Groundwater Resources

Groundwater resources

Age of groundwater or time of recharge, combined with knowledge of the hydrological setting, can provide valuable information for planning the sustainable management of groundwater resources.

Once water has entered the groundwater system the tracers become isolated from input sources and the time of recharge can be reconstructed from known historic concentrations.

Water dating has been hailed internationally as a breakthrough in managing aquifer systems and in detecting early signs of deteriorating water quality. The ability to accurately age-date young groundwater adds considerable value to groundwater resource or quality surveys because:

  • evidence of isotopic tracers in groundwater samples and the age distributions determined reveal recharge areas, flowpaths, aquifer structure, and groundwater mixing;
  • the potential for contamination of different geohydrologic environments is strongly related to the water age;
  • the effects of past land management practices on groundwater quality can be determined by examining waters of known age; and
  • groundwater flow models can be validated by comparison with water age.

Recent hydrological studies undertaken by the GNS Science team using age dating methods include:

  • EBOP – Future nitrate loads from streams and groundwaters into Lake Rotorua.
  • Wairarapa Valley Groundwater – residence time, flow patterns and hydrochemistry trends.
  • Relating sources and ages of groundwater to aquifer hydrogeology on the Canterbury Plains.
  • Examining the relationship between land-use and water quality in Southland.
  • Tracing of contaminant pathways and lag-times into lakes and streams in the Lake Taupo area.

Our capability to detect very low levels of tritium is particularly valuable as a complementary tool in carbon isotope studies of old groundwaters.


  • Morgenstern, U. 2005 Wairarapa Valley groundwater: residence time, flow pattern, and hydrochemistry trends.Lower Hutt: Institute of Geological & Nuclear Sciences Limited. Institute of Geological & Nuclear Sciences science report 2005/33. 36 p.
  • Morgenstern, U.; Reeves, R.R.; Daughney, C.J.; Cameron, S.; Gordon, D. 2005 Groundwater age and chemistry, and future nutrient load for selected Rotorua lakes catchments.Lower Hutt: Institute of Geological & Nuclear Sciences. Institute of Geological & Nuclear Sciences science report 2004/31. 73 p.
  • Morgenstern, U.; Reeves, R.R.; Daughney, C.J.; Cameron, S.; Gordon, D. 2005 Time trends in water chemistry and future nutrient load in the Lake Rotorua area.p. 23-28 In: Miller, N.; Miller, E. (eds) Proceedings : Rotorua Lakes 2004 : restoring lake health - nutrient targets and cyanobacteria, 16 - 17 September 2004, Park Heritage Hotel, Rotorua. Rotorua: LakesWater Quality Society.