From A to D: Marlborough's lakes’ health revealed
Bowscale Tarn in the Molesworth is in good health
Council's recent water quality testing of lakes in the region has revealed a mixed picture of lake health, with some pristine bodies of water and others facing challenges.
Five lakes are currently monitored: Grovetown Lagoon, Lake Elterwater, Lake Chalice, Bowscale Tarn and Lake McRae.
The lakes are evaluated for various water quality indicators, including chemical, physical, bacterial, and ecological factors, in accordance with the 2020 National Policy Statement for Freshwater Management (NPS-FM). The framework categorises conditions from A (good) to D (poor).
“Among the monitored lakes, Lake Elterwater was identified as having the poorest health,” says the report’s writer, Senior Environmental Scientist Steffi Henkel.
A local catchment group is working on improving its condition to eventually see the return of species such as freshwater mussels and bittern.
“Grovetown Lagoon presents a concerning case with total phosphorus concentrations nearing the D-band, indicating a need to carefully manage phosphorus sources in the surrounding area. The lagoon's submerged plant life falls within the D-band, primarily due to the prevalence of invasive species like oxygen weed.
“On a more positive note, the three lakes in remote areas generally show good health. Lake McRae stands out with an A grading, indicating excellent water quality. Bowscale Tarn and Lake Chalice show minor impacts, with Lake Chalice getting a D for native submerged plants. However, this may be a natural phenomenon,” says Steffi.
Monitoring and reporting on lakes is crucial for improving understanding of regional natural resources and is a requirement under the NPS-FM.
Council is considering broadening its monitoring efforts to include Argyle Pond, a top recreational area and Lake Grassmere/Kapara Te Hau, the region's largest lake, which was initially excluded due to its significant marine influence.
As Marlborough continues to assess and manage its lake resources, the monitoring programme will play a vital role in improving the health of these critical ecosystems for future generations.
