State assessments
Trophic lake index (TLI)
The Trophic Lake Index (TLI) measures water quality status of New Zealand lakes using chlorophyll a, Secchi depth (water clarity), total phosphorus and total nitrogen. The TLI is calculated for an annual and a three-year (rolling mean) period. See Hickson Rowden and Perrie (2018) and benchmarking for further information on calculation methods.
Trophic level values for each of the four TLI variables as well as an overall mean TLI score for each lake, based on both July 2018 to June 2019 and the three-year period July 2016 to June 2019 (note variable n between sites). Trophic level classes are provided in brackets. Units are chlorophyll a (mg/m3), secchi depth (m), nitrogen (g/m3), and phosphorus (g/m3).
Proposed natural resources plan thresholds (PNRP)
Comparison of lake data against PNRP outcomes for the three-year period July 2016 to June 2019. See Hickson Rowden and Perrie (2018) and benchmarking for further information on calculation methods.
Note that this only includes Lake Onoke data for the 8 times the lake mouth was closed out of 36 samples over the three-year period.
Values with asterixes indicated exceedances of PNRP thresholds. Units are chlorophyll a (mg/m3), nitrogen (g/m3), and phosphorus (g/m3).
National objectives framework (NOF)
Comparison of lake data against NPS-FM NOF attribute states for the one-year period July 2018 to June 2019. See benchmarking for more information. See Hickson Rowden and Perrie (2018) and benchmarking for further information on calculation methods.
Note that this only includes Lake Onoke data for the 9 times the lake mouth was open out of 12 samples during 2018/19.
Annual summaries with NOF state in brackets. Units are nitrogen (g/m3), phosphorus (g/m3), and chlorophyll a (mg/m3).
