Masters Thesis

Infiltration through Variably Saturated Soil

Infiltration is an important aspect to the hydrologic cycle as it allows for groundwater recharge. In California especially, groundwater is used for agriculture, industrial usage, and as drinking water. This Thesis presents an analytical model for time dependent infiltration through a variably saturated soil. Water is considered to begin infiltrating soil at the ground surface and moves through the vadose zone towards the datum of the system (the water table) where pressure head is constrained to zero. The developed model calculates important soil characteristic parameters such as hydraulic conductivity, K, water content, θ, and pressure head, ψ, as a function of depth. The solution introduces four parameters (ak,ψk,ac, and ψa) to represent K and θ as exponential functions. The proposed model is then compared to existing exponential function solutions for various times. The comparison illustrates the versatility of using a four parameter exponential representation for infiltration. Furthermore, the proposed solution is validated against the numerical solution of HYDRUS-1D, which employs the widely used van Genuchten-Mualem constitutive model. Additionally, once parameters ak and ψk are known, one can obtain van Genuchten parameters α and n. Finally, the constitutive exponential expressions for hydraulic conductivity and water content are compared to the van Genuchten-Mualem expressions.

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