Measuring hydraulic conductivity in a cracking clay soil using the Guelph Permeameter
Knowing the variation of field-saturated hydraulic conductivity (K) with space, time and antecedent soil moisture conditions can be important for optimum management of cracking clay soils. The Guelph Permeameter (GP) method is a potentially valuable technique for measuring K and its variation in cracking soils, but concerns exist regarding (1) impacts of smearing and compaction in the GP well on the K measurement, (2) accurate detection of when steady flow from the GP is attained, and (3) time required for the GP to reach steady flow (equilibration time). These concerns were investigated for a series of GP measurements in a cracking clay soil (Vertic Xerochrept) in Sicily by testing flow and equilibration time. The mean K values (11.4--22.1 mm/h) obtained from the GP measurements were 1--3 orders of magnitude larger than what might be expected for a clayey texture, indicating that ponded infiltration from the GP wells occurred primarily through highly permeable soil shrinkage cracks, rather than through the low permeability clayey matrix. Wells that were treated with the plucking implement produced a non-significant (P < 0.05) factor of 1.94 increase in mean K relative to untreated wells, suggesting that this method for removing smearing and compaction functioned primarily by reopening partially smeared-over shrinkage cracks or other macropores. Relatively short mean equilibration times were obtained for the GP measurements (11--42 min), suggesting that the GP method can measure the soil's antecedent K before wetting from the well causes enough soil swelling to produce a declining permeability. The traditional four equal readings (FR) procedure is estimating GP equilibration time substantially underestimated the more recent visual estimation (VE) and the new cumulative drop (CD) procedures. This underestimation by the FR procedure resulted in overestimates of K relative to the VE and CD procedures for K values less than about 4 mm/h. It was concluded that the GP method can be a viable technique for measuring K in cracking clay soil.
- Research Organization:
- Univ. degli Studi, Palermo (IT)
- OSTI ID:
- 20013705
- Journal Information:
- Transactions of the ASAE, Vol. 42, Issue 4; Other Information: PBD: Jul-Aug 1999; ISSN 0001-2351
- Country of Publication:
- United States
- Language:
- English
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