Ponded Infiltration From a Single Ring: I. Analysis of Steady Flow
- W. D. Reynolds and
- D. E. Elrick
A new analysis of steady, ponded infiltration from within a single ring takes soil hydraulic properties, ring radius, depth of ring insertion, and depth of ponding into account. It also provides a means for determining the field-saturated hydraulic conductivity (Kfs) and the matric flux potential (φm). The analysis employs numerically determined shape factors (G) that are found to depend significantly on ring radius (a) and depth of ring insertion (d), but only slightly on depth of ponding (H) and soil hydraulic properties. As a consequence, averaged G values (Ge) can be developed for specified d and a that apply to a wide range of ponded heads and soil types. Procedures for calculating Kfs and φm are based on G or Ge, and on the ponding of one, two, or multiple H levels in the ring. Test calculations based on Ge suggest that Kfs can be obtained with an accuracy of about ±20% for H = 0.05 to 0.25 m and α = 1 to 36 m−1, where α is the soil parameter of the exponential hydraulic conductivity-pressure head relationship. A similar level of accuracy (using Ge) is obtained for φm when α is small (α ≤ 4 m−1), and when both α and H are large (α > 4 m−1, H ≥ 0.20 m). Significant errors in φm can occur, however, when α is large but H is small. Potentially important features of this single ring method include low sensitivity of the Kfs calculation to errors in Ge, reduced measurement errors resulting from small-scale soil variability, and the ability to pond large heads in order to increase flow rates in low-permeability materials.
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