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WATER RESOURCES RESEARCH,
VOL. 43,
W06418,
doi:10.1029/2006WR004865,
2007
Potential effects of regional pumpage on groundwater age distribution
Brendan A. Zinn
U.S. Geological Survey National Center, Reston, Virginia, USA
Leonard F. Konikow
U.S. Geological Survey National Center, Reston, Virginia, USA
Abstract
Groundwater ages estimated from environmental tracers can help calibrate groundwater flow models. Groundwater age represents
a mixture of traveltimes, with the distribution of ages determined by the detailed structure of the flow field, which can
be prone to significant transient variability. Effects of pumping on age distribution were assessed using direct age simulation
in a hypothetical layered aquifer system. A steady state predevelopment age distribution was computed first. A well field
was then introduced, and pumpage caused leakage into the confined aquifer of older water from an overlying confining unit.
Large changes in simulated groundwater ages occurred in both the aquifer and the confining unit at high pumping rates, and
the effects propagated a substantial distance downgradient from the wells. The range and variance of ages contributing to
the well increased substantially during pumping. The results suggest that the groundwater age distribution in developed aquifers
may be affected by transient leakage from low-permeability material, such as confining units, under certain hydrogeologic
conditions.
Received 5
January
2006;
accepted 13
March
2007;
published 21
June
2007.
Keywords: Groundwater;
age;
transient.
Index Terms: 1829 Hydrology: Groundwater hydrology; 1832 Hydrology: Groundwater transport; 1846 Hydrology: Model calibration (3333).
Read Full Article (file size: 791648 bytes) Cited by
Citation: Zinn, B. A., and L. F. Konikow
(2007),
Potential effects of regional pumpage on groundwater age distribution,
Water Resour. Res.,
43,
W06418,
doi:10.1029/2006WR004865.
Copyright 2007 by the American Geophysical Union.
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