Health of lakes in New Zealand

Based on Trophic Level Index, 2009–2013, number of monitored lakes

Definitions

Trophic level index: The lake trophic level index (TLI) indicates the health of a lake based on its degree of nutrient enrichment. The trophic states represent increasing nutrient enrichment, from a state of microtrophic (very good) to supertrophic (very poor).

Microtrophic (TLI < 2; very good) lakes are very clean and often have snow or glacial sources (eg Lake Pukaki in Canterbury)
Oligotrophic (TLI 2–3; good) lakes are clear and blue, with low concentrations of nutrients and algae (eg Lake Rotoma in Bay of Plenty)
Mesotrophic (TLI 3–4; average) lakes have moderate concentrations of nutrients and algae (eg Lake Rerewhakaaitu in Bay of Plenty)
Eutrophic (TLI 4–5; poor) lakes are murky, with high concentrations of nutrients and algae (eg Lake Rotoroa in Northland)
Supertrophic or hypertrophic (TLI > 5; very poor) lakes have extremely high concentrations of phosphorus and nitrogen, and are overly fertile; they are rarely suitable for recreation and lack habitats for desirable aquatic species (eg Lake Forsyth in Canterbury).

Data calculation/treatment

Figure.NZ calculated the count of lakes by tropic state to mirror the analysis undertaken for the Environmental Reporting Series (see http://stats.govt.nz/browse_for_stats/environment/environmental-reporting-series/environmental-indicators/Home/Fresh%20water/lake-water-quality.aspx Figure 1)

Data provided by

Ministry for the Environment

Dataset name

Environmental Reporting: Lake water quality 2009–2013

Webpage:

https://data.mfe.govt.nz/layer/3310-lake-water-quality-200913

How to find the data

At URL provided, select 'Download' from the top right of the screen. You will have to register to download this dataset.

Import & extraction details

File as imported: Environmental Reporting: Lake water quality 2009–2013

From the dataset Environmental Reporting: Lake water quality 2009–2013, this data was extracted:

  • Sheet: Sheet1
  • Range: C4:C10
  • Provided: 7 data points

This data forms the table Environment - Lake water quality by trophic state 2009–2013.

Dataset originally released on:

February 18, 2016