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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2016-75
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
15 Mar 2016
Review status
This discussion paper is a preprint. A revision of the manuscript for further review has not been submitted.
Variable Saturation Infiltration Model for Highly Vegetated Regions
James Polsinelli and M. Levent Kavvas Department of Civil Engineering, University of California-Davis, Davis, California
Abstract. Observations have been made in studies that in watersheds with moist soils and lush vegetation, water does not pond on the soil surface, even during significant rainfall events. In these cases, all the water infiltrates into the soil. Furthermore, the water content in the pore space is below saturation.

The tools for modeling such situations are limited. A universal method for estimating groundwater in the unsaturated zone is the Richards' equation, a non linear system of 1D or 3D equations based on physical flow principles. While effective, the difficulties in solving Richards' equation can pose a significant problem in a complex system, which may require extensive amounts of calibration and numerical effort in procuring a solution. A second method is based on the idea of approximating the movement of moisture through the soil as a rectangular profile, e.g. assuming that the water moves through a soil column like a piston. Rectangular profile methods have been developed in the past for cases in which ponding occurs at the surface, and the water content inside the column is at saturation. More general rectangular profile methods allow the water in the column to move at sub-saturation. Both of these existing methods involve solving a non linear algebraic equation for the hydrologic system, involving constant flux at the boundary, due to a wetting event such as rainfall. The method proposed in this article may be used for situations in which the soil does not become saturated, and the soil and rainfall properties, specifically the rates of hydraulic conductance and rate of rainfall respectively, are allowed to vary in space or time. The method proposed is based on a simple principle in infiltration hydrology, that the rate at which water will infiltrate through the soil equilibrates with the rate of rainfall, when the rate of rainfall is smaller than the infiltration capacity of the soil. In application, this method does not require the solution of a non linear algebraic (or differential) system of equations, thus affording modelers computational economy.

Furthermore, this new method can be made to interact with the saturated profile methods in the event that the rainfall overwhelms the ability of soil to absorb moisture. If this happens, a portion of the field will come to saturation while other parts will be below saturation. The sub-saturation models can be made to interact with the redistribution and evapotranspiration processes by providing the initial and boundary condition for those events.


Citation: Polsinelli, J. and Kavvas, M. L.: Variable Saturation Infiltration Model for Highly Vegetated Regions, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2016-75, in review, 2016.
James Polsinelli and M. Levent Kavvas
Interactive discussionStatus: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version      Supplement - Supplement
 
RC1: 'Comments', Anonymous Referee #1, 08 Apr 2016 Printer-friendly Version 
AC1: 'Response to comments', James Polsinelli, 16 Jun 2016 Printer-friendly Version 
 
RC2: 'Review comments on "Variable Saturation Infiltration Model for Highly Vegetated Regions"', Anonymous Referee #2, 24 Apr 2016 Printer-friendly Version 
AC2: 'Response to comments', James Polsinelli, 16 Jun 2016 Printer-friendly Version 
James Polsinelli and M. Levent Kavvas
James Polsinelli and M. Levent Kavvas

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Short summary
A simple method is presented to model movement of water through soil in general conditions. Specifically, this method was designed to provide a rectangular profile approximation (e.g. the water moves through the soil like a piston) where the water content in the soil volumes is less than saturation. This method reverts to the classical saturated rectangular profile technique under heavy rainfall.
A simple method is presented to model movement of water through soil in general conditions. ...
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