Lake water quality trends 2008–2017 1998–2017 and 1990–2017

This dataset contains ten lake water quality variables based on measurements made at monitored lake sites: chlorophyll-a, nitrate-nitrogen, total nitrogen, ammoniacal nitrogen, dissolved reactive phosphorus, total phosphorus, Escherichia coli, water clarity, and lake trophic level index (TLI3 and TLI4). This dataset includes: - Median values for the period 2013 to 2017 - For selected indicators, how these values compare to the National Objectives Framework (NOF) (MfE, 2017) bands related to ecosystem health 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 variables: · 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.

More information on this dataset and how it relates to our environmental reporting indicators and topics can be found in the attached data quality pdf.

Summary report available at:

Data and Resources

Additional Info

Field Value
Author Ministry for the Environment
Maintainer Ministry for the Environment
Maintainer Email Ministry for the Environment
Created 2019-04-16T01:33:42.872076Z
Date modified 2019-04-17T04:43:17.531497Z
Language English
Source Identifier
Record created February 2, 2020, Last Updated March 1, 2021