Event Title

Overland Flow Implications on Infiltration Along a Hill Slope

Location

Space Dynamics Laboratory

Event Website

http://water.usu.edu/

Start Date

3-26-2004 1:00 PM

End Date

3-26-2004 1:15 PM

Description

Water flow and solute transport on a hill slope is a complex nonlinear problem. Rainwater initially infiltrates at a rate equal to the rainfall rate. Once the soil infiltration capacity is reached, surface runoff is generated redistributing water along sloped surfaces. More water usually infiltrates at the lower parts of a hill slope, even for homogeneous soil profiles, because of generally longer surface ponding times and vegetation density. The variable infiltration along a hill slope has significant consequences for plant growth and the overall water balance of evapotranspiration covers.

To describe these complex interactions we have coupled the HYDRUS-2D software package, simulating water flow and solute transport in variably saturated porous media, with a newly developed overland flow routine. The overland flow solver uses fully implicit four-point finite difference method to numerically solve the one-dimensional kinematic wave equation, with overland fluxes evaluated using Manning’s hydraulic resistance law. A Picard iterative solution scheme, similar to one used for solution of the Richards equation, is invoked to solve the resulting system of nonlinear equations. The subsurface flow module determines the main time step for the coupled system. If required for numerical stability, the overland flow module can use multiple smaller time steps during the main time step. This type of time management considers the fact that overland flow and variably-saturated subsurface flow often run at quite different time scales.

We will present several relatively small-scale examples of the updated HYDRUS-2D program showing the development of overland flow as a function of storm intensity and slope angle. Simple examples will verify the correctness of the numerical implementation against an analytical solution. More complex examples will examine infiltration with and without the overland flow modifications along a hill slope. The interaction of runon, vegetative growth, and permeability changes will be examined through these simulations.

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Mar 26th, 1:00 PM Mar 26th, 1:15 PM

Overland Flow Implications on Infiltration Along a Hill Slope

Space Dynamics Laboratory

Water flow and solute transport on a hill slope is a complex nonlinear problem. Rainwater initially infiltrates at a rate equal to the rainfall rate. Once the soil infiltration capacity is reached, surface runoff is generated redistributing water along sloped surfaces. More water usually infiltrates at the lower parts of a hill slope, even for homogeneous soil profiles, because of generally longer surface ponding times and vegetation density. The variable infiltration along a hill slope has significant consequences for plant growth and the overall water balance of evapotranspiration covers.

To describe these complex interactions we have coupled the HYDRUS-2D software package, simulating water flow and solute transport in variably saturated porous media, with a newly developed overland flow routine. The overland flow solver uses fully implicit four-point finite difference method to numerically solve the one-dimensional kinematic wave equation, with overland fluxes evaluated using Manning’s hydraulic resistance law. A Picard iterative solution scheme, similar to one used for solution of the Richards equation, is invoked to solve the resulting system of nonlinear equations. The subsurface flow module determines the main time step for the coupled system. If required for numerical stability, the overland flow module can use multiple smaller time steps during the main time step. This type of time management considers the fact that overland flow and variably-saturated subsurface flow often run at quite different time scales.

We will present several relatively small-scale examples of the updated HYDRUS-2D program showing the development of overland flow as a function of storm intensity and slope angle. Simple examples will verify the correctness of the numerical implementation against an analytical solution. More complex examples will examine infiltration with and without the overland flow modifications along a hill slope. The interaction of runon, vegetative growth, and permeability changes will be examined through these simulations.

https://digitalcommons.usu.edu/runoff/2004/AllAbstracts/20