Author:
Chang Chia-Hao,Huang Ching-Sheng,Yeh Hund-Der
Abstract
Abstract. In the process of groundwater recharge, surface water usually enters an
aquifer by passing an overlying unsaturated zone. Little attention has been
given to the development of analytical solutions to a coupled
unsaturated–saturated flow model due to localized recharge up to now. This
paper develops a mathematical model to depict three-dimensional transient
unsaturated–saturated flow in an unconfined aquifer with localized recharge
on the ground surface. The model contains Richards' equation for unsaturated
flow, a flow equation for saturated formation, and the Gardner constitutive
model describing the behavior of unsaturated soil properties. Both flow
equations are coupled through the continuity conditions of the head and flux
at the water table. The semi-analytical solution to the coupled flow model is
derived by the methods of Laplace transform and Fourier cosine transform. A
sensitivity analysis is performed to explore the head response to the change
in each of the aquifer parameters. A quantitative tool is presented to assess
the recharge efficiency signifying the percentage of the water from the
recharge to the aquifer. We found that the effect of unsaturated flow on the
saturated hydraulic head is negligible if two criteria associated with the
unsaturated soil properties and initial aquifer thickness are satisfied. The
head distributions predicted from the present solution match well with those
from finite-difference simulations. The predictions of the present solution
also agree well with the observed data from a field experiment at an
artificial recharge pond in Fresno County, California.
Subject
General Earth and Planetary Sciences,General Engineering,General Environmental Science
Cited by
9 articles.
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