Towards baseflow index characterisation at national scale in New Zealand

BaseFlow Index (BFI) was determined for all river reaches in New Zealand. A recursive digital filtering technique was applied to 482 gauged sites across New Zealand, then an individual filter parameter was determined for each catchment. BFI varies between 0.20 and 0.96 with an average of 0.53, which indicates 53% of long-term streamflow in New Zealand is likely to originate from groundwater discharge and other delayed sources. This dataset can support water resources planning and management in New Zealand, in particular water supply, stream ecology and pollution risk. The methodology is applicable to any region around the world.