Showing 14 results for Hydraulic Conductivity
M. Afyuni, M.r. Mosaddeghi,
Volume 5, Issue 2 (7-2001)
Abstract
Tillage system effect, Conventional (CT) vs. No-Till (NT), on soil physical properties and Br transport was studied at two locations in North Carolina. The soil types were a Typic Paleudults at Coastal Plain (site 1) and a Typic Kanhapludults at Piedmont (site 2). Bulk density (BD), total porosity (TP), macroporosity (MP), and saturated hydraulic conductivity (Ks) .were measured in plant row (R), and trafficked (T) and untrafficked (N) interrows. A rainfall simulator was used to apply two early season rainfalls to 1 m2 plots where KBr suspension was surface applied for Br leaching study. The first simulated rainfall event (30 min) consisted of a low (1.27 cm h-1) or a high (5.08 cm h-1) rate applied, 24 h after Br application. One week later, the high rainfall rate was repeated on all plots.
Soil samples were taken two days after applying first and second simulated rainfall (a week between them) and the end of season from different depths for measuring Br concentrations. Soil physical properties were affected by both tillage system and position.
Bulk density was higher in NT versus CT and in T position versus Rand N positions. Total porosity was lower in NT versus CT but MP was significantly higher in NT. Saturated hydraulic conductivity was about 90% lower at T position versus N and R positions. Coefficient of variation was quite large, making it difficult to obtain statistical differences between tillage systems. The surface l0-cm of soil contained the highest Br concentration for depth treatments with treatment differences occurring primarily in 0 to 25 cm depth. In first and second sampling dates, more Br leached under NT versus CT system. However, there was no significant difference between the two tillage systems in Br leaching at the end of the growing Season. In site 1, Br leached more due to the coarse texture and high Ks of the soil.
M. R. Bahremand, M. Afyuni, M. A. Hajabbassi, Y. Rezaeinejad,
Volume 6, Issue 4 (1-2003)
Abstract
A field experiment was conducted to investigate the effects of sewage sludge and of time lapse after sludge application on soil physical properties. Four sewage sludge treatments (0, 25, 50, and 100 ton/ha) in a complete randomized block design with three replications were applied and mixed to a depth of 20 cm. Wheat was planted and soil physical properties were measured 23, 85, 148, and 221 days after sewage sludge application.
Sewage sludge application significantly increased MWD, hydraulic conductivity, final infiltration rate, moisture percentage at 1/3 and 15 bars, and plant available soil moisture, while it significantly decreased soil bulk density. In general, the best results obtained with the 100 ton/ha sewage sludge treatment. Time lapse after sewage sludge application caused soil physical properties to approach the values of the control. However, even 221 days after sludge application, the 50 and 100 ton/ha treatments had significantly different values compared with the control treatment. The results in this research show that sewage sludge can help to improve soil physical conditions and this effect persists over long periods. This effect is specially important with plant available soil moisture and infiltration.
H. Rezaie, M.r. Neishabouri, A. R. Sepaskhah,
Volume 8, Issue 3 (10-2004)
Abstract
Hydraulic coefficients of a porous media such as hydraulic conductivity K(θ) and diffusivity D(θ) have a controlling role in the evaluation of groundwater flow and pollutant transport behavior. Therefore, successful porous media flow evaluation depends on the accurate determination of its hydraulic coefficients. But it is hard and time consuming to measure. Values for these coefficients accurately as measurements usually task place at a moisture range close to saturation. This situation justifies the preference for prediction models to be used. One method for evaluation of K(θ) and D(θ) coefficients is to use models which take measured soil moisture characteristic curve data into consideration. For the purposes of the present study, pressure plates apparatus measured the required data to develop soil moisture characteristic curve for nine various soil textures. The volume of instantaneous outgoing water was measured with respect to time and the total volume of water released at the end of each experiment was measured for a given pressure (0.1 to 1.5 Mpa) imposed on undisturbed soil samples. A simple equation based on Richard’s equation is provided for the estimation of K(θ) and D(θ). Application of Mualem, van Genuchten et. al, Burdine, Green and Corey, and Gardner models for estimation of the K(θ) and D(θ) values at a variety of nine varied soil textures under experiment showed a wide range of variation. Therefore, it is hard to simulate the accurate hydraulic conductivity behavior for the given varied soil textures by means of the models available. However, if the minimum and maximum simulated values obtained from the models at respective soil moisture contents are considered to be a permitted range, one may state that the results of the estimated hydraulic coefficients by the proposed method in this study lie within the permitted range or agree with the results of other models considered. Therefore, the proposed method for determination of K(θ) and D(θ) is capable of selecting the best simulation model to estimate hydraulic coefficient values.
A. Safadoust, M. R. Mosaddeghi, A. A. Mahboubi, A. Nouroozi, Gh. Asadian,
Volume 11, Issue 41 (10-2007)
Abstract
The increased potential for soil erosion and compaction due to continuous row crop production and intensive tillage is causing some concern and has led to the consideration of reduced tillage techniques as part of the solution. The objective of this study was to investigate the short-term (one-year) influences of different management practices on the physical properties of a sandy loam soil under corn crop. Treatments were the combinations of three tillage systems (no-till, NT chisel plow, CP and moldboard plow, MP) and three composted cattle manure rates [0, 30 and 60 ton (dry weight) ha-1]. The experiment was carried out in a split-plot design. Three replicates of the treatments were applied in a randomized block design. Saturated hydraulic conductivity (Ks), total porosity (TP), macro-porosity (Macro-P), micro-porosity (Micro-P) of soil and mean weight diameter (MWD) of aggregates, were measured to a depth of 22.5 cm when 100 percent of the tassels appeared. Tillage and manure combination had significant effects on Log[ Ks], TP, Macro-P and Micro-P. The MP system increased pore space and continuity due to complete inversion and loosening, and as a result Ks, TP, Macro-P and Micro-P were higher than NT system. Higher Macro-P observed for CP might have caused higher Ks versus MP. Reduced tillage systems increased MWD and the increment of manure caused an increase in MWD over all tillage treatments. The results indicate short-term positive effects of manure application on soil pore size characteristics and aggregate stability under moldboard and chisel plowings in the region.
H. Emami, M. Shorafa, M. R. Neyshabouri,
Volume 16, Issue 59 (4-2012)
Abstract
Direct measurement of soil unsaturated hydraulic conductivity (K(h) or K(θ)) is difficult and time-consuming, and often in many applied models, predicting hydraulic conductivity is carried out according to measurements of soil retention curve and saturated hydraulic conductivity (Ks). However, using KS as a matching point in many procedures may result in over-estimation of unsaturated hydraulic conductivity in dry regions. Therefore, the unsaturated hydraulic conductivity at inflection point of retention curve (Ki) and Ks was used as a matching point to predict K(h). For measurement of K(h), 30 soil samples were collected based on variety of soil texture (8 texture classes from sandy to clay) and other chemical and physical properties. In addition to Ks, K(θ) values of undisturbed samples were measured using multi-step outflow method at matric suctions of 0.1, 0.2, 0.3, 0.5 0.7, 1 bar and inflection point of retention curve by using hanging water column and pressure plate. Then, the measured K(h), and water diffusivity (D(θ)) values were compared to the predicted values of van Genuchten and Brooks and Corey models (with Mualem and Burdine constraint). The results showed that for 80% of the samples, the van Genuchten–Mualem model with Ki was the best model for predicting K(h) (i.e. using Ki as a matching point in the van Genuchten–Mualem model resulted in best fitting to measured data). Also, in 6.7 % of samples (two sandy clay samples), Brooks and Corey-Mualem model with Ki and in 13.3 % soil samples (2 silty clay and 2 silty clay loam samples), van Genouchten–Mualem model had a best fitting to K(h) measured data. Furthermore, in 20 % samples (4 clay loam, and 2 silt loam textures), the accuracy and efficiency of van Genuchten–Mualem with Ki and van Genuchten–Mualem models in predicting K(h) were almost similar. According to t-Student test, the mean of RMSE and GSDER of van Genuchten–Mualem model with Ki was significantly less than van Genuchten–Mualem model at P < 0.01. In 90 percent of samples, van Genuchten-Mualem and Brooks and Corey-Burdine theory had the best fitting to the measured data of water diffusivity, but in some cases van Genuchten-Burdine model with Ki was the best model for predicting D(θ).
Sh. Ghorbani Dashtaki, S. Dehghani Baniani, H. Khodaverdiloo, J. Mohammadi, B. Khalilmoghaddam,
Volume 16, Issue 60 (7-2012)
Abstract
Saturated hydraulic conductivity (Kfs) and macroscopic capillary length of soil pores are important hydraulic properties for water flow and solute transport modeling. Measuring these parameters is tedious, time consuming and expensive. One way is using indirect methods such as Pedotransfer functions (PTFs). The objective of this research was to develop some PTFs for estimating saturated hydraulic conductivity and inverse of macroscopic capillary length parameters (*). Therefore, the coefficients, Kfs and * from 60 points of Azadegan plain in Shahrekord were measured using single ring and multiple constant head method. Also, some of the readily available soil parameters from the two first pedogenic layers of the soils were obtained. Then, the desired PTFs were developed using stepwise multiple linear regression. The accuracy and reliability of the derived PTFs were evaluated using root mean square error (RMSE), mean error (ME), relative error (RE) and Pearson correlation coefficient (r). The highest correlation coefficients of 0.92 and 0.72 were found between Kfs-bulk density and *-bulk density, respectively. There was no significant correlation between soil particle size distribution and Kfs and *. This can be related to the fact that most of the soil samples were similar in texture and macro pores. The most efficient PTFs in predicting Kfs and * could explain 85 and 66 percent of the variability of these parameters, respectively. All the derived PTFs underestimated the Kfs and * parameters.
M. Akbari, B. Nazari, M. Parsinezhad , H. Ebrahimian,
Volume 16, Issue 62 (3-2013)
Abstract
This study was conducted on subsurface drainage network under operation in Behshahr. DRAINMOD model was used to simulate drainage system using measured data in 2006. The model was evaluated to estimate soil hydraulic conductivity by comparing the measured and predicted values of water table depth and drain discharge for different values of hydraulic conductivity. The results of this method were compared with the results of output drainage water method (as a baseline method). Use of water table depth simulation results in estimating hydraulic conductivity model resulted in considerable error, while the simulation results of drain discharge rate could be used with good accuracy for estimating it. There was a small difference between the output drainage water method and the inverse solution of DRAINMOD model to estimate soil hydraulic conductivity (2.3 and 2.5 cm/h, respectively). Thus, the comparison between the measured and predicted values of drain discharge could be a good criterion to estimate soil hydraulic conductivity using the inverse solution of the DRAINMOD model
P. Bagheri , S. M. A. Zomorodian,
Volume 17, Issue 63 (6-2013)
Abstract
Hydraulic conductivity is an important parameter in the design of geotechnical structures such as earth dam, floor construction, retaining walls and environmental structures. In unsaturated soils, hydraulic conductivity is a function of moisture content and soil water suction i.e. soil moisture characteristic curve. In this study, the values of unsaturated hydraulic conductivity in two soil types (Ramjerdi and Molasadra core dam series) at 5 different compactions using Gardner method were measured. Then, the unsaturated hydraulic conductivity was estimated by different models using the soil moisture characteristic curve and was compared with measured values. The results showed that Fredlund and Xing models predict the soil moisture characteristic curves more accurately compared with van Genuchten model. For Ramjerdi soil series and up to nearly 0.25 volumetric water content, (VGM) and (FM) models indicated a good estimation for unsaturated soil conductivity. Also, for Molasadra core dam none of the models resulted in acceptable estimations for unsaturated hydraulic conductivity.
S. M. J. Mirzaei, , S. H. Tabatabaei, M. Heidarpour, P. Najafi,
Volume 17, Issue 66 (2-2014)
Abstract
There chemical and organic matter content in garbage leachate that may affect soil physical and hydraulic properties. The main objective of this study was to evaluate the influences of the leachate of Isfahan Organic Fertilizer Factory (IOFF) on some soil physical and hydraulic properties in a soil chemically enriched by Zeolite. The treatments include two soil textures (clay loam and sandy loam) and three levels of zeolite (0, 5 and 10 percent). The treatments were applied on lysimeters scale. The results showed that irrigation with the leachate caused a reduction of infiltration and hydraulic conductivity in the clay loam soil. The hydraulic conductivities in clay loam soil without zeolite (B0) before and after irrigation with leachate were 1.73 and 0.36 m/day, respectively. In contrast, there were no changes in the sandy loam soil’s infiltration and hydraulic conductivity. The hydraulic conductivities in the sandy loam soil with 5 percent zeolite (A5) before and after irrigation with leachate were 3.17 m/day. Furthermore, zeolite had a decreasing effect on those processes. The results show that irrigation with leachate caused reduction of bulk density in two types of soil and all levels of zeolite.
M. Nouri, M. Homaee, M. Bybordi,
Volume 17, Issue 66 (2-2014)
Abstract
In order to assess hydraulics of LNAPLs in soil, the soil retention curves of petroleum and water were both determined through hanging column method. And, the hydraulic conductivity of petroleum and water were determined by steady head method. The water and petroleum hydraulic conductivities were 7.27 and 57.84 cm.day-1, respectively. The soil retention parameters were obtained based on van Genuchten, Brooks-Corey and Campbell models. In addition, the soil hydraulic conductivity for both fluids was predicted based on Mualem- Brooks-Corey, Burdine- Brooks-Corey, Mualem-van Genuchten and Campbell models. The accuracy assessment of models was performed by ME, RMSE, CD, EF and CRM. The results indicated that the magnitudes of the pore-size distribution parameters and the bubbling pressure parameters were reduced in NAPL-air system compared to water-air system. Due to unusual hydraulic behavior of petroleum and soil-petroleum interactions leading to remaining substantial petroleum content in porous media, more matric potential is needed to drain out petroleum from soils compared to water. Thus, soil provides more retention for petroleum at a given quantity of fluid. Owing to high amount of petroleum kinematic viscosity, the saturated soil hydraulic conductivity of petroleum was lower than that of water. However, soil hydraulic conductivity for petroleum was larger than water at more than 100 cm matric head.
M. Sarmast, M. H. Farpoor, M. Sarcheshmehpoor, M. Karimian Eghbal,
Volume 18, Issue 68 (9-2014)
Abstract
Biocalcite infilling and bridging in a sandy soil was studied in the present research. Effects of 2 bacterial species (Sporosarcina pasteurii and Sporosarcina ureae), 3 reactant concentrations (0.5, 1.0, and 1.5 M of urea and CaCl2 mixture), and 6 reaction times (12, 24, 48, 96, 192, and 288 hr) on saturated hydraulic conductivity and mechanical strength of a sandy soil were studied as a factorial experiment. Soil samples were selected from sand dunes of Joopar area, Kerman Province. Bacterial inoculums and reactant solutions were daily added to soil columns. Results of the study showed that S. pasteuriihad had a higher effect on decreasing hydraulic conductivity of the treated samples (11.57 cm/h) compared to the blank (41.61 cm/h) than S. ureae. Increasing reaction times (from 12 to 288 hrs) and reactant concentrations (from 0.5 to 1.5 M) decreased hydraulic conductivity by 49 and 16 %, respectively. S. pasteurii increased strength of treated samples up to 2.6 Mpa pressure compared to S. ureae. Reactant concentrations and reaction times increased soil strength significantly (2.13 and 4.1 Mpa, respectively). Micromorphological observation showed calcite crystals bridging soil particles and filling pore spaces.
B. Khalili Moghadam, M. Afyuni, A. Jalalian, K. C. Abbaspour, A. A. Dehghani,
Volume 19, Issue 71 (6-2015)
Abstract
With the advent of advanced geographical informational systems (GIS) and remote sensing technologies in recent years, topographic (elevation, slope, and aspect) and vegetation attributes are routinely available from digital elevation models (DEMs) and normalized difference vegetation index (NDVI) at different spatial (watershed, regional) scales. This study explores the use of topographic and vegetation attributes in addition to soil attributes to develop pedotransfer functions (PTFs) for estimating soil saturated hydraulic conductivity in the rangeland of central Zagros. We investigated the use of artificial neural networks (ANNs) in estimating soil saturated hydraulic conductivity from measured particle size distribution, bulk density, topographic attributes, normalized difference vegetation index (NDVI), soil organic carbon (SOC), and CaCo3 in topsoil and subsoil horizon. Three neural networks structures were used and compared with conventional multiple linear regression analysis. The performances of the models were evaluated using spearman’s correlation coefficient (r) based on the observed and the estimated values and normalized mean square error (NMSE). Topographic and vegetation attributes were found to be the most sensitive variables to estimate soil saturated hydraulic conductivity in the rangeland of central Zagros. Improvements were achieved with neural network (r=0.87) models compared with the conventional multiple linear regression (MLR) model (r=0.69).
T. Ahmady, M. Delbari, P. Afrasiab,
Volume 23, Issue 2 (9-2019)
Abstract
Nowadays, the Beerkan computational algorithms (BESTslope and BESTsteday) are known as the suitable indirect methods for estimating soil saturated hydraulic conductivity (Ks) and sorptivity (S), as well as the scale parameter (hg) in van Genuchten soil water retention equation through the data collected in the Beerkan infiltration experiment and other required data. The purpose of this study was to compare these algorithms in estimating Ks and S, as well as the soil water content corresponding to the suctions of 33 kPa, 100 kPa, 200 kPa, 300 kPa and 1500 kPa. For this purpose, a total of 40 Beerkan infiltration experiments were carried out in Sistan dam research field. From all Beerkan experiments, 30 tests in loam and sandy loam textures having a relative error less than 5.5% (Er <5.5%) were selected for further analysis. The statistical criteria RMSE, ME and ωr2 were used to compare the measured and estimated water content values at each suction. The results showed that the BESTsteday algorithm, which had a more simple calculating process than the main algorithm (i.e. BESTslope), could provide the Ks and S values and the soil water content of the near field capacity with an acceptable accuracy. The model performance in estimating water content corresponding to the 1500 kpa suction head (i.e. θfc) was not acceptable for both algorithms. Moreover, the relative error of estimating soil water content (Er(h,θ)) was decreased gradually by an increase in clay %.
B. Torabi Farsani, M. Afyuni,
Volume 25, Issue 1 (5-2021)
Abstract
Compost leachate is a liquid resulting from physical, chemical and biological decomposition of organic materials. The main objective of this study was to evaluate the influence of leachate compost on the physical, hydraulic and soil moisture characteristic curves. Also, the effect of leachate on the aerial organ fresh weight of corn was investigated. Leachate was added to clay loam and sandy clay loam soils at the rate of zero, 1.25 and 2.5 weight percent. The soil water characteristic curve and the estimation of the parameters of the van Gnuchten and Brooks and Corey models were performed using RETC software. Leachate increased the bulk density and decreased the available water of the clay loam soil. Only 1.25% of the leachate increased the available water in the sandy clay loam soil. Two levels of leachate decreased the bulk density of sandy clay loam soil. Leachate decreased the saturation hydraulic conductivity of the clay loam and increased this parameter of sandy clay loam soil. Leachate was more successful in increasing the aerial organ fresh weight of corn in the sandy clay loam soil. Therefore, leachate was more useful in sandy clay loam than in clay loam soil, and 1.25% treatment was better in the sandy clay loam soil. Also, the used leachate increased the repellency of both soils. Leachate caused the parameters of van Gnuchten and Brooks and Corey models to increase, as compared to the control in both soils.
