Comparison of the double ring and inverted well methods in the determination of hydraulic conductivity

Abstract

In order to verify the goodness of the double ring method, as an alternative for determining the hydraulic conductivity in unsaturated soil, this procedure was compared with the inverted well method. The experience was developed on the campus of the Agrarian University of Ecuador, on a 35 m² surface of vertisol, clay loam, in which 15 experimental units of 1.8 m² were delimited to jointly evaluate the two aforementioned methodologies. The inner ring was 33 cm in diameter and the outer 56 cm, both with a height of 35 cm; taking readings for 120 minutes and with hydraulic loads between 15 to 10 cm. The inverted wells had a diameter of 6 cm and a depth of 60 cm, maintaining mean initial and final hydraulic loads of 50.6 and 35.6 cm, respectively. In the double ring, the Kostiakov equation was used, verifying its adjustment by means of the coefficient of determination (R²); and in the inverted well, Darcy’s law was applied, considering infiltration both at the bottom and at the wall of the well. The comparison was made with the Student’s t test, after confirming the correlation between the readings. The double ring data were fitted to the Kostiakov model (R²>90%) and were significantly correlated (P= 0.048) with the inverted well data in a positive way; the first obtained a mean of 0.3421 and the second 0.3242 m·day^-1, whose difference was not significant (P= 0.6477). The double ring method offers similar hydraulic conductivity results with respect to the inverted well procedure.