Radial Water Flow Research Articles

A tale of two pumps: Blue light and abscisic acid alter Arabidopsis leaf hydraulics via bundle sheath cell H+-ATPases.

The bundle sheath cell (BSC) layer tightly enveloping the xylem throughout the leaf is recognized as a major signal-perceiving "valve" in series with stomata, regulating leaf hydraulic conductance (Kleaf) and thereby radial water flow via the transpiring leaf. The BSC blue light (BL) signaling pathway increases Kleaf and the underlying BSC water permeability. Here, we explored the hypothesis that BSCs also harbor a Kleaf-downregulating signaling pathway related to the stress phytohormone abscisic acid (ABA). We employed fluorescence imaging of xylem sap in detached leaves and BSC protoplasts from different genotypes of Arabidopsis (Arabidopsis thaliana) plants, using pH and membrane potential probes to monitor physiological responses to ABA and BL in combination with pharmacological agents. We found that BL-enhanced Kleaf required elevated BSC cytosolic Ca2+. ABA inhibited BL-activated xylem-sap-acidifying BSC H+-ATPase AHA2 (Arabidopsis H+-ATPase 2), resulting in depolarized BSCs and alkalinized xylem sap. ABA also stimulated BSC vacuolar H+-ATPase (VHA), which alkalinized the BSC cytosol. Each pump stimulation, AHA2 by BL and VHA by ABA (under BL), also required Ca2+. ABA stimulated VHA in the dark depending on Ca2+, but only in an alkaline external medium. Taken together with earlier findings on the pH sensitivity of BSC osmotic water permeability (i.e. aquaporin activity), our results suggest a Ca2+-dependent and pH-mediated causative link between the BL- and ABA-regulated activities of two BSC H+-ATPases and Kleaf.

Water flow in a cylindrical nanopore with an object

Understanding the physics of water movement through a nanopore with an object is critical for better control of water flow and object translocation. It should help in the design of nanopores as molecular and viral sensors. We evaluated how the external electric field and ion concentrations, pore wall charge density, disk radius and charge density, and ion mobility influence the water flow in a charged cylindrical nanopore using Poisson–Nernst–Planck–Navier–Stokes simulations. We dissected water flow induced by the external electric field (“external” component) from that generated by the field induced by the fixed and mobile charges (“charge” component). The velocity and direction of the axial flow “external” component were controlled directly by the external electric field. The pore wall charges also influenced them indirectly by altering the density and distribution of mobile charges. Higher external concentrations enhanced the axial water flow by lowering its charge component. The ion mobility and disk charge slightly influenced the axial water flow. The axial body forces near the wall drive the axial water flow near the pore wall. If the disk is large, water also flows axially in the opposite direction near the pore center. Local forces near the disk do not control the radial water flow near the disk. The axial body force and water flow near the pore wall do. If an annulus replaces a disk, the axial forces near the pore wall control the radial flow near the annulus and the axial flow within its hole.

Leaf hydraulic maze: Abscisic acid effects on bundle sheath, palisade, and spongy mesophyll conductance.

Leaf hydraulic conductance (Kleaf) facilitates the supply of water, enabling continual CO2 uptake while maintaining plant water status. We hypothesized that bundle sheath and mesophyll cells play key roles in regulating the radial flow of water out of the xylem by responding to abscisic acid (ABA). Thus, we generated transgenic Arabidopsis thaliana plants that are insensitive to ABA in their bundle sheath (BSabi) and mesophyll (MCabi) cells. We also introduced tissue-specific fluorescent markers to distinguish between cells of the palisade mesophyll, spongy mesophyll, and bundle sheath. Both BSabi and MCabi plants showed greater Kleaf and transpiration under optimal conditions. MCabi plants had larger stomatal apertures, higher stomatal index, and greater vascular diameter and biomass relative to the wild-type (WT) and BSabi plants. In response to xylem-fed ABA, both transgenic and WT plants reduced their Kleaf and transpiration. The membrane osmotic water permeability (Pf) of the WT's spongy mesophyll was higher than that of the WT's palisade mesophyll. While the palisade mesophyll maintained a low Pf in response to high ABA, the spongy mesophyll Pf was reduced. Compared to the WT, BSabi bundle sheath cells had a higher Pf, but MCabi spongy mesophyll had an unexpected lower Pf. These results suggest that tissue-specific regulation of Pf by ABA may be confounded by whole-leaf hydraulics and transpiration. ABA increased the symplastic permeability, but its contribution to Kleaf was negligible. We suggest that the bundle sheath spongy mesophyll pathway dynamically responds to the fluctuations in water availability, while the palisade mesophyll serves as a hydraulic buffer.

Evaluation of the susceptibility to erosion of materials used as a base of rigid pavements using a vertical shaking table

ABSTRACT Erosion of the base layers in rigid pavements is a complex hydro-mechanical process that rapidly reduces the structural integrity of these structures. This research revisits a vertical shaking table testing method to characterise the erosion susceptibility of the materials used on base layers in rigid pavements. The procedure consists of applying a vertical vibration to a cylindrical sample of the material under evaluation, which is partially immersed in water in a cylindrical metallic container with a high-strength concrete base. The vertical movement of the sample causes a radial flow of water on its base, which induces high shear forces that eventually erode the bottom of the sample. The volumetric loss of material from the testing sample under different water velocities and pressure conditions is used to quantify its susceptibility to erosion. After presenting the theoretical principles and the numerical formulation of the hydro-mechanical erosion processes occurring in this test, the experimental method was applied to characterise the erosion susceptibility of five different materials. The results suggest that the vertical shaking experimental technique is more versatile and accurate in quantifying the erosion susceptibility of base materials than available standardised tests.

Physically-based reduction function to model unsaturated flow associated with plant transpiration

Vegetation plays an important ‘hydrological’ role in stabilising geostructures. Soil water is extracted by the roots due to transpiration, this increases soil suction and, hence, soil shear strength. Transpiration occurs in two different regimes, energy-limited and the water-limited regimes respectively. These two regimes are reflected in the two branches of the transpiration reduction function used to model the hydraulic boundary conditions for vegetated ground. The water-limited branch accounts for the reduced transmissivity of the soil-root system when the degree of saturation and, hence, the hydraulic conductivity declines. The water-limited branch of existing reduction functions (e.g., Feddes function) is defined in purely phenomenological fashion with parameters that have no clear link with the complex interaction between soil hydraulic properties and root architecture. A paradigm shift can be achieved through physically-based reduction functions. These require analytical closed-form solutions of radial water flow at the soil-root interface that, in turn require introducing simplifying assumptions, i.e., steady-state flow and a simplified hydraulic conductivity function. This paper explores the implications of these assumptions by i) benchmarking the water-limited branch of the reduction function derived analytically against the one derived numerically for more realistic hydraulic behaviour and ii) assessing the steady-state assumption.

Using the Maize Nested Association Mapping (NAM) Population to Partition Arbuscular Mycorrhizal Effects on Drought Stress Tolerance into Hormonal and Hydraulic Components.

In this study, a first experiment was conducted with the objective of determining how drought stress alters the radial water flow and physiology in the whole maize nested association mapping (NAM) population and to find out which contrasting maize lines should be tested in a second experiment for their responses to drought in combination with an arbuscular mycorrhizal (AM) fungus. Emphasis was placed on determining the role of plant aquaporins and phytohormones in the responses of these contrasting maize lines to cope with drought stress. Results showed that both plant aquaporins and hormones are altered by the AM symbiosis and are highly involved in the physiological responses of maize plants to drought stress. The regulation by the AM symbiosis of aquaporins involved in water transport across cell membranes alters radial water transport in host plants. Hormones such as IAA, SA, ABA and jasmonates must be involved in this process either by regulating the own plant-AM fungus interaction and the activity of aquaporins, or by inducing posttranscriptional changes in these aquaporins, which in turns alter their water transport capacity. An intricate relationship between root hydraulic conductivity, aquaporins and phytohormones has been observed, revealing a complex network controlling water transport in maize roots.

Analytical modeling of mine water rebound: Three case studies in closed hard-coal mines in Germany

Purpose.In this paper we present and validate an analytical model of water inflow and rising level in a flooded mine and examine the model robustness and sensitivity to variations of input data considering the examples of three closed hard-coal mines in Germany. Methods. We used the analytical solution to a boundary value problem of radial ground water flow to the shaft, treated as a big well, and water balance relations for the series of successive stationary positions of a depression cone to simulate a mine water rebound in the mine taking into account vertical distribution of hydraulic conductivity, residual volume of underground workings, and natural pores. Findings. The modeling demonstrated very good agreement with the measured data for all the studied mines. The maximum relative deviation for the mine water level during the measurement period did not exceed 2.1%; the deviation for the inflow rate to a mine before its flooding did not exceed 0.8%. Sensitivity analysis revealed the higher significance of the residual working volume and hydraulic conductivity for mine water rebound in the case of thick overburden and the growing significance of the infiltration rate and the flooded area size in the case of lower overburden thickness. Originality.The developed analytical model allows realistic prediction of transient mine water rebound and inflow into a mine with layered heterogeneity of rocks, irregular form of the drained area, and with the inflow/outflow to a neighboring mine and the volume of voids as a distributed parameter without gridding the flow domain performed in numerical models. Practical implications.The study demonstrated the advantages of analytical modeling as a tool for preliminary evaluation and prediction of flooding indicators and parameters of mined out disturbed rocks. In case of uncertain input data, modeling can be considered as an attractive alternative to usually applied numerical methods of modeling ground and mine water flow.

Poplar aquaporin PIP1;1 promotes Arabidopsis growth and development

BackgroundRoot hydraulic conductance is primarily determined by the conductance of living tissues to radial water flow. Plasma membrane intrinsic proteins (PIPs) in root cortical cells are important for plants to take up water and are believed to be directly involved in cell growth.ResultsIn this study, we found that constitutive overexpression of the poplar root-specific gene PtoPIP1;1 in Arabidopsis accelerated bolting and flowering. At the early stage of the developmental process, PtoPIP1;1 OE Arabidopsis exhibited faster cell growth in both leaves and roots. The turgor pressure of plants was correspondingly increased in PtoPIP1;1 OE Arabidopsis, and the water status was changed. At the same time, the expression levels of flowering-related genes (CRY1, CRY2 and FCA) and hub genes in the regulatory networks underlying floral timing (FT and SOC1) were significantly upregulated in OE plants, while the floral repressor FLC gene was significantly downregulated.ConclusionsTaken together, the results of our study indicate that constitutive overexpression of PtoPIP1;1 in Arabidopsis accelerates bolting and flowering through faster cell growth in both the leaf and root at an early stage of the developmental process. The autonomous pathway of flowering regulation may be executed by monitoring developmental age. The increase in turgor and changes in water status with PtoPIP1;1 overexpression play a role in promoting cell growth.

Seeking the "point of no return" in the sequence of events leading to mortality of mature trees.

Drought-related tree mortality is increasing globally, but the sequence of events leading to it remains poorly understood. To identify this sequence, we used a 2016 tree mortality event in a semi-arid pine forest where dendrometry and sap flow measurements were carried out in 31 trees, of which seven died. A comparative analysis revealed three stages leading to mortality. First, a decrease in tree diameter in all dying trees, but not in the surviving trees, 8 months "prior to the visual signs of mortality" (PVSM; e.g., near complete canopy browning). Second, a decay to near zero in the diurnal stem swelling/shrinkage dynamics, reflecting the loss of stem radial water flow in the dying trees, 6 months PVSM. Third, cessation of stem sap flow 3 months PVSM. Eventual mortality could therefore be detected long before visual signs were observed, and the three stages identified here demonstrated the differential effects of drought on stem growth, water storage capacity and soil water uptake. The results indicated that breakdown of stem radial water flow and phloem function is a critical element in defining the "point of no return" in the sequence of events leading to mortality of mature trees.

Dynamics Simulation of Radial Flow Water in Aerial Roots of Corn by Deposit of Dew in Atmosphere Aerial Roots Continuum

Maize plants have different aerial roots from those that serve as an anchor and develop on the stem and live in the atmosphere. Much literature has reported that aerial roots are able to absorb moisture from the air, and even reduce water loss. But very little is known about the exchange of condensed atmospheric water between the aerial roots and the surrounding air. The main purpose of this article is to simulate the absorption of condensed atmospheric moisture by the aerial roots of corn plants. The evaluation of the amount of dew deposited on the roots and the radial water flow through the root is made using the Penman-Monteith equation and the Fick’s law correlated with the Ohm’s law respectively. The various simulations prove that the aerial roots condense atmospheric humidity and that the latter have expressed the transpiration function for certain angles of inclination with a particularity for the inclination of 30° which, from a certain amount of dew expressed the function of dew absorption. On the other hand, for other inclinations, the roots expressed the function of the absorption of humidity with an optimization for the inclination of 60 °. The absorption and transpiration mechanism needs further studies in the future about the characteristics of the radial conductivity through the parameters which influence the coefficient of radial conductivity in the terminal parts of the root than in the lateral parts. In addition, the comparative study of the Priestley-Taylor and Penman-Monteith models is necessary to better understanding of the specific parameters.

Coarse-Grained Model of Underground Thermal Energy Storage Applied to Efficiency Optimization

Seasonal storage of thermal energy, by pumping heated water through a borehole array in the summer, and reversing the water flow to extract heat in the winter, can ameliorate some of the intermittency of renewable energy sources. Simulation can be a valuable tool in enhancing the efficiency of such storage systems. This paper develops a simple, efficient mathematical model of spatial temperature dynamics that focuses on the radial water flow in a cylindrical borehole array. The model calculates the time course of the temperature difference between outgoing and incoming water accurately, and allows new optimization strategies to be explored easily. A strategy based on discharging water heated by the array before it reaches the array center can increase the storage capacity by 25% for a system with a 20% smaller radius than the well-studied Drake Landing system. If the density of boreholes is also doubled, the improvement is 29%.

Modification of the Expression of the Aquaporin ZmPIP2;5 Affects Water Relations and Plant Growth.

The plasma membrane intrinsic protein PIP2;5 is the most highly expressed aquaporin in maize (Zea mays) roots. Here, we investigated how deregulation of PIP2;5 expression affects water relations and growth using maize overexpression (OE; B104 inbred) or knockout (KO; W22 inbred) lines. The hydraulic conductivity of the cortex cells of roots grown hydroponically was higher in PIP2;5 OE and lower in pip2;5 KO lines compared with the corresponding wild-type plants. While whole-root conductivity decreased in the KO lines compared to the wild type, no difference was observed in OE plants. This paradox was interpreted using the MECHA hydraulic model, which computes the radial flow of water within root sections. The model hints that the plasma membrane permeability of the cells is not radially uniform but that PIP2;5 may be saturated in cell layers with apoplastic barriers, i.e. the endodermis and exodermis, suggesting the presence of posttranslational mechanisms controlling the abundance of PIP in the plasma membrane in these cells. At the leaf level, where the PIP2;5 gene is weakly expressed in wild-type plants, the hydraulic conductance was higher in the PIP2;5 OE lines compared with the wild-type plants, whereas no difference was observed in the pip2;5 KO lines. The temporal trend of leaf elongation rate, used as a proxy for that of xylem water potential, was faster in PIP2;5 OE plants upon mild stress, but not in well-watered conditions, demonstrating that PIP2;5 may play a beneficial role in plant growth under specific conditions.

Drought-Induced Modifications on the Outer Part of the Root (OPR) and Root Endodermis of Selected Rice Genotypes

Rice production is oftentimes confronted by environmental constraints such as drought which affects the water uptake of roots. The internal apoplastic barriers in the roots are believed to regulate/constrain the radial water flow through the gaps in between the cells. Thus, in this study, a screenhouse experiment was conducted using four rice cultivars namely, Jasmine, Arabon, Basmati, and UPLRi-3 (drought-tolerant variety), to determine the effects of 3 weeks of drought stress in the common sites of root apoplastic barriers, such as the outer part of the root (OPR) (composed of epidermis, exodermis, and sclerenchymatous layer) and root endodermis, and to identify from these tissues putative responses that may be relevant to drought-tolerance of rice roots. The exodermis was not affected during drought while the epidermis shrank extremely. The second week of drought imposition resulted in a significant increase in exodermal and endodermal cell sizes. Drought enhanced the lignification in the sclerenchymatous layer and suberization in the endodermis. The drought-tolerant variety UPLRi-3 developed the thickest lignification of sclerenchymatous layer (2.15 μm), followed by Jasmine (1.9 μm), and lastly Arabon and Basmati (1.59 and 1.51 μm, respectively). The varieties UPLRi-3, Arabon, and Jasmine produced high suberin deposition in the endodermis, which were not significantly different from each other (3.76, 3.51, and 3.49 μm, respectively), while Basmati produced the lowest (2.81 μm). The control variety UPLRi-3 demonstrated a highly positive root response which can be associated to its drought-tolerance trait. The results obtained suggest rice root’s dynamic coping mechanisms with the effects of drought to protect itself from rapid dying and prevent internal water loss.

Composite Consolidation Coefficient Analysis of Soft Soil with Drainage Water

The consolidation coefficient is the most basic parameter to calculate the consolidation rate of soil layer, and the horizontal consolidation coefficient controls the radial water flow into the drainage well. Based on the background of the soft soil in Shantou, Guangdong Province, a series of experimental studies on the consolidation characteristics were carried out by using the modified consolidation instrument. And the concept of the composite consolidation coefficient of the drained water body was put forward. The composite consolidation coefficient reflects the consolidation characteristics of soft soil with drainage water, The test results showed that: 1) The consolidation test with drainage plate is basically consistent with the load compression curve, but its consolidation rate is fast, which is reflected by the composite consolidation coefficient. 2) In the consolidation test of water bodies with drainage, the vertical consolidation coefficient and radial consolidation coefficient are calculated by “three-point method”, and then the composite consolidation coefficient is obtained. The composite consolidation coefficient decreases with the increase of drain spacing ratio, effective drainage diameter and drainage height, which is basically consistent with the theoretical formula. 3) The vertical consolidation coefficient and radial consolidation coefficient decrease with the increase of the diameter of the sample, and the difference is obvious when the load is large. The large-size model with a diameter of 100 mm and a height of 100 mm is about 1.35 times of the vertical consolidation coefficient of the conventional consolidation test.

Computational models evaluating the impact of sieve plates and radial water exchange on phloem pressure gradients.

The sugar conducting phloem in angiosperms is a high resistance pathway made up of sieve elements bounded by sieve plates. The high resistance generated by sieve plates may be a trade-off for promoting quick sealing in the event of injury. However, previous modeling efforts have demonstrated a wide variation in the contribution of sieve plates towards total sieve tube resistance. In the current study, we generated high resolution scanning electron microscope images of sieve plates from balsam poplar and integrated them into a mathematical model using Comsol Multiphysics software. We found that sieve plates contribute upwards of 85% towards total sieve tube resistance. Utilizing the Navier-Stokes equations, we found that oblong pores may create over 50% more resistance in comparison with round pores of the same area. Although radial water flows in phloem sieve tubes have been previously considered, their impact on alleviating pressure gradients has not been fully studied. Our novel simulations find that radial water flow can reduce pressure requirements by half in comparison with modeled sieve tubes with no radial permeability. We discuss the implication that sieve tubes may alleviate pressure requirements to overcome high resistances by regulating their membrane permeability along the entire transport pathway.

Radial stem flow and its importance when measuring xylem hydraulic conductance

Despite the importance of water transport efficiency for plant productivity, the current methods to measure the hydraulic conductance in stem segments are limited and can be tricky. These measurements may be unstable for several hours and there are no satisfactory procedures that allow choosing the moment to get reliable measures. Such instability may be generated by background flow, when there is a flow even without applying water pressure to induce the axial flow. Underlying mechanisms related to background flow are still unknown and based on available literature, we propose that the background flow is affected, or even explained, by the radial water flow and tissue capacitance. For this reason, both phenomena are fundamental for understanding plant water transport, the coupling between the phloem and xylem, and water relations under drought conditions. Besides addressing this issue, we suggest ways to study the radial water flow and capacitance in stem segments.

Dynamics of Water Flow in the Atmosphere-Aerial Roots Continuum

The study of the parameters influencing the absorption of atmospheric humidity not condensed by plants with aerial roots is a challenge in the current context of climatic disturbance where methods of adapting plants to water stress have become the concern of many scientific researchers. Based on Poiseuille and Fick laws, leaf water potential depending on solar radiation and atmospheric water potential around aerial roots; the influence of temperature, relative humidity, inclination angle of roots and solar radiation wavelength on the radial and axial water flow through a root segment is simulated. The various simulations show that a low temperature of the air surrounding the root favors a significant entry of water into the root as well as a relative humidity of the high air approaching 100%. The angle of inclination has an influence on the quantity of water entering the root and that rising in the xylem. These different streams of water are optimized for root tilting of 60°. The wavelength of the red radiation received by the leaves favors more entry and rise of water in the root. Future studies for transgenes should be taken into account the influence of all these parameters.

Water movement through plant roots – exact solutions of the water flow equation in roots with linear or exponential piecewise hydraulic properties

Abstract. In 1978, Landsberg and Fowkes presented a solution of the water flow equation inside a root with uniform hydraulic properties. These properties are root radial conductivity and axial conductance, which control, respectively, the radial water flow between the root surface and xylem and the axial flow within the xylem. From the solution for the xylem water potential, functions that describe the radial and axial flow along the root axis were derived. These solutions can also be used to derive root macroscopic parameters that are potential input parameters of hydrological and crop models. In this paper, novel analytical solutions of the water flow equation are developed for roots whose hydraulic properties vary along their axis, which is the case for most plants. We derived solutions for single roots with linear or exponential variations of hydraulic properties with distance to root tip. These solutions were subsequently combined to construct single roots with complex hydraulic property profiles. The analytical solutions allow one to verify numerical solutions and to get a generalization of the hydric behaviour with the main influencing parameters of the solutions. The resulting flow distributions in heterogeneous roots differed from those in uniform roots and simulations led to more regular, less abrupt variations of xylem suction or radial flux along root axes. The model could successfully be applied to maize effective root conductance measurements to derive radial and axial hydraulic properties. We also show that very contrasted root water uptake patterns arise when using either uniform or heterogeneous root hydraulic properties in a soil–root model. The optimal root radius that maximizes water uptake under a carbon cost constraint was also studied. The optimal radius was shown to be highly dependent on the root hydraulic properties and close to observed properties in maize roots. We finally used the obtained functions for evaluating the impact of root maturation versus root growth on water uptake. Very diverse uptake strategies arise from the analysis. These solutions open new avenues to investigate for optimal genotype–environment–management interactions by optimization, for example, of plant-scale macroscopic hydraulic parameters used in ecohydrogolocial models.

Flow behavior analysis of two-phase (gas/water) flowback and early-time production from hydraulically-fractured shale gas wells using a hybrid numerical/analytical model

In recent years, quantitative analysis of flowback and early-time production data for interpretation of hydraulic fracture properties in shale has received significant attention. With high-resolution phase rates and flowing pressures, analysis of flowback and early-time production data provides an early opportunity to determine key parameters for well performance forecasting. The main purpose of this paper is to quantify flow characteristics associated with two-phase flowback and early-time production of shale gas wells exhibiting both planar fractures and a complex fracture network using a rigorous and efficient flow model.To study flow characteristics of this complex system, a hybrid numerical/analytical model is developed in which matrix and hydraulic fracture flow is accounted for. The finite-difference method is used to numerically model unsteady-state two-phase fracture flow. The analytical matrix flow model, derived using the line-source function, is dynamically coupled with the fracture flow model by imposing continuity of pressure and flux on the fracture surface. The main advantage of the hybrid solution over more conventional numerical simulation is reduced model setup and run time, without loss of the important physics.Detailed flow regime analysis reveals that the gas/water flowback and early-production of a horizontal well with a planar fracture geometry may the following complex sequence of flow-regime: 1) radial flow of water in the fracture; 2) a first transient linear flow of water in the fracture; 3) a second transient linear flow of water in the fracture; 4) boundary-dominated flow of water in the fracture and gas linear flow in matrix. Water primarily depletes in the first three flow periods. Development of the water boundary-dominated flow and gas linear flow indicates the system indicate that the system is at the end of flowback period and proceeds early-time production. Specially, the second water linear flow period develops when both gas and water production are dominating the system, and is caused by the pressure maintenance associated with gas flux from matrix. A complex fracture network with the same total fracture length as a planar fracture system will exhibit the same sequence of flow regimes. Due to the accelerated water drainage caused by multiple contact points between fractures and the wellbore in complex fracture network, the system also exhibits a shortened second water transient linear flow period and earlier water boundary-dominated flow.Finally, the new model is also applied to match flowback data obtained from a multi-fractured horizontal well completed in the Marcellus Shale. The results demonstrate the practical application of the new model for deriving reservoir/fracture properties from flowback data and for forecasting.

Experimental study of the temporal variation of drain water salinity at different drain depths and spacing in the presence of saline groundwater

Drain depth and spacing are two factors that affect drain water quality by radial flow of underground water. In this study, temporal variations of drain water salinity and groundwater salinity are evaluated using different drain depths and spacing installations. Experiments were performed in a flume of 1.8 m length, 1 m width and 1.2 m height. Drains were installed at 20, 40 and 60 cm depths at 180, 90 and 60 cm spacing. The salinity of the groundwater and the salinity of irrigation water at the study were about 65 and 0.321 dS/m, respectively. Irrigation water deliveries were 0.14, 0.11 and 0.07 l/s. The results show that increasing the drain depth and irrigation water increases the salinity of drain water. Also in all the cases, the trend of drain water salinity tends to decrease with passing of time. However, the leached salt increases with increase in the drain spacing. In addition, drainage water quality decreases with increase in the drain spacing for each drain depth and discharge. On the other hand, the degree of time stability increases with increasing drain spacing. However, it was noticed that faster removal of salt from groundwater can be achieved with increasing drain spacing, depth and discharge.