A Simple Deterministic Model for Steady Evaporation under Shallow Water Table Conditions

Abstract

Evaporation from soil surface plays a significant role in water resources management. Evaporation is an important component of hydrological cycle and is needed for most soil, water, plant and atmosphere-dependent models. The objective of this study was to derive an improved model for estimating steady evaporation from bare soil when water table is shallow. While in the original Gardner’s solution the integral form of upward flow has been simplified, in our derivation an exact analytical solution for upward flow is proposed. To come up with an exact comparison, our proposed model was further evaluated with the same Gardner and Fireman [6] experimental data. Results indicated that both original and the modified models cannot account for the vapor phase, tending to underestimate the evaporation rate compares to the measured data. However, both models could reasonably well estimate the evaporation values particularly under deeper water table depths. The reason can be attributed to the boundary conditions governing the evaporation process. Evaluating the models performance by CD, RMSE and EF statistics demonstrated that our proposed model could better predict the evaporation rates compares to the original model.