Determining groundwater discharge and chemistry from multiple aquifers by longitudinal river sampling

Groundwater discharge into rivers has traditionally been estimated by assuming knowledge of groundwater chemistry, often based on results obtained from wells located at some distance from rivers. This relies on field access and may result in large costs if new bores need to be drilled.

This project presents a new method for identifying the locations of and quantities of groundwater discharge into a river, based on river water sampling, river flow information, and knowledge of the geology of the region. It does not require direct access to groundwater.

The method was tested on a 400km stretch of the Mitchell River, a tropical river in far north Queensland, Australia. Taking samples of river water from a helicopter approximately every 5km along 400 km of the river and its main tributaries, these samples were analysed for a variety of environmental tracers, including major ions and selected trace elements. The water composition, along with information about the catchment’s geology and flow discharge data, was then used to feed a one-dimensional water and mass balance model of the river.

The method enables the inference of groundwater inflows from various sources along the length of a river, as well its chemistry. The ability of this method to provide information about groundwater discharge from river sampling is particularly attractive in remote areas where access to groundwater is limited or impossible, and to identify contamination sources.

Research Program

Surface Water – Groundwater Interactions

Principle Researcher

Dr Jordi Batlle-Aguilar

Collaborators or Co-authors

Professor Peter Cook
Ms Chani Welch
Dr Glenn Harrington
Dr Marc LeBlanc