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Tracing long‐term vadose zone processes at the Nevada Test Site, USA
Author(s) -
Hunt James R.,
Tompson Andrew F. B.
Publication year - 2005
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.5976
Subject(s) - vadose zone , groundwater recharge , aquifer , groundwater , hydrology (agriculture) , geology , ditch , groundwater flow , hydrogeology , capillary fringe , environmental science , soil science , geotechnical engineering , ecology , biology
Abstract The nuclear weapons testing programme of the USA has released radionuclides to the subsurface at the Nevada Test Site. One of these tests has been used to study the hydrological transport of radionuclides for over 25 years in groundwater and the deep unsaturated zone. Ten years after the weapon's test, a 16 year groundwater pumping experiment was initiated to study the mobility of radionuclides from that test in an alluvial aquifer. The continuously pumped groundwater was released into an unlined ditch where some of the water infiltrated into the 200 m deep vadose zone. The pumped groundwater had well‐characterized tritium activities that were utilized to trace water migration in the shallow and deep vadose zones. Within the near‐surface vadose zone, tritium levels in the soil water are modelled by a simple one‐dimensional, analytical wetting front model. In the case of the near‐surface soils at the Cambric Ditch experimental site, water flow and salt accumulation appear to be dominated by rooted vegetation, a mechanism not included within the wetting front model. Simulation results from a two‐dimensional vadose groundwater flow model illustrate the dominance of vertical flow in the vadose zone and the recharge of the aquifer with the pumped groundwater. The long‐time series of hydrological data provides opportunities to understand contaminant transport processes better in the vadose zone with an appropriate level of modelling. Copyright © 2005 John Wiley & Sons, Ltd.