Filtering of cyclic period infiltration in a layered vadose zone: 1. Approximation of damping and time lags

Vadose Zone Journal
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Abstract

Infiltration and downward percolation of water in the vadose zone are important processes that can define the availability of water resources. We present an approach that provides insight into how periodic infiltration forcings at the land surface filter in a layered vadose zone in terms of changes in the timing and magnitude of hydrologic responses. To represent geologically realistic systems, we used vertical sequences of one-dimensional periodic solutions, where each solution represents a single soil in a layered profile. The overall approach is based on a linearized Richards equation and assumes that the effects on flow of continuous pressure head changes at soil interfaces are negligible. We evaluated the limit of these approximations by comparison with results from the numerical model HYDRUS-1D, which uses the full Richards equation. We compared (i) the depth at which flux variations became steady, and (ii) the travel time of wetting fronts to reach a depth of 3 m. The solution was reasonably accurate (error less than a factor of 2) for infiltration cycles with periods from 30 to 365 d and for fluxes common in arid and semiarid environments (0–2 mm d−1). Lag times between a surface forcing and response at any depth were accurate (error less than a factor of 1.1). The approximation generally provided consistent estimates of the damping and time lag, such that it overestimated the depths where fluxes were steady and underestimated the time for a forcing to reach a specific depth.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Filtering of cyclic period infiltration in a layered vadose zone: 1. Approximation of damping and time lags
Series title Vadose Zone Journal
DOI 10.2136/vzj2018.03.0047
Volume 17
Issue 1
Year Published 2018
Language English
Publisher ACSESS
Contributing office(s) Arizona Water Science Center
Description 16 p.
First page 1
Last page 16