Complementary use of tracer and pumping tests to characterize a heterogeneous channelized aquifer system in New Zealand

The combined use of pumping and tracer test data enabled the derivation of equivalent average hydraulic conductivities (K avg) for each test in a heterogeneous channelized alluvial aquifer, whereas K values of the preferential flow paths were two orders of magnitude higher. Greater and earlier drawd...

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Veröffentlicht in:Hydrogeology journal 2008-09, Vol.16 (6), p.1177-1191
Hauptverfasser: Dann, R. L, Close, M. E, Pang, L, Flintoft, M. J, Hector, R. P
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Sprache:eng
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Zusammenfassung:The combined use of pumping and tracer test data enabled the derivation of equivalent average hydraulic conductivities (K avg) for each test in a heterogeneous channelized alluvial aquifer, whereas K values of the preferential flow paths were two orders of magnitude higher. Greater and earlier drawdown was generally observed along preferential flow lines in a pumping test, within an array of 21 wells. The study aim was to characterize hydraulic properties of a channelized aquifer system in New Zealand by combining tracer and pumping test data. Estimates were able to be made of the percentage of highly permeable channels within the profile (~1.2%), effective porosity that reflected the maximum fraction of highly permeable channels within the aquifer ([Greek Phi symbol] eff ₋pc ~0.0038), and flows through highly permeable channels (~98%) and the sandy gravel matrix material (~2%). Using [Greek Phi symbol] eff ₋pc, a tracer test K avg value (~93 m/day) was estimated that was equivalent to pumping test values (~100 m/day), but two orders of magnitude smaller than K calculated solely from transport through permeable channels (K pc ~8,400 m/day). Derived K values of permeable and matrix material were similar to values derived from grain size distribution using the Kozeny-Carman equation.
ISSN:1431-2174
1435-0157
DOI:10.1007/s10040-008-0291-4