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Estimating groundwater recharge in fractured rock from environmental 3 H and 36 Cl, Clare Valley, South Australia
Author(s) -
Cook P. G.,
Robinson N. I.
Publication year - 2002
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2001wr000772
Subject(s) - groundwater recharge , piezometer , aquifer , geology , fracture (geology) , evapotranspiration , groundwater , hydrology (agriculture) , tracer , soil science , geomorphology , geotechnical engineering , ecology , physics , nuclear physics , biology
Vertical profiles of 3 H and 36 Cl concentrations are obtained from piezometer nests installed in fractured metasedimentary aquifers in the Clare Valley, South Australia. Because 3 H is lost during evapotranspiration with negligible fractionation, while 36 Cl is retained within the soil, comparison of 3 H and 36 Cl concentrations allows estimation of the aquifer recharge rate. An analytical solution for the transport of 3 H and 36 Cl through planar, parallel fractures is used to investigate the effect of variations in matrix porosity, tortuosity, fracture aperture, fracture spacing and aquifer recharge rate on tracer profiles and then to reproduce observed profiles within piezometer nests. While the measured distributions of these tracers are not able to constrain most model parameters, they are able to tightly constrain the aquifer recharge rate. The broad nature of the 36 Cl and 3 H peaks measured at our sites is simulated using a constant fracture spacing, lognormal distributions of fracture apertures, and mean recharge rates of 60–75 mm yr −1 .