Using terrigenic 4He to identify and quantify regional groundwater discharge to streams

We present a new technique for identifying and quantifying the discharge of long residence time, regional groundwater to rivers using naturally occurring tracers measured within the river. Terrigenic 4He and 222Rn, synoptically sampled along a 100 km reach in the Fitzroy River in northern Western Au...

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Bibliographic Details
Published in:Water resources research 2011-06, Vol.47 (6), p.n/a
Main Authors: Gardner, W. Payton, Harrington, Glenn A., Solomon, D. Kip, Cook, Peter G.
Format: Article
Language:English
Subjects:
Age
base flow
Catchments
Chlorofluorocarbons
Creeks & streams
environmental tracers
Freshwater
Groundwater
Groundwater discharge
groundwater stream water interactions
Helium
Hydrology
isotope hydrology
regional groundwater
River systems
Rivers
Sediments
Stream flow
Streams
Sustainability management
travel time distribution
Water inflow
Watersheds
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Summary:We present a new technique for identifying and quantifying the discharge of long residence time, regional groundwater to rivers using naturally occurring tracers measured within the river. Terrigenic 4He and 222Rn, synoptically sampled along a 100 km reach in the Fitzroy River in northern Western Australia, are used to identify areas of groundwater inflow to the river and to distinguish shallow, local and deep, regional groundwater. Models of tracer transport in the river can be numerically optimized to calculate total groundwater discharge and to separate regional and local discharge fractions. Discharge of regional groundwater composes close to 15% of the total groundwater discharge along the entire reach, varying spatially along the reach from 0% to 100% of total groundwater discharge. This method should be applicable in river systems where groundwater with elevated terrigenic helium could be discharging to the river. The ability to separate locally from regionally derived groundwater discharge has significant implications for calculating catchment water budgets, for predicting catchment response to changes in precipitation, and for sustainable management of the catchment. Key Points Elevated helium in river water indicates discharge of regional groundwater Regional discharge can be separated from locally derived groundwater discharge Total, local and regional groundwater discharge volumes can be calculated
ISSN:0043-1397
1944-7973
DOI:10.1029/2010WR010276