Post-fire soil water repellency, sorptivity, and the measurement of infiltration

2021 ◽  
Author(s):  
Rose Shillito ◽  
Markus Berli ◽  
Teamrat Ghezzehei ◽  
Ian Floyd
Keyword(s):  
Water Repellency ◽  
Accurate Method ◽  
Silica Sand ◽  
Water Repellent ◽  
Field Methods ◽  
Physically Based ◽  
Soil Hydraulic Property ◽  
Infiltration Tests ◽  
The Relationship ◽  
Common Field

<p>Wildfires are frequently associated with the increased potential for runoff, flooding and debris flows during and after subsequent rainfall events. Specifically, wildfires can cause soils to become water repellent, which is believed to slow, if not halt, the infiltration of water into the soil. However, there exists no mechanistic way to determine the effect of post-wildfire water repellency on infiltration and runoff—until now. We have recently developed a simple physically-based model to account for the effect of water repellency on the soil hydraulic property of sorptivity. Further, since sorptivity is crucial to understanding the relationship between water repellency and post-fire infiltration, there is a need for a robust and accurate method to measure sorptivity in the field. All research was conducted in the laboratory using a fine silica sand, some of which was treated with Scotchgard<sup>TM</sup> to induce water repellency. Treated and untreated sand was mixed proportionally by weight to create various degrees of water repellent sand. Upward infiltration tests (wicking experiments) were used to validate the sorptivity model. Then, two common field methods (a 1D infiltrometer ring and a 3D tension infiltrometer) were used to measure downward infiltration and extract sorptivity data. Results showed that we able to predict sorptivity given the degree of water repellency and basic soil properties, that sorptivity measured using common field methods reflected the degree of water repellency, and that both downward infiltration measurement methods yielded similar sorptivity values.</p>

Quantifying the effect of post-wildfire soil water repellency on runoff

2021 ◽  
Author(s):  
Rose Shillito ◽  
Markus Berli ◽  
Ian Floyd ◽  
Li Chen ◽  
Teamrat Ghezzehei
Keyword(s):  
Soil Water ◽  
Water Repellency ◽  
Silica Sand ◽  
Watershed Model ◽  
Soil Water Repellency ◽  
Physically Based Model ◽  
San Gabriel Mountains ◽  
Physically Based ◽  
Dry Soil ◽  
Moisture Conditions

<p>Several factors are believed to contribute to post-wildfire flooding and debris flows. One contributing factor—the occurrence of post-wildfire soil water repellency—lacks a quantitative mechanism to incorporate the effects in physically-based runoff models. For this study, a physically-based model was developed linking the contact angle (degree of water repellency) to sorptivity. The model was verified in laboratory experiments using a silica sand proxy. The effects of water repellency on infiltration were illustrated. Further, the effect of water repellency on runoff was simulated using the AGWA-KINEROS2 watershed model with data from rainfall following the 2009 Station fire in the San Gabriel Mountains of southern California, USA. Results show water repellency has a quantifiable effect on runoff production, an effect enhanced by the dry soil moisture conditions common after wildfires.</p>

Field measurement of soil water repellency and its impact on water flow under different vegetation

Biologia ◽  
2007 ◽  
Vol 62 (5) ◽  
Author(s):  
L’ubomír Lichner ◽  
Paul Hallett ◽  
Debbie Feeney ◽  
Olívia Ďugová ◽  
Miloslav Šír ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Forest Soil ◽  
Soil Water ◽  
Water Flow ◽  
Water Repellency ◽  
Water Repellent ◽  
Dry Spell ◽  
Physically Based ◽  
Low Levels ◽  
The Impact

AbstractNumerous recent laboratory studies have shown that vegetation can influence soil water flow by inducing very low levels of water repellency. In this study we extended on this previous research by developing a field-based test using a miniature infiltrometer to assess low levels of water repellency from physically based measurements of liquid flow in soil. The field-based test was verified through a simple laboratory experiment and then applied to determine the impact of vegetation and antecedent soil water content. The soil hydraulic properties determined were hydraulic conductivity, sorptivity, as well as the persistence and index of water repellency. Tests were conducted following a dry spell and wet spell on (1) forest soil (0 cm depth), (2) glade soil (0 cm depth) and (3) glade soil (50 cm depth). It was found that both the persistence and index of water repellency, R, decreased in the order as follows: forest soil > glade soil (0 cm) > glade soil (50 cm) for both dry and wet spell. The range of values of R was 0.28 (wettable) to 360 (highly water repellent), which affected hydraulic conductivity k r(−2 cm). R increased and hence k r(−2 cm) decreased in the order: forest soil < glade soil (0 cm) < glade soil (50 cm) for both the dry and wet spell. There were clear interactions between vegetation and changes to water flow caused by presence of repellency.

scholarly journals Peculiarities of Infiltration Measurements in Water-Repellent Forest Soil

Forests ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 472
Author(s):  
Tomáš Orfánus ◽  
Anton Zvala ◽  
Malvína Čierniková ◽  
Dagmar Stojkovová ◽  
Viliam Nagy ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Forest Soil ◽  
Forest Floor ◽  
Water Repellency ◽  
Water Infiltration ◽  
Water Repellent ◽  
Runoff Generation ◽  
Field Methods ◽  
Single Ring ◽  
Guelph Permeameter

The paper deals with measurements of water infiltration carried out on a well-developed forest floor formed by needle-leaf litter of Norway spruce. Three field methods (tension disk permeameter, single-ring infiltrometer and Guelph permeameter) were used to determine the soil hydraulic conductivity. The results were strongly influenced by the water repellency at the interface between the O- and A-horizons. This interface was severely water repellent during the hot and dry summer season, regardless of the generally humid mountain climate of the High Tatras foothill. The single-ring method paradoxically provided lower hydraulic conductivity (3.2 × 10−4 ± 1.3 × 10−4) compared to the tension disk permeameter (8.5 × 10−4 ± 3.3 × 10−4) due to the presence of the water-repellent O/A-interface. This effect was also observed with the Guelph permeameter method, which gave the lowest value (5.6 × 10−5 ± 4.3 × 10−5). Abrupt retardation of infiltration on the water-repellent interface may generate shallow subsurface runoff (as was proved by the irrigation experiment) or litter splash during extreme rainfall events and promote water flow to deeper soil horizons through preferential pathways. The observed effects of the forest floor on rainfall infiltration will depend on the seasonal variability of soil water repellency. Although the forest floor is a source of hydrophobic substances that cause water repellency at the O/A-interface and can trigger runoff generation, at the same time its cohesive duff layer protects the forest soil from erosion.

scholarly journals Quantifying the effect of subcritical water repellency on sorptivity : a physically based model

2021 ◽  
Author(s):  
Rose Shillito ◽  
Markus Berli ◽  
Teamrat Ghezzehei
Keyword(s):  
Contact Angle ◽  
Hydraulic Conductivity ◽  
Subcritical Water ◽  
Water Drop ◽  
Water Repellency ◽  
Quantitative Model ◽  
Saturated Hydraulic Conductivity ◽  
Silica Sand ◽  
Water Repellent ◽  
Burned Areas

Soil water wettability or water repellency is a phenomenon that can affect infiltration and, ultimately, runoff. Thus, there is a need to develop a model that can quantitatively capture the influence of water repellency on infiltration in a physically meaningful way and within the framework of existing infiltration theory. The analytical model developed in this study relates soil sorptivity (an infiltration parameter) with contact angle (a direct measure of water repellency) for variably saturated media. The model was validated with laboratory experiments using a silica sand of known properties treated to produce controlled degrees of water repellency. The measured contact angle and sorptivity values closely matched the model‐predicted values. Further, the relationship between the frequently used water drop penetration time test (used to assess water repellency) and sorptivity was illustrated. Finally, the direct impact of water repellency on saturated hydraulic conductivity was investigated due to its role in infiltration equations and to shed light on inconsistent field observations. It was found that water repellency had minimal effect on the saturated hydraulic conductivity of structureless sand. A quantitative model for infiltration incorporating the effect of water repellency is particularly important for post‐fire hydrologic modeling of burned areas exhibiting water repellent soils.

scholarly journals Effect of kaolinite and Ca-montmorillonite on the alleviation of soil water repellency

2011 ◽  
Vol 50 (No. 8) ◽  
pp. 358-363 ◽  
Author(s):  
P. Dlapa ◽  
S.H. Doerr ◽  
Ľ. Lichner ◽  
M. Šír ◽  
M. Tesař
Keyword(s):  
Water Drop ◽  
Water Repellency ◽  
Silica Sand ◽  
Water Repellent ◽  
Mineral Surfaces ◽  
Adhesion Forces ◽  
Key Factors ◽  
High Adhesion ◽  
Phase Water ◽  
Amphiphilic Organic Compounds

The effects of adding 1&ndash;3% (weight) kaolinite or Ca-montmorillonite on the wettability of silica sand, made highly water repellent with stearic acid, was studied during wetting and prolonged drying phases at 50&deg;C. The persistence of water repellency was estimated with the water drop penetration time (WDPT) test. After wetting water repellency disappeared in all the samples. During the drying phase, water repellency re-appeared in all samples (untreated and clay-treated) as the water content decreased below 1%. Repellency did, however, not reach pre-wetting levels. The effect of clay additions on water repellency differed strongly between the two clay types. Kaolinite reduced WDPT, while Ca-montmorillonite caused an increase in WDPT in the already highly repellent sand. Potential mechanisms for the alleviation effectiveness of kaolinite are proposed, with key factors being the high adhesion forces between water and clay mineral surfaces, and the ability kaolinite to disperse. In the case of Ca-montmorillonite, its lower affinity for water may lead to a displacement of water molecules at mineral surfaces by amphiphilic organic compounds, which may result in increased repellency. This phenomenon clearly requires further investigation.

Non-adhesive lotus and other hydrophobic materials

2008 ◽  
Vol 366 (1870) ◽  
pp. 1539-1556 ◽  
Author(s):  
David Quéré ◽  
Mathilde Reyssat
Keyword(s):  
Solid Surface ◽  
Room Temperature ◽  
Water Repellency ◽  
Short Review ◽  
Water Repellent ◽  
Practical Applications ◽  
Hydrophobic Materials ◽  
Volatile Liquid ◽  
Air Cushion ◽  
The Stability

Superhydrophobic materials recently attracted a lot of attention, owing to the potential practical applications of such surfaces—they literally repel water, which hardly sticks to them, bounces off after an impact and slips on them. In this short review, we describe how water repellency arises from the presence of hydrophobic microstructures at the solid surface. A drop deposited on such a substrate can float above the textures, mimicking at room temperature what happens on very hot plates; then, a vapour layer comes between the solid and the volatile liquid, as described long ago by Leidenfrost. We present several examples of superhydrophobic materials (either natural or synthetic), and stress more particularly the stability of the air cushion—the liquid could also penetrate the textures, inducing a very different wetting state, much more sticky, due to the possibility of pinning on the numerous defects. This description allows us to discuss (in quite a preliminary way) the optimal design to be given to a solid surface to make it robustly water repellent.

Performance Study of Nano-TiO2 Modified Fabric

2012 ◽  
Vol 549 ◽  
pp. 733-736
Author(s):  
Xiao Mian Chen ◽  
Jing Jing Shi ◽  
Hong Sha Su ◽  
Chun Ting Lin ◽  
En Long Yang
Keyword(s):  
Titanium Dioxide ◽  
Catalytic Activity ◽  
Catalytic Properties ◽  
Antibacterial Property ◽  
Wear Behavior ◽  
Water Repellency ◽  
Innovative Technology ◽  
Water Repellent ◽  
High Catalytic Activity ◽  
Performance Study

The catalytic properties of nano-TiO2 modified fabric suits the demand for self-cleaning in recent years. In this paper, advanced and innovative technology were used to synthesize water sol of titanium dioxide photocatalyst with high catalytic activity for fabric finishing. The wear behavior, antibacterial property and water repellency of treated and untreated fabric were tested. Results indicate that finishing and washing of the titanium dioxide had no effect on wear behavior; finished and washed fabric has a certain antibacterial and water repellent properties.

USABLE SECURITY IN BIOMETRIC AUTHENTICATION SYSTEMS

2021 ◽  
Vol 17 (1) ◽  
pp. 287-292
Author(s):  
Adriana-Meda UDROIU ◽  
Ștefan-Antonio DAN-ȘUTEU
Keyword(s):  
Iris Recognition ◽  
Accurate Method ◽  
Biometric Authentication ◽  
Usable Security ◽  
Security Systems ◽  
Field Methods ◽  
Secure Systems ◽  
Authentication System ◽  
Secure Authentication ◽  
Pattern Variability

Abstract: We introduce the term usable security to refer to security systems, models, mechanisms and applications that have as the main goal usability. Secure systems cannot exist without secure authentication methods. Thus we outline biometric authentication methods and we focus on iris recognition because is the most reliable and accurate method for human identification]. The most important advantage of iris biometric over other biometrics is that irises have enormous pattern variability meaning that the variation between individual is almost maximum and variation for any person across time or conditions is minimum. Taking into consideration this observations, this survey covers researches in this field, methods of technical implementation and the usability of this method as an authentication system on iOS environment.

scholarly journals Water repellency of clay, sand and organic soils in Finland

2008 ◽  
Vol 16 (3) ◽  
pp. 267 ◽  
Author(s):  
K. RASA ◽  
R. HORN ◽  
M. RÄTY
Keyword(s):  
Preferential Flow ◽  
Management Practice ◽  
Soil Surface ◽  
Water Repellency ◽  
Organic Soil ◽  
Water Infiltration ◽  
Organic Soils ◽  
Water Repellent ◽  
Moisture Regime ◽  
Wetting Process

Water repellency (WR) delays soil wetting process, increases preferential flow and may give rise to surface runoff and consequent erosion. WR is commonly recognized in the soils of warm and temperate climates. To explore the occurrence of WR in soils in Finland, soil R index was studied on 12 sites of different soil types. The effects of soil management practice, vegetation age, soil moisture and drying temperature on WR were studied by a mini-infiltrometer with samples from depths of 0-5 and 5-10 cm. All studied sites exhibited WR (R index >1.95) at the time of sampling. WR increased as follows: sand (R = 1.8-5.0) < clay (R = 2.4-10.3) < organic (R = 7.9-undefined). At clay and sand, WR was generally higher at the soil surface and at the older sites (14 yr.), where organic matter is accumulated. Below 41 vol. % water content these mineral soils were water repellent whereas organic soil exhibited WR even at saturation. These results show that soil WR also reduces water infiltration at the prevalent field moisture regime in the soils of boreal climate. The ageing of vegetation increases WR and on the other hand, cultivation reduces or hinders the development of WR.;

scholarly journals Spatially variable soil water repellency enhances soil respiration rates (CO<sub>2</sub> efflux)

2017 ◽  
Author(s):  
Emilia Urbanek ◽  
Stefan H. Doerr
Keyword(s):  
Soil Moisture ◽  
Soil Respiration ◽  
Soil Water ◽  
Water Distribution ◽  
Preferential Flow ◽  
Water Repellency ◽  
Water Repellent ◽  
Co2 Efflux ◽  
Soil Co2 ◽  
Soil Water Repellency

Abstract. Soil CO2 emissions are strongly dependent on water distribution in soil pores, which in turn can be affected by soil water repellency (SWR; hydrophobicity). SWR restricts infiltration and movement of water, affecting soil hydrology as well as biological and chemical processes. Effects of SWR on soil carbon dynamics and specifically on soil respiration (CO2 efflux) have been studied in a few laboratory experiments but they remain poorly understood. Existing studies suggest that soil respiration is reduced in water repellent soils, but the responses of soil CO2 efflux to varying water distribution created by SWR are not yet known. Here we report on the first field-based study that tests whether soil water repellency indeed reduces soil respiration, based on in situ field measurements carried out over three consecutive years at a grassland and pine forest site under the humid temperate climate of the UK. CO2 efflux was reduced on occasions when soil exhibited consistently high SWR and low soil moisture following long dry spells. However, the highest respiration rates occurred not when SWR was absent, but when SWR, and thus soil moisture, was spatially patchy, a pattern observed for the majority of the measurement period. This somewhat surprising phenomenon can be explained by SWR-induced preferential flow, directing water and nutrients to microorganisms decomposing organic matter concentrated in hot spots near preferential flow paths. Water repellent zones provide air-filled pathways through the soil, which facilitate soil-atmosphere O2 and CO2 exchanges. This study demonstrates that SWR have contrasting effects on CO2 fluxes and, when spatially-variable, can enhance CO2 efflux. Spatial variability in SWR and associated soil moisture distribution needs to be considered when evaluating the effects of SWR on soil carbon dynamics under current and predicted future climatic conditions.

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