A Simple Numerical Solution for Two-Dimensional Moisture Distribution Under Trickle Irrigation

Sen, H. S.; Paul, D. K.; Bandyopadhyay, B. K.; Dash, N. B.

doi:10.1097/00010694-199211000-00003

Cited by 6 publications

(5 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…he assumption of a constant k [i.e., of a linear K(q) relationship] does not permit reproduction of the shapes of the wetting fronts that arise in immediate proximity to the water source at the irst wetting of an initially dry soil (Clothier and Scotter, 1982). However, when a soil is subjected to periodic wetting-drying cycles with a relatively small range of water-content luctuations, use of a constant k value yields quite realistic results (Ben-Asher et al, 1978;Sen et al, 1992). In such a case, the coeicient k can be attributed to the average water content at the points of measurement (Coelho and Or, 1997).…”

Section: Resultsmentioning

confidence: 99%

“…hey showed that steady solutions provide an approximate prediction of intermittent pressure head patterns for continuously repeated application cycles over part of the low region and during part of the time. Temporal superposition of unsteady-point-source solutions for cyclic input enables quite realistic reproduction of the highly dynamic conditions associated with frequent irrigation (Ben-Asher et al, 1978;Sen et al, 1992;Coelho and Or, 1997). Coelho and Or (1997) used a two-step procedure, in which the coeicients a and K s were determined by itting the steady-pointsource solution to the pressure heads measured during several steady-low tests, ater which the coeicient k was evaluated by itting the solution of Warrick (1974) for cyclic-step input to the pressure heads measured under cyclic irrigation.…”

Section: P 2 Of 12mentioning

confidence: 99%

See 1 more Smart Citation

Determination of Soil Hydraulic Parameters with CyclicIrrigation Tests

Communar

Friedman

2014

Vadose Zone Journal

View full text Add to dashboard Cite

A method for determining soil hydraulic parameters based on periodic point source solutions of the linearized Richards equation is proposed. Closed‐form solutions were derived for buried and surface point sources with a sinusoidally varying flux. These solutions describe the dependence of the matric flux potential (MFP) amplitude and phase shift on the distance from the point sources, frequency of source flux alternations, and soil hydraulic parameters. The Fourier series representation of square waves was used to extend the point source solutions for sinusoidally varying flux to square‐wave cyclic inputs of water with a 50% duty cycle—a preferable operating mode for field experiments. Close to the sources, the amplitudes and shape of MFP waves from a step input were more pronounced than those from a sinusoidal input, but the difference diminished as distance increased. The proposed method involves recording the pressure head variations with a continuously reading tensiometer installed below a pressure‐compensating emitter controlled by an irrigation computer. Among 16 cyclic step‐input irrigation tests, one series involved pressure‐head measurements at a single depth and varied water‐pulse durations; the second involved pressure‐head measurements at various depths with a fixed water‐pulse duration. The soil saturated hydraulic conductivity, the coefficient α of Gardner's conductivity model, and the coefficient k of the linearized unsteady‐flow equation were estimated by matching the periodic solution for cyclic step inputs to the measured pressure‐head data with a two‐step inversion procedure: an amplitude‐shift (AS) estimation procedure followed by the Levenberg–Marquardt (LM) optimization algorithm. The AS procedure was effective, and the LM optimization yielded only minor improvements. Our main findings are: (i) the periodic solution for step inputs yields reasonably good predictions of pressure‐head variations measured at various depths below an emitter for different periods of water application; and (ii) the proposed point‐source method seems to yield consistent and reliable estimates of the three soil hydraulic parameters.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: P 2 Of 12mentioning

confidence: 99%

Determination of Soil Hydraulic Parameters with CyclicIrrigation Tests

Communar

Friedman

2014

Vadose Zone Journal

View full text Add to dashboard Cite

show abstract

“…, (6) em que a integral da eq. (5) pode ser dada pela fórmula de 15 pontos de Gauss-Leguerre, com Z = Z + x/2 (Sen et al, 1992), sendo a solução dada pela expressão:…”

Section: Introductionunclassified

Modelo de distribuição de água e de potencial matricial no solo sob gotejamento com extração de água por raízes

Coelho

1999

Pesq. agropec. bras.

View full text Add to dashboard Cite

A maior dificuldade em descrever e estimar a distribuição de água no bulbo molhado sob gotejamento reside na extração de água pelo sistema radicular, que é mais complexa devido à geometria de fluxo tridimensional. Os modelos existentes são, na maioria, unidimensionais ou multidimensionais de acessibilidade limitada. Este trabalho propõe um modelo semi-analítico para distribuição bidimensional de umidade ou de potencial no bulbo molhado, através da superposição da solução analítica de Warrick, para ponto-fonte em condições de regime não-permanente, com um modelo paramétrico de extração de água pelas raízes, considerando o balanço de água num volume unitário do solo. O modelo foi ajustado com sucesso a dados experimentais para a cultura do milho num solo franco-siltoso. Simulações de distribuição de água no bulbo molhado mostraram que o modelo permite estimar ou descrever a dinâmica de água do solo no bulbo molhado em qualquer tempo ao longo do ciclo de irrigação, o que pode contribuir significativamente na avaliação do manejo da irrigação, no estudo de posicionamento de sensores de umidade ou de potencial matricial, e em estudos relacionados à atividade das raízes no bulbo molhado.

show abstract

“…Revol et al [14] recorded large discrepancies between Wooding [15], Raats [16] and Philip's [17] solutions for predicting the radius of the ponded spot R s (t) beneath a surface point source. In bare soils, Sen et al, [18] and Coelho and Or [19] reported that the accuracy of Warrick's solution [20] hinges on the selection of the constant k (k = dK/dθ). Coelho and Or [19] have shown that the superposition of plant uptake with Warrick's [20] solution seems to provide reliable results.…”

Section: Introductionmentioning

confidence: 99%

Optimizing Emitters’ Density and Water Supplies in Trickle Irrigation Systems

Moncef¹

2019

AJWSE

View full text Add to dashboard Cite

The usual approaches for designing trickle irrigation systems are based upon empirical estimation of the emitters' density and the moistened soil volume. The objective of this paper is to implement a quasi-analytical approach that allows the inference of these two parameters. The emitters' density is determined so that the rooted soil volume would be moistened even at the peak period. The proposed approach enables to adjust the irrigation time in order to replenish the rooted soil volume up to a threshold for an optimal plant growth. The required inputs are: the water retention curve, the hydraulic conductivity at the wetting front, the radius of the moistened spot at the soil surface, and the rooted soil depth. The method is assessed with respect to study cases for sandy and silty soils. The used emitters' discharge were 2 l/h and 4 l/h. The present approach has the advantage of preserving the mass conservation as well as the dynamic aspect of irrigation management. For design purpose, the irrigation time is set equal to the time required to attain a quasi-state flow conditions within the rooted zone. Nevertheless, irrigation time should vary so that design errors are adjusted for irrigation scheduling needs.

show abstract

A Simple Numerical Solution for Two-Dimensional Moisture Distribution Under Trickle Irrigation

Cited by 6 publications

References 0 publications

Determination of Soil Hydraulic Parameters with CyclicIrrigation Tests

Determination of Soil Hydraulic Parameters with CyclicIrrigation Tests

Modelo de distribuição de água e de potencial matricial no solo sob gotejamento com extração de água por raízes

Optimizing Emitters’ Density and Water Supplies in Trickle Irrigation Systems

Contact Info

Product

Resources

About