Prediction of hydraulic conductivity changes using soil characteristics

Abstract

Permeameter experiments were performed on six Arizona soils using a solution of 12.5 meq/1 and varied sodium concentrations. Hydraulic conductivities for five soils were reduced 60 to 95 percent for input solutions having maximum sodium adsorption ratios (SAR) of 25. Effective soil sealing occurred even though the soils were alkaline. Sealing with sodium appears nearly irreversible at low solution concentrations and saturated conditions. The soil having the highest initial hydraulic conductivity recovered less than 20 percent of the original conductivity upon reapplication of a calcium solution. These results are useful when considering sealing small ponds by sodium applications. Hydraulic conductivity changes from increases in solution SAR were described mathematically using two empirically determined parameters that appear unique for each soil at a constant concentration. The parameters found for this study, plus those found from data of previous studies, were compared using multiple regression analysis to determine the most significant soil properties in predicting conductivity changes. Soil texture has the greatest influence on the parameters. An equation derived by combining data from eleven alkaline soils was selected as best for predicting hydraulic conductivities resulting from SAR changes. Predictions should be improved if additional soil data were available for analysis.