Determining the likelihood and cost of detecting reductions of nitrate nitrogen concentrations in groundwater across New Zealand

Nitrate‑nitrogen (NO3-N) is a contaminant of concern in groundwater worldwide.

Stakeholders need information on the ability to detect changes in NO3-N concentrations to prove that land management practices are meeting water quality aims.

We created a database of quarterly to monthly NO3-N measurements in 948 sites across New Zealand; 186 of those sites had mean residence time (MRT) data. New Zealand has set a target of sufficient land use mitigations in the next 30 years to ensure steady state surface water concentrations do not exceed 2.4 mg L− 1.