Improved measurement of conductivity on swelling clay soils using a modified disc permeameter method
J. L. Foley A C , P. E. Tolmie A and D. M. Silburn A BA Agricultural Production Systems Research Unit, Queensland Department of Natural Resources and Water, PO Box 318, Toowoomba, Qld 4350, Australia.
B Cooperative Research Centre for Catchment Hydrology.
C Corresponding author. Email: Jenny.Foley@nrm.qld.gov.au
Australian Journal of Soil Research 44(7) 701-710 https://doi.org/10.1071/SR05195
Submitted: 12 December 2005 Accepted: 10 August 2006 Published: 20 October 2006
Abstract
Disc permeameters are the preferred method for measuring unsaturated hydraulic conductivity (Kψ) in situ. However, in swelling clays, Kψ measured using 3-D measurement and analysis methods are often several orders of magnitude too high and are of no value for modelling internal drainage. During a series of experiments, the causes of inflated Kψ values were identified and a modified method developed to accurately measure Kψ.
On a Black Vertosol, Kψ was strongly correlated with water content and measurement period, with higher flow rates occurring until the soil profile had fully wet up. Near-saturated Kψ measured under permeameters was up to 2 orders of magnitude higher than field-saturated conductivity (KFS) measured in ponded rings. This discrepancy was caused by residual capillarity and unrestricted swelling at the wetting front in unsaturated soils. In addition, lateral flow was common and surface depressions around permeameters filled with water, erroneously contributing to measured infiltration and invalidating assumptions in the 3-D analysis. To prevent this, permeameters were confined within rings to restrict flow to 1D, and measured Kψ (confined) was then compared with Kψ (unconfined) and KFS (ponded rings). Confining flow to 1D reduced Kψ by up to 2 orders of magnitude for a Black Vertosol and by a factor of 3 for a Red Ferrosol. Near-saturated Kψ from confined permeameters agreed well with KFS after similar short measurement durations (e.g. 0.5 h), but Kψ was still overestimated until steady-state flow was established. Therefore, to derive estimates of Kψ that reflect natural flow during internal drainage, we recommend (i) pre-wetting the soil and extending measurement time to attain steady-state flow, and (ii) confining permeameters within rings to restrict flow to 1 dimension.
This method was used to compare lucerne ley and annual cropping treatments on 2 Black Vertosols (Bongeen and Waco). Kψ was similar between cropping treatments, suggesting that initial differences in structure and porosity were transient and related to soil moisture content. The Bongeen soil had a significantly lower Kψ (K–1 cm of 0.8 mm/h) than the Waco soil (2.0 mm/h).
Additional keywords: hydraulic conductivity, infiltration rate, infiltrometer, ponded ring, cracking clay.
Acknowledgments
This project was funded by GRDC projects DNR3 and DNR15, NAPWQS-SIP project Ag07 and Department of Natural Resources, Mines and Water, in collaboration with the GRDC Eastern Farming Systems Project DAQ 0050. Thanks go to farm owners Rob Taylor and Jamie Grant for providing field sites, also to Leslie Research Centre for the use of Kingsthorpe Research Station. A special thank you to the dedicated CSIRO team led by Neal Dalgliesh and Brett Cocks, for conducting the third experiment, and to Kerry Bell for advice on statistical methods. Special thanks also go to Dr Bryan Bridge and Dr Steven Raine for reviewing this manuscript and providing invaluable comments.
Bell MJ,
Bridge BJ,
Harch GR, Orange DN
(2005) Rapid internal drainage rates in Ferrosols. Australian Journal of Soil Research 43, 443–455.
| Crossref | GoogleScholarGoogle Scholar |
Bird TL,
Willis TM, Melville GJ
(1996) Subsoil hydraulic conductivity estimates for the lower Macquarie Valley. Australian Journal of Soil Research 34, 213–228.
| Crossref | GoogleScholarGoogle Scholar |
Connolly RD,
Bell M,
Huth N,
Freebairn DM, Thomas G
(2002) Simulating infiltration and the water-balance in cropping systems with APSIM–SWIM. Australian Journal of Soil Research 40, 221–242.
| Crossref | GoogleScholarGoogle Scholar |
Connolly RD,
Freebairn DM, Bridge BJ
(1997) Change in infiltration characteristics associated with cultivation history of soils in south-east Queensland. Australian Journal of Soil Research 35, 1341–1358.
| Crossref | GoogleScholarGoogle Scholar |
Cook FJ
(1994) Effects of gypsum slotting on the hydraulic properties of a red-brown earth. Soil and Tillage Research 28, 239–252.
| Crossref | GoogleScholarGoogle Scholar |
Lin HS, McInnes KJ
(1995) Water flow in clay soil beneath a tension infiltrometer. Soil Science 159, 375–382.
Lin HS,
McInnes KJ,
Wilding LP, Hallmark CT
(1997) Low tension water flow in structured soils. Canadian Journal of Soil Science 77, 649–654.
Lin HS,
McInnes KJ,
Wilding LP, Hallmark CT
(1998) Macroporosity and initial moisture effects on infiltration rates in Vertisols and Vertic Intergrades. Soil Science 163, 2–8.
| Crossref | GoogleScholarGoogle Scholar |
McKenzie N, Jacquier D
(1997) Improving the field estimation of saturated hydraulic conductivity in soil survey. Australian Journal of Soil Research 35, 803–825.
| Crossref | GoogleScholarGoogle Scholar |
McKenzie NJ,
Cresswell HP,
Rath H, Jacquier D
(2001) Measurement of unsaturated hydraulic conductivity using tension and drip infiltrometers. Australian Journal of Soil Research 39, 823–836.
| Crossref | GoogleScholarGoogle Scholar |
Perroux KM, White I
(1988) Designs for disc permeameters. Soil Science Society of America Journal 52, 1205–1215.
Philip JR
(1986) Linearized unsteady multidimensional infiltration. Water Resources Research 22, 1717–1727.
Reynolds WD, Elrick DE
(1990) Ponded infiltration from a single ring: I. Analysis of steady flow. Soil Science Society of America Journal 54, 1233–1241.
Reynolds WD, Elrick DE
(1991) Determination of hydraulic conductivity using a tension infiltrometer. Soil Science Society of America Journal 55, 633–639.
Schaap MG,
Leij FJ, van Genuchten MTh
(1998) Neural network analysis for hierarchical prediction of soil water retention and saturated hydraulic conductivity. Soil Science Society of America Journal 62, 847–855.
Talsma T, van der Lelij AJ
(1976) Infiltration and water movement in an in situ swelling soil during prolonged ponding. Australian Journal of Soil Research 14, 337–349.
| Crossref | GoogleScholarGoogle Scholar |
Turpin JE,
Bridge BJ,
Orange D, Thompson JP
(1999) Water and bromide movement in a Vertosol under four fallow management systems. Australian Journal of Soil Research 37, 75–89.
| Crossref | GoogleScholarGoogle Scholar |
Vervoort RW,
Cattle SR, Minasny B
(2003) The hydrology of Vertosols used for cotton production: I. Hydraulic, structural and fundamental soil properties. Australian Journal of Soil Research 41, 1255–1272.
| Crossref | GoogleScholarGoogle Scholar |