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A screening tool for delineating subregions of steady recharge within groundwater models

Vadose Zone Journal

By:
, , ,
DOI: 10.2136/vzj2013.10.0184

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Abstract

We have developed a screening method for simplifying groundwater models by delineating areas within the domain that can be represented using steady-state groundwater recharge. The screening method is based on an analytical solution for the damping of sinusoidal infiltration variations in homogeneous soils in the vadose zone. The damping depth is defined as the depth at which the flux variation damps to 5% of the variation at the land surface. Groundwater recharge may be considered steady where the damping depth is above the depth of the water table. The analytical solution approximates the vadose zone diffusivity as constant, and we evaluated when this approximation is reasonable. We evaluated the analytical solution through comparison of the damping depth computed by the analytic solution with the damping depth simulated by a numerical model that allows variable diffusivity. This comparison showed that the screening method conservatively identifies areas of steady recharge and is more accurate when water content and diffusivity are nearly constant. Nomograms of the damping factor (the ratio of the flux amplitude at any depth to the amplitude at the land surface) and the damping depth were constructed for clay and sand for periodic variations between 1 and 365 d and flux means and amplitudes from nearly 0 to 1 × 10−3 m d−1. We applied the screening tool to Central Valley, California, to identify areas of steady recharge. A MATLAB script was developed to compute the damping factor for any soil and any sinusoidal flux variation.

Geospatial Extents

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
A screening tool for delineating subregions of steady recharge within groundwater models
Series title:
Vadose Zone Journal
DOI:
10.2136/vzj2013.10.0184
Volume
13
Issue:
6
Year Published:
2014
Language:
English
Publisher:
Soil Science Society of America
Publisher location:
Madison, WI
Contributing office(s):
Arizona Water Science Center
Description:
15 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Vadose Zone Journal
Number of Pages:
15
Country:
United States
State:
California
Other Geospatial:
Central Valley