Innovative In-Situ Determination of Unsaturated Hydraulic Properties in Deep Loess Sediments in North-West Bulgaria

2007 ◽  
Author(s):  
Dirk Mallants ◽  
Doncho Karastanev ◽  
Dimitar Antonov ◽  
Janez Perko
Keyword(s):  
Hydraulic Properties ◽  
Large Scale ◽  
Ground Surface ◽  
Time Domain Reflectometry ◽  
Hydraulic Parameters ◽  
Wetting Front ◽  
Field Scale ◽  
North West ◽  
Infiltration Tests ◽  
Migration Pathways

In the framework of selecting a suitable site for final disposal of low- and intermediate level short-lived radioactive waste (LILW-SL) in Bulgaria, site characterization is ongoing at the Marichin Valog site, North-West Bulgaria. The site is characterized by a complex sequence of loess, clayey gravel, and clay layers, of which the first 30–40 m are unsaturated. Proper knowledge about unsaturated water flow and concomittant radionuclide transport is key input to safety assessment calculations. Constant-head infiltrometer tests were carried out at several meters below ground surface to determine the unsaturated hydraulic properties of silty loess, clayey loess, and clayey gravel layers. Individual infiltrometers were equipped with 0.5-m-long filter sections; the shallowest filter was from 2 to 2.5 m depth, whereas the deepest was from 9.5 to 10 m depth. Infiltration tests provided data on cumulative infiltration and progression of the wetting front in the initially unsaturated sediments surrounding the infiltrometer. A cylindrical time-domain reflectometry TRIME probe was used to measure water content variations with time during progression of the wetting front. Access tubes for the TRIME probe were installed at 0.3 to 0.5 m from the infiltrometer tubes. By means of an inverse optimization routine implemented in the finite element code HYDRUS-2D, field-scale soil hydraulic parameters were derived for all layers. Results show a great consistency in the optimized parameter values, although the test sites were several meters apart. Apparently the size of the affected volume of soil was large enough to reduce the effect of spatial variability and to produce average field-scale hydraulic parameters that are relevant for large-scale predictions of flow patterns and radionuclide migration pathways.

Feldspathic sandstone addition and its impact on hydraulic properties of sandy soil

2018 ◽  
Vol 98 (3) ◽  
pp. 399-406 ◽  
Author(s):  
Junchao Jia ◽  
Pingping Zhang ◽  
Xiaofeng Yang ◽  
Xingchang Zhang
Keyword(s):  
Sandy Soil ◽  
Hydraulic Properties ◽  
Field Capacity ◽  
Water Retention Curve ◽  
Hydraulic Parameters ◽  
Wetting Front ◽  
Land Restoration ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Feldspathic Sandstone

Feldspathic sandstone could be used as an effective conditioner to improve the physical quality of sandy soil, and increase the crop yield there. To determine the effects of feldspathic sandstone content on soil hydraulic properties in a sandy soil, the present study added 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% (no sandy soil) of feldspathic sandstone to sandy soil. Changes in hydraulic parameters were investigated and the results showed addition of feldspathic sandstone increased saturated water content by 37%–61% and field capacity by 29%–44%, and decreased saturated hydraulic conductivity from 10.19 to 0.58 cm h−1 of the sandy soil. Further data analysis demonstrated that with increasing content of feldspathic sandstone, the parameter n of soil water retention curve in Van Genuchten model dropped from 1.807 to 1.333. The same decreasing trend is detected in parameter a of infiltration rate (3.841–0.703) in Kostiakov formula (i = at−b) and parameter a1 of wetting front (6.901–1.174) in the empirical equation (X = a1tb1). In terms of hydraulic parameters, 40% feldspathic sandstone and 60% sandy soil, optimally matching indices of loess soil, were the best mixing ratio for sandy land restoration.

scholarly journals Field-scale apparent hydraulic parameterisation obtained from TDR time series and inverse modelling

2009 ◽  
Vol 13 (10) ◽  
pp. 1953-1966 ◽  
Author(s):  
U. Wollschläger ◽  
T. Pfaff ◽  
K. Roth
Keyword(s):  
Time Series ◽  
Hydraulic Properties ◽  
Past Research ◽  
Time Domain Reflectometry ◽  
Inverse Modelling ◽  
Soil Conditions ◽  
Small Scale ◽  
Field Scale ◽  
Time Period ◽  
One Year

Abstract. Due to the large heterogeneity in the hydraulic properties of natural soils, estimation of field-scale hydraulic parameters is difficult. Past research revealed that data from accurate but small-scale laboratory measurements could hardly ever be transferred to the field scale. In this study, we explore an alternative approach where apparent hydraulic properties of a layered soil profile are directly estimated from hydraulic inverse modelling of a time series of in situ measured soil water contents obtained from time domain reflectometry. The data covered a one-year period with both wet and dry soil conditions. For the time period used for inversion, the model is able to reproduce the general evolution of water content in the different soil layers reasonably well. However, distinct drying and wetting events could not be reproduced in detail which we explain by the complicated natural processes that are not fully represented in the rather simple model. The study emphasises the importance of a correct average representation of the soil-atmosphere interaction.

scholarly journals Field scale effective hydraulic parameterisation obtained from TDR time series and inverse modelling

2009 ◽  
Vol 6 (2) ◽  
pp. 1489-1522 ◽  
Author(s):  
U. Wollschläger ◽  
T. Pfaff ◽  
K. Roth
Keyword(s):  
Time Series ◽  
Hydraulic Properties ◽  
Preferential Flow ◽  
Time Domain Reflectometry ◽  
Inverse Modelling ◽  
Soil Conditions ◽  
Small Scale ◽  
Field Scale ◽  
Time Period

Abstract. Due to the large heterogeneity in the hydraulic properties of natural soils, estimation of field scale effective hydraulic parameters is difficult. Past research revealed that data from accurate but small scale laboratory measurements could hardly ever be transferred to the field scale. In this study, we explore an alternative approach where hydraulic properties of a layered soil profile are directly estimated from hydraulic inverse modelling using a time series of in situ measured soil water contents obtained from time domain reflectometry. Simulations were conducted for natural boundary conditions and run for a one-year time period including both wet and dry soil conditions. For the time period used for inversion, the model is able to reproduce the general evolution of water content in the different soil layers reasonably well. However, distinct drying and wetting events could not be reproduced in detail which we explain by the complex natural processes that are not included in the rather simple model, e.g. an accurate site-specific representation of the evapotranspiration process and, potentially, preferential flow. The study emphasizes the importance of a correct representation of the various processes occuring in the soil-plant-atmosphere continuum. Still, we conclude that – for time periods where measured data for calibration are available – this simple estimation of effective hydraulic properties from in situ data is a good approach to obtain effective parameters for describing unsaturated water movement in field soils which are not dominated by complex processes like preferential flow.

scholarly journals Experimental investigation to characterize simple versus multi scaling analysis of hydraulic conductivity at a mesoscale

2021 ◽  
Author(s):  
Guglielmo Federico Antonio Brunetti ◽  
Samuele De Bartolo ◽  
Carmine Fallico ◽  
Ferdinando Frega ◽  
Maria Fernanda Rivera Velásquez ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Spatial Variability ◽  
Hydraulic Properties ◽  
Scaling Laws ◽  
Scaling Analysis ◽  
Field Scale ◽  
Porous Formation ◽  
Proper Design ◽  
First Time

AbstractThe spatial variability of the aquifers' hydraulic properties can be satisfactorily described by means of scaling laws. The latter enable one to relate the small (typically laboratory) scale to the larger (typically formation/regional) ones, therefore leading de facto to an upscaling procedure. In the present study, we are concerned with the spatial variability of the hydraulic conductivity K into a strongly heterogeneous porous formation. A strategy, allowing one to identify correctly the single/multiple scaling of K, is applied for the first time to a large caisson, where the medium was packed. In particular, we show how to identify the various scaling ranges with special emphasis on the determination of the related cut-off limits. Finally, we illustrate how the heterogeneity enhances with the increasing scale of observation, by identifying the proper law accounting for the transition from the laboratory to the field scale. Results of the present study are of paramount utility for the proper design of pumping tests in formations where the degree of spatial variability of the hydraulic conductivity does not allow regarding them as “weakly heterogeneous”, as well as for the study of dispersion mechanisms.

scholarly journals Measurement of unsaturated meltwater percolation flux in seasonal snowpack using self-potential

2021 ◽  
pp. 1-16
Author(s):  
Wilson S. Clayton
Keyword(s):  
Method Development ◽  
Water Saturation ◽  
Field Measurements ◽  
Time Domain Reflectometry ◽  
Electrode Spacing ◽  
Glacier Mass Balance ◽  
Wetting Front ◽  
Electrical Field Strength ◽  
Water Redistribution ◽  
Self Potential

Abstract This paper presents a feasibility study of in situ field measurements of unsaturated meltwater percolation flux within the vertical profile of a snowpack, using the self-potential (SP) method. On-site snowmelt column tests calibrated the SP measurements. The SP data measured electrical field strength with an electrode spacing of 20 cm, and coincident water saturation (Sw) measurements using time domain reflectometry allowed calculation of SP-modeled vertical percolation flux (qsp), expressed as Darcy velocity. The results reflected transient diurnal snowmelt dynamics, with peak flux lagging arrival of a saturation wetting front. Peak daily qsp was 60 to >300 mm d−1, whereas daily snowmelt was 20–50 mm w.e. Surface refreezing events appeared to cause upward flow, possibly representing water redistribution toward the freezing boundary. Calculated fluxes were comparable to actual fluxes, although average errors ranged from −15 to +46% compared to average of melt expected from surface energy-balance and ablation stake measurements. By advancing method development to measure unsaturated meltwater percolation flux in snowpacks this study creates opportunities to study fundamental snowmelt processes, may improve mathematical modeling and may supplement glacier mass-balance studies and studies of snowmelt interactions with avalanches, groundwater and surface water.

scholarly journals On the effects of membrane viscosity on transient red blood cell dynamics

Soft Matter ◽  
2020 ◽  
Vol 16 (26) ◽  
pp. 6191-6205 ◽  
Author(s):  
Fabio Guglietta ◽  
Marek Behr ◽  
Luca Biferale ◽  
Giacomo Falcucci ◽  
Mauro Sbragaglia
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Blood Circulation ◽  
Hydraulic Properties ◽  
Large Scale ◽  
Mechanical Response ◽  
Cell Dynamics ◽  
Membrane Viscosity

Computational Fluid Dynamics is currently used to design and improve the hydraulic properties of biomedical devices, wherein the large scale blood circulation needs to be simulated by accounting for the mechanical response of RBCs at the mesoscale.

scholarly journals Fishing out collective memory of migratory schools

2014 ◽  
Vol 11 (95) ◽  
pp. 20140043 ◽  
Author(s):  
Giancarlo De Luca ◽  
Patrizio Mariani ◽  
Brian R. MacKenzie ◽  
Matteo Marsili
Keyword(s):  
Collective Memory ◽  
Large Scale ◽  
Group Formation ◽  
Individual Preference ◽  
Relative Number ◽  
Collective Behaviour ◽  
Control Group ◽  
Adaptive Networks ◽  
Modelling Framework ◽  
Migration Pathways

Animals form groups for many reasons, but there are costs and benefits associated with group formation. One of the benefits is collective memory. In groups on the move, social interactions play a crucial role in the cohesion and the ability to make consensus decisions. When migrating from spawning to feeding areas, fish schools need to retain a collective memory of the destination site over thousands of kilometres, and changes in group formation or individual preference can produce sudden changes in migration pathways. We propose a modelling framework, based on stochastic adaptive networks, that can reproduce this collective behaviour. We assume that three factors control group formation and school migration behaviour: the intensity of social interaction, the relative number of informed individuals and the strength of preference that informed individuals have for a particular migration area. We treat these factors independently and relate the individuals’ preferences to the experience and memory for certain migration sites. We demonstrate that removal of knowledgeable individuals or alteration of individual preference can produce rapid changes in group formation and collective behaviour. For example, intensive fishing targeting the migratory species and also their preferred prey can reduce both terms to a point at which migration to the destination sites is suddenly stopped. The conceptual approaches represented by our modelling framework may therefore be able to explain large-scale changes in fish migration and spatial distribution.

SPATIAL LAYOUT OF THE SOVIET UNION TIMBER PROCESSING COMPLEX: THE IDEA BEHIND THE FIRST FIVE-YEAR PLAN

2021 ◽  
Vol 7 (3) ◽  
pp. 131-154
Author(s):  
Ivan V. ZYKIN
Keyword(s):  
Soviet Union ◽  
Large Scale ◽  
Far East ◽  
Spatial Layout ◽  
Capital Investments ◽  
Wood Industry ◽  
North West ◽  
The North ◽  
The Soviet Union ◽  
Central Regions

During the years of Soviet power, principal changes took place in the country’s wood industry, including in spatial layout development. Having the large-scale crisis in the industry in the late 1980s — 2000s and the positive changes in its functioning in recent years and the development of an industry strategy, it becomes relevant to analyze the experience of planning the spatial layout of the wood industry during the period of Stalin’s modernization, particularly during the first five-year plan. The aim of the article is to analyze the reason behind spatial layout of the Soviet wood industry during the implementation of the first five-year plan. The study is based on the modernization concept. In our research we conducted mapping of the wood industry by region as well as of planned construction of the industry facilities. It was revealed that the discussion and development of an industrialization project by the Soviet Union party-state and planning agencies in the second half of the 1920s led to increased attention to the wood industry. The sector, which enterprises were concentrated mainly in the north-west, west and central regions of the country, was set the task of increasing the volume of harvesting, export of wood and production to meet the domestic needs and the export needs of wood resources and materials. Due to weak level of development of the wood industry, the scale of these tasks required restructuring of the branch, its inclusion to the centralized economic system, the direction of large capital investments to the development of new forest areas and the construction of enterprises. It was concluded that according to the first five-year plan, the priority principles for the spatial development of the wood industry were the approach of production to forests and seaports, intrasectoral and intersectoral combining. The framework of the industry was meant to strengthen and expand by including forests to the economic turnover and building new enterprises in the European North and the Urals, where the main capital investments were sent, as well as in the Vyatka region, Transcaucasia, Siberia and the Far East.

Systematic Position of Pistacia atlantica Desf. Subsp. atlantica in North-West Algeria: Anatomy and Biometry of Leaves

2020 ◽  
Vol 4 (1) ◽  
pp. 48-53
Author(s):  
Mohamed Amara ◽  
Mohammed Bouazza ◽  
Kheira Errouane ◽  
Meriem Kaid-Harche ◽  
Djamel Nafil ◽  
...  
Keyword(s):  
Natural Resources ◽  
Large Scale ◽  
Systematic Position ◽  
Pistacia Atlantica ◽  
North West ◽  
Anthropic Activity ◽  
West Algeria

Abstract The area of Algerian western north already subjected to a strong climatic rigour and an excessive anthropic activity for several decades, has been confronted with the threats of the alarming degradation of its natural resources, following the example Pistacia atlantica which occupies today only one quite thin proportion of the territory. The study method was based on the phytoecological approach on a very large scale by approaching the anatomical and biometric study of the leaves of Pistacia atlantica in order to identify and confirm the name of the subspecies. The analysis of the results obtained revealed that this subspeciesis atlantica, phenotypically very variable.

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