Discussion of “Explicit Solution to Green and Ampt Infiltration Equation” by Sergio E. Serrano

Green–Ampt approximations

“…This approximation turns out to be identical to that of Brutsaert [12]; it has a maximum relative error of 0.47% [7]. A slight variation of Eq.…”

“…As mentioned already the approximation of Serrano [33] consists of the first few terms of one of the asymptotic expansions of W À1 . It is divergent at the branch point and thus its practical use is limited to situations with large ponding times [7][8][9].…”

“…(7). However, the maximum relative errors for each approximation will not necessarily be the same for the GA solution as Eq.…”

“…(7) accentuates errors for small t * , the approximations that have their maximum error in this region show the largest increases in relative error when considering Eq. (7). Note that the approximations where coefficients have been adjusted to improve the fit of W À1 could be re-adjusted to improve the fit to F * .…”

“…Approximations giving F * explicitly in terms of t * have been receiving considerable attention recently (e.g., [7][8][9][33][34][35]). It is therefore appropriate to investigate the gamut of available approximations and further to rank them according to their relative complexity and utility.…”