New Method for Estimation of Contaminant Travel Rate in Unsaturated Zone under Irrigated Soils

1993 ◽  
Vol 27 (7-8) ◽  
pp. 173-178 ◽  
Author(s):  
M. Zilberbrand
Keyword(s):  
Water Content ◽  
Unsaturated Zone ◽  
Sandy Loam ◽  
Chestnut Soil ◽  
Deep Penetration ◽  
Groundwater Recharge Rate ◽  
Capillary Tension ◽  
Travel Rate ◽  
Tracer Experiments ◽  
Irrigated Soils

In a thick unsaturated zone, when quick deep penetration of rain and irrigation water is absent, at the depths below 3-5 m there exists a zone of downwards quasi-steady water flow. Darcy's water velocity in this zone remains constant with depth and equal to the groundwater recharge rate; unit hydraulic head gradient occurs above the capillary fringe. Therefore, contaminant travel rate is equal to the ratio of hydraulic conductivity (K) and effective volumetric water content (θef). Field tracer experiments and laboratory K and θef determinations were carried out for several representative irrigated lots in the South Ukraine. The dependence of θef on capillary tension was studied for the first time. For loess loam with a capillary tension decreasing from 46 kPa to 0, θef nonlinearly increases from 12% to 27-28%. The effective water content portion (β1) of the total water content increases nonlinearly from 0.38 to 0.65-0.7. The β1 values were estimated for different unsaturated sedimentary rocks. For a capillary tension of about 5 kPa β1 values were: 0.88-0.99 for sands, about 0.65 for loess loam and chestnut soil, about 0.6 for sandy loam, about 0.32 for limestone and about 0.07 for clay. Calculated chloride travel rates in loess loams under irrigated soils fit the values of 0.001-0.003 m/day, determined by the results of field tracer experiments.

Determination of water content in drying soils: incorporating transition from liquid phase to vapour phase

Soil Research ◽  
2004 ◽  
Vol 42 (1) ◽  
pp. 1 ◽  
Author(s):  
F. Konukcu ◽  
A. Istanbulluoglu ◽  
I. Kocaman
Keyword(s):  
Water Content ◽  
Transition Zone ◽  
Sandy Loam ◽  
Vapour Phase ◽  
Coarse Sand ◽  
Arid Environments ◽  
Evaporation Front ◽  
Matric Potential ◽  
Silty Loam

In arid and semi-arid environments, soil profiles often exhibit a liquid–vapour displacement known as evaporation front characterised by a critical matric potential (ψme) or water content (θe) located somewhere inside the unsaturated zone above a watertable (WT). The objective of this study was to determine the θe including the range of water content (θ) in the transition zone from liquid to vapour both theoretically and experimentally for different soil textures under saline and non-saline WTs. Characteristic shapes of water content and salt concentration profiles were the criteria to obtain θe experimentally, and the θ–diffusivity relationship was used to compute the θe and θ range in the transition zone. Measured θe values of 0.05 and 0.12 m3/m3 under non-saline WT and 0.07 and 0.15 m3/m3 under saline WT were in agreement with the computed values of 0.05 and 0.10 m3/m3 for sandy loam and clay loam soils, respectively. The model calculates roughly the same θe for saline and non-saline conditions. Besides experimental soils, θe and range of θ in the transition zone were calculated for silty loam and coarse sand. The lighter the soil texture, the smaller is θe and the steeper the transition zone. The results were further compared with those calculated by different authors.

Coupled Liquid Water, Water Vapor, and Heat Transport Simulations in an Unsaturated Zone of a Sandy Loam Field

Soil Science ◽  
2011 ◽  
Vol 176 (8) ◽  
pp. 387-398 ◽  
Author(s):  
Sanjit K. Deb ◽  
Manoj K. Shukla ◽  
Parmodh Sharma ◽  
John G. Mexal
Keyword(s):  
Water Vapor ◽  
Heat Transport ◽  
Liquid Water ◽  
Unsaturated Zone ◽  
Sandy Loam

Phosphorus sorption and nitrogen transformation in two soils treated with piggery wastewater

Soil Research ◽  
2002 ◽  
Vol 40 (2) ◽  
pp. 335 ◽  
Author(s):  
I. R. Phillips
Keyword(s):  
Cation Exchange ◽  
Root Zone ◽  
Sandy Loam ◽  
Sorption Kinetics ◽  
Land Application ◽  
Piggery Wastewater ◽  
Wastewater Disposal ◽  
P Sorption ◽  
High Affinity ◽  
Irrigated Soils

Land application of piggery wastewater has the potential to contaminate receiving water bodies due to the presence of elevated concentrations of nitrogen (N) and phosphorus (P). This paper investigates P sorption and N transformation using soil from 2 wastewater disposal sites in south-east Queensland. Soil from Site 1 was classified as a clay (Vertosol) and soil from Site 2 was classified as a sandy loam (Sodosol). Soil was collected from wastewater disposal (irrigated) and non-disposal (non-irrigated) areas of each site. Nutrient sorption kinetics and transformation were studied by reacting each soil with either wastewater or an inorganic salt solution over a period of 21 days. Solution P concentrations decreased with time for all soils. These changes were greatest during the early stage of the study (<10 days), after which time solution P concentrations remained relatively stable. Concentrations of solution P tended to remain higher in irrigated than non-irrigated soils. This was attributed to a loss of high-affinity sorption sites due to past wastewater additions. Cation exchange (for times <3 days) and nitrification (for times >3 days) were found to be the primary mechanisms responsible for decreases in solution ammonium (NH4-N) over the 21-day period. Phosphorus and NH4-N sorption isotherms were determined using a leaching procedure, and the data were adequately described (r2 >0.95) by the Freundlich equation. Irrigated samples generally sorbed less P than non-irrigated soils. This was attributed to the loss of high-affinity P sorption sites due to previous wastewater additions. Cation exchange and competition between added and resident cations for the exchange sites was found to govern NH4-N sorption by these soils. Results from this study suggest that long-term land application of piggery wastewater may encourage leaching of N and P from the plant root-zone in soils with limited capacity to retain these nutrients. Appropriate management strategies to minimise these losses need to be developed to avoid degradation of the receiving soil and/or water environments. sorption kinetics, nitrification, ammonium, nitrate.

Bacterial leaching from dairy shed effluent applied to a fine sandy loam under irrigated pasture

Soil Research ◽  
2008 ◽  
Vol 46 (7) ◽  
pp. 552 ◽  
Author(s):  
Shuang Jiang ◽  
Graeme D. Buchan ◽  
Mike J. Noonan ◽  
Neil Smith ◽  
Liping Pang ◽  
...  
Keyword(s):  
Water Content ◽  
Water Flow ◽  
Sandy Loam ◽  
Volumetric Water Content ◽  
Faecal Coliform ◽  
Bacterial Transport ◽  
Flood Irrigation ◽  
Bacterial Leaching ◽  
Fine Sandy Loam ◽  
Spray Irrigation

This experiment investigated bacterial transport from land-applied dairy shed effluent (DSE), via field lysimeter studies, using 2 contrasting irrigation methods. Transient water flow and bacterial transport were studied, and the factors controlling faecal coliform (FC) transport are discussed. Two trials (Trial 1, summer; Trial 2, autumn) were carried out, using 6 undisturbed soil monolith lysimeters, 500 mm diameter by 700 mm deep, with a free-draining, Templeton fine sandy loam. DSE with inert chemical tracers was applied at the start of both trials using the same method, followed with repeated 14-day cycles of either flood or spray irrigation of water. A bacterial tracer, antibiotic-resistant faecal coliform, was added to the DSE in Trial 2 only, to distinguish applied FC from external or resident FC. Leachates were collected after each water application (or heavy rainfall when applicable) for enumeration of FC and measurement of tracers. All lysimeters were instrumented for monitoring volumetric water content, matric potential, and soil temperature at 4 depths (100, 250, 450, and 600 mm). The results showed that bacteria could readily penetrate through 700-mm-deep soil columns, when facilitated by water flow. The highest post-water irrigation concentration was 3.4 × 103 cfu/100 mL under flood irrigation, which resulted in more bacterial and Br– leaching than spray irrigation. Trial 2 (autumn) results also showed significant differences between irrigation treatments in lysimeters sharing similar drainage class (moderate or moderately rapid), flood irrigation again gave more bacterial and tracer (Cl–) leaching. In the summer trial, FC in leachate as high as 1.4 × 106 cfu/100 mL, similar to the concentration of DSE, was detected in one lysimeter that had a higher clay content in the topsoil immediately after DSE application, and before any water irrigation. This indicates that applied DSE leached through preferential flow paths without any dilution. Bacterial concentration in the leachate was positively correlated with both volumetric water content and water potential, and sometimes drainage rate. Greater bacterial leaching was found in the lysimeter with rapid whole-column effective hydraulic conductivity, Keff, for both flood and spray treatments. Occasionally, the effect of Keff on water movement and bacterial transport overrode the effect of irrigation. The ‘seasonal condition’ of the soil (including variation in initial water content) also influenced bacterial leaching, with less risk of leaching in autumn than in summer. These findings contribute to our increased understanding of bacterial transport processes on the field scale.

scholarly journals The influence of ammonia on groundwater quality during wastewater irrigation

2018 ◽  
Vol 13 (No. 3) ◽  
pp. 161-169
Author(s):  
Kriška Michal ◽  
Němcová Miroslava ◽  
Hyánková Eva
Keyword(s):  
Water Content ◽  
Goodness Of Fit ◽  
Municipal Wastewater ◽  
Sandy Loam ◽  
Field Capacity ◽  
Water Source ◽  
Ammonia Nitrogen ◽  
Drainage Water ◽  
Significant Information ◽  
Alternative Sources

Currently, agriculture in many countries including the Czech Republic is increasingly facing the problem of drought. The lack of precipitation results in a reduced harvest, which implies added irrigation and freshwater requirements. One of the ways to overcome the scarcity of fresh water is to search for alternative sources of irrigation water. The paper deals with a water source, which has not been preferred yet, but theoretically provides a wide application - treated municipal wastewater. Under a pilot plant, several selected soils were tested, placed in 2.0 m high filtration columns. Our observation was focused on ammonia nitrogen and its gradual decline during the flow through the soil profile. Samples from the filtration columns (inflow = irrigation; outflow = drainage water) were periodically taken, while the collected data were used for calibration of the numerical model. The model was calibrated in two successive separate steps, both were compiled in HYDRUS-2D. In the first step the model was calibrated according to the measured soil water content of materials. Subsequently, a second calibration was performed using the measured seepage concentrations of ammonia. Despite certain simplifications caused by the focus only on ammonia nitrogen, the model shows very favourable results. The hydraulic model’s goodness of fit (between observed vs. measured values of water content) is R<sup>2</sup> = 0.88 for sand, 0.76 for loam, 0.72 for sandy-loam with vegetation on surface and 0.74 for sandy-loam without vegetation. The calibrated hydraulic model for solute transport (between observed vs. measured values of NH<sub>4</sub><sup>+</sup>-N concentration) showed the value of R<sup>2</sup> = 0.89 for sand, 0.95 for loam, 0.95 for sandy-loam with vegetation on surface and 0.92 for sandy-loam without vegetation. The model provides significant information on the dependence of decrease of ammonia pollution by the depth. Inflow concentration of ammonia on surface 17 ± 1 mg/l is reduced to the value of 2.0 mg/l at a depth of 110 cm. It is crucial for real application to maintain the hydraulic criteria - the field capacity should not be exceeded in praxis. The value of field capacity was deliberately slightly exceeded because of understanding of the situation: how the pollution proceeds below if this rule is not followed. As a result, if wastewater is applied, the groundwater level should not be at a depth of less than 1.5 m.

HYDRUS (2d/3d) simulation of water flow through sandy loam soil under potato cultivation in Southern Manitoba

2017 ◽  
pp. 1.9-1.19 ◽  
Author(s):  
Afua Mante ◽  
Ramanathan Sri Ranjan
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Flow ◽  
Sandy Loam ◽  
Crop Evapotranspiration ◽  
Reference Crop Evapotranspiration ◽  
Loam Soil ◽  
Flow Through ◽  
Reference Crop

The HYDRUS (2D/3D) modeling tool was used to simulate water flow through subsurface-drained sandy loam soil under potato (Solanum tuberosum) cultivation in Southern Manitoba. The model was used to simulate water flow through a 2-D model domain of dimensions, 15 m width × 2.5 m depth. The model was calibrated and validated with field data measured during the growing season of year 2011 at the Hespler Farms, Winkler, Manitoba. Field measurements, including soil water content and watertable depth, for two test plots under subsurface free drainage were used for the calibration and validation. Weather data were also obtained to estimate reference crop evapotranspiration, which was used as input data in the model. Based on the reference crop evapotranspiration, and crop coefficient of the potato crop, the actual crop evapotranspiration was estimated and compared to the simulated actual crop evapotranspiration results. The results showed that the model was able to account for 50% to 78% of the variation in the estimated actual crop evapotranspiration. With respect to water flow through the soil, the observed soil water content and the simulated soil water content were compared using graphical and quantitative analysis. Based on the coefficient of determination (R2), the model accounted for 68% to 89% variation in the observed data. The intercept of the regression line varied from 0.01 to 0.08, and the slope, 0.75 to 0.99. The Nash–Sutcliffe modeling efficiency coefficient (NSE) varied from 0.62-0.89, the Percent bias (PBIAS) values varied from -1.99% to 1.16%. The root mean square error-observations standard deviation ratio (RSR) values varied from 0.33 to 0.61. The values for the evaluation parameters show that the model was able to simulate the water flow through the soil profile reasonably well.

Variability in soil moisture and infiltration on two Riverina soils

1951 ◽  
Vol 2 (2) ◽  
pp. 126 ◽  
Author(s):  
AL Tisdall
Keyword(s):  
Soil Moisture ◽  
Sandy Loam ◽  
Brown Soil ◽  
Soil Group ◽  
Coefficients Of Variation ◽  
Irrigated Soils

Studies of variability in soil moisture and of a method for determining infiltration were conducted on two irrigated soils in the Riverina region, a sandy loam of the red-brown earth group and a clay of the grey and brown soil group respectively. Coefficients of variation were high in all cases. It is concluded that the use of 16 replicates gives adequate precision in the estimate of infiltration (C.V. of 8 and 12 per cent, for the two soils studied). Similarly, the use of 16 gravimetric determinations, each bulked from four sites, would give a satisfactory estimate for soil moisture (C. V. of less than 10 per cent. for the two soils studied). This number of samples is not excessive from practical considerations. Sampling for soil-moisture increment, following the type of irrigation used on these soils, should be carried out to a depth of two feet, but the duplication of gravimetric determinations is not warranted by the small increase in precision obtained.

scholarly journals Glasshouse study of a sprayable, degradable polymer to reduce water use in cotton establishment

Soil Research ◽  
2020 ◽  
Vol 58 (4) ◽  
pp. 379
Author(s):  
Priscilla Johnston ◽  
Michael Braunack ◽  
Philip S. Casey ◽  
Keith L. Bristow ◽  
Raju Adhikari
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Plant Biomass ◽  
Sandy Loam ◽  
Seedling Emergence ◽  
Chemical Properties ◽  
Water Evaporation ◽  
Degradable Polymer ◽  
Extensive Degradation

This glasshouse pot experiment demonstrated that a new sprayable and degradable polymer reduced soil water evaporation and promoted cotton seedling emergence and establishment. The polymer was tested on two contrasting soils (sandy loam and clay), representative of those used to grow cotton in Australia. Changes in soil water content in non-treated and polymer-treated pots were monitored over 80 days, after surface or subsurface watering. Plant biomass, soil water content and soil chemical properties were determined at harvest. The polymer reduced soil water evaporation by up to 35% in sandy loam and up to 20% in clay, did not compromise seedling emergence and improved plant growth per unit water applied by up to 26.2%. The polymer underwent extensive degradation after 80 days to produce low molecular-weight polymers or oligomers and water-extractable silicon species that may have implications for plant nutrition.

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