Oral presentation at the New Zealand Hydrological Society Annual Conference, 20-23 November 2007, Rotorua, New Zealand.In the Pukemanga catchment, nitrate is leaching from soil under agricultural land use, and is being transported by subsurface water flow to surface waters. Groundwater is the suspected dominant transport pathway. This study proposes to determine the proportion of groundwater discharge to streamflow by partitioning of daily and hourly streamflow on the basis of groundwater dynamics