Changes In Hydraulic Conductivity Research Articles

Thermally-induced changes in tropical soils properties and potential implications to sequential nature-based solutions

Some remediation techniques, such as thermal remediation, can significantly change the soil properties. These changes can be beneficial or detrimental to the sequential application of Nature-based Solutions. This work evaluated the effects of thermal remediation on the properties of two tropical soils (Technosol and Oxisol), and discuss how these changes might impact both biotic and abiotic degradation processes. Bench tests using disturbed samples were performed under oxic and anoxic conditions, whereas 3D physical models were used to simulate the heat distribution along undisturbed samples. The changes in soils texture, density, hydraulic conductivity, iron concentration, mineralogy and microbiota were evaluated. The properties of Oxisol were more affected than those of Technosol due to the higher levels in Fe(III), organic carbon and finer texture. When heated in the range of 120 to 300 °C under oxic and anoxic conditions, the Fe(II) content and the magnetism intensity increased in Oxisol, probably due to the formation of magnetite. Under oxic conditions, the burning of Oxisol organic matter promoted an anoxic atmosphere, favoring the formation of Fe(II). However, the continuous increase of the temperature (>300 °C) lead to the decrease of Fe(II) due to the transformation of magnetite to maghemite, and then to hematite. The heating process also promoted some minerals decomposition and cementation of the clay fraction, increasing the soil texture. Bacterial populations were impacted, but showed ability to recover at 60 °C. However, above 100 °C no culturable cells were recovered and at temperatures above 270 °C soil sterilization occurred. The changes observed, especially in Oxisol samples, indicated that mild heating (between 120 and 240 °C), in turn, can increase the potential for abiotic degradation of some contaminants, such as chlorinated solvents. Therefore, heating conditions up to 240 °C during thermal remediation can be defined as to promote beneficial changes in soil properties, increasing its potential for natural attenuation by abiotic processes even when the microbiota is affected, and improving its sustainability.

A hydro-mechanical coupled solution for electro-osmotic consolidation in unsaturated soils considering the decrease in effective voltage with time

For electro-osmotic consolidation in unsaturated soils, coupled deformation, inconsistent changes in hydraulic conductivity and electro-osmotic permeability with matric suction, and a decrease in effective voltage with time occur simultaneously. To consider all of these processes, an analytical solution was proposed. The time-stepping method was adopted in the calculation of the solution to depict the nonlinear change in shrinkage deformation with matric suction. The accuracy of the proposed analytical solution was validated by comparison with results from laboratory tests and from a previously presented solution without considering coupled deformation. Then, a parametric study was conducted. The results indicate that the dissipation of the pore water pressure is slow when considering coupled deformation, but a large volume of water is discharged in the end, especially for soils with a large volumetric shrinkage index Cm. A larger final negative pore water pressure and discharged water can be predicted by considering the inconsistent changes in hydraulic conductivity and electro-osmotic permeability. Finally, with the consideration of the decrease in effective voltage over time, both the maximum negative pore water pressure and final drainage decrease, which is consistent with field observations.

اثر دما بر ضریب نفوذپذیری خاک رسی متراکم و عایق رسی ژئوسینتتیک (GCL)

تاثیر دما در خواص نفوذپذیری خاک‌های رسی متراکم یکی از پارامترهای اساسی در طراحی لایه‌های عایق مهندسی است که در معرض شیرابه‌ها هستند. در این تحقیق اثر دما بر ضریب نفوذپذیری رس متراکم منطقه نازلوی ارومیه و عایق های رسی ژئوسینتتیک و همچنین تاثیر میزان تنش موثر و دانسیته بر نرخ تغییر ضریب نفوذپذیری نمونه های رسی بررسی شده است. دستگاه تعیین ضریب نفوذپذیری سه محوری با دیواره انعطاف پذیر برای اندازه گیری ضریب نفوذپذیری نمونه ها تحت تاثیر دما مورد استفاده قرار گرفته است. با افزایش دما ویسکوزیته محلول کاهش یافته و اثرات دمایی ساختار خاک را تغییر می دهد و تولید حفرات بزرگتر بین ذرات رس می کند و باعث ایجاد تغییر در سطح مقطع موثر جریان شده و آب جذب شده تبدیل به آب آزاد می شود و در نتیجه باعث افزایش ضریب نفذپذیری خاک رسی می شود. افزایش تنش موثر باعث می شود نرخ افزایش در ضریب نفوذپذیری در اثر افزایش دما کاهش یابد. همچنین با افزایش دانسیته خاک رسی، ضریب نفوذپذیری و نرخ افزایش آن کاهش می یابد. بر خلاف خاک‌های رسی، در عایق های رسی ژئوسینتتیک افزایش دما تاثیر چندانی در ضریب نفوذپذیری این لایه ها نداشته و زمانی که این لایه ها در معرض افزایش دما قرار گیرند به عملکرد خوب خود به عنوان یک مانع هیدرولیکی ادامه می‌دهند.

Влияние засоления на устьичную и гидравлическую проводимость, а также на уровень аквапоринов в клетках листьев растений ячменя, различающихся по солеустойчивости

We studied participation of aquaporins in the regulation of leaf hydraulic conductivity and relationship of hydraulic conductivity with accumulation of ABA and stomatal closure during salt stress. Using the method of immunohistochemical localization we showed that salinity led to greater decline in the level of aquaporins in the region of the vascular leaf bundles of the more salt-tolerant Prairia cultivar, accompanied by a noticeable decrease in hydraulic conductivity of the leaf. In the less salt-tolerant plants of the Mikhailovsky cultivar, significant changes in the level of aquaporins under the influence of salt stress were not found. The degree of decrease in the hydraulic conductivity of the leaf in plants of two cultivars under the influence of salt stress correlated with a decrease in transpiration. Immunohistochemical localization of abscisic acid (ABA) in leaf cells showed that during salt stress this hormone accumulated in leaf mesophyll cells and stomata. The uptake of exogenous hormone from the nutrient solution and its entry into the leaf through the vascular bundles was accompanied by an increase in staining for aquaporins and the hydraulic conductivity of the leaves, which is characteristic of the ABA action. Differences in the localization of exogenous and endogenous hormones were obviously the cause of the opposite directions of changes in hydraulic conductivity: its increase under the influence of an exogenous ABA and a decrease - under the influence of salt stress. ABA concentration assessment in xylem showed the absence of its increase during salt stress, which explains the absence changes of staining for this hormone in the region of the leaf vascular bundles and indicates that accumulation of ABA in a short-term salt stress is not the result of its delivery from the roots, but the result of its synthesis in the shoot itself.

Weather-driven deterioration processes affecting the performance of embankment slopes

Deterioration of earthworks and the resultant implications for serviceability and increased occurrence of failures have a significant negative impact on transport networks both in the UK and internationally. There is evidence in the field that deterioration processes are occurring over the life of an asset, comprising cracking and loss of suction. These are weather-driven processes that occur in the absence of increased mechanical loads and can lead to failure many years after construction. To demonstrate the progressive loss in mechanical performance of clay fill due to a purely environmentally driven deterioration process, a programme of unsaturated triaxial testing was carried out. A new mechanism of soil deterioration driven by cyclic wetting and drying is proposed, based on an extensive laboratory and field experimental programme. The underlying cause for this is the micro-structural changes to the soil fabric leading to loss of suction generation capacity. In addition, cracking leads to changes in hydraulic conductivity and the movement of water into and out of the soil. The implications for slope stability assessment include the need for changeability of soil parameters and of the ground model, with changes occurring both seasonally and gradually over time.

Empirical evaluation of sand filters to evolve practical designs for artificial recharge through dry wells

• Agricultural runoff can be filtered for groundwater recharge through dry wells. • Hydraulic conductivity of filters reduced exponentially with cumulative filtration. • Provision of sedimentation tank or raised filter helped maintain high conductivity. • The top deposition and entrapment in 5 cm accounted for 87.5% of the total sediment. • Removal of top 3–4 cm of layer resulted in 70–80% recovery of hydraulic conductivity. A laboratory based empirical assessment of hydraulics of sand filters was carried out under the compelling practical condition of exposure to alternate cycles (wet and dry spell) of filtration. The lab-scale simulations purportedly attempted to mimic the field scale condition of sediment loading in runoff as suspended sediment. The sand filters having a layer thickness of 50 cm and 30 cm with a particle size of <2 mm and 0.2–0.5 mm on the gravel-pebble base were tested for the progressive change in hydraulic conductivity and sediment removal during the filtration event under a combination of treatments using different sediment concentrations (1.5 g l −1 , 2 g l −1 , and 2.5 g l −1 ) and water heads (20 cm and 40 cm). A sharp reduction in filter hydraulic conductivity was observed in the case of higher sediment concentration. A filtration hiatus of 2 days between tests resulted in significant improvement in the hydraulic conductivity of the filter matrix. The provisions of pre-entry sedimentation trap before filtration could maintain a scaled-up hydraulic conductivities for a longer duration. A layer of additional reinforcement of an agro-net above the filter matrix, though facilitated easy cleaning after a filtration event, but resulted in a scaled-down hydraulic efficiency. Removal of the top 3 to 4 cm of the filter top could recover about 70 to 80% of the initial hydraulic conductivity. After filtration of sediment equivalent to 16.1 and 17.0 kg m −2 , the top deposition accounted for 72.07 and 73.12%, respectively, which along with the sediment entrapped in the top 5 cm accounted for more than 87% of the total sediment. A steady state concentration of sediment in the filtrate in all the above combinations was found to converge asymptotically below 0.10 g l −1 which, in a limited means used as a basis to custom designed field scale recharge filter using the sand as matrix filter.

Characterizing natural degradation of tetrachloroethene (PCE) using a multidisciplinary approach

A site in mid-western Sweden contaminated with chlorinated solvents originating from a previous dry cleaning facility, was investigated using conventional groundwater analysis combined with compound-specific isotope data of carbon, microbial DNA analysis, and geoelectrical tomography techniques. We show the value of this multidisciplinary approach, as the different results supported each interpretation, and show where natural degradation occurs at the site. The zone where natural degradation occurred was identified in the transition between two geological units, where the change in hydraulic conductivity may have facilitated biofilm formation and microbial activity. This observation was confirmed by all methods and the examination of the impact of geological conditions on the biotransformation process was facilitated by the unique combination of the applied methods. There is thus significant benefit from deploying an extended array of methods for these investigations, with the potential to reduce costs involved in remediation of contaminated sediment and groundwater.

Experimental study on clogging and water quality change during artificial recharge

In this paper, an experimental sand column was used to investigate the clogging process and water quality changes simultaneously during artificial recharge. Clogging was described quantitatively according to the changes of hydraulic conductivity, whilst several important water quality parameters, such as SS, total bacterial count, DO, TOC, total nitrogen, total phosphorus were measured at regular time intervals during recharge. After 80 hours of continuous recharge, the hydraulic conductivity of the upper column (10-15cm) and the lower(15-55cm) decreased from 1.23×10−4m/s to 9.84×10−5m/s and from 1.23×10−4m/s to 1.06×10−4m/s, respectively. This was thought to be due to physical clogging by suspended solids and then biological clogging by biomass accumulation along the columns. The sand column had significant self-purification effect on suspended matter, bacteria, TOC, permanganate index, total nitrogen, total phosphorus, copper, etc. The filtration and adsorption effect of the upper column were much stronger than that of the lower, so the clogging of the upper was more severe. The results of this study will provide technical support for the implementation of large-scale artificial recharge in the Liaolan groundwater funnel area of Qingdao.

Unsaturated Soil Hydraulic Properties according to Double-Ring Infiltration of Saline Water

Inverse modeling is a relatively complex procedure that allows quick estimation of soil hydraulic properties, yielding parameters for both soil water retention and unsaturated hydraulic conductivity function from a single experiment. The purpose of this research was to evaluate saline water effect on unsaturated hydraulic properties of clay loamy nonsaline-sodic soil layers and estimate these properties inversely from infiltration data using a double-ring infiltrometer.Three levels of water salinity (EC) 1.1, 2.2 and 5.8 dS/m were used for each treatment (T1, T2, and T3, respectively). Soil samples at three depths (0–20, 20–40 and 40–60 cm) were taken to measure Mualem–van Genuchten (MVG) hydraulic parameters (θr, residual water content, θs, saturated water content, α and n, shape parameters, and Ks, lab saturated hydraulic conductivity). Soil hydraulic parameters were estimated with an inverse solution using HYDRUS-1D model and infiltration data. Besides, the most sensitive MVG parameters to infiltration data (n, θs, and Ks) were inversely estimated due to difficulty in estimating several parameters simultaneously. Results showed that salinity had no significant effect on soil water infiltration and soil hydraulic conductivity changes in the specified salinity range according to the variance analyses (ANOVA).The Nash–Sutcliffe coefficient of efficiency (Ce) between simulated (HYDRUS) and measured values of cumulative infiltration data was about 0.998, indicating an excellent match. Soil water retention, as well as unsaturated soil hydraulic conductivity, were optimized with reasonable accuracy when the soil profile was assumed to be homogenous. In addition, simulated soil-water contents were quite similar to the measured values in which the values of Nash–Sutcliffe efficiency (Ce) for T1, T2, and T3 were 0.83, 0.85, and 0.85, respectively. In conclusion, the soil hydraulic parameters can be inversely estimated using the measured infiltration data through the double ring method if the soil is homogeneous.

Improving aggregate stability and hydraulic properties of Sandy loam soil by applying polyacrylamide polymer

Improving soil properties, especially in arid and semiarid regions, is an urgent need for sustainable food production. This study aims to evaluate the effect of applying two types of anionic polyacrylamide polymers (PAMs) with different molecular weights on: (1) soil aggregate stability, (2) infiltration rate and (3) saturated hydraulic conductivity of sandy loam soil and introduce a novel modelling approach to predict the effect of PAM addition on the mentioned soil properties. Polymers were applied at five different concentrations; 0, 100, 250, 500 and 1000 mg L−1. Direct positive relations between the concentrations of PAM (low and high molecular weight) and saturated hydraulic conductivity and infiltration rate were observed. Nevertheless, the relations were more pronounced in case of low molecular weight PAM. The difference between the effect of the two PAMs on infiltration rate was statistically significant at α = 0.05. On the other hand, the differences were not significant except for the 1000 mg L−1 concentration in case of saturated hydraulic conductivity. Meanwhile, concentration has an effect on increasing soil aggregate stability only in case of low molecular weight PAM. At the concentration 1000 mg L-1 of low molecular weight PAM, aggregate stability and saturated hydraulic conductivity increased 3-fold while infiltration rate increased by more than 7-fold compared to the control. It is hypothesized that the change in the mentioned properties is correlated to the amount of PAM adsorbed by the soil and hence they can be used as surrogate parameters of adsorption. Modified versions of the Langmuir and Freundlich isotherm equations were used to model the change in aggregate stability and saturated hydraulic conductivity in response to the PAM concentration. The pseudo-first and second kinetics models were applied to predict the change in infiltration rate. The models showed excellent fit to the experimental data, thus supporting our hypothesis. The results suggest that low molecular weight PAM is more efficient in improving the physical properties of sandy loam soil. The modelling approach presented in this work may be extended to other types of soil. Other isotherm models may be used to predict the response of soil to PAM concentration where the Langmuir or Freundlich isotherms do not apply. This modelling approach provides land managers with a decision support tool to optimize PAM application.

Groundwater flow below construction pits and erosion of temporary horizontal layers of silicate grouting

Injection of silicate grouting materials is widely used to create temporary horizontal layers for reducing inflow of groundwater at construction sites, in regions with shallow water tables. The erosion of a grouting layer was investigated by means of analytical solutions for groundwater flow and transport within a pit after construction finished. Erosion is assumed to occur by dissolution of the temporary injection layer and subsequent advective transport. Thereby, the hydraulic conductivity changes with time. This paper presents novel analytical solutions and approximate solutions for the major fluxes in the construction pit as a function of the domain settings, aquifer gradient and hydraulic conductivity. In addition, the mass flux and the dilution ratio of erosion-related components leaving the construction pit and entering the aquifer are quantified. Derived solutions are verified against numerical simulations. A sensitivity study shows the impact of domain settings on fluxes and dilution ratio. The results confirm that mass flux of grout components increases with ongoing erosion. Thus, its effect on groundwater quality increases with time after construction ceased.

Biochar application alters soil structure but not soil hydraulic conductivity of an expansive clayey soil under field conditions

Biochar amendment is considered as a soil management practice worldwide for the sustainable agricultural production by improving soil physical property, fertility, and microbial activity. However, the change of soil structure and hydraulic conductivity over time after applying biochar to expansive clayey soil under field conditions are unclear. In this study, biochar was applied to soil at the rates of 0% (CK), 1% (BC1), and 3% (BC3) (w/w) to assess the variation in soil physical properties after day 10, day 193, and day 375, respectively. The results showed that the total soil porosity estimated based on bulk density and the average particle density of 2.65 g cm−3 was significantly higher than the total porosity as measured by water retention curve (P 300 μm) significantly increased by 114.25%/164.58% under BC1/BC3 after 375 days (P < 0.05). There were no significant differences in the saturated hydraulic conductivity among all treatments after 1 year (P < 0.05). Our findings indicate that the estimated total porosity is not suitable for evaluating the change of soil porosity over time after biochar application. Biochar in size less than 2 mm can improve soil structure in expansive clayey soil under field conditions. However, these positive changes may be insufficient to facilitate the improvement of saturated hydraulic conductivity after 1 year at the biochar application rates of 1% and 3%. Our findings provide insights into the application of biochar as a soil amendment for management practices in expansive clayey soil.

Evaluating Treatment Requirements for Recycled Water to Manage Well Clogging during Aquifer Storage and Recovery: A Case Study in the Werribee Formation, Australia

Managed aquifer recharge (MAR) is the intentional recharge of water to suitable aquifers for subsequent beneficial use or to achieve environmental benefits. Well injection techniques for MAR, such as Aquifer Storage and Recovery (ASR), rely on implementing appropriate design and defining the operational parameters to minimise well clogging and maintain sustainable rates of recharge over the long term. The purpose of this study was to develop water quality targets and pre-treatment requirements for recycled water to allow sustained recharge and recovery in a medium-coarse siliceous aquifer. The recharge water is a blend of 40% Class A recycled water and 60% reverse osmosis (RO)-treated Class A recycled water. Four source waters for MAR were evaluated: (1) this blend with no further treatment, and this blend with additional treatment using: (2) a 20 µm sediment cartridge filter, (3) a 5 µm sediment cartridge filter, or (4) a 5 µm granular activated carbon (GAC) cartridge filter. All four treatment options were also further disinfected with chlorine. The four blended and treated recycled waters were used in laboratory columns packed with aquifer material under saturated conditions at constant temperature (20.7 °C) with light excluded for up to 42 days. Substantial differences in the changes in hydraulic conductivity of the columns were observed for the different treatments within 14 days of the experiment, despite low turbidity (&lt;2 NTU) of the blend waters. After 14 days, the GAC-treated water had a 7% decline in hydraulic conductivity, which was very different from the other three blend waters, which had declines of 39–52%. Based on these results and consistent with previous studies, a target biodegradable dissolved organic carbon (BDOC) level of &lt;0.2 mg/L was recommended to ensure a biologically stable source of water to reduce clogging during recharge.

Experimental study about the influence of cyclic load on the hydraulic conductivity of clay

The hydraulic conductivity k, one of the most important engineering properties of soft clay, plays a great role during the whole life cycle of underwater tunnel. Therefore, it is necessary to systematically study the responses of k to the dynamic load under the background of the great development of geotechnical engineering in the world. In this study, a series of seepage tests after cyclic loading were conducted on reconstituted kaolin clay using a modified hollow cylinder apparatus. The influence of cyclic load on the permeability characteristics of soft clay was illustrated in two aspects. The cumulative axial deformation of clay induced by cyclic loading resulted in the smaller hydraulic conductivity of the specimens, and also, the dynamic load reconstructed the microstructure of clay and made the number of large pores getting decreased and the small pores increased. There was a positive correlation between the deformation of soil and the change of hydraulic conductivity, but the reconstruction effect was irregular with the frequency of dynamic load. The measured k values got affected at the beginning, this phenomenon appropriately explains the positive correlation between the number of cycles of dynamic load and the change of hydraulic conductivity.

Effects of Land Use Changes on the Soil Physicochemical Properties in South-Western Algeria

Abstract This study shows the impact of the reforestation program by some tree species (Pinus halepensis, Cupressus sempervirens and Eucalyptus camaldulensis) on the soil physicochemical parameters in south-western Algeria steppe. The study was realized on soil samples from the Touadjeur site. One hundred soil samples were taken from the field, followed by physicochemical analyses in the laboratory. A comparison of the soil elements between reforested and unreforested sites considered as a control was carried out. The results show that there are differences in the physicochemical parameters of the soil between the reforestation and the non-reforestation ones constituted by a steppe vegetation. The ANOVA one way test shows a highly significant difference change in soil physical parameters, moisture, holding capacity and saturated hydraulic conductivity, but no change in apparent density, actual density and color. Also, from a chemical point of view, the differences concern the organic matter, organic carbon, pH and certain soil contents. The main differences in soil properties between the reforestation sites and the control site, reflect the consequences of forest management adopted by the forest services, most probably the choice of reforestation species.

Temporal changes in soil hydraulic conductivity in saturated and unsaturated fields

Soil hydraulic conductivity ( $$K$$ ) is an important soil property that exhibits relatively large uncertainty. The temporal variability of $$K$$ is often ignored when calculating water movement in soil. Various factors such as tillage, rain, temperature, wetting/drying, soil surface crusting, solution concentration, and biological activity can influence field $$K$$ . We investigated soil $$K$$ in a central Iowa field as a function of time and tillage by using tension infiltrometer measurements with pressure head tension settings of 0 cm and − 3 cm. No clear relationship was found between bulk density ( $$\rho_{\text{b}}$$ ) and $$K$$ . Path analysis was conducted to assess the contribution ratios and causal relationships between factors affecting $$K$$ . The $$K$$ values were influenced by physical impacts such as tillage, precipitation, and surface crusting with contributions of 24%, − 32%, and 49%, respectively, and with error of 60%. Soil surface crusting had a particularly large impact on saturated $$K$$ . The maximum volume fraction influenced $$K$$ . Earthworm activity that impacted the soil pore structure was also noticed in the field. Owing to this biological mechanism, no relationship was observed between $$\rho_{\text{b}}$$ and $$K$$ . It is important to recognize the multiple combined effects of soil physical processes and biological activities when documenting $$K$$ in field soils.

Fungal pathogens of canker disease trigger canopy dieback in poplar saplings by inducing functional failure of the phloem and cambium and carbon starvation in the xylem

Tree canker diseases are mainly caused by necrotrophic fungal pathogens, which induce canker lesions, wilting, or dieback in many species. We hypothesized that canker-associated canopy dieback is related to functional failure of the phloem and cambium, carbon starvation and/or hydraulic failure. Using a girdling and inoculation system, we evaluated gas exchange and hydraulic parameters, concentrations of non-structural carbohydrates (NSCs), leaf characteristics, stem phenotyping and symptoms of 6-month-old poplar saplings with Botryosphaeria or Valsa canker disease. Pathogen inoculations inhibited callus formation and phloem regeneration and altered the physiological parameters, water potential, NSC content in stems, and symptoms on leaves and stems, while the girdling-only control did not. Results suggest that the functional and structural integrity of the phloem and cambium play crucial roles in the pathogenesis of canker disease. Botryosphaeria canker decreased photosynthetic rate (−54% to −75%), stomatal conductance (−71% to −80%) and transpiration rate (−58% to −66%), while Valsa canker decreased photosynthetic rate (−53% to −83%), stomatal conductance (−71% to −87%) and transpiration rate (−53% to −76%) at 20, 25, and 30 days after inoculation. Results suggest that the two fungal pathogens induce carbon starvation by inhibiting photosynthesis. The leaf water potential was higher and the change in specific hydraulic conductivity was smaller in the canker region than in the adjacent regions, while the NSC content was lower in the region below cankers than above them, suggesting that the fungal pathogens caused poplar canopy dieback by initially inducing carbon starvation, not hydraulic failure.

Hierarchical multiscale numerical modelling of internal erosion with discrete and finite elements

This paper presents a coupled finite and discrete-element model (FEM and DEM) to simulate internal erosion. The model is based on ICY, an interface between COMSOL, an FEM engine, and YADE, a DEM code. With this model, smaller DEM subdomains are generated to simulate particle displacements at the grain scale. Particles in these small subdomains are subjected to buoyancy, gravity, drag and contact forces for short time steps (0.1 s). The DEM subdomains provide the macroscale (continuum) model with a particle flux distribution. Through a mass conservation equation, the flux distribution allows changes in porosity, hydraulic conductivity and hydraulic gradient to be evaluated for the same time steps at a larger, continuum scale. The updated hydraulic gradients from the continuum model provide the DEM subdomains with updated hydrodynamic forces based on a coarse-grid method. The number of particles in the DEM subdomains is also updated based on the new porosity distribution. The hierarchical multiscale model (HMM) was validated with the simulation of suffusion. Results for the proposed HMM algorithm are consistent with results based on a DEM model incorporating the full sample and simulation duration. The proposed HMM algorithm could enable the modelling of internal erosion for soil volumes that are too large to be modelled with a single DEM subdomain.

Calculation Crop Coefficient of Okra with respect to Multi parameters by using dimensional analysis

The dimension analysis is solve to more difficult problem, simplify to difficult equation, reduce the many parameters in equations and search on the parameters more effect of equations. Increase the evaporation from soils and surfaces water with increase transpiration from plants because of raising in temperatures and reducing in humidity are problems of the times which effect on reducing of water. To solve the problems must research on formulas which give actual effects to control on the water reduction by evapotranspiration. In this study will search on methods to solve the crop coefficient (Kc) and evapotranspiration (ET) with multi variables. In this research will be driven equations by statistic of excel program of reference evapotranspiration (ETo) and crop evapotranspiration (ETc) with respect to. From equations and drawings were obtained on maximum value of correlation coefficient(R2). In addition to use the dimension analysis to multi variables (time, number hours of days, relative humidity, change of moisture content, hydraulic conductivity, root depth and temperature) with maximum value of (R2). Researching on equations and methods help to obtain results instead of going back to tables and curves as well reducing field tests that are tired. From equations of ETo and ETc are obtained on R2=0.999 and R2=0.997, respectively from data. From statistic and dimension analysis equations are obtained on result very close with field data with little difference 10% and 4.28%, respectively.

A NUMERICAL GROUNDWATER FLOW MODEL OF WADI SAMAIL CATCHMENT USING MODFLOW SOFTWARE

The climate in most of Gulf Cooperation Council (GCC) countries is considered arid with limited water resources. Proper management of scarce water resources is therefore necessary for sustainable water supply while meeting the growing water demands. A three-dimensional finite-difference groundwater flow model of Wadi Samail Catchment was developed to simulate groundwater flow and to evaluate the sensitivity of the model to the varying of input parameters. Model inputs include lithology of the aquifer derived from borehole data, observed groundwater levels, rainfall, and initial hydraulic conductivity values from pumping tests. The aquifer was divided into four layers. The steady-state calibration was carried out using data in 14 monitoring wells in July 2016. The hydraulic conductivity (k) and recharge values were calibrated using observed groundwater levels with the estimated root mean squared error (RMSE) of 0.8m. The estimated parameters were verified with groundwater levels in October 2016. The RMSE between observed and simulated water levels was 0.81m. The calibrated model was then used to assess the sensitivity of the model to the changes in pumping rate, hydraulic conductivity (k), and recharge. Results showed that the water levels were most sensitive to the changes in hydraulic conductivity of the first layer. While pumping rates and recharge were less sensitive compared to the hydraulic conductivity. In conclusion, the sensitivity analysis results can be used as a management tool for sustainable water resources.