Lake water quality trends 2008–2017, 1998–2017 and 1990-2017
New Zealand's Environment Reporting Series: The Ministry for the Environment and Statistics New Zealand
This dataset measures how water quality in New Zealand’s lakes is changing over time. This dataset contains ten parameters of water quality based on measurements made at monitored lake sites: chlorophyll-a, nitrate-nitrogen, total nitrogen, ammoniacal nitrogen, dissolved reactive phosphorus, total phosphorus, E. coli, water clarity, and lake trophic level index (TLI3 and TLI4).
When nitrogen and phosphorus accumulate above certain concentrations in lakes (referred to as ‘nutrient enrichment’), they can stimulate excessive growth of algae and cyanobacteria. Chlorophyll-a is a measure of the phytoplankton (algae) biomass.
The lake trophic level index (TLI) indicates the health of a lake based on concentrations of three parameters:
- total nitrogen - total phosphorus - chlorophyll-a.
Water clarity is a measure of underwater visibility. Lakes with poor clarity and TLI are poor habitats for some species of animals and plants, and they may not be suitable for recreation. Ammoniacal nitrogen can be toxic to aquatic life if concentrations are high enough.