In situ estimation of hydraulic conductivity using simplified methods (original) (raw)
Related papers
Quick Estimation of Hydraulic Conductivity in Unsaturated Sandy Loam Soil
1999
Laboratory experiments were conducted for determining hydraulic conductivity during infiltration in an unsaturated sandy loam soil, using both steady state and equilibrium methods. A constant head Guelph permeameter and a volumetric pressure plate extractor were used. Based on two ponded heights in the permeameter, the parameters of Gardner's equation expressing the unsaturated hydraulic conductivity as a function of pressure head (i.e. the saturated hydraulic conductivity K s and the exponent α), were estimated simultaneously. Furthermore, it was found that the parameter α, could also be predicted from the soil-water retention curve based on equilibrium data obtained from the extractor. This indicated that, for the soil type studied, one-ponded height in the permeameter method could be sufficient for the determination of the exponent α, provided that the soil-water retention curve is known.
On the use of soil hydraulic conductivity functions in the field
Soil and Tillage Research, 2007
The estimation of soil water fluxes using the Darcy-Buckingham flux-gradient approach is, after a century of use, still problematic under field conditions. Two features of the soil hydraulic conductivity (K) function are the main causes of failure, first the exponential character of the K versus soil water content (u) relations, which lead to large variations in K for minimal variations of u. Due to this, the level of precision of field measurements of u and the spatial variability of u itself, make the deterministic estimation of soil water fluxes unfeasible using this approach. Secondly, the spatial variability of the parameters of the K(u) relations also contribute heavily to errors in soil water flux estimation from site to site. In a coffee crop water balance experiment, soil water fluxes below the root zone were estimated over one year, comparing the use of a soil hydraulic conductivity function obtained in the field, with an indirect climatologic approach in which the deep drainage is estimated from a water balance excess. Five replicates gave the possibility of calculating variances of both forms of calculation and their respective coefficients of variation (CV). Results show that CVs of the estimates made through the Darcy-Buckingham approach varied from 78 to 122%, in comparison to 8-23 for the indirect climatologic approach. It is therefore concluded that Darcy-Buckingham approach used deterministically under field conditions does not yield consistent results.
Comparison of Six Methods To Determine Unsaturated Soil Hydraulic Conductivity
Soil Science Society of America Journal, 1994
Knowledge of soil hydraulic properties is required for soil-water flow models. Although many studies of individual methods exist, comparisons of methods are uncommon. Therefore, we compared application ranges and results for six laboratory methods for determining hydraulic conductivity or diffusivity on eolian sand, eolian silt loam, marine sandy loam, and fluviatile silt loam. The methods, hot air, sorptivity, crust, drip inflltrometer, Wind's evaporation, and one-step outflow, fall into three groups: (i) those that only yield a conductivity curve; (ii) those that yield a simultaneous estimate of conductivity, diffusivity, water content, and pressure head; and (iii) those that yield a diffusivity curve. Diffusivities were converted to conductivities with a water retention curve. One main difference between the methods was the pressure head-water content range. Despite the large differences between the methods, the results for the first two groups tended to be similar. The results of the third group did not match well with those of the first two. It proved difficult to compare these methods correctly due to hysteresis.
European Journal of Soil Science, 2017
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Soil & Tillage Research, 1998
The determination and the use of soil hydraulic conductivity functions obtained from internal drainage experiments, performed in ®eld soil pro®les, using the Darcy±Buckingham¯ux gradient approach are discussed. Details of the calculation procedures indicate the sensitivity of the methodologies used, and of the most commonly adopted model for K() relations: K()K 0 .exp[À.( 0 À)]. It is shown that the unit total water potential gradient cannot prevail in the whole soil pro®le during internal drainage after in®ltration and that, as a consequence of this assumption, several methods of hydraulic conductivity determination yield K() relations which are depth dependent, even for homogeneous soils. The dif®culties of using K() relations in modeling soil water dynamics due to their very strong exponential behaviour are also discussed. #
Testing a simplified approach to determine field saturated soil hydraulic conductivity
Four Decades of Progress in Monitoring and Modeling of Processes in the Soil-Plant-Atmosphere System: Applications and Challenges, 2013
Interpreting and simulating hydrological processes need a large number of field saturated soil hydraulic conductivity, K fs , data that should be collected with simple and rapid field experiments. A Simplified method based on a Beerkan Infiltration run (SBI method) was recently developed and tested successfully on Burundian soils. With the SBI method, a cylinder is inserted to a short depth into the soil and the infiltration time of a few small volumes of water repeatedly applied at the surface of the confined soil is measured. Calculating K fs needs the slope of the linearized cumulative infiltration vs. time relationship and an estimate of the so called * parameter. In this investigation, the SBI method was validated with reference to a larger dataset, also including different Sicilian soils. The * value of first approximation (0.012 mm -1 ) yielded an estimate of K fs differing in general by not more than a factor of three from the K fs values obtained by the more complete and onerous BEST (Beerkan Estimation of Soil Transfer parameters) procedure of soil hydraulic characterization. The K fs values obtained with SBI method were also very close (means differing by a factor of 1.01) to the ones determined with the One Ponding Depth relationship for the single ring pressure infiltrometer technique. Detection of physically plausible relationships between * and the slope of the linearized infiltration curve indicated that the measured infiltration process contains the necessary information to estimate *. Different * predictive relationships for Sicily and Burundi allowed to obtain estimates of K fs never differing by more than a factor of three from the corresponding values obtained with BEST. The developed method is a good candidate method for intensively sampling an area of interest. Points needing developments include tests with other datasets, comparisons with independent measurements of both * and K fs , and maybe development of an improved experimental methodology to obtain the infiltration data.
Measurement and Estimation of Saturated Hydraulic Conductivity of Soil
Determination of the saturated hydraulic conductivity (k) is needed in many studies and applications related to irrigation, drainage, water movement and solute transport in the soil. Although many advances are made for direct measurements of k, they are usually time consuming and costly. Some attempts have been made to indirectly predict the saturated hydraulic conductivity from the more easily or readily available basic soil properties. The objective of this study is to develop and validate Pedo-transfer Functions (PTFs) for estimation of saturated hydraulic conductivity using linear and multiple regression technique. Sixty soil samples were collected at 15cm depth, at different locations in the Sal river basin that lies in the southern coastal region of Goa, India. Saturated hydraulic conductivity was measured, by variable falling head method through Permeameter in the laboratory. Prediction accuracies were evaluated using coefficient of determination, root mean square error, and mean error, between measured and predicted values. The results show that, the PTFs for the estimation of saturated hydraulic conductivity could be used appropriately for the soils with sandy and sandy loam textures falling in this area of the coastal region of southern India.
A Comparison of Three Field Methods for Measuring Saturated Hydraulic Conductivity
Canadian Journal of Soil Science, 1985
The saturated hydraulic conductivity, Ks, was measured on a loamy sand, a fine sandy loam, a silt loam and a clay at four 100-m2-area sites in southern Ontario. Twenty measurements of Ks were obtained by each of three different measurement techniques at each of the four sites. The techniques included: (1) the air-entry permeameter method; (2) the constant head well permeameter method using the Guelph Permeameter; and (3) the falling-head permeameter method applied to small soil cores. The Ks data were found to be better described by the log-normal frequency distribution than by the normal frequency distribution. Statistical comparison of the mean Ks values [Formula: see text] indicated significant differences between some or all of the methods within each site. This site-method interaction was interpreted in terms of the influence of macropores and air entrapment on each of the measurement techniques. The measured Ks values ranged over an order of magnitude on the sand, one to two o...
Indirect estimation of near-saturated hydraulic conductivity from readily available soil information
Geoderma, 2002
Application of process-based water flow and solute transport models is often hampered by insufficient knowledge of soil hydraulic properties. This is certainly true for dual-or multi-porosity models that account for non-equilibrium flow of water in macropores, where the saturated 'matrix' hydraulic conductivity is a particularly critical parameter. Direct measurement is possible, but this is impractical for larger scale studies (i.e. catchment or regional), where estimation methods (pedotransfer functions) are usually required. This paper presents pedotransfer functions for hydraulic conductivity at a pressure head of À10 cm, K 10 , based on measurements of near-saturated hydraulic conductivity made with tension infiltrometers in 70 soil horizons at 37 different sites in 0016-7061/02/$ -see front matter D 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 1 6 -7 0 6 1 ( 0 1 ) 0 0 1 5 4 -9 (N.J. Jar vis).