Filtering of Period Infiltration in a Layered Vadose Zone: 1. Approximation of Damping and Time Lags

Abstract

Citation: Dickinson, J.E., and T.P.A. Ferré. 2018. Filtering of period infiltration in a layered vadose zone: 1. Approximation of damping and time lags. Vadose Zone J. 17:180047.

Filtering of Periodic Infiltration in a Layered Vadose Zone: 2. Applications and a Freeware Screening Tool

“…Specifically, we examine how the damping and time lags can accumulate as periodic forcings are transmitted through sequences of soil layers to conceptualize these responses at any depth. Dickinson and Ferré (2018) demonstrated that the approximate solution generally overpredicts these responses but provides the conditions in which the error in the responses is relatively small. Here we identify areas in a model that can be treated as having steady recharge or cyclical recharge with no significant time delays by using the approximate solution.…”

“…Thus, the damping and time lag were likely to be accurate in the northern areas and for shorter infiltration cycles. The evaluation of the damping depth (Dickinson and Ferré, 2018, Fig. 7) provides insight into the accuracy of the damping maps.…”

“…The approximate solution was acceptably accurate for silty clay and sandy loam soils at the long‐term flux used here (0.5 × 10 −3 m d −1 ) and the tested periods. However, the error is likely to increase where ψ increases across thick transitions ( z T in Dickinson and Ferré, 2018) between fine soils, which often have lower (more negative) ψ e , to a coarser underlying soil. That is, when soils coarsen with depth.…”

“…Full details of the solution were provided by Dickinson and Ferré (2018) and Bakker and Nieber (2009). Consider one-dimensional vertical flow described by the Richards equation:…”

“…The approximate solution for the damping and lag time of cyclical flux forcings in a layered vadose zone is summarized below. Full details of the solution were provided by Dickinson and Ferré (2018) and Bakker and Nieber (2009). Consider one‐dimensional vertical flow described by the Richards equation: where ψ [L] is pressure head, t is time, z [L] is the vertical dimension (positive downward), K (ψ) [L T −1 ] is the hydraulic conductivity, and C [L −1 ] is the water capacity.…”