Faecal contamination (poo) in recreational waters poses an ongoing risk to public health. The only way to manage the risk in the short term is to monitor and report the levels of contamination in the water so that the public can make informed decisions before going into the water and exposing themselves to the risk.

Safeswim integrates several methods to provide the most timely and accurate information on water quality conditions and public health risk. These include:

• Sampling: Safeswim continues to collect water quality samples all year round. This includes ongoing regular and targeted sampling for model validation and calibration, and targeted sampling to support the investigation and monitoring of pollution sources and to demonstrate the beneficial water quality outcomes of infrastructure improvements. Find out more about Safeswim’s modelling here
• Real-time environmental data: Safeswim draws on continuous monitoring and forecast data of rainfall and other environmental conditions (wind, tide, and sunlight), which are essential inputs to Safeswim’s models.
• Predictive modelling: Safeswim uses a range of water quality models to predict when the concentration of faecal indicator bacteria (FIB) in the water is above predefined thresholds that pose an elevated risk to health from swimming. Safeswim’s model predictions of water quality risk are updated every 15 minutes. Find out more about Safeswim’s models here
• Continuous monitoring of wastewater overflows: Sensors on the wastewater network detect when overflows occur and these are automatically communicated in real-time as black pins on the Safeswim website. Find out more about black pins here
• Monitoring and alerting of other health safety issues: These may include unexplained water quality exceedances detected by sampling, leaks or overflows from the wastewater network, environmental hazards such as toxic algae, or major incidents such as extreme rainfall. In these situations, the Safeswim model results are manually overridden by temporary black or red pins as appropriate.
• A user-friendly public interface: Safeswim proactively communicates public health risk forecasts and warnings through a map-based public interface which is accessible online and via a mobile app.

Safeswim meets globally accepted standards for water quality prediction. The overall accuracy of the Safeswim system has been estimated to be between 86% - 90% over the last five summers. This is much better than sampling only, which is estimated to only be about 10% accurate. The performance of the Safeswim system is under constant review, including independent reviews coordinated annually by Audit NZ, and Safeswim’s models are refined regularly in response to ongoing water quality sampling.

Find out more:

• Safeswim's water quality programme: Professor Gillian Lewis from the School of Biological Sciences at Auckland University gives us an overview of the Safeswim water quality programme, explains how the Safeswim water quality samples and models work together and describes what it means when Safeswim issues a ‘red’ alert at a beach.