Lake Tarawera is a nationally significant lake that is highly valued by tangata whenua, local residents and the regional community. Monitoring shows that lake water quality does not presently meet the target, based on a Trophic Level Index (TLI) value of 2.6 identified in the Tarawera Lakes Restoration Plan1. Between 2010 and 2020 annual observed TLI was frequently as high as 2.9. Managing nutrient loads to the lake is necessary to achieve desired lake water quality and interim nutrient reduction targets have been established. An objective of this study was to evaluate these targets by improving estimates of ‘sustainable nutrient loads’, which are the external loads of nitrogen and phosphorus that would result in meeting the TLI target.