Oral Presentation NCGRT/IAH Australasian Groundwater Conference 2019

We use environmental isotope and chemical tracer tools to understand complex groundwater flow and evolution processes including nitrate contamination. Examples where these environmental tracers, in addition to conventional hydrologic investigations, have significantly improved the understanding of groundwater processes include:

• Nitrate contamination of groundwater and subsequent discharge into streams in the Horizons region
• Source and lag time of legacy nutrient loads and future loads in the lakes Rotorua and Taupo catchments
• Connection and disconnection of rivers and aquifers, groundwater recharge source, flow rates, and young water fractions with potential to carry live pathogens in the Heretaunga Plains aquifer
• Dynamics of the water movement through the entire catchment of the Wairau River, Marlborough, from rain, through the river catchment, and connection to Holocene and Pleistocene gravel aquifers

This summary aims to show where the combination of the age tracers, water and nitrate stable isotopes, gas tracers, nutrients and major ions enabled us to understand recharge source and rate, interaction between surface and groundwater, lag times, discharge pathways, and denitrification processes, in order to enable better management of groundwater problems and resources.