subduction zone in the Pacific Coast of Mexico. A total of 1690 nonlinear time history analyses (NLTHA) were carried out in longitudinal and transverse directions of the structures. The maximum pier drifts, bending moments and shear forces demands were analyzed to identify the best isolation properties for reducing the concentration of damage in one or two elements and for improving the structural behavior of irregular bridges. Additionally, the analysis of the seismic response of the bridges supported on traditional neoprene bearings was carried out.  相似文献   

The changing rotational excitation of C3 in comet 9P/Tempel 1 during Deep Impact     

Máté Ádámkovics  Imke de Pater  Hy Spinrad 《Astrophysics and Space Science》2012,342(2):309-315

The 4050 Å band of C₃ was observed with Keck/HIRES echelle spectrometer during the Deep Impact encounter. We perform a 2-dimensional analysis of the exposures in order to study the spatial, spectral, and temporal changes in the emission spectrum of C₃. The rotational population distribution changes after impact, beginning with an excitation temperature of ～45 K at impact and increasing for 2 hr up to a maximum of 61±5 K. From 2 to 4 hours after impact, the excitation temperature decreases to the pre-impact value. We measured the quiescent production rate of C₃ before the encounter to be 1.0×10²³ s^?1, while 2 hours after impact we recorded a peak production rate of 1.7×10²³ s^?1. Whereas the excitation temperature returned to the pre-impact value during the observations, the production rate remained elevated, decreasing slowly, until the end of the 4 hr observations. These results are interpreted in terms of changing gas densities in the coma and short-term changes in the primary chemical production mechanism for C₃.  相似文献   

Numerical modelling: a useful tool to simulate collapsing volcanoes     

Solène Pouget  Tim Davies  Ben Kennedy  Karim Kelfoun  Hervé Leyrit 《Geology Today》2012,28(2):59-63

Since the nineteenth century scientists have tried to reproduce natural events in order to study and understand them through the technique of modelling. However, technology has evolved rapidly in the past two decades and now sophisticated numerical models are widely used to reproduce past events or simulate new scenarios. These models are particularly useful to reproduce the large scale and complexity of geological events. To illustrate the use and potential of numerical modelling in geological sciences, we describe a simulation of a large debris avalanche caused by the collapse of the north flank of the Taranaki volcano in New Zealand and the value of this information in the context of disaster planning.  相似文献   

On viscoplastic regularisation of strain-softening rocks and soils     

René de Borst  Thibault Duretz 《国际地质力学数值与分析法杂志》2020,44(6):890-903

Constitutive models for rocks and soils typically incorporate some form of strain softening. Moreover, many plasticity models for frictional materials use a nonassociated flow rule. Strain softening and nonassociated flow rules can cause loss of well-posedness of the initial-value problem, which can lead to a severe mesh dependence in simulations and poor convergence of the iterative solution procedure. The inclusion of viscosity, which is a common property of materials, seems a natural way to restore well-posedness, but the mathematical properties of a rate-dependent model, and therefore the effectiveness with respect to the removal of mesh dependence, can depend strongly on how the viscous element is incorporated. Herein, we show that rate-dependent models, which are commonly applied to problems in the Earth's lithosphere, such as plate tectonics, are very different from the approach typically adopted for more shallow geotechnical engineering problems. We analyse the properties of these models under dynamic loadings, using dispersion analyses and one-dimensional finite difference analyses, and complement them with two-dimensional simulations of a typical strain localisation problem under quasi-static loading conditions. Finally, we point out that a combined model, which features two viscous elements, may be the best way forward for modelling time-dependent failure processes in the deeper layers of the Earth, since it not only enables modelling of the creep characteristics typical of long-term behaviour but also regularises the initial/boundary-value problem.  相似文献   

Comparisons between marine productivity and terrestrial input records in the Gulf of California over the last 28 ka     

Elsa Arellano-Torres  Astrid J. Mora-Rivera  Paola Vázquez-Romero  Enrique H. Nava-Sánchez  Juan José Kasper-Zubillaga  M. Socorro Lozano-García 《第四纪科学杂志》2020,35(3):479-491

We study the marine and terrestrial contributions in the Gulf of California (GC) to understand the relationship between continental climate and oceanographic variability over the last 28 ka. In Core AII125-8-JPC-20, we examine aeolian and riverine inputs as nutrients for biological productivity. We use biogenic silica (%opal), total organic carbon (%TOC) and calcium carbonate (%CaCO₃) as proxies for primary productivity, and lithic fraction distributions as proxies for terrigenous transport. At the core site, biogenic and lithic components are in phase at millennial-scale in response to regional climate conditions. During the Late Pleistocene, the GC shelf area was above sea level and the western margin showed transient episodes of increased fluvial inputs. Episodic increases in %opal and reduced %TOC suggest upwelling events but ineffective C-export to the sediment. During stadial events (Heinrich 2, Heinrich 1, Younger Dryas), regional declines in %opal, but increases in %CaCO₃ and TOC, suggest efficient C-export by carbonate organisms. During most of the Holocene, dust inputs are higher. Episodic increases in %TOC suggest higher C-accumulation, although this is not controlled by siliceous or calcareous organisms. In the GC, besides upwelling and current advection, nutrient inputs driven by terrestrial climate have an impact on the biological C-pump. © 2020 John Wiley & Sons, Ltd.  相似文献   

Tracer hydrology of the data-scarce and heterogeneous Central American Isthmus     

Ricardo Sánchez-Murillo  Germain Esquivel-Hernández  José L. Corrales-Salazar  Laura Castro-Chacón  Ana M. Durán-Quesada  Manuel Guerrero-Hernández  Valeria Delgado  Javier Barberena  Katia Montenegro-Rayo  Heyddy Calderón  Carlos Chevez  Tania Peña-Paz  Saúl García-Santos  Pedro Ortiz-Roque  Yaneth Alvarado-Callejas  Laura Benegas  Antonio Hernández-Antonio  Marcela Matamoros-Ortega  Lucia Ortega  Stefan Terzer-Wassmuth 《水文研究》2020,34(11):2660-2675

Numerous socio-economic activities depend on the seasonal rainfall and groundwater recharge cycle across the Central American Isthmus. Population growth and unregulated land use changes resulted in extensive surface water pollution and a large dependency on groundwater resources. This work combines stable isotope variations in rainfall, surface water, and groundwater of Costa Rica, Nicaragua, El Salvador, and Honduras to develop a regionalized rainfall isoscape, isotopic lapse rates, spatial–temporal isotopic variations, and air mass back trajectories determining potential mean recharge elevations, moisture circulation patterns, and surface water–groundwater interactions. Intra-seasonal rainfall modes resulted in two isotopically depleted incursions (W-shaped isotopic pattern) during the wet season and two enriched pulses during the mid-summer drought and the months of the strongest trade winds. Notable isotopic sub-cloud fractionation and near-surface secondary evaporation were identified as common denominators within the Central American Dry Corridor. Groundwater and surface water isotope ratios depicted the strong orographic separation into the Caribbean and Pacific domains, mainly induced by the governing moisture transport from the Caribbean Sea, complex rainfall producing systems across the N-S mountain range, and the subsequent mixing with local evapotranspiration, and, to a lesser degree, the eastern Pacific Ocean fluxes. Groundwater recharge was characterized by (a) depleted recharge in highland areas (72.3%), (b) rapid recharge via preferential flow paths (13.1%), and enriched recharge due to near-surface secondary fractionation (14.6%). Median recharge elevation ranged from 1,104 to 1,979 m a.s.l. These results are intended to enhance forest conservation practices, inform water protection regulations, and facilitate water security and sustainability planning in the Central American Isthmus.  相似文献   

Accuracy of grid precipitation data for Brazil: application in river discharge modelling of the Tocantins catchment          下载免费PDF全文

José A. F. Monteiro  Michael Strauch  Raghavan Srinivasan  Karim Abbaspour  Björn Gücker 《水文研究》2016,30(9):1419-1430

Here, we compared grid precipitation data — Climate Forecast System Reanalysis (CFSR) and WATCH Forcing Data methodology applied to ERA‐Interim (WFDEI) data — with Brazilian Weather Bureau (INMET) and Brazilian Water Agency (ANA) rain gauge data (n = 2027) for the period 1980–2010 in order to evaluate which grid data set better represents precipitation, and is thus more suitable for hydrological modelling of Brazilian water resources. We found that WFDEI outperformed CFSR according to three statistical indicators. We then applied and interpolated a simple bias correction to further improve WFDEI data before we used these data to model river discharge of the Tocantins catchment with the Soil and Water Assessment Tool (SWAT). Calibration (validation in parentheses; weighted averages of all gauges) had satisfactory statistical metrics: p‐factor = 0.52 (0.47); r‐factor = 0.84 (0.99); R² = 0.78 (0.71); bR² = 0.68 (0.47); NS = 0.70 (0.66); Pbias = ?4.5 (4.0). Finally, the calibrated SWAT model was used to assess the spatial distribution of the catchment's water resources. Annual green water flow (evapotranspiration) increased from the south‐east (640–840 mm yr^?1) to north‐west (1140–1440 mm) of the Tocantins catchment, while green water storage (soil water content) increased from south (330–1070 mm) to north (2180–3290 mm). Blue water (water yield) had a less clear pattern, with lower values in the south and the central borders of the catchment (20–560 mm) and higher values along the central axis and the north (920–1460 mm). Our analysis suggested that WFDEI was an accurate representation of Brazilian precipitation. For large catchments, we therefore recommend the use of WFDEI instead of sparse and often missing rain gauge data in modelling Brazilian water resources. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Ardières-Morcille in the Beaujolais,France: A research catchment dedicated to study of the transport and impacts of diffuse agricultural pollution in rivers     

Véronique Gouy  Lucie Liger  Samira Ahrouch  Chloé Bonnineau  Nadia Carluer  Arnaud Chaumot  Marina Coquery  Aymeric Dabrin  Christelle Margoum  Stéphane Pesce 《水文研究》2021,35(10):e14384

The 8-km² Morcille catchment, which is a sub-catchment of the 150-km² Ardières catchment in the Beaujolais region of France, is one of the first sites in Europe where research has been conducted on surface water contamination by pesticides. A consolidated hydrological and chemical dataset has been set up with data collected since 2002 on the Morcille River and since 2011 on the Ardières River. Additional data on the ecotoxicological and ecological impacts of pesticides on aquatic microbial communities and macroinvertebrates has also been recorded in both rivers since 2005. The ‘Site Atelier Ardières-Morcille Dataset’ described here combines rainfall and stream water height measurements at gauged stations with concentrations of two trace elements and nine pesticides (mainly herbicides, fungicides and some of their metabolites) in both the Ardières and Morcille rivers. All contaminant concentration data showed spatial and temporal variability in water quality associated with pesticide use and rainfall patterns. This long-term monitoring framework made it possible to estimate the persistence of two herbicides (diuron and norflurazon) after legislation banning them. It took 4 years for diuron and more than 10 years for norflurazon concentrations to fall below 0.1 μg/L. Concurrent biological data showed a gradient of impacts consistent with chemical anthropogenic pressure, and rapid recovery of phototrophic microbial communities after the diuron ban. Finally, monitoring data on pesticide transport in a grassed strip set on a slope of the Morcille catchment confirmed that vegetative filter strips can effectively reduce diuron fluxes in surface runoff (>80% abatement) and infiltration water (>70% abatement). The full dataset offers a valuable resource for the validation of hydrological models and the development of global approaches to better understand the pressure–transport–exposure–impact chain and aquatic community resilience at the small catchment scale.  相似文献