scholarly journals Big and small: menisci in soil pores affect water pressures, dynamics of groundwater levels, and catchment-scale average matric potentials

2010 ◽  
Vol 7 (5) ◽  
pp. 6491-6523
Author(s):  
G. H. de Rooij
Keyword(s):  
Soil Water ◽  
Large Scale ◽  
Soil Surface ◽  
Subsurface Water ◽  
Vertical Position ◽  
Pore Scale ◽  
Catchment Scale ◽  
Matric Potential ◽  
Groundwater Levels ◽  
Interface Curvature

Abstract. Soil water is confined behind the menisci of its water-air interface. Catchment-scale fluxes (groundwater recharge, evaporation, transpiration, precipitation, etc.) affect the matric potential, and thereby the interface curvature and the configuration of the phases. In turn, these affect the fluxes (except precipitation), creating feedbacks between pore-scale and catchment-scale processes. Tracking pore-scale processes beyond the Darcy scale is not feasible. Instead, for a simplified system based on the classical Darcy's Law and Laplace-Young Law we i) clarify how menisci transfer pressure from the atmosphere to the soil water, ii) examine large-scale phenomena arising from pore-scale processes, and iii) analyze the relationship between average meniscus curvature and average matric potential. In stagnant water, changing the gravitational potential or the curvature of the air-water interface changes the pressure throughout the water. Adding small amounts of water can thus profoundly affect water pressures in a much larger volume. The pressure-regulating effect of the interface curvature showcases the meniscus as a pressure port that transfers the atmospheric pressure to the water with an offset directly proportional to its curvature. This property causes an extremely rapid rise of phreatic levels in soils once the capillary fringe extends to the soil surface and the menisci flatten. For large bodies of subsurface water, the curvature and vertical position of any meniscus quantify the uniform hydraulic potential under hydrostatic equilibrium. During unit-gradient flow, the matric potential corresponding to the mean curvature of the menisci should provide a good approximation of the intrinsic phase average of the matric potential.

Renewal of a national soil water management category system and legacy map by data mining methods, digital primary and hydrological soil property maps

2020 ◽  
Author(s):  
Brigitta Szabó ◽  
Annamária Laborczi ◽  
Gábor Szatmári ◽  
Zsófia Bakacsi ◽  
András Makó ◽  
...  
Keyword(s):  
Water Management ◽  
Hydraulic Conductivity ◽  
Soil Water ◽  
Large Scale ◽  
Soil Property ◽  
Spatial Information ◽  
Pedotransfer Functions ◽  
Catchment Scale ◽  
Category System ◽  
Soil Hydraulic

<p>Soil physical properties and soil water regime have been in the focus of soil surveys and mapping in Hungary due to their importance in various environmental processes and hazards, like waterlogging and drought, which endanger extended areas. <br>In the late ‘70s a category system was elaborated for the planning of water management, which was used as the legend of a nationwide map prepared at a scale of 1:500.000. Soils were characterized qualitatively (e.g.: soil with unfavorable water management was defined with low infiltration rate, very low permeability and hydraulic conductivity, and high water retention), without quantification of these features. The category system was also used for creating large-scale (1:10.000) water management maps, which are contained legally by expert’s reports prepared on the subject of drainage, irrigation, liquid manure, sewage or sewage-sludge disposal. These maps were prepared eventually, essentially for individual plots and are not managed centrally and are not available for further applications.<br>Recently a 3D Soil Hydraulic Database was elaborated for Europe at 250 m resolution based on specific pedotransfer functions and soil property maps of SoilGrids. The database includes spatial information on the soil water content at the most frequently used matric potential values, saturated hydraulic conductivity, Mualem-van Genuchten parameters of the moisture retention and hydraulic conductivity curves. Based on similar idea, the work has been continued to produce more accurate and spatially more detailed hydrophysical maps in Hungary by generalizing the applied pedotransfer functions and using national soil reference data and high resolution, novel, digital soil property maps.<br>We initiated a study in order to formalize the built-in soil-landscape model(s) of the national legacy map on water management, together with the quantification of its categories and its potential disaggregation. The relation of the legacy map with the newly elaborated 3D estimations were evaluated at two scales: nationwide with 250 m resolution and at catchment scale with 100 m resolution. Hydrological and primary soil property maps were used as predictor variables. Unsupervised classifications were performed for spatial-thematic aggregation of the soil hydraulic datasets to identify their intrinsic characteristics, which were used for the elaboration of a renewed water management classification. Hydrological interpretation of the categories provided by the optimum classifications has been carried out (i) by their spatial cross-tabulation with the categories of the legacy map and (ii) using the interval estimation of the applied soil hydraulic properties provided for the individual water management categories. Machine learning approaches were used to analyze the information content of the legacy maps’s category system, whose results were used for its disaggregation. Conditionally located random points were sequentially generated for virtual sampling of the legacy map to produce reference information. The disaggregated maps with the legend of the traditional water management classes were produced both on national and catchment level.</p><p>Acknowledgment: The research has been supported by the Hungarian National Research, Development and Innovation Office (NRDI) under grants KH124765, KH126725, the János Bolyai Research Scholarship of the Hungarian Academy of Sciences and the MTA Cloud infrastructure (https://cloud.mta.hu/).</p>

scholarly journals The Influence of a Water Absorbing Geocomposite on Soil Water Retention and Soil Matric Potential

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1731 ◽  
Author(s):  
Michał Śpitalniak ◽  
Krzysztof Lejcuś ◽  
Jolanta Dąbrowska ◽  
Daniel Garlikowski ◽  
Adam Bogacz
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Soil Water ◽  
Water Retention ◽  
Soil Moisture Content ◽  
Soil Surface ◽  
Soil Matric Potential ◽  
Soil Water Retention ◽  
Matric Potential ◽  
Control Samples

Climate change induces droughts that are becoming more intensive and more frequent than ever before. Most of the available forecast tools predict a further significant increase in the risk of drought, which indicates the need to prepare solutions to mitigate its effects. Growing water scarcity is now one of the world’s leading challenges. In agriculture and environmental engineering, in order to increase soil water retention, soil additives are used. In this study, the influence of a newly developed water absorbing geocomposite (WAG) on soil water retention and soil matric potential was analyzed. WAG is a special element made from geotextile which is wrapped around a synthetic skeleton with a superabsorbent polymer placed inside. To describe WAG’s influence on soil water retention and soil matric potential, coarse sand, loamy sand, and sandy loam soils were used. WAG in the form of a mat was used in the study as a treatment. Three kinds of samples were prepared for every soil type. Control samples and samples with WAG treatment placed at depths of 10 cm and 20 cm were examined in a test container of 105 × 70 × 50 cm dimensions. The samples had been watered and drained, and afterwards, the soil surface was heated by lamps of 1100 W total power constantly for 72 h. Soil matric potential was measured by Irrometer field tensiometers at three depths. Soil moisture content was recorded at six depths: of 5, 9, 15, 19, 25, and 30 cm under the top of the soil surface with time-domain reflectometry (TDR) measurement devices. The values of soil moisture content and soil matric potential were collected in one-minute steps, and analyzed in 24-h-long time steps: 24, 48, and 72 h. The samples with the WAG treatment lost more water than the control samples. Similarly, lower soil matric potential was noted in the samples with the WAG than in the control samples. However, after taking into account the water retained in the WAG, it appeared that the samples with the WAG had more water easily available for plants than the control samples. It was found that the mechanism of a capillary barrier affected higher water loss from soil layers above those where the WAG had been placed. The obtained results of water loss depend on the soil type used in the profile.

scholarly journals Averaged water potentials in soil water and groundwater, and their connection to menisci in soil pores, field-scale flow phenomena, and simple groundwater flows

2011 ◽  
Vol 15 (5) ◽  
pp. 1601-1614 ◽  
Author(s):  
G. H. de Rooij
Keyword(s):  
Potential Energy ◽  
Scale Effects ◽  
Hydrostatic Equilibrium ◽  
Subsurface Water ◽  
Depth Range ◽  
Pore Scale ◽  
Field Scale ◽  
Matric Potential ◽  
Water Potentials ◽  
Soil Pores

Abstract. The movement of subsurface water is mostly studied at the pore scale and the Darcian scale, but the field and regional scales are of much larger societal interest. Volume-averaging has provided equations at these larger scales, but the required restrictions rendered them of little practical interest. Others hypothesized a direct connection at hydrostatic equilibrium between the average matric potential of a subsurface body of water and the average pressure drop over the menisci in the soil pores. The link between the volume-averaged potential energy of subsurface water bodies and large-scale fluxes remains largely unexplored. This paper treats the effect of menisci on the potential energy of the water behind them in some detail, and discusses some field-scale effects of pore-scale processes. Then, various published expressions for volume-averaged subsurface water potentials are compared. The intrinsic phase average is deemed the best choice. The hypothesized relationship between average matric potential and average meniscus curvature is found to be valid for unit gradient flow instead of hydrostatic equilibrium. Still, this restriction makes the relationship hold only for a specific depth range in the unsaturated zone under specific conditions, and certainly not for entire fields or catchments. In the groundwater, volume-averaged potential energy is of more use: for linearized, steady flows with flow lines that are parallel, radially diverging, and radially converging, proofs are derived for proportionality between averaged hydraulic potentials and fluxes towards open water at a fixed potential. For parallel flow, a simplified but relevant transient flow case also exhibits this proportionality.

scholarly journals Hydrology influences breeding time in the white-throated dipper

BMC Ecology ◽  
2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Anna L. K. Nilsson ◽  
Thomas Skaugen ◽  
Trond Reitan ◽  
Jan Henning L’Abée-Lund ◽  
Marlène Gamelon ◽  
...  
Keyword(s):  
Climate Change ◽  
River Discharge ◽  
Large Scale ◽  
Time Window ◽  
River System ◽  
Open Water ◽  
Local Conditions ◽  
Environmental Indices ◽  
Groundwater Levels ◽  
Breeding Time

Abstract Background Earlier breeding is one of the strongest responses to global change in birds and is a key factor determining reproductive success. In most studies of climate effects, the focus has been on large-scale environmental indices or temperature averaged over large geographical areas, neglecting that animals are affected by the local conditions in their home ranges. In riverine ecosystems, climate change is altering the flow regime, in addition to changes resulting from the increasing demand for renewable and clean hydropower. Together with increasing temperatures, this can lead to shifts in the time window available for successful breeding of birds associated with the riverine habitat. Here, we investigated specifically how the environmental conditions at the territory level influence timing of breeding in a passerine bird with an aquatic lifestyle, the white-throated dipper Cinclus cinclus. We relate daily river discharge and other important hydrological parameters, to a long-term dataset of breeding phenology (1978–2015) in a natural river system. Results Dippers bred earlier when winter river discharge and groundwater levels in the weeks prior to breeding were high, and when there was little snow in the catchment area. Breeding was also earlier at lower altitudes, although the effect dramatically declined over the period. This suggests that territories at higher altitudes had more open water in winter later in the study period, which permitted early breeding also here. Unexpectedly, the largest effect inducing earlier breeding time was territory river discharge during the winter months and not immediately prior to breeding. The territory river discharge also increased during the study period. Conclusions The observed earlier breeding can thus be interpreted as a response to climate change. Measuring environmental variation at the scale of the territory thus provides detailed information about the interactions between organisms and the abiotic environment.

scholarly journals Is environmental legislation conserving tropical stream faunas? A large-scale assessment of local, riparian and catchment-scale influences on Amazonian fish

2017 ◽  
Vol 55 (3) ◽  
pp. 1312-1326 ◽  
Author(s):  
Cecília G. Leal ◽  
Jos Barlow ◽  
Toby A. Gardner ◽  
Robert M. Hughes ◽  
Rafael P. Leitão ◽  
...  
Keyword(s):  
Large Scale ◽  
Environmental Legislation ◽  
Tropical Stream ◽  
Catchment Scale ◽  
Large Scale Assessment ◽  
Amazonian Fish ◽  
Scale Assessment

scholarly journals Ocean deoxygenation, the global phosphorus cycle and the possibility of human-caused large-scale ocean anoxia

2017 ◽  
Vol 375 (2102) ◽  
pp. 20160318 ◽  
Author(s):  
Andrew J. Watson ◽  
Timothy M. Lenton ◽  
Benjamin J. W. Mills
Keyword(s):  
Chemical Weathering ◽  
Large Scale ◽  
Oxygen Demand ◽  
Subsurface Water ◽  
Phosphorus Cycle ◽  
Low Oxygen ◽  
Positive Feedbacks ◽  
Future Possibility ◽  
Warming World ◽  
Ocean Deoxygenation

The major biogeochemical cycles that keep the present-day Earth habitable are linked by a network of feedbacks, which has led to a broadly stable chemical composition of the oceans and atmosphere over hundreds of millions of years. This includes the processes that control both the atmospheric and oceanic concentrations of oxygen. However, one notable exception to the generally well-behaved dynamics of this system is the propensity for episodes of ocean anoxia to occur and to persist for 10 5 –10 6 years, these ocean anoxic events (OAEs) being particularly associated with warm ‘greenhouse’ climates. A powerful mechanism responsible for past OAEs was an increase in phosphorus supply to the oceans, leading to higher ocean productivity and oxygen demand in subsurface water. This can be amplified by positive feedbacks on the nutrient content of the ocean, with low oxygen promoting further release of phosphorus from ocean sediments, leading to a potentially self-sustaining condition of deoxygenation. We use a simple model for phosphorus in the ocean to explore this feedback, and to evaluate the potential for humans to bring on global-scale anoxia by enhancing P supply to the oceans. While this is not an immediate global change concern, it is a future possibility on millennial and longer time scales, when considering both phosphate rock mining and increased chemical weathering due to climate change. Ocean deoxygenation, once begun, may be self-sustaining and eventually could result in long-lasting and unpleasant consequences for the Earth's biosphere. This article is part of the themed issue ‘Ocean ventilation and deoxygenation in a warming world’.

Accumulation patterns of soil organic matter in forests as a legacy of historical charcoal burning

2021 ◽  
Author(s):  
Anna Schneider ◽  
Alexander Bonhage ◽  
Florian Hirsch ◽  
Alexandra Raab ◽  
Thomas Raab
Keyword(s):  
Land Use ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Large Scale ◽  
Soil Surface ◽  
Landscape Scale ◽  
Legacy Effects ◽  
Charcoal Production ◽  
Study Region ◽  
Land Use Legacies

<p>Human land use and occupation often lead to a high heterogeneity of soil stratigraphy and properties in landscapes within small, clearly delimited areas. Legacy effects of past land use also are also abundant in recent forest areas. Although such land use legacies can occur on considerable fractions of the soil surface, they are hardly considered in soil mapping and inventories. The heterogenous spatial distribution of land use legacy soils challenges the quantification of their impacts on the landscape scale. Relict charcoal hearths (RCH) are a widespread example for the long-lasting effect of historical land use on soil landscapes in forests of many European countries and also northeastern USA. Soils on RCH clearly differ from surrounding forest soils in their stratigraphy and properties, and are most prominently characterized by a technogenic substrate layer with high contents of charcoal. The properties of RCH soils have recently been studied for several regions, but their relevance on the landscape scale has hardly been quantified.</p><p>We analyse and discuss the distribution and ecological relevance of land use legacy soils across scales for RCH in the state of Brandenburg, Germany, with a focus on soil organic matter (SOM) stocks. Our analysis is based on a large-scale mapping of RCH from digital elevation models (DEM), combined with modelled SOM stocks in RCH soils. The distribution of RCH soils in the study region shows heterogeneity at different scales. The large-scale variation is related to the concentration of charcoal production to specific forest areas and the small-scale accumulation pattern is related to the irregular distribution of single RCH within the charcoal production fields. Considerable fractions of the surface area are covered by RCH soils in the major charcoal production areas within the study region. The results also show that RCH can significantly contribute to the soil organic matter stocks of forests, even for areas where they cover only a small fraction of the soil surface. The study highlights that considering land use legacy effects can be relevant for the results of soil mapping and inventories; and that prospecting and mapping land use legacies from DEM can contribute to improving such approaches.</p>

scholarly journals Transient flow between aquifers and surface water: analytically derived field-scale hydraulic heads and fluxes

2012 ◽  
Vol 16 (3) ◽  
pp. 649-669 ◽  
Author(s):  
G. H. de Rooij
Keyword(s):  
Surface Water ◽  
Transient Flow ◽  
Hydrological Cycle ◽  
Realistic Model ◽  
Water Levels ◽  
Subsurface Water ◽  
Water Model ◽  
Infinite Strip ◽  
Catchment Scale ◽  
Basin Scale

Abstract. The increasing importance of catchment-scale and basin-scale models of the hydrological cycle makes it desirable to have a simple, yet physically realistic model for lateral subsurface water flow. As a first building block towards such a model, analytical solutions are presented for horizontal groundwater flow to surface waters held at prescribed water levels for aquifers with parallel and radial flow. The solutions are valid for a wide array of initial and boundary conditions and additions or withdrawals of water, and can handle discharge into as well as lateral infiltration from the surface water. Expressions for the average hydraulic head, the flux to or from the surface water, and the aquifer-scale hydraulic conductivity are developed to provide output at the scale of the modelled system rather than just point-scale values. The upscaled conductivity is time-variant. It does not depend on the magnitude of the flux but is determined by medium properties as well as the external forcings that drive the flow. For the systems studied, with lateral travel distances not exceeding 10 m, the circular aquifers respond very differently from the infinite-strip aquifers. The modelled fluxes are sensitive to the magnitude of the storage coefficient. For phreatic aquifers a value of 0.2 is argued to be representative, but considerable variations are likely. The effect of varying distributions over the day of recharge damps out rapidly; a soil water model that can provide accurate daily totals is preferable over a less accurate model hat correctly estimates the timing of recharge peaks.

Using soil surface gray level to determine surface soil water content

2010 ◽  
Vol 53 (10) ◽  
pp. 1527-1532 ◽  
Author(s):  
YuanJun Zhu ◽  
YunQiang Wang ◽  
MingAn Shao
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Surface Soil ◽  
Soil Surface ◽  
Gray Level
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