Determining the mean depth of overland flow in field studies of flow hydraulics

Trees have been used extensively by river managers for improving the river environment and ecology. The link between flow hydraulics, bed topography, habitat availability, and organic matters is influenced by vegetation. In this study, the effect of trees on the mean flow, bed topography, and bed shear stress were tested under different flow conditions. It was found that each configuration of trees produced particular flow characteristics and bed topography patterns. The SR (single row of trees) model appeared to deflect the maximum velocity downstream of the bend apex toward the inner bank, while leading the velocity to be more uniformly distributed throughout the bend. The entrainment of sediment particles occurred toward the area with higher values of turbulent kinetic energy (TKE). The results showed that both SR and DR (double rows of trees) models are effective in relieving bed erosion in sharp ingoing bends. The volume of the scoured bed was reduced up to 70.4% for tests with trees. This study shows the effectiveness of the SR model in reducing the maximum erosion depth.

Download Full-text

Effect of Temperature on the Synthesis of Jojoba Wax

Functional Plant Biology ◽

10.1071/pp9850355 ◽

1985 ◽

Vol 12 (4) ◽

pp. 355 ◽

Cited By ~ 7

Author(s):

RL Dunstone ◽

A Benzioni ◽

ML Tonnet ◽

P Milthorpe ◽

A Shani

Keyword(s):

Field Studies ◽

Effect Of Temperature ◽

Maximum Temperature ◽

Wax Ester ◽

Controlled Environment ◽

Percentage Elongation ◽

Jojoba Wax ◽

Seed Growth ◽

The Mean ◽

Long Chain

Seed was collected from jojoba [Simmondsia chinensis (Link) Schneider] plants growing at three field sites in two years. The wax percentage was determined by nuclear magnetic resonance and the compositions of the wax and the ethanolysis products (one site only) were determined by gas chromatography. The mean wax concentration varied from 49.2 to 55.1% over all sites and years. The percentage of long-chain wax esters (>C40) decreased linearly with increase in mean maximum temperature during the period of linear seed growth (r� = 0.93). The decrease in long-chain esters was associated with a decrease in the C22 and C24 fatty acids and alcohols. Data from controlled environment studies and from field studies were used to assess the effect of temperature on the percentage elongation, reduction and esterification of acyl-CoAs of carbon lengths 18-22. High temperature lowered the specificity for elongation of C20-C22 and of C22-C,24 and increased the specificity for reduction of the C20 acid to its corresponding alcohol. The amount of C42 wax ester was greater than would be expected by random association of the alkoxy-acyl groups but this preference was not as great at high temperatures.

Download Full-text

PROCEDURES TO MEASURE MEAN AMBIENT DOSE EQUIVALENT RATES USING ELECTRET ION CHAMBERS

Radiation Protection Dosimetry ◽

10.1093/rpd/ncaa061 ◽

2020 ◽

Vol 190 (1) ◽

pp. 6-21

Author(s):

F Leontaris ◽

A Boziari ◽

A Clouvas ◽

M Kolovou ◽

J Guilhot

Keyword(s):

Gamma Spectrometry ◽

Voltage Drop ◽

Field Studies ◽

Dose Equivalent ◽

Ionization Chambers ◽

Ambient Dose Equivalent ◽

The Mean ◽

Ion Chambers ◽

Ambient Dose

Abstract The capabilities of electret ion chambers (EICs) to measure mean ambient dose equivalent rates were investigated by performing both laboratory and field studies of their properties. First, EICs were ‘calibrated’ to measure ambient gamma dose equivalent in the Ionizing Calibration Laboratory of the Greek Atomic Energy Commission. The EICs were irradiated with different gamma photon energies and from different angles. Calibration factors were deduced (electret’s voltage drop due to irradiation in terms of ambient dose equivalent). In the field studies, EICs were installed at eight locations belonging to the Greek Early Warning System Network (which is based on Reuter-Stokes ionization chambers) for three periods, averaging 5 months each. In the same locations, in situ gamma spectrometry measurements were performed with portable germanium detectors. Gamma ambient dose equivalent rates were deduced by the in situ gamma spectrometry measurements and by soil sample analysis. The mean daily electret potential drop (in Volts) was compared with the mean daily ambient dose equivalent, measured with a portable HPGe detector and Reuter-Stokes high-pressure ionization chambers. From these measurements, ‘field’ calibration factors (electret’s voltage drop due to gamma radiation in terms of ambient dose equivalent) were deduced and found in very good agreement with the values deduced in Laboratory. The influence of cosmic radiation and the intrinsic voltage loss when performing long-term environmental gamma measurements with EICs, was estimated.

Download Full-text

Evaluating the Road-Bioretention Strip System from a Hydraulic Perspective—Case Studies

Water ◽

10.3390/w10121778 ◽

2018 ◽

Vol 10 (12) ◽

pp. 1778 ◽

Cited By ~ 5

Author(s):

Xiaoning Li ◽

Xing Fang ◽

Yongwei Gong ◽

Junqi Li ◽

Jianlong Wang ◽

...

Keyword(s):

Case Studies ◽

Overland Flow ◽

Flow Simulation ◽

Soil Infiltration ◽

Rainfall Events ◽

Safety Hazard ◽

The Road ◽

Total Runoff ◽

The Mean ◽

Infiltration Parameters

The two-dimensional overland flow simulation program, FullSWOF_2D, was revised to include submodules of determining infiltration by zones (Z) and grate-inlet (G) drainage from a 2D surface to a 1D pipe flow. The updated program, FullSWOF-ZG, was used to evaluate the performance of a road-bioretention strip (RBS) system and explore/understand key parameters of continuous RBS design. The program was validated using eight pervious surfaces under simulated rainfall events and tested with 20 experimental cases of a locally depressed curb inlet. The mean difference of simulated interception efficiencies (36.6%–86.0%) and observed interception efficiencies (34.8%–84.0%) of the curb inlet was 3.5%, which proves the program predicts the curb-inlet interception efficiency accurately. The 20 road-only and 20 RBS modeling cases were designed and modeled using the FullSWOF-ZG program. These case studies have different road lengths, curb inlet lengths, longitudinal slopes, cross slopes, bioretention-overflow inlet heights, and bioretention soil infiltration parameters. Only 34.6%–48.4% of the total runoff volume is intercepted by the RBS’s curb inlet under heavy rainfall (250 mm/h) and the remaining part of the runoff flows downstream along the road, which may cause local inundation and become a safety hazard. The curb inlet becomes the bottleneck of the RBS system that could impede the runoff flowing into the bioretention strip for detention and infiltration to improve the stormwater quality.

Download Full-text

Overland flow: Hydraulics and erosion mechanics edited by A. J. Parsons and A. D. Abrahams, UCL Press, London, 1992. No. of pages: 464. Price: £60.00. ISBN 1–85728–006–7

Earth Surface Processes and Landforms ◽

10.1002/esp.3290200408 ◽

1995 ◽

Vol 20 (4) ◽

pp. 383-383

Author(s):

R. P. C. Morgan

Keyword(s):

Overland Flow ◽

Flow Hydraulics

Download Full-text

Silica metabolism of the Merino sheep

Australian Journal of Agricultural Research ◽

10.1071/ar9660175 ◽

1966 ◽

Vol 17 (2) ◽

pp. 175 ◽

Cited By ~ 9

Author(s):

MC Nottle

Keyword(s):

Urine Volume ◽

Urinary Calculi ◽

Field Studies ◽

Combined Effects ◽

Wheat Grain ◽

Merino Sheep ◽

Silica Concentration ◽

The Mean ◽

Particulate Silica ◽

Total Excretion

Diets of wheat or oat grain with or without chaff, mixtures of all three, and a diet of chaff, oats, and bran with and without lucerne chaff were fed to sheep for the purpose of determining silica metabolism on diets approximating those in the field. These diets supplied from 0.08 to 16.6 g silica per day. Silica digestibilities and balances showed marked positive and negative values, which were considered to be due to variable retention in, or passage of particulate silica from, the rumen. The mean urinary silica excretion on wheat was 22 and 25 mg/day and oats 126 and 163 mg/day for two levels of feeding. Values for wheat plus chaff and oats plus chaff were respectively 190 and 224 mg/day and for mixed diets from 169 to 205 mg/day. No relationship between total urinary silica excretion and apparent absorption of silica was observed, but excretion seemed dependent on silica intake up to a level of about 8 g/day. Beyond this intake, urinary excretion plateaued at approximately 200 mg/day. Urine volumes on wheat grain diets were greater than on the corresponding oat grain diets, and these in turn were greater than on the mixed diets. The combined effects of urine volume and total excretion of silica resulted in urinary silica concentrations of 30 and 32 µg/ml on wheat grain diets, 255 and 336 µg/ml on oat grains, 266 µg/ml on wheat plus chaff, 419 µg/ml on oats plus chaff, and 421–728 µg/ml on mixed diets. A hyperbolic relationship between silica concentration and volume of urine, similar to one obtained in field studies, and also one between specific gravity and volume of urine were demonstrated. These findings are discussed in relation to the absorption and excretion of silica and the formation of siliceous urinary calculi.

Download Full-text

Deliberation of Hilly Areas for Water Harvesting Application in Western Crete, Greece.

Global NEST Journal ◽

10.30955/gnj.001978 ◽

2016 ◽

Vol 18 (3) ◽

pp. 621-629 ◽

Cited By ~ 8

Keyword(s):

Overland Flow ◽

Annual Runoff ◽

Annual Rainfall ◽

Water Harvesting ◽

Hydrological Conditions ◽

Monthly Average ◽

Dry Seasons ◽

Harvesting Techniques ◽

The Mean ◽

Water Problems

<div> The meteorological, physical and hydrological conditions prevailing in a hilly area, namely the region around Malaxa (Western Crete), are analyzed and investigated in relation to water harvesting applications. The literature relating to water harvesting techniques and applications is reviewed and the conclusions that have been drawn by other investigators concerning methods of water harvesting techniques and applications are outlined and discussed. Specific reasons for choosing this particular study area was given and the types and installation of equipment used are also described. The results indicate that despite the fact that the mean annual rainfall can be considered as high (940 mm), its distribution is very uneven and only 6% of it falls from May to September. This fact creates serious water problems in the area during the dry seasons. Also, mean annual and monthly average temperatures have values which contribute to the evapotranspiration of high amount of precipitation and may form frost and overland flow respectively, during some days. Furthermore, the annual runoff is estimated to be 248 mm and a part of this can be overland flow while the other part can be a throughflow. The occurrence of overland flow is also proved by the comparison of the infiltration and the intensities of rainfall with the return periods of 5 and 10 years. Additionally, the quantification of overland flow is made by collecting and analyzing it from experimental plots. By this method, we clarified that the quantity of overland flow is affected by the inclination of the ground, the density of vegetation and the compaction of the soil. These results, although all of them are not wholly conclusive, can present an advance for understanding the use of meteorological, physical and hydrological conditions for water harvesting applications in an area. </div>

Download Full-text

Surface Detention on Cropland, Rangeland, and Conservation Reserve Program Areas

Transactions of the ASABE ◽

10.13031/trans.12569 ◽

2018 ◽

Vol 61 (3) ◽

pp. 955-966

Author(s):

John . E Gilley

Keyword(s):

Overland Flow ◽

Thin Sheet ◽

Conservation Reserve Program ◽

Soil Surface ◽

Field Studies ◽

Rainfall Simulation ◽

Vegetative Cover ◽

No Till ◽

Corn Residue ◽

Study Sites

Abstract. One of the factors contributing to overland flow on upland areas is water stored temporarily in a thin sheet on the soil surface as surface detention. This study was conducted to quantify surface detention on selected cropland, rangeland, and Conservation Reserve Program (CRP) sites. Surface detention was determined from the recession portion of runoff hydrographs corresponding with the period when rainfall had ceased but runoff continued. The hydrographs were generated from six previously reported rainfall simulation studies conducted on paired 3.7 m wide × 10.7 m long plots on which approximately 128 mm of rainfall was applied. Surface detention values were found to increase as crop residue or vegetative cover increased. Eleven fallow cropland sites in the eastern U.S. had surface detention values that varied from 1.7 to 4.6 mm. Surface detention on plots in southwestern Oklahoma containing Old World bluestem, no-till wheat, and conservation-till wheat was 9.4, 7.3, and 5.2 mm, respectively. No-till sorghum, tilled sorghum, no-till wheat, and tilled wheat plots in southeast Nebraska had surface detention values of 6.7, 4.5, 6.7, and 4.6 mm, respectively. Mean surface detention on no-till and tilled cropland sites in southwest Iowa containing corn residue was 7.2 and 5.9 mm, respectively. CRP study sites in southwestern Iowa had mean surface detention of 10.8 mm. When data from the six field studies were combined, mean surface detention values for fallow cropland, tilled cropland, no-till cropland, rangeland, and CRP areas were 3.1, 5.0, 6.9, 9.6, and 10.8 mm, respectively. Keywords: Depressional storage, Hydrographs, Hydrologic modeling, Overland flow, Runoff volume, Surface detention.

Download Full-text

Analysis, prevalence and impact of microplastics in freshwater and estuarine environments: an evidence review

10.5194/egusphere-egu2020-22468 ◽

2020 ◽

Author(s):

John Iwan Jones ◽

John Francis Murphy ◽

Amanda Arnold ◽

James Laurence Pretty ◽

Kate Spencer ◽

...

Keyword(s):

Sublethal Effects ◽

Field Studies ◽

Threshold Concentration ◽

Taxonomic Group ◽

Lethal Effects ◽

Growth And Survival ◽

Test Organisms ◽

Evidence Review ◽

The Mean ◽

Size Of Particles

We used the systematic review procedure to assess the evidence available on the analysis, prevalence and impact of microplastics in freshwater and estuarine environments. As the study of microplastics in freshwaters is relatively new, measurement methods are yet to be standardized, and a wide variety of methods of variable robustness have been used. Critically, the sampling methodology used in the literature had a systematic influence on the concentration of microplastic particles returned. The volume of water sampled varied over many orders of magnitude, and there was a direct relationship between the size of the smallest particles studied and the volume of water sampled in both freshwater and estuaries: large volumes of water can only be sampled using nets of relatively coarse mesh, which in turn do not capture smaller particles. Consequently, the mean abundance of microplastic particles reported was inversely correlated with both the volume of water sampled and the size of particles studied.The size of microplastic particles had a substantial and overriding effect on threshold concentrations above which microplastics affect freshwater and estuarine biota. For the ecotoxicological endpoints of feeding, behaviour, growth and survival there was a clear relationship between the size of the particles used in the test and the threshold concentration at which an effect was seen. Although the taxonomic coverage of test organisms was limited, there were sufficient data to test the influence of taxonomic group used on size-specific thresholds for Crustacea, fish and algae. There was no significant effect of either the endpoint measured or the taxonomic group used, suggesting that there might not be any difference in sensitivity among different taxa.In order to establish a threshold concentration where microplastics present a hazard to a limited number of taxa, quantile regression was used to determine the size-specific concentration of microplastics that was lower than 90% of the thresholds identified for survival and, as a more conservative limit, across all endpoints tested including sublethal effects. By comparing these thresholds with the data on concentrations of microplastics reported by field studies, it was apparent that the calculated size specific threshold concentration for lethal effects was considerably higher than 99% of reported environmental concentrations. Lethal effects of microplastics on freshwater and estuarine biota are likely to be limited to exceptional circumstances. Over certain size ranges the calculated size specific threshold concentration for sublethal effects was exceeded by the highest 10% of concentrations reported from environmental samples, suggesting that there is a risk of sublethal effects in a small proportion of sites.&#160;

Download Full-text

Metals Leak from Tilled Soil in a Century – A Review

Journal of Agricultural Science ◽

10.5539/jas.v7n12p15 ◽

2015 ◽

Vol 7 (12) ◽

pp. 15

Author(s):

Gunnar Bengtsson

Keyword(s):

Large Scale ◽

Penetration Rate ◽

Modern Society ◽

Field Studies ◽

Basic Set ◽

Metal Contents ◽

Significant Difference ◽

Supplementary Material ◽

The Mean

Toxic metals are mobilized on a large scale in modern society. Many of those metals end up in sewage sludge. The objective of this review was to elucidate the threat to groundwater due to a few metals lost from tilled sludge amended soils. It is sometimes suggested that these metals are immobilized in the topsoil and do not move downward. In contrast, dozens of long term field studies around the world indicate that penetration depths for metals increase with time since deposition.Such studies were examined in depth in the current analysis. An equation was developed for calculation of long term mean metal penetration rates into the topsoil for copper and silver. The equation is valid for about a century but not much longer. The mean depths of a basic set of 11 cases from studies over 4 years to 100 years were predicted with a standard deviation of 11%. A typical penetration rate was 3 mm per year. There was no significant difference in penetration rate between several cations. Extremely large amendments were associated with larger penetration rates.When metals have traversed the topsoil, the groundwater will be contaminated. The European Groundwater Pollution Directive stipulates that pesticide levels should be kept below 0.1 µg/l. When sludge is applied to agricultural soil, this level may by far be exceeded for many metals, even if strict limitations are applied to the metal contents of the sludge. This calls for careful assessment of the groundwater consequences of sludge amendment.Extensive supplementary material provides many detailed tables, texts and references.

Download Full-text