Lake Rotoiti, Nelson Lakes National Park

This page has information on water quality in Lake Rotoiti.

See the lake for yourself on the St Arnaud webcam.

Water Quality

Very good water quality was found in Lake Rotoiti, the only lake that has been sampled in Tasman District. Sampling of Lake Rotoiti was undertaken in 1999. Results indicated that the lake is fully oxygenated and has low levels of nutrients, as would be expected for a lake that is virtually unaffected by human activities. Comparing these results with earlier investigations (in 1976, 1990 and 1992-94) indicates that the quality of the lake environment has not changed significantly in the past 25 years.

Water Quality Survey of Lake Rotoiti 1999

Black Valley Stream Water Quality

Black Valley Stream is the only waterway with any potential to adversely affect water quality of Lake Rotoiti as it flows through a low-density housing (holiday homes) area and campground in St Arnaud. Monitoring Black Valley Stream has shown very good water quality (over the period 2000 to present). Nutrient concentrations in the stream were almost always within guidelines and the waterway was always suitable for contact recreation. Macro-invertebrate health was also very good over this period.

However, water quality in the stream has not always been good with high concentrations of disease-causing organisms. A survey of septic tanks was carried out in St Arnaud in 1996. This showed that the majority of septic tanks were faulty or inadequate. In response to this issue a reticulated sewerage system for the township was completed in 1999 and all property owners were required by June 2000 to be connected.

Results of the water quality monitoring for Black Valley Stream, Travers River and Buller River at the outlet of Lake Rotoiti from April to August 1999 can be downloaded below.

Water Quality Graphs for the Rotoiti Catchment 1999