Linearized Moisture Flow with Loss at the Soil Surface

Abstract

AbstractThe general solution of a linearized moisture flow equation is derived for point and line sources whether buried or on the soil surface. The surface flux is taken to be proportional to the matric flux potential, which is consistent with the physical situation of small evaporative losses for dry soil and larger losses for wet soil. The fraction of water lost at the surface turns out to be identical for point and line sources and for the steady‐state case is [m/(2 + m)] exp(−ad) where m is the surface flux proportionality constant, d the depth of source, and α a constant from the assumed unsaturated hydraulic conductivity function. This fraction is plotted as a function of time for a fixed source depth. Also given are curves depicting the total water loss as a function of source depth. A generalized solution is derived for any type of source located in a horizontal plane.