Chemistry of groundwater discharge inferred from longitudinal river sampling

Batlle-Aguilar, J., Harrington, G.A., Leblanc, M., Welch, C., and Cook, P.G. (2014) Chemistry of groundwater discharge inferred from longitudinal river sampling. Water Resources Research, 50 (2). pp. 1550-1568.

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We present an approach for identifying groundwater discharge chemistry and quantifying spatially distributed groundwater discharge into rivers based on longitudinal synoptic sampling and flow gauging of a river. The method is demonstrated using a 450 km reach of a tropical river in Australia. Results obtained from sampling for environmental tracers, major ions, and selected trace element chemistry were used to calibrate a steady state one-dimensional advective transport model of tracer distribution along the river. The model closely reproduced river discharge and environmental tracer and chemistry composition along the study length. It provided a detailed longitudinal profile of groundwater inflow chemistry and discharge rates, revealing that regional fractured mudstones in the central part of the catchment contributed up to 40% of all groundwater discharge. Detailed analysis of model calibration errors and modeled/measured groundwater ion ratios elucidated that groundwater discharging in the top of the catchment is a mixture of local groundwater and bank storage return flow, making the method potentially useful to differentiate between local and regional sourced groundwater discharge. As the error in tracer concentration induced by a flow event applies equally to any conservative tracer, we show that major ion ratios can still be resolved with minimal error when river samples are collected during transient flow conditions. The ability of the method to infer groundwater inflow chemistry from longitudinal river sampling is particularly attractive in remote areas where access to groundwater is limited or not possible, and for identification of actual fluxes of salts and/or specific contaminant sources.

Item ID: 33887
Item Type: Article (Research - C1)
ISSN: 1944-7973
Keywords: groundwater-surface water interaction, groundwater discharge, river sampling, PEST, parameter identifiability
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© 2014. American Geophysical Union. All Rights Reserved. Further reproduction or electronic distribution is not permitted.

Funders: Australian Research Council (ARC), National Water Commission
Date Deposited: 18 Jun 2014 09:59
FoR Codes: 04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040603 Hydrogeology @ 100%
SEO Codes: 96 ENVIRONMENT > 9611 Physical and Chemical Conditions of Water > 961103 Physical and Chemical Conditions of Water in Fresh, Ground and Surface Water Environments (excl. Urban and @ 100%
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