Water Flux Density Research Articles

Comparison of different soil temperature algorithms in permafrost regions of Qinghai-Xizang (Tibet) Plateau of China

Soil thermal diffusivity is a crucial physical parameter that affects soil temperature. By applying sinusoidal boundary conditions, an analytical solution using separated variables for the heat conduction-convection equation was developed. The thermal diffusivity and liquid water flux density were calculated with data collected at field observation sites in permafrost regions of Qinghai-Xizang (Tibet) Plateau (QXP). By taking the soil layer at the depth of 5cm as the upper boundary, the soil temperature at a depth of 10cm was modeled by the thermal conduction-convection method, amplitude method and phase method. The statistical analysis of the standard error of the estimate (SEE), the normalized standard error (NSEE) and the root mean square error (RMSE) demonstrated that the thermal conduction-convection method provided the most accurate prediction of soil temperature, with average SEE, NSEE, and RMSE of 0.72°C, 9.26% and 0.72°C, respectively. The thermal conduction-convection method provides a useful tool for calculating soil thermal parameters, simulating soil temperature and land surface processes parameterization for permafrost changes modelling under global warming.

An improved model for soil surface temperature from air temperature in permafrost regions of Qinghai-Xizang (Tibet) Plateau of China

Soil temperature plays a key role in hydro-thermal processes in environments and is a critical variable linking surface structure to soil processes. There is a need for more accurate temperature simulation models, particularly in Qinghai-Xizang (Tibet) Plateau (QXP). In this study, a model was developed for the simulation of hourly soil surface temperatures with air temperatures. The model incorporated the thermal properties of the soil, vegetation cover, solar radiation, and water flux density and utilized field data collected from Qinghai-Xizang (Tibet) Plateau (QXP). The model was used to simulate the thermal regime at soil depths of 5 cm, 10 cm and 20 cm and results were compared with those from previous models and with experimental measurements of ground temperature at two different locations. The analysis showed that the newly developed model provided better estimates of observed field temperatures, with an average mean absolute error (MAE), root mean square error (RMSE), and the normalized standard error (NSEE) of 1.17 °C, 1.30 °C and 13.84 %, 0.41 °C, 0.49 °C and 5.45 %, 0.13 °C, 0.18 °C and 2.23 % at 5 cm, 10 cm and 20 cm depths, respectively. These findings provide a useful reference for simulating soil temperature and may be incorporated into other ecosystem models requiring soil temperature as an input variable for modeling permafrost changes under global warming.

Evolution of micro-deformation in inner-selective thin film composite hollow fiber membranes and its implications for osmotic power generation

Since thin film composite (TFC) hollow fiber (HF) membranes may experience micro-deformation under high hydraulic pressures in the pressure retarded osmosis (PRO) process due to their polymeric nature and self-supported configuration, this paper aims to elucidate (1) the micro-deformation of polyethersulfone (PES) TFC HF membranes within the pressure range from 0 to 20bar and (2) its effects on water and salt permeability of the polyamide layer, and structure parameter and tortuosity of the substrate layer for osmotic power generation. It is found that pre-stabilization of the TFC HF membranes at a high pressure close to their burst pressures for a certain period of time is a powerful way to maximize their PRO performance. After stabilization at 20bar for 30min, the power density of the PES TFC HF membranes increase from 15.37 to 22.05W/m2 due to the increased membrane surface area, stretched polyamide selective layer (i.e., decreased water transport length and resistance) and decreased membrane structure parameter (i.e., lower tortuosity and internal concentration polarization (ICP)). The intermittent cycle tests have confirmed the sustainability of the enhanced water flux and power density after stabilization of the TFC HF membranes at 20bar without compromising their selectivity.

Evapotranspiration and Ecosystem Water Use Efficiency of Switchgrass and High Biomass Sorghum

Water and energy flux densities of co‐located cellulosic feedstocks, switchgrass (Panicum virgatum L.) and high biomass sorghum (Sorghum bicolor L. Moench), were measured using the eddy covariance technique during the 2012 and 2013 growing seasons to quantify and compare evapotranspiration (ET) and ecosystem water use efficiency (EWUE). Peak growing season ET from the switchgrass field was approximately 6 mm d−1 in both years; whereas, the sorghum ET reached 6.7 in 2012 and 4.8 mm d−1 in 2013. While both species showed similar water use patterns during the active growing period, seasonal cumulative ET was higher in switchgrass due to a longer growing season. Monthly ET integrals were strongly correlated with monthly integrals of gross primary production (GPP) and net ecosystem production (NEP) for both species, suggesting a strong linkage between C gain and water loss over the season. Different methods of EWUE estimations yielded different EWUE values. The ratio of seasonal sums of GPP to ET yielded EWUE of 9.41 to 11.32 and 8.98 to 9.17 g CO2 mm−1 ET in switchgrass and sorghum, respectively. The ratio of seasonal sums of NEP to ET was 2.75 to 2.81 and 2.06 to 2.18 g CO2 mm−1 ET in switchgrass and sorghum, respectively. Slightly larger EWUE in switchgrass than sorghum shows that the switchgrass was more efficient than the sorghum on using water to gain C. Results suggest that larger seasonal C uptake by switchgrass was enough to offset its higher water use due to the longer growing season. Eddy covariance technique can be used to assess bioenergy crops ecosystem water use efficiency. Swithcgrass has higher ET than sorghum due to longer growing season. Greater seasonal carbon uptake by switchgrass than sorghum was enough to offset higher water use.

Unique roles of aminosilane in developing anti-fouling thin film composite (TFC) membranes for pressure retarded osmosis (PRO)

Pressure retarded osmosis (PRO) has been identified as a promising technology to harvest the salinity gradient energy. For practical applications of PRO process, membrane fouling is a challenging issue as it leads to severe decline of PRO performance in terms of water flux and power density. It is imperative to develop anti-fouling membranes for PRO process. The current study demonstrated the unique roles and the great potential of aminosilane in developing anti-fouling thin film composite (TFC) PRO membranes. Experimental results revealed that aminosilane as a grafting agent can modify both the support layer (interior) and the selective layer of PRO membranes with remarkably enhanced hydrophilicity via a very simple grafting procedure. In the grafting, aminosilane was able to minimize the pore-blocking issue with almost no increase in the membrane structural parameter (S). Meanwhile, the membrane mechanical strength was well maintained with the grafting due to the capability of aminosilane as a cross-linker. With enhanced hydrophilicity, it was interestingly found that the water permeability (A) was doubled, while the salt rejection was maintained nearly unchanged. The combination of these effects brought in remarkably enhanced water flux, power density and anti-fouling property to the resultant membrane.

Outer-selective thin film composite (TFC) hollow fiber membranes for osmotic power generation

The pressure-retarded osmosis (PRO) process is a green technique for power generation to respond the world's need of energy sustainability. In this study, we have developed the vital component of the process, i.e. membrane, in the configuration of the outer-selective thin-film composite (TFC) hollow fiber, which is more practical than other configurations in the real applications. The support layer morphology and the formation of the selective polyamide layer have been optimized for a good PRO performance. The results show that the bore fluid with higher amount of the solvent N-methyl-2-pyrrolidone leads to full finger-like hollow fibers, which provide higher flux but lower pressure tolerance. The addition of higher amount of diethylene glycol into the dope solution, improves the pore formation and suppresses the macrovoid formation, while properly lowering the take-up speed increases their wall thickness and pressure tolerance. A simple alcohol-pre-wetting approach on the fiber support leads to a smooth and thin polyamide layer, which is favorable for a high water flux and power density. Its efficiency follows this order: n-propanol>ethanol>methanol>water. The n-propanol pre-wetted TFC membrane can tolerate 17bar with a peak power density of 9.59W/m2 at room temperature, using 1M NaCl solution as the draw solution and DI water as feed. This work demonstrates the potential of outer-selective TFC hollow fiber membranes for energy conversion via PRO process, provides useful database to fabricate suitable support morphology and raise a simple technique to practically form a thin and smooth polyamide layer.

New Fourier-series-based analytical solution to the conduction–convection equation to calculate soil temperature, determine soil thermal properties, or estimate water flux

Temperature is an important physical variable of soil. Heat transfer in soils predominantly occurs due to conduction and convection. In this paper, we present a new analytical solution, based upon the Fourier series boundary conditions for soil surface temperature, in which the separation of variables for the heat conduction–convection equation was established. Data that had been collected from the Qinghai-Xizang (Tibet) Plateau (QXP) were used to calculate the thermal diffusivity and the liquid water flux density using different methods. The results of the soil thermal diffusivity using 5cm as the upper boundary for the soil depth were used to calculate the soil temperature using both the single sine wave conduction and conduction–convection model and the Fourier series conduction–convection model. These results were then compared with the values for the temperature of the field soil measured at a depth of 10cm. The average standard error of the estimate (SEE), the normalized standard error (NSEE) and Bias were 0.16°C, 2.70% and 0.11°C for the Fourier series conduction–convection method. The results indicate that the Fourier series model provides a better estimate of observed field temperatures than the sine wave model. This method provides a useful tool for determining soil thermal parameters, simulating soil temperature and the parameterization of land surface processes for modeling permafrost changes under global warming conditions.

Robust outer-selective thin-film composite polyethersulfone hollow fiber membranes with low reverse salt flux for renewable salinity-gradient energy generation

This study reports outer-selective thin-film composite (TFC) hollow fiber membranes with extremely low reverse salt fluxes and robustness for harvesting salinity-gradient energy from pressure retarded osmosis (PRO) processes. Almost defect-free polyamide layers with impressive low salt permeabilities were synthesized on top of robust polyethersulfone porous supports. The newly developed TFC-II membrane shows a maximum power density of 7.81Wm−2 using 1M NaCl and DI water as feeds at 20bar. Reproducible data obtained in the 2nd and 3rd runs confirm its stability under high hydraulic pressure differences. Comparing to other PRO membranes reported in the literature, the newly developed membrane exhibits not only the smallest slope between water flux decline and ΔP increase but also the lowest ratio of reverse salt flux to water flux. Thus, the effective osmotic driving force could be well maintained even under high pressure operations. For the first time, the effect of feed pressure buildup induced by feed flowrate was evaluated towards PRO performance. A slight increment in feed pressure buildup was found to be beneficial to water flux and power density up to 10.06Wm−2 without comprising the reverse salt flux. We believe this study may open up new perspectives on outer-selective PRO hollow fiber membranes and provide useful insights to understand and design next-generation outer-selective TFC hollow fiber membranes for osmotic power generation.

Water Balance Components in Covered and Uncovered Soil Growing Irrigated Muskmelon

ABSTRACT Knowledge of the terms (or processes) of the soil water balance equation or simply the components of the soil water balance over the cycle of an agricultural crop is essential for soil and water management. Thus, the aim of this study was to analyze these components in a Cambissolo Háplico (Haplocambids) growing muskmelon (Cucumis melo L.) under drip irrigation, with covered and uncovered soil, in the municipality of Baraúna, State of Rio Grande do Norte, Brazil (05º 04’ 48” S, 37º 37’ 00” W). Muskmelon, variety AF-646, was cultivated in a flat experimental area (20 × 50 m). The crop was spaced at 2.00 m between rows and 0.35 m between plants, in a total of ten 50-m-long plant rows. At points corresponding to ⅓ and ⅔ of each plant row, four tensiometers (at a distance of 0.1 m from each other) were set up at the depths of 0.1, 0.2, 0.3, and 0.4 m, adjacent to the irrigation line (0.1 m from the plant row), between two selected plants. Five random plant rows were mulched using dry leaves of banana (Musa sp.) along the drip line, forming a 0.5-m-wide strip, which covered an area of 25 m2 per of plant row with covered soil. In the other five rows, there was no covering. Thus, the experiment consisted of two treatments, with 10 replicates, in four phenological stages: initial (7-22 DAS - days after sowing), growing (22-40 DAS), fruiting (40-58 DAS) and maturation (58-70 DAS). Rainfall was measured with a rain gauge and water storage was estimated by the trapezoidal method, based on tensiometer readings and soil water retention curves. For soil water flux densities at 0.3 m, the tensiometers at the depths of 0.2, 0.3, and 0.4 m were considered; the tensiometer at 0.3 m was used to estimate soil water content from the soil water retention curve at this depth, and the other two to calculate the total potential gradient. Flux densities were calculated through use of the Darcy-Buckingham equation, with hydraulic conductivity determined by the instantaneous profile method. Crop actual evapotranspiration was calculated as the unknown of the soil water balance equation. The soil water balance method is effective in estimating the actual evapotranspiration of irrigated muskmelon; there was no significant effect of soil coverage on capillary rise, internal drainage, crop actual evapotranspiration, and muskmelon yield compared with the uncovered soil; the transport of water caused by evaporation in the uncovered soil was controlled by the break in capillarity at the soil-atmosphere interface, which caused similar water dynamics for both management practices applied.

Thin-film nanocomposite membrane with CNT positioning in support layer for energy harvesting from saline water

The pressure retarded osmosis (PRO) process has been considered as an alternative and renewable technology to generate electricity from mixing two solutions of different salinities. However, improving the osmotic performance of semi-permeable membrane is still a major challenge in the PRO system. Therefore, thin-film nanocomposite (TFN) membrane was synthesized by using carbon nanotubes (CNT)-embedded-polyethersulfone (PES) supporting layer and polyamide active layer in this study. The prepared membranes were further employed in the PRO process to harvest energy from saline water. The water flux increase of the TFN membrane was promoted by CNT-induced porosity and the hydrophilicity of the support layer as well as by the chemical etching of the active layer. The water flux and maximum power density of the developed TFN membrane was found to be 87% (averaged from 2bar to 10bar) and 110% greater than for bare thin-film composite (TFC) membranes, respectively. Furthermore, the TFN membrane preparation could easily be scaled up using conventional fabrication methods with less than 2% additional material cost. Therefore, this finding could contribute to the commercialization of sustainable energy generation by utilizing the tremendous potential of fresh- and salt-water mixing.

Peculiarities of the transport properties of chitosan films. 1. Concentration prehistory of pervaporation

Chitosan films prepared by the thermal method from molding solutions containing ethanol as a chitosan precipitant have been used as separating membranes for pervaporation of an aqueous isopropanol solution. The flux density and permeate composition have been determined as functions of the composition of a molding solution and a solution to be separated, as well as the concentration prehistory of the separation process. The concentration prehistory reflects the specific features of swelling polymer sorbents, which are distinguished by a labile structure and macroscopic sorption deformations. The existence of a concentration prehistory implies that, at a fixed concentration of an initial solution, parameters characterizing the transport properties of a polymer depend on the process route in which this concentration has been achieved. The composition of a molding solution and the route of variations in the initial concentration of a solution to be separated that correspond to the highest value of our criterion for the process efficiency have been determined. It has been shown that, in the case of films formed from a solution containing 20 wt % ethanol, the water flux density reversibly increases by more than 100 times as compared with the flux density of a water-alcohol solution.

Structural stability and mass transfer properties of pressure retarded osmosis (PRO) membrane under high operating pressures

The fabrication of new membrane that is able to produce stable high power density is essential for the development of pressure retarded osmosis (PRO) technology. In this work, thin film composite (TFC) polyetherimide membranes with three different substrate structures were fabricated and characterized. The PRO performance of the resultant membrane was evaluated through two pressure cycle experiments and stability tests. The primary objective of this work is to systematically study PRO membrane’s mechanical stability and mass transfer properties under high operating pressures, which determine the power density of the membrane in the PRO process.Experiments revealed that water permeability (Ap) and salt permeability (Bp) under different pressures varied. The Ap and Bp are better indicators for examining the variation of PRO membrane structure under pressure. Within the operating pressure range of 17.2bar, the top polyamide layer of TFC PEI-2# membrane mainly experienced a reversible deformation. In the two pressure cycle tests, the water flux, specific salt flux and power density obtained in the upward and downward measurements in each cycle are close to each other. The first cycle and the second cycle also show excellent reproducibility. The membrane was able to maintain almost unchanged water flux and power density of 12.8W/m2 at 17.2bar over the 10h testing time, suggesting the membrane’s great potential to be used in practical application in the future.

Impact of temperature on power density in closed-loop pressure retarded osmosis for grid storage

Closed-loop pressure retarded osmosis (PRO) has been recently proposed as a means of transforming unusable forms of energy, such as waste heat, into valuable electricity. The process, which is also referred to as an osmotic heat engine (OHE), also enables a form of osmotic grid storage for intermittently available renewable energy sources, where available energy is stored as an osmotic potential and that energy is released via PRO when energy demand is high. The OHE has the potential to generate greater power than conventional open loop PRO because the draw solution can be engineered to have very high osmotic pressures, via enhanced temperature, solute concentration, or a combination of both. These variables change fluid properties and the performance of the membrane, which may or may not be beneficial to overall OHE operation. Using a custom-built, bench-top PRO system, a commercially available forward osmosis membrane from Hydration Technology Innovations™ (HTI) was evaluated for water flux and power density at two temperatures (20°C and 40°C) and three draw solution concentrations (0.5, 1.0, and 1.5M sodium chloride) that are similar to temperatures and draw solution osmotic pressures capable in an osmotic heat engine. In general, power densities increased with the increasing draw solution concentration and system temperature. The highest observed power density (18.0±2.3W/m2) was measured at 20.7bar (300psi) using a 1.5M sodium chloride draw solution at a system temperature of 40°C. Experimental data compared favorably to predicted performance using previously published governing equations for PRO water flux and power density.

<i>FluxPro</i> as a realtime monitoring and surveilling system for eddy covariance flux measurement

To understand how terrestrial ecosystems respond to global climate change, researchers have globally measured the energy, water and carbon dioxide flux densities (F) globally over various types of vegetation by the eddy covariance (EC) method. However, the process of F calculation and the method of quality control and quality assurance (QCQA) are complex and site specific. Moreover, instantly maintaining remote EC flux measurement sites against instrumentation problems and administrative difficulties is laborious. To overcome these issues, particularly those of realtime F monitoring and prompt site management, FluxPro was created. FluxPro consists of three functional systems: 1) a gathering system that transports EC measurements from various sites to the FluxPro management server; 2) a cooking system that computes F and its frictional uncertainty (ε) together with micrometeorological variables (V); and 3) a serving system that presents the results of the gathering and cooking systems as charts to be distributed over the internet in realtime. Consequently, FluxPro could become an appropriate system for realtime-multi-site management, since it not only automatically monitors F with ε and V but also continuously surveils EC sites, including copious information and an email alert system.

Nutrient leaching in an Ultisol cultivated with sugarcane

Solute leaching below the crop-rooting zone represents not only a valuable loss of nutrients for the plant, but also a potential pollution source of groundwater. The objective of this work was to quantify nutrient-leaching losses at 0.9m depth in an Ultisol that was cultivated with sugarcane, located in the county of Jaboticabal-SP, Brazil. The following ions were evaluated: nitrite, nitrate, ammonium, sulfate, phosphate, calcium, magnesium and potassium. The first ratoon cycle was monitored from November 16, 2006, to July 9, 2007. The experimental design was organized as four random blocks and three treatments: T1: without fertilizer; T2: 100kgha−1 of N and 114kgha−1 of S; and T3: 150kgha−1 of N and 172kgha−1 of S. To determine the fate of the N-fertilizer and S-fertilizer, four microplots were installed, in which 2.15% atoms of 15N- and 10.5% atoms of 34S-enriched ammonium sulfate were applied. The input and output of anions and cations were quantified from the flux density of water and the ion concentration. The NO3−, K+, Mg2+ and Ca2+ concentrations in the soil increased in January following both rainfall and drainage. The leaching of N was between 3.9 and 34.9kgha−1. The N leached derived from the 100kgha−1 applied N fertilizer was 22.5kgha−1. The S leached was between 4.6 and 8.4kgha−1. From the 114kgha−1 S applied as fertilizer the leaching was 0.480kgha−1. The maximum leaching of P, K, Ca, and Mg were 1.2, 53.6, 135.7 and 39.8kgha−1, respectively. From the results, it is not possible to determine whether the local groundwater will be contaminated, but caution should be taken to maintain soil quality by reducing the leaching loss of nutrients.

Comparison of Uniform and Non-uniform Water Flux Density Approaches Applied on a Mathematical Model of Heat Transfer and Solidification for a Continuous Casting of Round Billets

Luiz F.P. Pereira’s name appeared incorrectly on the original publication of this article. It has been corrected here.

Simultaneous production of high-quality water and electrical power from aqueous feedstock’s and waste heat by high-pressure membrane distillation

A new membrane distillation (MD) concept (MemPower) has been developed for the simultaneous production of high-quality water from various aqueous feedstocks with cogeneration of mechanical power (electricity). Driven by low-grade heat (waste, solar, geothermal, etc.) a pressurized distillate can be produced by operating TNO’s Memstill® process at high hydraulic pressures. These pressures are theoretically limited by the liquid entry pressure (LEP) of the membrane. The proof of principle has been shown and is based on the transport of water vapor against a hydraulic pressure gradient. Various commercially available membranes have been evaluated in order to obtain high yields in water flux and power densities. Power densities have been measured which are sufficient to drive the pumps in MD. This allows standalone Memstill® units without electricity consumption to be possible, which are fully driven by waste heat. The application of new incompressible hydrophobic membranes, combining a high permeance with a high LEP, will allow for much higher power densities.

Modelling of osmotic energy from natural salt gradients due to pressure retarded osmosis: Effects of detrimental factors and flow schemes

In this investigation, a simplified pressure retarded osmosis (PRO) model incorporating the detrimental effects of internal polarization concentration (ICP), external polarization concentration (ECP) and reverse salt permeation (RSP) is proposed and verified using published data. The results demonstrate the accuracy of the model to address decreased water flux and power density due to the performance limiting effects. Based on the model, the discharge behaviour of a PRO process is reported with respect to different applied pressures on the draw solution and two flow schemes, co-current and counter-current flows. In the co-current flow PRO process, from the flow profiles in the draw and feed channels, it is found that the adverse effects on the process dynamics, such as water flux and power density, and required membrane area, can be regarded as a further retardation by applying ‘an extra applied pressure’ on the draw solution. In addition, the capacity of extractable energy of the full scale PRO discharge is significantly reduced due to the ICP, ECP and RSP effects. Furthermore, the termination conditions of the PRO discharge and its effects on the dynamics of the PRO process are also investigated in the case of the counter-current flow PRO process.

Improvement in secondary cooling of continuous casting of round billets through analysis of heat flux distribution

A mathematical model of heat transfer and solidification for a continuous casting of round billets was developed. The water flux density of the secondary cooling zone was experimentally measured, using an apparatus in industrial scale with two types of nozzles, flat jet and full cone jet. The profiles of water distribution were applied on the mathematical model. The results showed that the water distribution is not uniform in both longitudinal and angular directions owing to the unevenness of the spray and to the curvature effect of the round billet. This non-uniformity causes important variation of the heat transfer coefficients and superficial temperature of the billet, especially in the first cooling zones, where the temperature is higher. The mathematical model was used to simulate a change of nozzle type in the first cooling zone. The results showed that the heat flux and superficial temperature variations were reduced with a full cone jet nozzle in comparison with the flat jet nozzles.

Análise espaço-temporal de componentes do balanço hídrico em um Latossolo

O monitoramento das variáveis que constituem a equação do balanço hídrico do solo em campo cultivado é necessário para avaliar com confiabilidade os períodos de déficits hídricos durante o ciclo das culturas, manejar a irrigação e quantificar perdas de nutrientes por lixiviação. Os componentes da equação do balanço hídrico podem variar no espaço e no tempo, e o estudo da estabilidade temporal da variabilidade espacial desses componentes é essencial para determinar quais são os pontos de observação no campo (locais) para monitorar a água do solo com precisão e esforço amostral reduzido. Assim, os objetivos deste trabalho foram avaliar os componentes do balanço da água (especificamente a variação de armazenamento de água do solo, drenagem interna e evapotranspiração real) de plantas de milho em um Latossolo Vermelho-Amarelo e analisar a variabilidade espacial e temporal, por meio da técnica de estabilidade temporal. O estudo foi realizado em uma área do Campus da ESALQ/USP, município de Piracicaba, Estado de São Paulo, Brasil. O relevo da área experimental, que tem 1.500 m², é plano. Nessa área foram instalados 60 tubos de alumínio para acesso de uma sonda de nêutrons e 120 tensiômetros com manômetro de mercúrio (60 na profundidade de 0,75 m e 60 na profundidade de 0,85 m). Isso permitiu estimar a densidade de fluxo de água do solo na profundidade de 0,80 m por meio da equação de Darcy-Buckingham e o armazenamento de água na camada de 0,0-0,80 m, ao longo do ciclo da cultura. A precipitação pluvial foi medida por meio de um pluviômetro instalado no centro da área experimental, e a evaporação real foi considerada como desconhecida da equação do balanço hídrico. A pesquisa foi realizada dividindo o ciclo de cultivo em 13 períodos (P1 a P13). O uso da estatística descritiva foi feito para evidenciar a variação do comportamento dos dados após a remoção dos pontos discrepantes, que representaram entre 0,0 e 3,9 % dos pontos amostrais por período. O uso da estatística descritiva foi útil por ter apresentado a mudança no comportamento dos dados, após a retirada de valores discrepantes e extremos em alguns períodos. A técnica da estabilidade temporal é viável para avaliação do balanço hídrico no espaço e no tempo. Os coeficientes de correlação de Spearman entre os períodos indicaram estabilidade temporal para a armazenagem da água independentemente do teor de umidade do solo, mas não expressaram confiabilidade para a avaliação da drenagem interna e a evapotranspiração real da cultura. A evapotranspiração oscilou ao longo do ciclo da cultura mantendo-se praticamente constante nos períodos P5 a P9, em que houve maior desenvolvimento vegetativo das plantas.