Steady Infiltration from a Surface Point Source into a Two-Layered Cylindrically Confined and Unconfined Soil Region with Root Water Extraction

Abstract

Steady infi ltra on from surface point sources into two-layered cylindrically confi ned and unconfi ned soil regions with roots extrac ng water is analyzed with a linearized form of the Richards equa on. In the upper layer, from which plant roots withdraw water with a uniform extrac on coeffi cient (λ), the hydraulic conduc vity at satura on decreases (−1 ≤ β < 0) or increases (β > 0) exponen ally with depth. The lower soil layer is homogeneous, and the soil texture coeffi cient α is the same for both layers. The evapora on loss is taken to be propor onal to the matric fl ux poten al (MFP) at the soil surface, with a propor onality coeffi cient m. It is shown that the point-source solu ons for the modeled systems are physically relevant, i.e., consistent with an exponen al hydraulic conduc vity func on, not only for posi ve but also for nega ve β if λ ≥ 0.5α 2 (1 − β). Also, the frac ons of water lost via evapora on at the soil surface, extrac on by plant roots, and deep percola on are found to be iden cal for both laterally confi ned and unconfi ned regions. Numerical examples illustrate the behavior of the solu ons for various combina ons of the coeffi cients λ, β and m, the root-zone depth, and the lateral extent of the soil domain. The water uptake rate (q up ) increases with increasing λ and root-zone depth and the we ed regions contract as the water uptake increases. Without evapora on, the water uptake rate decreases in the order q up (β < 0) > q up (β = 0) > q up (β > 0). Evapora on losses signifi cantly reduce both the water uptake rate and the extent of we ng. For β < 0 the eff ect of evapora on on q up is larger than for β ≥ 0.Abbrevia ons: ev, evapora on; MFP, matric fl ux poten al; per, deep percola on; up, water uptake.

The soil–water flow system beneath a cotton field in arid north-west China, serviced by mulched drip irrigation using brackish water

“…The water uptake and extent of wetting pockets can be significantly decreased by the soil evaporation (Communar and Friedman 2012). Comparing the mulch covering fractions (0, 30, 70 and 100 %), 70 % treatment was most beneficial for the utilization of soil water and seedling growth.…”

Interweaving Monitoring Activities and Model Development towards Enhancing Knowledge of the Soil-Plant-Atmosphere Continuum

“…To save water, drip irrigation is commonly used, making point source models of interest for management of irrigation. Communar and Friedman (2012) presented a solution to the steady infiltration from surface point sources into a two‐layered, cylindrically (un)confined soil domain, with root water extraction from the upper layer and evaporation from the soil surface. They used a linearized water flow equations expressed by the matric flux potential that allows for depth dependent hydraulic conductivity variations in the upper layer.…”