Vertical Water Distribution Research Articles

Stratified substrates enhance water storage and distribution between irrigation events

AbstractThe specialty crop industry requires copious amounts of water to meet production needs; however, current substrates are highly porous to mitigate risks and are subsequently inefficient with regard to water use. Therefore, more sustainable soilless substrates are needed to ensure the future success/profitability of the horticultural industry, especially as finite fresh water sources become limiting. Substrate stratification (i.e., vertically layering unique substrates atop one another) provides opportunities to augment an existing system by maintaining substrate porosity, while strategically redistributing the air‐ and water‐filled pores, retaining more water when applied, and controlling vertical water distribution. The aim of this research was to further understand the complex stratified systems of hydraulics. Herein, the hydraulic properties of individual substrate components were measured and modeled using HYDRUS 1 d. Furthermore, matric tensions and volumetric water content (VWC) were measured continuously under two different irrigation schedules (single [1×] and cyclic applications [3×]) for 15 days with a fully established Dianthus barbatus ‘Amazon Neon Purple’ crop. The results showed that screened bark particles have more pore homogeneity assessed by steep declines in VWC with small changes in water potential. Moreover, HYDRUS 1 d modeling demonstrated that stratified substrates have more uniform hydraulic gradients (difference in moisture content from the top to the bottom of the substrate profile; 21%) present in the container profile when compared to non‐stratified systems (45%). Non‐stratified upper layers experienced greater diurnal tension fluctuations under single irrigation than in cyclic applications. Stratifying substrates resulted in a significant reduction in these fluctuations in the top layer when compared to non‐stratified systems. Additionally, when both substrate (stratifying) and irrigation (cyclic) management strategies are implemented, tension fluctuations can be even further reduced, and hydraulic gradients become more uniform due to improved moisture infiltration and distribution.

Water Separation Performance in Bitumen Recovery from Athabasca Oil Sands: Implementation of Separation Efficiency Index

The oil (diluted bitumen)–water separation efficiency at steam-assisted gravity drainage (SAGD) process conditions has been evaluated in a laboratory environment by using a custom-built batch gravity setup, using SAGD field fluids and commercial gas condensate as a diluent. The key parameters and conditions investigated are solvent amount, shear conditions, water-to-oil ratio, and the presence and wettability of fine solids. The results demonstrate the complexity of the oil–water separation process, affected by the dependence of the investigated parameters from one another. A new quantification approach is introduced to facilitate the oil–water separation efficiency evaluation, based on the proposed descriptor, referred to as a separation efficiency index (SEI). Defined as the average of the residual water-in-oil and oil-in-water indices, SEI ranges from 0 to 1, where 1 represents a “perfect” (complete) separation and 0 corresponds to a complete emulsification. The SEI allows one to describe the separation efficiency throughout the entire separation vessel volume, using discrete vertical water distribution profiles, and represents the separation efficiency with a single number, regardless of the experimental approach taken. The findings show that in the range of solvent concentrations of 30 vol % or lower, the mixing speed affects the separation performance and becomes predominant at the relatively low solvent concentrations of 10 and 20 vol %. The amount of solvent added becomes predominant in the oil–water separation process and overcomes all other effects in the highest solvent addition (40 and 50 vol %) range. The presence of water-wet solids improves the separation performance, while the presence of oil-wet solids impedes the oil–water separation. The results presented in this study, in particular the proposed SEI, are important for improving the oil–water separation efficiency and can be used to develop operational envelopes and new solvent injection strategies, in terms of location, amount, and stages, further improving the quality of the oil product obtained in SAGD.

Towards Understanding the Influence of Vertical Water Distribution on Radar Backscatter from Vegetation Using a Multi-Layer Water Cloud Model

For a good interpretation of radar backscatter sensitivity to vegetation water dynamics, we need to know which parts of the vegetation layer control that backscatter. However, backscatter sensitivity to different depths in the canopy is poorly understood. This is partly caused by a lack of observational data to describe the vertical moisture distribution. In this study, we aimed to understand the sensitivity of L-band backscatter to water at different heights in a corn canopy. We studied changes in the contribution of different vertical layers to total backscatter throughout the season and during the day. Using detailed field measurements, we first determined the vertical distribution of moisture in the plants, and its seasonal and sub-daily variation. Then, these measurements were used to define different sublayers in a multi-layer water cloud model (WCM). To calibrate and validate the WCM, we used hyper-temporal tower-based polarimetric L-band scatterometer data. WCM simulations showed a shift in dominant scattering from the lowest 50 cm to 50–100 cm during the season in all polarizations, mainly due to leaf and ear growth and corresponding scattering and attenuation. Dew and rainfall interception raised sensitivity to upper parts of the canopy and lowered sensitivity to lower parts. The methodology and results presented in this study demonstrate the importance of the vertical moisture distribution on scattering from vegetation. These insights are essential to avoid misinterpretation and spurious artefacts during retrieval of soil moisture and vegetation parameters.

Modelling vertical water distribution and separation in the unsaturated coal and iron ores during oscillation

The effect of oscillation on the water distribution in unsaturated coal and iron ores plays a significant role in the material processing but has not been analysed quantitatively. This paper developed a model based on the Richards equation to describe the transient residual water distribution in the unsaturated coal and iron ores, and predicted the separated water with time. In this model, the effect of oscillation was quantised as a dynamic potential of the unsaturated water. The model was experimentally verified and applied to characterise the separated and residual water. The effects of initial water content, hydraulic conductivity, dynamic potential and bottom boundary were quantitatively analysed. The results showed that the dynamic potential affects the transient and steady water distribution for the overall height of the coal and iron ores. These findings can be applied to the minimisation of water distribution in wet coal or iron ores and optimisation of their processing.

Water absorption analysis of a peat‐perlite horticultural substrate in response to various subirrigation conditions using a thermal imaging camera

Subirrigation systems are widely used in commercial greenhouses for efficient and high-quality production of potted plants. However, proper criteria of the water level and retention time need to be quantified for more efficient irrigation. This study analyzed the water absorption and vertical water distribution in a horticultural substrate in 10-cm pots under various subirrigation water levels and retention times. To analyze the water absorption dynamics, we continuously measured changes in the actual substrate volumetric water content using capacitance soil moisture sensors. The vertical distribution of water in the pot was measured using a thermal imaging camera, with a small temperature difference indicating more water absorption. As expected, the volumetric water content in the pots increased as the subirrigation water level and retention time increased; however, significantly less water was absorbed near the top surface of the substrate, and the variation of the vertical water distribution increased at lower subirrigation water levels or shorter retention times. This suggests that young plants with smaller root systems would require a higher water level and retention time for subirrigation if their roots are distributed near the top of the pot. This study provides a better understanding of water absorption and its vertical distribution across a horticultural substrate when using a subirrigation system and supports decision making for the suitable management of subirrigation conditions according to the type of plant species or crop growth stage.

Gap thinning improves soil water content, changes the vertical water distribution, and decreases the fluctuation

Although it is clear that gap thinning significantly increases the soil water content (SWC) of the topsoil, less is known about whether and how this treatment affects deeper layers. From December 2008 to April 2012, we monitored the SWC at depths of 10, 20, 30, 45, 60, and 90 cm in gap creation treatments (small gap size of 30 m2, intermediate gap size of 80 m2, and unthinned plots) in a typical pine plantation in the eastern Tibetan Plateau. Among gap treatments, differences in SWC and its coefficient of variation (CV) at each depth and the soil water content proportion (SWCP) of the whole soil profile at specific depths were compared. Gap thinning improved SWC and decreased the CV at each depth. The SWCPs in thinned plots were lower at depths from 10 to 30 cm compared with unthinned plots but higher at depths of 45 and 60 cm. Also, in each season, the patterns were similar to the general results. In conclusion, gap thinning improves the SWC, changes the vertical soil water distribution, and decreases the SWC heterogeneity. The soil water conditions in intermediate gaps are more appropriate for local forest restoration.

Hydrogen escape from Mars enhanced by deep convection in dust storms

Present-day water loss from Mars provides insight into Mars’s past habitability1–3. Its main mechanism is thought to be Jeans escape of a steady hydrogen reservoir sourced from odd-oxygen reactions with near-surface water vapour2, 4,5. The observed escape rate, however, is strongly variable and correlates poorly with solar extreme-ultraviolet radiation flux6–8, which was predicted to modulate escape 9 . This variability has recently been attributed to hydrogen sourced from photolysed middle atmospheric water vapour 10 , whose vertical and seasonal distribution is only partly characterized and understood11–13. Here, we report multi-annual observational estimates of water content and dust and water transport to the middle atmosphere from Mars Climate Sounder data. We provide strong evidence that the transport of water vapour and ice to the middle atmosphere by deep convection in Martian dust storms can enhance hydrogen escape. Planet-encircling dust storms can raise the effective hygropause (where water content rapidly decreases to effectively zero) from 50 to 80 km above the areoid (the reference equipotential surface). Smaller dust storms contribute to an annual mode in water content at 40−50 km that may explain seasonal variability in escape. Our results imply that Martian atmospheric chemistry and evolution can be strongly affected by the meteorology of the lower and middle atmosphere of Mars. Mars Climate Sounder’s multi-annual observations of the vertical distribution of water and dust in the Martian atmosphere show that deep convection from dust storms transports water from the lower to the middle atmosphere, enhancing water loss to space.

Evaluation of Thermal Stratification and Flow Field Reproduced by a Three-Dimensional Hydrodynamic Model in Lake Biwa, Japan

Water temperature near the surface of a lake increases with increasing air temperature, which results in stratification. The strength of stratification substantially influences the transport of water parcels from the surface to the bottom of a lake. In recent years, the stratification in Lake Biwa—the largest freshwater lake in Japan—has been stronger. However, it is difficult to reproduce the stratification well in the simulations. In the present study, we built a hydrodynamic model for the purpose of analyzing the structure of the stratification in detail. Using the model, we evaluated the reproducibility of the seasonal and annual changes of vertical water distribution and flow field in Lake Biwa from 2007 to 2011. The hydrodynamic model results show that the vertical water distribution approximately agrees with the field observations based on the statistical analysis. The seasonal change of thermal stratification is reasonably reproduced by the hydrodynamic model simulations. In the simulation, there are mainly two circulation flows at the surface layer of the lake. The first flows anticlockwise and the second flows clockwise in the northern part of Lake Biwa. In order to compensate for the surface water flow, the water under the thermocline sometimes flows in the opposite direction under each circulation flow.

Root growth of perennials in vertical growing media for use in green walls

The vertical orientation of green walls causes a risk of uneven water distribution within the growing medium, and thereby stress on the plant roots. Therefore it was studied how the root and top growth of different species were affected by the water holding characteristics of the growing media.Five species of hardy perennials (Campanula poscharskyana ‘Stella’, Fragaria vesca ‘Småland’, Geranium sanguineum ‘Max Frei’, Sesleria heufleriana and Veronica officinalis ‘Allgrün’) were grown in 3 types of growing media (coir and 2 of rockwool) in vertical boxes under greenhouse conditions. Root distribution was registered over 52 days and the activity of individual root systems was studied via 15N uptake and plant parameters were measured. The water holding characteristics of the growing media was determined on a sandbox.From day 21 and throughout the experiment, the plants growing in the coir medium showed stronger root growth compared to the two rockwool media. From day 28 onwards, there was also a difference between the two rockwool media, with a higher root frequency in the less dense medium. This pattern was consistent for all species, even if they showed different root growth dynamics. Fragaria, Geranium and Veronica showed steadily increasing root growth throughout the experiment, whereas Campanula started slow, but showed a strong root growth towards the end of the experiment. Sesleria showed little root growth throughout the experiment. Dry weight and root activity measured as 15N uptake was higher for plants grown in coir than rockwool. The coir medium showed a more gradual water release with increasing tension than either of the rockwool media, corresponding to the water content measured locally in the boxes.The results confirmed that the growing media affect root and aboveground plant growth. This is consistent with the differences in water retention, as the more even vertical water distribution in the coir medium resulted in stronger growth compared to the rockwool media. The five species showed different root growth dynamics and different abilities to grow in the different media, and 15N uptake showed that low root growth in the rockwool media also resulted in low root uptake activity.

Analysis of projected hydrological behavior of catchments based on signature indices

Abstract. To precisely map the changes in hydrologic response of catchments (e.g. water balance, reactivity or extremes), we need sensitive and interpretable indicators. In this study we defined nine hydrologically meaningful signature indices: five indices were sampled on the flow duration curve, four indices were closely linked to the distribution of event runoff coefficients. We applied these signature indices to the output from a hydrologic catchment model for three different catchments located in the Nahe basin (Western Germany) to detect differences in runoff behavior resulting from different meteorological input data. The models were driven by measured and simulated (COSMO-CLM) meteorological data. It could be shown that the application of signature indices is a very sensitive tool to assess differences in simulated runoff behavior resulting from climatic data sets of different sources. Specifically, the selected signature indices allow assessing changes in water balance, vertical water distribution, reactivity, seasonality and runoff generation. These indices showed that the hydrological model is very sensitive to biases in mean and spatio-temporal distribution of precipitation and temperature because it acts as a filter for the meteorological input. Besides model calibration and model structural deficits, we found that bias correction of temperature fields and further adjustment of bias correction of precipitation fields is absolutely essential. We conclude that signature indices can act as indirect "efficiency measures" or "similarity measures" for output from regional or local climate models.

水色要素垂直分布对其遥感反演算法精度的影响

水色要素垂直分布对其遥感反演算法精度的影响

Vertical distribution of water within the polythermal Storglaciären, Sweden

Knowledge of water content and its distribution in polythermal glaciers is required to model their flow and thermal state. However, observations of water content variations with depth in polythermal glaciers are scarce. Water content can be estimated from radio wave speed because they depend on one another. We obtained continuous profiles of radio wave speed variations with depth from zero‐offset radar profiles collected in boreholes approximately 80 m deep in the upper ablation area of Storglaciären, northern Sweden. These profiles show that the microcrystalline water system in the temperate ice is relatively homogeneous. The overall hydrothermal structure at this location is composed of a 20 m thick upper layer of cold, water‐free ice, underlain by a temperate ice layer whose average water content is 0.6% ± 0.3%. These results are corroborated by surface radar and thermistor measurements, which show that the depth of the cold temperate transition is 21 m and the calculated water content at that transition is 0.6% ± 0.1%. These findings imply that the whole temperate ice layer is from 3 to 4 times softer than the cold ice and, consequently, that realistic ice flow models of polythermal glaciers should include the effect of water content on viscosity.

Laboratory Study of Immiscible Contaminant Flow in Unsaturated Layered Sands

Little quantitative experimental data are available describing the behavior of immiscible contaminants in unsaturated heterogeneous porous media. Such data are, however, essential to the fundamental understanding of the processes governing nonaqueous phase liquid behavior and for the validation of modeling tools. The effect of macro‐heterogeneity on light nonaqueous phase liquid (LNAPL) flow and distribution in the unsaturated zone was investigated experimentally by simulating LNAPL spills in layered soil systems consisting of sands with various textures. Two multiphase flow experiments were conducted in a two‐dimensional flume (180 × 120 × 8 cm). The vertical distribution of water and LNAPL pressure were measured using hydrophilic and hydrophobic tensiometers. An image analysis technique was used to estimate the saturation distribution of the fluids in a two‐dimensional vertical plane. The experiments show that LNAPL entrapment, which contributes to long‐term soil and water contamination, depends strongly on the initial water saturation and water pressure at the layer interfaces and on the texture contrasts between the soil layers, which lead to permeability and capillary barrier effects. Thus, the knowledge of the initial water pressure and saturation distribution in unsaturated layered soil formations is critical to the correct prediction of LNAPL infiltration and drainage.

Water ice clouds in the Martian atmosphere: General circulation model experiments with a simple cloud scheme

We present the first comprehensive general circulation model study of water ice condensation and cloud formation in the Martian atmosphere. We focus on the effects of condensation in limiting the vertical distribution and transport of water and on the importance of condensation for the generation of the observed Martian water cycle. We do not treat cloud ice radiative effects, ice sedimentation rates are prescribed, and we do not treat interactions between dust and cloud ice. The model generates cloud in a manner consistent with earlier one‐dimensional (1‐D) model results, typically evolving a uniform (constant mass mixing ratio) vertical distribution of vapor, which is capped by cloud at the level where the condensation point temperature is reached. Because of this vertical distribution of water, the Martian atmosphere is generally very far from fully saturated, in contrast to suggestions based upon interpretation of Viking data. This discrepancy results from inaccurate representation of the diurnal cycle of air temperatures in the Viking Infrared Thermal Mapper (IRTM) data. In fact, the model suggests that only the northern polar atmosphere in summer is consistently near its column‐integrated holding capacity. In this case, the column amount is determined primarily by the temperature of the northern polar ice cap. Comparison of the water cycle generated by the model with and without atmospheric ice condensation and precipitation shows two major roles for water ice cloud. First, clouds are essential to the observed rapid return of atmospheric water to the surface in late northern summer, as ice sedimentation forces the water column to shrink in response to the downward motion of the condensation level, concentrating water near surface sinks. Second, ice sedimentation limits the amount of water that is transported between the hemispheres through the Hadley circulation. This latter effect is used to greatly improve the model simulation of the annual water cycle by increasing ice sedimentation rates. The model is thus shown to be able to reasonably reproduce the annual cycles of vapor and ice cloud as compared to Viking data. In addition, the model is shown able to reproduce near‐instantaneous maps of water ice derived from Hubble Space Telescope images. The seasonal evolution of the geographic distribution of water ice compares reasonably well with Viking and Mars Global Surveyor (MGS) Mars Orbiter Laser Altimeter (MOLA) observations, except in the prediction of a weak tropical cloud belt in southern summer. Finally, it is shown that the tropical cloud belt is generated in the model by the cooling of water vapor entrained in the upwelling branch of the Hadley cell. Decline of the tropical cloud belt in mid northern summer is shown to be related to an increase in air temperatures, rather than to decreases in water vapor supply or the vigor of Hadley cell ascent. By equinox, the cloud belt experiences a second major decline event, this time due to a reduction in vapor supply. The ability of the model to emulate many aspects of observed cloud behavior is encouraging, as is the ability of enhanced ice sedimentation to improve the overall quality of the water cycle simulation. However, significant work remains to be done before all observational constraints can be matched simultaneously. Specifically, in order for the generally good fit to all other data to be attained, cloud ice particle sizes about an order of magnitude too large must be used.

Vertical water distribution during the drying of polymer films cast from aqueous emulsions.

We present a systematic study of the vertical uniformity of water distribution during the drying of waterborne colloidal films, testing the predictions of a Peclet number Pe defined for this system. Pe indicates the relative contributions of water evaporation and Brownian diffusion in determining the concentration profile in the vertical direction ( i.e. normal to the substrate). When Pe < 1, the water concentration in films cast from an alkyd emulsion is found via magnetic-resonance profiling to be uniform with depth, which is consistent with expectations. When Pe > 1, a gradient in the water concentration develops, with less water near the interface with air. The water profiles reveal that the alkyd particles do not coalesce immediately upon contact in close-packing. At later times, a concentrated surface layer develops, but particles are not coalesced in this layer to form a continuous "skin", but rather the structure is likely to be that of a biliquid foam.

A model of water streaking down a wall

Rainwater streaking down a vertical wall exhibited the characteristics of “fingered flow.” The wall serves as an analogy to film flow in a relatively smooth and wide aperture fracture. A digital photograph of the wall suggests that the vertical distribution of water is heavy‐tailed. A fractional‐order advection‐dispersion equation is used as a model.

Effect of desalination on the littoral tecturid gastropods in early development

The effect of decreased salinity on the limpetsCollisella dorsuosa, C. versicolor, C. radiata, andNotoacmea concinna (Mollusca, Gastropoda) is studied at early stages of development. It is shown that, for normal development from fertilization to the veliger stage, the salinity must be not less than 22–24‰. A decrease in salinity depressed the behavior of larvae. At earlier stages, the larvae were less sensitive to changes in salinity than at later stages. At the same time, veligers were better able to adapt to changes in salinity than trochophores. The vertical water distribution of larvae depended on their age. Two days after fertilization, the larvae sank down to start a benthic life. It is proposed that the narrow tolerance range of littoral limpet larvae to changes in salinity is connected with the fact that they spend a relatively small part of their life in plankton.

Delineation of Air/Water Capillary Transition Zone From GPR Data

Summary Spilled petroleum products spread laterally in the capillary transition zone above the water table. Ground penetrating radar (GPR) is a technique that can potentially delineate the air/water capillary transition zone (CTZ), because a varying water content strongly influences the reflected signal through its effect on the electrical properties. The vertical water distribution is determined on the pore scale by the grain size distribution and on the reservoir scale, mainly, by the permeability distribution. We present the integral equations for the reflected signal from a inhomogeneous slab with a depth-dependent dielectric constant and electrical conductivity. The numerical solution of the equations allows us to compute the signal reflected from different sand profiles. The results show that the reflected signal is strongly influenced by both the grain size distribution and the variation in permeability. A strong frequency dependence is also observed. We present a two-dimensional GPR profile measured in the field that shows a clear effect of the CTZ on the reflection of the radar signal. All these results are considered of importance for the interpretation of GPR data involving the capillary transition zone.

Vertical Distribution of Water in the Near-Equatorial Troposphere of Mars: Water Vapor and Clouds

Solar occultation spectrometry of the martian atmosphere was performed during the Phobos mission with the Auguste experiment in the UV, visible, and NIR spectral ranges. The entire domain of data in the range of 1.9 μm has been reanalyzed to retrieve all available information about the water vapor vertical profile. Accurate consideration of the instrumental corrections and a probabilistic concept of the inverse problem provide estimated water vapor contents at the level of 135 ppm with an accuracy of a factor of 2 at 10–25 km. Explicit detection of water above 30 km is proven statistically at the level of 3 ± 2 ppm with a variety of occultations, giving an upper limit of 10 ppm. The vertical structure of the water profiles demonstrates a sharp decrease above 23–25 km, whereas the lower portion has an approximately constant mixing ratio. The assumption that the latter is constant down to the surface results in a total column abundance of 8.3 +2.5 −1.5pr. μm. The temperature profile derived from saturation conditions reveals a gradient of 2 ± 1 km −1at 25–35 km. The vertical distribution of water vapor accounts for the previous study of continuous absorption at 1.9 and 3.7 μm that resulted in vertical profiles and size distributions of dust particles. The upper boundary of the confined part of the water vapor profile coincides with the altitude of considerable enhancement of aerosol extinction. This peculiarity is interpreted as a low level (20–25 km) of clouds formed by condensation of water vapor interacting with dust particles. Microphysical parameters of clouds are estimated with the adopted value of the eddy mixing coefficient, and constraints on size distribution are deduced from the modeling of dust dynamics.

Numerical simulation of the seasonal variation of mesospheric water vapor

A two‐dimensional radiative/dynamical/chemical model is used to investigate the role of varying vertical diffusivity on the distribution and temporal variability of water vapor in the mesosphere. Model runs in which the effective turbulent Prandtl number varies over 2 orders of magnitude (values of 1, 10, and 100) are compared. The results indicate that a Prandtl number of 10 or more gives a simulation of mesospheric water vapor characterized by a strong decrease with height and a seasonal cycle with maximum mixing ratios during late summer. The test with a small Prandtl number gives, in contrast, very weak vertical gradients of concentration and a semiannual cycle with maxima in late winter and late summer. The very high Prandtl number case was included to test the role of vertical diffusion in the model when the effective diffusivity coefficient is very small. Comparison of these three cases indicates that the vertical structure of water is sensitive to the effective diffusivity over the range tested. The results also indicate that meridional advection by the mean circulation has a significant influence on the vertical distribution of water in the mesosphere.