Laboratory studies to examine the impacts of polyacrylamide (PAM) on soil hydraulic conductivity

Polyacrylamide (PAM) is being suggested as a new technology to reduce seepage losses in unlined irrigation canals. The goals of this thesis were to quantify the optimum concentrations of PAM and suspended sediment (SSC) that would reduce Ksat to the greatest extent, and to better understand the mechanisms contributing to reduced Ksat. Testing was conducted using a constant head method in soil columns (15 cm length, 6.35 cm diameter). An unbalanced multi-factorial design was used with experimental variables including soil type (#70 mesh sand, C33 sand, loam soil), PAM concentration (5, 10, 20, 40 lbs/ca), and SSC (0, 150, 300 ppm). Results show that PAM reduced Ksat 40% to 98% in sandy soils, but reductions were less in loam. Adding suspended sediment reduced Ksat 8-11 times versus PAM alone. Mechanisms that reduced Ksat included higher viscosity from dissolved PAM, creation of a separate and distinct PAM layer, and the plugging of larger soil pores. Significance of these mechanisms was found to be a function of experimental conditions.