Predicting the field characteristics of drip irrigation

Revol, Ph.; Clothier, Brent; Vachaud, G.; Thony, J.L.

doi:10.1016/0933-3630(91)90024-h

Cited by 11 publications

(4 citation statements)

References 11 publications

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“…A point source method has been developed to estimate the soil hydraulic properties in situ (Shani et al, 1987;Or, 1996;Revol et al, 1991Revol et al, , 1997Yitayew et al , 1998). Wooding (1968) presented an approximate solution for water flow, at steady state flow conditions, from a shallow circular pond on the soil surface (point source) as:…”

Section: Field Determination Of Soil Hydraulic and Chemical Transportmentioning

confidence: 99%

Field Determination of Soil Hydraulic and Chemical Transport Properties 1

Al-Jabri

Horton

Jaynes³

et al. 2002

Soil Science

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Section: Field Determination Of Soil Hydraulic and Chemical Transportmentioning

confidence: 99%

Field Determination of Soil Hydraulic and Chemical Transport Properties 1

Al-Jabri

Horton

Jaynes³

et al. 2002

Soil Science

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“…Although the size sample is somewhat small, the water contents can be considered to have a Gaussian distribution. As in work by Revol et al [1991], we consider here that in using (7) to derive water content from matric flux potential, (1) [Raats, 1971] is more robust than using (10) of paper 1 to derive the soil water pressure. This could also explain the better success found here for water content prediction, than for soil water pressure prediction in the previous paper.…”

Section: Water Content Behind the Wet Front Four Sitesmentioning

confidence: 99%

Infiltration from a surface point source and drip irrigation: 2. An approximate time‐dependent solution for wet‐front position

Revol¹,

Clothier²,

Mailhol³

et al. 1997

Water Resources Research

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Abstract. Raats' [1971] steady state theory is here extended to provide an approximate analysis of the transient pattern of wetting around a point source. The assumption that a steady state regime prevails behind the wet front and the use of the Clothier [1984] and Philip [1984] theories on water movement along the streamlines allows an approximate transient solution for surface point source infiltration to be developed. This procedure was previously tested against absorption theory and laboratory experiments [Revol et al., 1995], but now this new analysis is evaluated via a field test. The vertical elongating influence of gravity is found to be well predicted. Application of this analysis to design purposes is also mentioned. The role of the macroscopic characteristic capillary length of unsaturated flow, Xc, is highlighted by this approximate solution. Finally, we propose a method that allows estimation of Xc from a point-source infiltration experiment. IntroductionThe lateral spread of water away from a dripper, compared to its depth of penetration, is determined by the relative importance of the soil's capillarity and its hydraulic conductivity. The ability to predict the dimensions of the wetted bulb is important, both to ensure efficient irrigation and to avoid the environmentally deleterious passage of irrigation water beyond the root zone. The main advantage of analytical solutions is their fewer parameters requirements and the generalization they offer in relating inputs to system response, which are essential for making general inferences and developing recommendations. Existing analytical theories for three-dimensional infiltration, which can be used for drip irrigation, either are applicable only to the early stages of wetting [

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“…The first is due to Wooding [1968]. As an approximation of his complicated solution, Wooding [1968] gave, in conclusion, a simple expression for the asymptotic steady state flux F from a shallow circular pond of radius rp: Q 4 F= Wrp2= Ks + ,r•pp CbS (4) Wooding [1968], and many others [Bresler, 1978;Russo, 1983;Clothier et al, 1985;Shani et al, 1987;Revol et al, 1991] implicitly consider the reciprocal to be true. That is, a dripper discharging at a volumetric rate Q creates a free-water pond of radius rp given by: -2(bs + (4(b• 2 + QyrKs) •/2 rp = w.Ks ' (5) Wooding [1968] indicated that the validity of this approximation (equation (4)) is restricted to when arp < 10.…”

Section: Linearized Solution For Steady Infiltrationmentioning

confidence: 99%

Infiltration from a surface point source and drip irrigation: 1. The midpoint soil water pressure

Revol¹,

Vauclin²,

Vachaud³

et al. 1997

Water Resources Research

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Abstract. Bresler [1978] proposed a procedure for drip irrigation design which is focused on the midpoint soil water pressure hc. We present a practical field test of this approach in order to evaluate the validity of the underlying assumptions. The simulated h c values were obtained from Raats' [1971] steady state theory for 32 points in the field where the hydraulic conductivity parameters K s and a were measured. The h c values were measured at the same locations during microirrigation of a maize crop. Measured hc's appear to be lower than the simulated ones, especially late in the season. The measured spatial variability in h c appeared to be higher than the simulated ones. This could well have been caused by root uptake activity, which is not considered in the analysis, as well as by the large but typical drippers spacing of d = 1.00 m. Thus the tensiometers could have been beyond the practical limit of wetting. Consequences for design and management are important. For design, even if a high h c value is chosen, there is no real guarantee that the wetting would be effective at the midpoint. For irrigation management, tensiometer placement too far from the dripper would lead to overirrigation, so for a large dripper spacing d, the midpoint placement is not judicious. IntroductionIt is well known that drip irrigation efficiency is critically dependent upon the soil's hydraulic properties. Nowadays, with increasing environmental concerns about water use and the recent development of new devices for measuring the soil's hydraulic properties, there is a requirement and opportunity to consider better the soil's properties in designing and operating drip irrigation systems. In this series of two papers we examine how the theory of point source infiltration can help in this task. This first paper deals with the soil water pressure at the point midway between drippers. The second paper IRevol et al.

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Predicting the field characteristics of drip irrigation

Cited by 11 publications

References 11 publications

Field Determination of Soil Hydraulic and Chemical Transport Properties 1

Field Determination of Soil Hydraulic and Chemical Transport Properties 1

Infiltration from a surface point source and drip irrigation: 2. An approximate time‐dependent solution for wet‐front position

Infiltration from a surface point source and drip irrigation: 1. The midpoint soil water pressure

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