Bathing water quality

Why we monitor recreational bathing water quality

Nelson’s swimming holes and beaches are regularly used by locals and visitors over summer, and having clean, swimmable water at key locations is a priority for Council. Bacteria levels are monitored at our recreational bathing water sites over summer to minimise the risk of illness from harmful water borne bacteria and viruses that may be present. The summer of 2015-16 was the first year that water samples were collected in both wet and dry weather conditions, which means that some readings may be higher due to rainfall effects.

Bathing water quality in Nelson is generally very good. However, higher bacteria levels can occur from various sources such as wild birds, animals, farm stock and wastewater. An increase in bacteria often occurs after periods of rainfall, when river flow increases from land run-off and stormwater.

Toxic Algae Cyanobacteria

Toxic algae (also known as Cyanobacteria) is naturally present in many New Zealand waterways. It's found in ‘clean’ rivers but can grow when river flows are low and stable, and temperatures are consistently warm. Council routinely monitors its level and informs the community when action needs to be taken. Learn more in the Toxic Algae section.

Key results for recreational bathing water quality

Nelson’s beach monitoring sites at Tahunanui Beach and Cable Bay have retained Good recreation grades, with Nelson Haven (Atawhai) and Monaco (Wharf) attaining Fair grades. Occasional exceedences have been associated with rainfall events and high spring tides re-suspending washed up debris from the beach.

The Maitai River bathing holes between Maitai Camp and Girlies Hole continue to have Fair-Good grades, with few exceedances over the last five years.

The recreation grade for the Maitai River at Collingwood Street remains at Very Poor due to the risk of contamination from stormwater and other sources such as dogs and wildfowl.

The Wakapuaka River at Paremata Flats remains at Very Poor, due to contamination from sources including livestock, feral animals and wildfowl upstream of the sampling site.

The Fair grade was assigned to the Wakapuaka River at Hira Reserve due to the long term trend of elevated bacteria counts.

People are advised not to swim at sites with Poor grades, which are generally unsuitable for swimming, as indicated by historical water quality results.

Initiatives for improving recreational bathing water quality

Working with land owners

The Nelson City Council Land Management Adviser provides free advice for land owners and financial assistance towards fencing and native plants for riparian planting and biodiversity enhancement. Improving water quality in Nelson’s streams and rivers is a key focus. Further advice is also available on best practice land management and related issues, including maintenance of septic tanks. If you are interested in receiving advice please contact Lynne Hall, Environmental Programmes Officer 546 0308.

Nelson City Council work in progress

Council has launched Project Maitai/Mahitahi with the goal of improving the water quality of the Maitai River. A team including Cawthron scientists, Council and NELMAC staff is undertaking investigations to find the sources of bacteria in the Maitai River, including microbial source tracking to test for the presence of human faeces, dye testing waste water mains to identify leaks, and undertaking continuous bacteria sampling to understand the bacteria transport pathway in the lower Maitai River, Brook Stream and Saltwater Creek.

Annual Monitoring summaries