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Tracer Validation in Hydrogeology (TVH)

Funder: New Zealand Ministry of Business, Innovation & Employment

Programme leader: Chris Daughney

Project type: Research Programme (TVH)

Programme objectives

This programme aims to improve groundwater models by calibration and validation using hydrochemical, temperature and age tracer data. This programme includes case study areas in the Bay of Plenty, Wellington and Southland regions.

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Novel Age Tracers Halon-1301

We have identified a new age tracer, Halon-1301, and established its behaviour as a groundwater age tracer in aquifers of the Greater Wellington Region. The use of Halon-1301 is extremely efficient as it can be analysed simultaneously with SF6 from the same sample, for little additional cost. It is expected that Halon-1301 will be used routinely in NZ and internationally, enabling rapid, qualitative mapping of river gain and losses.

Groundwater Age Proxies

Hydrochemical proxies for groundwater age have been identified in two groundwater systems (Hutt Valley and Lake Rotorua), and samples are currently being processed for two additional systems (Upper Waikato River and Lake Taupo). These age proxies will reduce the cost for characterising groundwater lag times and can assist with calibration of groundwater models.

Using hydrochemistry to conceptualise groundwater systems

By using the isotope and hydrochemistry signature of the water in a unique way, transient modelling has shown that the majority of streams discharge water older than 50 years into the lake, and that the nutrients that cause lake eutrophication are nitrate from agricultural activities and phosphate from geologic sources.

Transient modelling of age distributions

A new numerical technique to model transient distributions of water age.