A framework for sourcing of evaporation between saturated and unsaturated zone in bare soil condition

Sourcing subsurface evaporation (E-ss) into groundwater (E-g) and unsaturated zone (E-u) components has received little scientific attention so far, despite its importance in water management and agriculture. We propose a novel sourcing framework, with its implementation in dedicated post-processing software called SOURCE (used along with the HYDRUS1D model), to study evaporation sourcing dynamics, define quantitatively shallow and deep water table conditions and test the applicability of water table fluctuation (WTF) and bucket methods for estimation of E-g and E-u separately.For the shallow and deep water table we propose E-g>0.95E(ss) and E-g=0 criteria, respectively. Assessment of the WTF method allowed sourcing of very small fluxes otherwise neglected by standard hydrological methods. Sourcing with SOURCE software was more accurate than the standard bucket method mainly because of greater flexibility in spatio-temporal discretization. This study emphasized the dry condition relevance of groundwater evaporation which should be analysed by applying coupled flow of heat, vapour and liquid water.