New method for monitoring soil water infiltration rates applied to a disc infiltrometer

doi:10.1016/j.jhydrol.2009.10.017

Journal of Hydrology

Volume 379, Issues 3–4, 30 December 2009, Pages 315-322

https://doi.org/10.1016/j.jhydrol.2009.10.017 Get rights and content

Summary

Disc infiltrometers commonly use low-capacity water-supply reservoirs made of small diameter tubes. This reservoir geometry allows accurate measurements of water levels, but makes it necessary to stop the infiltration measurements to refill the water-supply reservoir when long-term infiltration experiments are conducted. The purpose of this study is to determine if a double Mariotte system provides accurate infiltration rate data from disc infiltrometer. To this end, infiltration rates (Q) is calculated from the head losses (ΔH_T) produced by the water flowing along a flexible silicone pipe that connects a high-capacity water-supply reservoir and the disc of the infiltrometer. The method was calibrated in the laboratory using 2- and 3-mm internal diameter (i.d.) and 50- and 100-cm-long silicone pipes by comparing the measured ΔH_T with the corresponding theoretical values, for different Q measured from the drop in water level in the water-supply reservoir. This method was next applied to field conditions, where the infiltration rates (at four supply pressure heads in five different soils) measured from the water-level drop in the water-supply reservoir of a double Mariotte disc infiltrometer (using 2- and 3-mm-i.d. and 100-cm-long silicone pipes) were compared with the corresponding values calculated from ΔH_T measured in the Mariotte tube. An excellent correlation was found in the laboratory experiment between the calculated and the measured ΔH_T (r² = 0.99), and between Q measured from the water-supply reservoir and that calculated from the measured ΔH_T (r² = 0.99). In the field experiments, excellent correlation was shown between the infiltration rates measured from the water-level drop in the water-supply reservoir and the corresponding values calculated from the ΔH_T measured in the Mariotte tube. This correspondence indicated that this method would be a consistent alternative to the standard procedure used in the disc infiltrometry technique.

Introduction

The disc infiltrometer (Perroux and White, 1988) has become a very popular instrument for estimations of soil hydraulic properties at the near-zero soil water pressure head. The relatively rapid and portable nature of this technique and its easy applicability in situ makes the disc infiltrometer a very valuable tool in many hydrological and soil science studies. Soil hydraulic properties such as hydraulic conductivity (K), sorptivity (S) (White et al., 1992), and the size and number of the soil’s macro- and meso-water-conductive pores (Moret and Arrúe, 2007) are commonly calculated from the cumulative water-infiltration curves measured with the disc infiltrometer.

Typically, this instrument consists of three parts made of Plexiglass: a base disc covered by a nylon cloth, a graduated reservoir that provides the water-supply, and a bubble tower with a moveable air-entry tube that imposes the pressure head of the water at the cloth base (Angulo-Jaramillo et al., 2000). Commonly, the water-supply reservoir consists of a low-water-capacity clear plastic tube of small diameter, which makes it possible to reduce the infiltrometer weight on the soil surface, and allows for more accurate measurements of water-level changes in the tube. However, this reservoir geometry has the limitation that it results in interruptions of the infiltration measurements to refill the water-supply reservoir when long-term infiltration experiments (i.e. infiltration at successive supply pressure heads at the same sampling point) are performed.

Cumulative soil water-infiltration curves obtained with disc infiltrometers are commonly measured by visually noting, at constant intervals of time, the drop in water level in the water-supply reservoir. This method, however, is time-consuming and can lead to errors in water-level measurements due to reader distractions when long-time infiltration samplings are performed. This limitation was satisfactorily solved by Ankeny et al., 1988, Casey and Derby, 2002, who monitored drops in the water level by incorporating two gage transducers or a single differential transducer in the water-supply reservoir, respectively. Similarly, Moret et al. (2004) developed an automated method to measure the changes in water level in the water-supply reservoir by means of a long three-rod coated Time Domain Reflectometry (TDR) probe vertically inserted in the water-supply reservoir.

Other advances in disc infiltrometry technique have addressed new designs in which the disc has been separated from the water-supply reservoir and the bubble tower (Casey and Derby, 2002, Moret and Arrúe, 2005). This reduces the weight of the infiltrometer on the soil surface, reduces the risk of macrostructure collapse when applied on unstructured or freshly tilled soils (Moret and Arrúe, 2005) and consequently results in more accurate estimations of the actual soil hydraulic properties.

The objective of this study is to present an alternative procedure and experimental set-up for disc infiltrometry: a double Mariotte system method which makes it possible to calculate infiltration rates from the head losses produced by the water flowing along a flexible silicone pipe that connects a high-capacity water-supply reservoir and the disc of the infiltrometer. The method was calibrated in the laboratory using 2- and 3-mm internal diameter (i.d.) and 50- and 100-cm-long silicone pipes, and subsequently tested in five field experiments for measuring infiltration rates at different supply water pressure heads.

Section snippets

Theory

An incompressible fluid moving along a circular pipe can be described by the Bernoulli equation (Giles et al., 1994). When there is no energy input, this equation is $\frac{V_{1}^{2}}{2 g} + \frac{P_{1}}{γ} + Z_{1} = \frac{V_{2}^{2}}{2 g} + \frac{P_{2}}{γ} + Z_{2} + Δ H_{T}$ where V_i (m s⁻¹), Z_i (m) and P_i (kg m⁻¹ s⁻²) are the average flow velocity, the elevation in the direction of gravity from a reference level, and the pressure at point i, respectively. The g (m s⁻²) parameter is the acceleration due to gravity; γ (kg m⁻² s⁻²) is the specific weight of the fluid, defined as

Calibration of the silicone pipe head losses

A first laboratory experiment was performed to determine the relationship between the water flow (Q) through a pipe and the total head losses (ΔH_T). The experimental design consisted of a double Mariotte system with two silicone pipes (defined as 100 cm length and 3- and 2-mm i.d., respectively) that connected the base of a water-supply reservoir (a clear plastic tube of 75 cm height and 5 cm i.d.) with the base of a Mariotte tube (a clear plastic tube of 35 cm height and 2.5 cm i.d.), and a third

Results and discussion

The excellent correlation between the outlet water flow measured with a single Mariotte tube and the corresponding values measured with the double Mariotte system when the 2- or 3-mm-i.d. and 100-cm-long water-flow silicone pipes were opened (Fig. 3) demonstrates that head losses in the silicone pipe do not have any significant effect on the outlet water from the Mariotte tube. As already observed by Casey and Derby, 2002, Madsen and Chandler, 2007 in similar infiltrometer designs, Fig. 4,

Conclusions

This paper presents a new procedure which, applied to a disc infiltrometer, allows estimations of infiltration rates by measuring the head losses produced by the water flowing along a silicone pipe. The system, which consists of 2- or 3-mm-i.d. and 100-cm-long silicone pipes that connect a Mariotte tube with a water-supply reservoir, calculates the head losses from the drop in water level that occurs in the Mariotte tube. In the calibration experiment on the laboratory, the measured head losses

Acknowledgements

This research was supported by the Ministerio de Ciencia e Innovación of Spain (Grants AGL2007-66320-CO2-02/AGR; 200840I214). The authors are grateful to Darío Testón and Valero Pérez for their help in various technical aspects of this study.

References (10)

R. Angulo-Jaramillo et al.
Field measurement of soil surface hydraulic properties by disc and ring infiltrometers. A review and recent developments
Soil and Tillage Research
(2000)
D. Moret et al.
TDR application for automated water level measurement from Mariotte reservoirs in tension disc infiltrometers
Journal of Hydrology
(2004)
M.D. Ankeny et al.
Design for an automated tension infiltrometer
Soil Science Society of America Journal
(1988)
F.X.M. Casey et al.
Improved design for an automated tension infiltrometer
Soil Science Society of America Journal
(2002)

There are more references available in the full text version of this article.

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