Low tension water flow in structured soils Academic Article uri icon

abstract

  • Water transport through structured clayey soils may be prone to by-pass flow, a mechanism that may lead to rapid transport of contaminants to ground water. To quantify the significance of low-tension water flow in structured soils, apparent steady-state infiltration rates at water potentials from 0.24 to 0m were measured using tension infiltrometers on 18 soils of varying texture and structure. Each infiltration measurement was conducted sequentially at 0.24, 0.12, 0.06, 0.03, 0.02, 0.01, and 0m supply potentials (supply), all at the same soil location, to separate different size pores effective in transmitting water. Results from 96 soil horizons showed that 7618% (meanSD) of the water fluxes at supply=0m (total water flux) were transmitted through macropores (active at supply0.03m), although macropores usually constituted a small portion of a soil's total porosity. Mesopores (active at supply0.24m) contributed 1913% of total water flux. Micropores dominated the soils' total porosities, but generally contributed <10% of the total water flux. Macropores and mesopores showed greater influence on water flow in clays than in sands at supply0.24m. Values of soil macroscopic c and microscopic m capillary length scales were determined from the change in infiltration rates with supply. Values of c, a hydraulic conductivity-weighted mean capillary water potential, were greater for sands (63mm) than loams (50mm), and greater for loams than clays (22mm). Values of m, the mean hydraulically effective pore size, were greater for clays (0.33mm) than loams (0.15mm), and greater for loams than sands (0.12mm). Most of the soils studied showed hydraulic characteristics associated with by-pass flow. Key words: Infiltration, tension infiltrometer, macropore flow, by-pass flow, capillary length scale, parameter

published proceedings

  • Canadian Journal of Soil Science

author list (cited authors)

  • Lin, H. S., McInnes, K. J., Wilding, L. P., & Hallmark, C. T.

citation count

  • 39

complete list of authors

  • Lin, HS||McInnes, KJ||Wilding, LP||Hallmark, CT

publication date

  • November 1997