Example 4.1The Safeswim predictive model for Auckland, New Zealand

In 2017, Auckland City launched the Safeswim website and mobile application as a joint initiative between the Auckland Council, Watercare (the city water and wastewater utility), Surf Lifesaving Northern Region and the Auckland Regional Public Health Service. This initiative was partly funded by a targeted council rates increase for water quality improvement.

Safeswim encourages users to “jump online before you jump in”, directing users to the nearest of more than 100 classified beaches in the region. The system allows users to decide when and where they swim by indicating safety using a red and green coding system. A small number of beaches are permanently closed or unclassified.

Safeswim uses a predictive model built using real-time rainfall and tide data, together with a historical time series of water quality testing results for intestinal enterococci and E. coli. The model provides real-time estimates of the likelihood of an exceedance and classifies beaches as red when the risk of illness by ingestion exceeds 5%.

All Safeswim’s water quality models are overseen by an independent panel of public health experts, which meets quarterly to evaluate performance and provide direction. An independent audit of Safeswim completed by Audit New Zealand in 2020 found that a random sample of Safeswim’s water quality predictions was 89% accurate.

Generally, water quality, especially on the north shore, is good for 95–97% of days. However, exceedances are more common in areas of the city with CSOs where rainfall of more than 15 mm occurs in a 24-hour period, particularly after extended dry periods. In areas with permanently closed beaches, exceedance can occur in dry weather or with as little as 3–4 mm of rain.

The system is a marked improvement over the previous system, which had a 48-hour delay between sample collection and public reporting of results. Transparent public reporting has also increased public awareness and scrutiny about the causes of water pollution, and willingness to pay via targeted council rates for improvement. This has increased the capacity of local authorities to address the primary sources of pollution.

A range of improvement projects are under way, including a large central sewer interceptor (designed in preparation for future growth and impacts of climate change) that will divert overflows away from the harbour to the main wastewater treatment plant. The interceptor is due for completion in 2028. In the meantime, water quality is continually being improved through detection of damaged pipes, and misconnections of sewer and stormwater; restoration of natural treatment in streams and wetlands; and sewer and pump station upgrades. These are all combined with streetscape improvement, where possible.

Source: https://www.safeswim.org.nz/

From: 4, Faecal pollution

Cover of Guidelines on Recreational Water Quality
Guidelines on Recreational Water Quality: Volume 1 Coastal and Fresh Waters [Internet].
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