Hydraulic Conductivity Measurements Research Articles

Hydraulic properties determination from pumping test in Northern areas of Ondo state, South-western Nigeria for groundwater development

Groundwater potential evaluation of the Northern area of Ondo State using information obtained from hydrogeological measurements of hydraulic conductivity, transmissivity, and yield aquifer characteristics from 37 drilled boreholes. These data were analyzed alongside the information gathered during the pumping test at each site which includes drawdown values, static water level, and pumping rate. The average depth of the borehole and installation depth are 30.76 m and 28.9 m respectively. The static water level ranges from 2.7 m to 14.0 m with an average of 6.0 m. The drawdown recorded from the observation wells varies from 1.9 m and 15.1 m. The yield capacity of the boreholes ranges between 0.40 – 2.98 L/s, and an average of 25.5654 m3/d. The values of hydraulic conductivity conducted in the area vary from 0.37 to 23.29 m/d, and an average of 3.67 m/d. The calculated transmissivity for the study area ranges from 4.79 (gneiss) to 165.32m2/d (migmatite) and an average of 30.08m2/d. The values of specific capacity vary from 4.07 – 140.53, while storativity within the range of 0.0002 – 0.001 are the most dominant showing a corresponding low specific capacity values generally less than 10 m2/d. Consequently, specific yield, hydraulic conductivity, and transmissivity values were integrated to generate a groundwater potential map for Ondo Northern area.

Data for: No effect of pyrolysis temperature and feedstock type on biochar hydraulic properties

Laboratory and field measurements of water retention characteristics and hydraulic conductivity of 12 standard biochars, as well as field saturated conductivity values of these same biochars incorporated into a sandy soil.

Correction Method for Hydraulic Conductivity Measurements Made Using a Fixed Wall Permeameter

Hydraulic conductivity measurement through a fixed wall permeameter is a common practice to obtain the fluid transmissibility characteristics of soil matrix; however, sidewall leakage due to rigid wall effect may significantly influence the observed values for coarse-grained soils. In this study, the boundary flow error was identified through characterizing the geometrical properties of voids adjacent to the sidewall, and a parameter known as the boundary void ratio (eb) was proposed to account for this effect. The findings suggest that a fixed wall cell containing coarse soils would unavoidably generate extra voids at the interface between soil grains and inner rigid wall, contributing to a larger eb at the wall than void ratio within the soil bed; the measured hydraulic conductivity is increased primarily due to the apparatus-induced error. A two-dimensional geometric model was then established to estimate the eb value for uniformly sized coarse soils confined by a rigid permeameter wall, based on which a method was obtained for eliminating the boundary flow error from a fixed wall cell. The mathematical method was finally validated against experimental data from existing literature. It can be concluded that the boundary condition at sidewall featuring unwanted gaps lead to overestimation of the coefficient of permeability; however, the proposed correction method could adequately eliminate the boundary flow error for uniformly sized coarse-grained soils tested within a rigid wall cell.

Effect of earthworms on soil physico-hydraulic and chemical properties, herbage production, and wheat growth on arable land converted to ley

Effects of earthworms on soil physico-hydraulic and chemical properties, herbage production and wheat growth in long-term arable soils following conversion to ley were investigated. Seven intact soil monoliths were collected from each of four arable fields. One monolith per field served as a control. The other six were defaunated by deep-freezing; three were left defaunated (DeF) and three (DeF+E) were repopulated with earthworms to mimic pasture field density and diversity. The monoliths were planted with a grass-clover ley and inserted into pre-established ley strips in their original fields for 12 months. Hydraulic conductivity measurements at −0.5 cm tension (K0.5) were taken five times over the year. K0.5 significantly increased in summer 2017 and spring 2018 and decreased in winter 2017–18. K0.5 was significantly greater (47%) for DeF+E than DeF monoliths. By the end of the experiment, pores >1 mm diameter made a significantly greater contribution to water flow in DeF+E (98%) than DeF (95%) monoliths. After only a year of arable to ley conversion, soil bulk density significantly decreased (by 6%), and organic matter (OM) content increased (by 29%) in the DeF treatments relative to the arable soil. Earthworms improved soil quality further. Compared to DeF monoliths, DeF+E monoliths had significantly increased water-holding capacity (by 9%), plant-available water (by 21%), OM content (by 9%), grass-clover shoot dry biomass (by 58%), water-stable aggregates >250 μm (by 15%) and total N (by 3.5%). In a wheat bioassay following the field experiment, significantly more biomass (20%) was produced on DeF+E than DeF monolith soil, likely due to the changed soil physico-hydraulic properties. Our results show that earthworms play a significant role in improvements to soil quality and functions brought about by arable to ley conversion, and that augmenting depleted earthworm populations can help the restoration of soil qualities adversely impacted by intensive agriculture.

New Concepts for Water Well Screen Opening and Gravel Pack Size

The purpose of the study to obtained well screens opening size and gravel packs size, and to access within the groundwater inter through the aquifer to the well screen and prevent running sand from entering the well. The use of properly designed screen and gravels are important and this paper is an important reference for the design of groundwater wells. In this study, the purpose of the circle method is to design water well and the benefits of sand control. The determination of screen slot size and its variation in the opening is often a major aim of hydrogeological studies. However, measurement of hydraulic conductivity (K) at a high spatial resolution in sedimentary aquifers is a challenge. One commonly used approach is to estimate slot size from grain size analysis. The objectives of this study are to compare between curve of grain size analysis, bar graph and circle method used applied different formulas for the determination of slot size from grain-size data and to evaluate how well this method predicts slot size and gravel pack. Correlation between the mechanical analysis curve, bar graph and the circle methods were found for the used applied different formulas. Based on circle results, the applied circle formulas appear to be suitable for an initial assessment of aquifer properties. However, considering the difference in calculated aquifer parameter values, results are smaller significantly and reliable for the high analysis of aquifer materials.

Interaction effect of Nd:YAG laser and universal adhesive system for dentin sealing.

BackgroundTo evaluate the influence of the association of the universal adhesive system to different energy densities of the Nd:YAG laser on the hydraulic conductance of dentin. Material and MethodsFifty bovine dentin discs were made. The samples were stratified into four groups (n = 10) according to the treatment performed; SBU- Adper Single Bond Universal (3M ESPE), SBU_60 - SBU associated with the Nd:YAG laser (60mJ, 10Hz, 0.6W - 47.77 J / cm²), SBU_80 - SBU associated with the Nd:YAG laser (80mJ, 10Hz, 0.8 W - 63.69 J / cm2) and C – dentin without treatment (smear layer). Hydraulic conductance measurements were taken 24 hours after the treatments (HC1) and after erosive challenge (HC2). Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX) helped to visualize the dentin after the different treatments. Scheffe and Games-Howell statistical tests were used to analyze hydraulic conductance (α = 0.05). ResultsThe treated dentin (SBU, SBU_60, and SBU_80) reduced HC1 when compared to dentin with smear layer (C) (p< 0.001). The erosive challenge has increased HC2 in SBU_60 and C (p< 0.001), and did not promote a significant difference in SBU_80 and SBU. The SEM / EDX analyzes showed an irregular and semi-permeable barrier on the surfaces of the treated dentin. ConclusionsThe association of universal adhesive with Nd:YAG can be an effective alternative for the occlusion of dentinal tubules, whereas higher energy per pulse Nd:YAG (SBU_80) can increase the resistance to permeability when exposed to the erosive challenge. Key words:Dentin, permeability of dentin, Nd:YAG Laser, adhesives.

Wetted front advance under point-source field dripper system for estimation of unsaturated hydraulic conductivity function

Unsaturated soil hydraulic conductivity function is often required for designing a drip irrigation system. Point-source field dripper methods are available for quick measurement of saturated hydraulic conductivity (Ks) and scaling parameters of the soil. However, steady-state saturated front radii is difficult to differentiate compared to the wetted front radii, which is easy and precise. Field dripper methods were used for estimation of Ks and scale parameters using saturated front radii for four different soils viz ., cultivated tilled and no-tilled normal and sodic soils. There exists a good consistency among the values obtained by using saturated as well as wetted front radii. Use of wetted front radii could be useful for measurement of Ks and scale parameter of the soil with more accuracy.

The impact of different desensitizing agents on dentin permeability

The exposure of dentinal tubules, dentin permeability and dentin hypersensitivity are closely related. This study evaluated the dentin permeability treatment using two desensitizing agents: nano-hydroxyapatite (n-HAP) and strontium chloride (SrCL2). Thirty healthy third molars were extracted for orthodontic reasons from patients aged 18 to 30 years. 5x5x1mm specimens were obtained from the selected molar crowns and were randomly assigned to one of the three treatment groups (n = 10): GC- no desensitizing treatment, stored only in distilled water; GE- application of 10% strontium chloride for 5 min on the dentin surface; GnHAP- application of n-HAP following the same protocol used for GE. An in vitro fluid transport model was used for the measurement of dentin hydraulic conductance, associated with qualitative analysis by Scanning Electron Microscopy (SEM). Results of flow (Q) and hydraulic conductance of dentin (Lp) were analyzed by one-way ANOVA, with Tukey post-hoc test, α = 5%. The mean Q and Lp of the CG group differed statistically (p 0.05). Photomicrographs obtained from the GC specimens showed more open dentinal tubules when compared to GE and GnHAP. It was concluded that desensitizing treatments with SrCL2 and n-HAP were effective in reducing dentin permeability.

Rock outcrops change infiltrability and water flow behavior in a karst soil

AbstractRock outcrops are widespread across the surface of the earth, particularly in karst environments, and they play an important role in infiltration‐runoff processes by triggering preferential flow. However, the characteristics of the preferential flow network at the soil–rock interface and its influencing factors in karst areas remain poorly understood. To clarify how the emergence of outcrops on the land surface affects soil infiltrability and water flow behavior, soil hydraulic conductivity (K) measurements and dye tracing experiments were conducted in a karst area with two contrasting surface features (i.e., rock outcrop plot [RP] and non‐rock‐outcrop plot [NRP]) in Yunnan Province, Southwest China. Results showed that (i) in the immediate vicinity of rock outcrops in the RP, K values were significantly increased, and other soil properties and plants were also improved when compared with results 1 m away from outcrops and in the NRP; and (ii) in the RP, the soil–rock interface dominated the preferential flow network surrounding outcrops, and the connected conduits produced by plant roots and soil fauna were also involved in this infiltration process. Matrix flow was the dominant flow behavior in the NRP. We concluded that rock outcrops, by improving soil properties and building a well‐connected preferential flow network, can greatly change infiltrability and water flow behavior in karst soil. This implied that outcrops will facilitate quick infiltration after most rainfall events and thus reduce rain‐induced surface runoff and soil erosion, as well as increasing groundwater recharge and the water supply to nearby plants.

Assessing field-scale variability of soil hydraulic conductivity at and near saturation

Saturated hydraulic conductivity (Ks) is a crucial hydraulic property for assessing soil water dynamics. Understanding the spatial variability of Ks in a field is important for site-specific resource management. However, direct measurement of hydraulic conductivity K as a function of soil water pressure head h [K(h)] is time consuming and laborious. Alternatively, pedotransfer functions (PTFs) have been developed to predict Ks indirectly based on more easily measurable soil properties. Although PTFs have been used for decades, their validity for estimating the field-scale spatial variability of Ks remains unclear. The objectives of this study were to characterize the spatial pattern of K(h) at and near saturation in an agricultural field by a coregionalization technique, and in comparison, to evaluate the performance of ROSETTA PTF in characterizing the spatial variability of K(h) at the field scale. Surface soil (7–13 cm) K(h) in the vertical direction was measured at 48 locations in a 71-m by 71-m grid within a no-till farmland. Apparent electrical conductivity was densely measured using a contact sensor Veris 3150 and used as ancillary variable in a coregionalization approach. Experimental semivariograms and cross semivariograms were derived and applied in cokriging to generate K(h) maps. Geostatistical analysis presented similarities in maps of measured K(h) with ROSETTA-predicted K(h) data for a matric potential of −10 cm. However, the strong spatial heterogeneity of measured Ks, which was caused by macropores, observed in the field was not captured by ROSETTA estimates. The results indicated that texture dominated PTFs like ROSETTA, in which soil structure is not considered, might be useful in characterizing the spatial pattern of unsaturated hydraulic conductivity rather than Ks. Field scale Ks maps based on PTF estimates should be evaluated carefully and handled with caution.

How to Improve the Quality of Laboratory Permeability Tests in Rigid-Wall Permeameters: A Review

ASTM D2434, Standard Test Method for Permeability of Granular Soils (Constant Head) (Withdrawn 2015), and ASTM D5856, Standard Test Method for Measurement of Hydraulic Conductivity of Porous Material Using a Rigid-Wall, Compaction-Mold Permeameter, are used to measure the saturated hydraulic conductivity, Ksat, of soil specimens in rigid-wall permeameters (RWPs). Several laboratory conditions and settings explain why the tests do not give Ksat values but unsaturated hydraulic conductivity, K(Sr), values for a degree of saturation, Sr, that is often in the 80–85 % range. It is suggested to improve ASTM D2434 and ASTM D5856 by adding two requirements: (1) use a watertight-and-airtight RWP (a control method is provided), and (2) use a mass-and-volume method to obtain the true Sr value of the tested specimen. To illustrate potential detrimental impacts of current standards, the article describes a case where sand was planned to be used as a filter layer for a solid waste project. Large quantities of sand had been delivered at the construction site. The Ksat value of the sand, as compacted, had to exceed 10−4 m/s to satisfy a bylaw. To prove this, two laboratories followed ASTM D2434 for their tests but found K values of 5−8 × 10−5 m/s. The project engineers asked the authors to make verifications. The prior tests were redone and yielded similar K values. However, it was found that the real Sr value was close to 80 % instead of being assumed to be 100 %. Other tests were performed after using vacuum and deaired water in a watertight-and-airtight permeameter: the specimens reached Sr = 100 % and gave Ksat values of about 2 × 10−4 m/s, 3–4 times higher than initial tests. As a result, the already delivered sand satisfied the bylaw condition and there was no need to return large quantities of sand already delivered, to purchase a new type of sand after having done laboratory tests, and to have a time delay in construction, all these items having a high economic impact.

Measurement of hydraulic conductivity under horizontal paths in granular soils

In geotechnical structures, the permeability-dependent stability analysis is generally evaluated under vertical trajectories, because most permeameters are configured so that the water passes through the porous medium in this way. However, it is clear from the physical point of view that water can flow along different paths, including preferential ways that can include horizontal trajectories, parallel to the deposit of the stratum. The foregoing implies that both the vertical and horizontal component of the hydraulic conductivity or permeability coefficient must be estimated for a given stratum. The current research aims to explore possibilities for measuring the coefficient of permeability in horizontal trajectories, on granular soils, under a constant condition of relative density. For this purpose, a special chamber attached to a constant head permeameter was designed and constructed, which allows to measure the permeability in conditions of horizontal flow parallel to the soil layers. The proposed camera also admits the estimation of the permeability coefficient by combining stratifications of different granular soils, where the trajectories are not perfectly horizontal, but have diagonal paths. The results are compared with data obtained by conventional vertical flow permeameters, in order to check the difference in the measurements considering both situations in the samples. As a conclusion, it is important to report that there is evidently a difference in the permeability coefficients measured under different trajectories,

A study on the geotechnical characterization and water retention characteristic curve of pond ash.

The understanding of the engineering behaviour of unsaturated soil is totally dependent on the water retention characteristic curve (WRCC). In this paper, a comprehensive study of the WRCCs of pond ash along with the ash's geotechnical behaviour has been made. The WRCC has been drawn experimentally using a Fredlund device based upon the pressure plate technique for both wetting and drying cycles. Further, an investigation was carried out to study WRCC hysteresis of pond ash. There exists a considerable hysteresis in drying and wetting curves of pond ash sample. The different WRCC models were used to fit the experimental WRCC data. The effect of compaction on WRCC was also studied. The air entry value in the case of a loose sample is low and the sample gets nearly desaturated at low soil suction as compared to a dense sample. Also, the wetting WRCC is predicted using the Feng and Fredlund model as it is difficult and time consuming to measure the whole hysteresis. The predicted results are compared with the measured wetting WRCC. Since the direct measurement of unsaturated hydraulic conductivity is difficult to obtain in engineering practices, the unsaturated hydraulic conductivity function is predicted using the measured WRCC as the input parameter using SEEP/W software.

A database of saturated hydraulic conductivity of fine-grained soils: probability density functions

ABSTRACTSaturated hydraulic conductivity is a key soil mechanics parameter which has widespread use in many geotechnical applications. In order to set up stochastic analyses, geotechnical modellers require databases to calibrate the parameter ranges and distributions employed. This letter uses a recently compiled database of saturated hydraulic conductivity measurements called FG/KSAT-1358 and reports on the fitting of various probability density functions to the data of void ratio, liquid limit, water content ratio and the negative natural logarithm of ksat. It is shown that the best fit distribution is the lognormal for void ratio, while the loglogistic distribution is most favoured for liquid limit and water content ratio, and the best fit distribution for -ln[ksat(m/s)] is the logistic function. The data of -ln[ksat(m/s)] is then subdivided according to liquid limit level, silt or clay classification, type of hydraulic conductivity test used and sample preparation/condition. When some subdivisions of the database are analysed, the best fit distribution is more variable with GEV and logistic being the most favoured for most of the studied subsets.

Hydraulic conductivity estimation by using groundwater modelling system program for upper zone of Iraqi aquifers

Estimating of soil hydraulic conductivity was so important and essential parameter for designing systems. Hydraulic conductivity measurements need many activities beginning from extract samples. Therefore it is having been found costly and time-consuming. At the present time, geo-statistical ways were used to estimate the hydraulic conductivity on the basis of restricted data. The aim of this research is to characterize hydraulic conductivity for the upper zone of Iraqi aquifers using groundwater modelling system (GMS) software and to build two dimensions geo-statistical analysis model depending on the application of 868 wells.These wells were divided into 778 wells for building the model and 90 wells for the verification. The hydraulic conductivity parameter which was obtained from the geo-statistical analysis model results indicated that the best fitted theoretical model was the inverse distance weighted (IDW) model with a coefficient of determination (R2 ) equal to 87.43% and root mean square error (RMSE) equal to 1.853. Also, by conducting many trails, it was found that the optimal distance range for estimating the hydraulic conductivity was 3800 to 5000 meters. A comparison between the kriging and IDW interpolation methods indicated that both methods could estimate the hydraulic conductivity with good accuracy and less error.

Using high-resolution electrical resistivity to estimate hydraulic conductivity and improve characterization of alluvial aquifers

Shallow alluvial aquifers are important local and regional water resources but obtaining sufficient hydrogeologic data to properly characterize their spatial extent and hydraulic conditions can often be difficult, time-consuming, and expensive. In this study, we used over 40,000 measurements of electrical resistivity tomography (ERT) data and hydraulic conductivity (K) data from 33 pump tests across eight shallow alluvial and glacial outwash aquifer field sites in Iowa to: (1) assess the relation between hydraulic K tests and electrical resistivity (ER) in alluvial and glacial outwash systems; and (2) evaluate the application of the ER-K relationship as input data for local-scale groundwater flow modeling. Average field-measured K across the eight sites was 95 m/day and ranged from 29 to 246 m/day, whereas aquifer resistivity ranged from 27 to 896 (ohm-m). Both K and ER were greater at the glacial outwash aquifer sites compared to the alluvial aquifer sites and a linear relationship (R2 = 0.90) was observed between field-measured K and ER when incorporating all field sites. We evaluated how K derived from the ER-K relationship compared to K estimated from pump tests and calibrated K in a local-scale groundwater flow model. The K estimated by the ER-K relationship was comparable to the K estimated from the pump tests in terms of providing reasonable values for model development. Utilizing the ER-K relationship to estimate K would save significant time compared to conducting pump tests. Hence, estimating K from electrical resistivity can provide a non-intrusive, cost and time efficient way to evaluate and model alluvial aquifers.

Random forest, M5P and regression analysis to estimate the field unsaturated hydraulic conductivity

Hydraulic conductivity of soil reveals its influencing role in the studies related to management of surface and subsurface flow, e.g. irrigation and drainage projects, and solute mass transport models. Direct measurements of hydraulic conductivity have many difficulties due to spatial variation of the property in the field. Pertaining to this problem, in this study, estimation models have been developed using machine learning methods (M5 tree model and random forest model) in an attempt to estimate the accurate values of unsaturated hydraulic conductivity related to basic soil properties (clay, silt and sand content, bulk density and moisture content). Data set was collected from the experimental measurements of cumulative infiltration using mini disc infiltrometer at the study area (Kurukshetra, India). A multivariate nonlinear regression (MNLR) relationship was derived, and the performance of this model was compared with the machine learning-based models. The evaluation of the results, based on statistical criteria (R2, RMSE, MAE), suggested that random forest regression model is superior in accurate estimations of the unsaturated hydraulic conductivity of field data relative to M5 model tree and MNLR.

Variations in near-saturated hydraulic conductivity of arable mineral topsoils in south-western and central-eastern Finland

Soil hydraulic properties play an important role in determining the level of crop productivity and the extent of environmental loading. Consequently, measurement of near-saturated soil hydraulic conductivity (K(h)) by tension infiltrometer (TI) is an interesting technique. To provide reference values for near-saturated K(h) in arable mineral topsoils of Finland and to investigate variability in these values caused by tillage, antecedent soil moisture content and earthworm burrows, field measurements were conducted in south-western and central-eastern Finland using the TI technique, at supply pressure head –6, –3, and –1 cm. The range of near-saturated K(h) values obtained was 0.02–12.6 mm h-1 at –6 cm, 0.30–85.9 mm h-1 at –3 cm, and 2.55–250 mm h-1 at –1 cm. At –6 cm pressure head, clay soils tended to show lower values than coarser-structured soils, but the order was reversed at –1 cm. The spatial variation in near-saturated K(h) was moderate and was exceeded by the temporal variation.

Vertical Hydraulic Conductivity Measurement by Gravity Drainage.

Vertical Hydraulic Conductivity Measurement by Gravity Drainage.

Digital interface device for field soil hydraulic conductivity measurement

Accurate and reliable measurements of field-saturated hydraulic conductivity (Kfs) are essential for accurate determinations of soil and solution water fluxes. Kfs is a crucial parameter to design drainage, irrigation systems and many other environmental, agricultural and industrial installations Reynolds et al. (1983). There is a high demand for Kfs data. Its evaluation is preferable to be done in situ. A popular device to measure the Kfs is the head well permeameter such as the Guelph Permeameter. However, it is an analog equipment based on a Mariotte’s bottle that requires full attention and training to be manually operated, where the reading of the flux values (Q, in cm3/min) is time-consuming and costly. In this paper, we describe a device, with a digital readout, to measure the steady state rate of water level change Rs, in order to obtain Qs and Kfs. The method is based on the monitoring of the vacuum variation of the Mariotte’s bottle. Our results show no statistical differences between the measurements values of manual and automatic recording using paired t-test. In addition, our device identifies measurement artifacts due to the variation of the ambient temperature during measurements. The necessary accuracy for the digitalization method becomes feasible due to the availability of accurate piezoelectric transducers (Micro-Electro-Mechanical System – MEMS). Automating and digitizing these processes will reduce time, costs and increase the accuracy and availability of data. The device can be directly adapted to commercially available head well permeameters as shown in our experimental results. The more widespread use and understanding of this parameter can improve the rational use of water for irrigation and use in risk models for forecasting available soil water and therefore crop productivity.