Website to tell swimmers if Durban beaches are safe

The University of KwaZulu Natal recently launched a website – Woz’Olwandle – that will provide realtime and forecast guidance to people who want to swim at six of Durban’s beaches.

Meaning ‘come to sea’, the website (www. wozolwandle.com) uses a computer model that processes a large amount of data to estimate the likely concentrations of E. coli at the Country Club Beach, Pirates Beach, North Beach, South Beach, uShaka Beach and Point Beach over a 24-hour period.

The new website draws on the experience of the Beach Report Card, developed for the Greater Los Angeles area in the USA. It will provide guidance on whether it is safe to swim, using easy-tounderstand icons denoting whether water conditions are:

• Good : excellent water quality with E. coli levels <250 cfu/100 mℓ

• Acceptable : acceptable water quality with E. coli levels between 200 cfu and 500 cfu/100 mℓ

• Poor : poor water quality with E. coli levels >500 cfu/100 mℓ

“Information on water quality is often out of date by the time it reaches beach users, either because samples are not collected daily or because of the time it takes (minimum of 24 to 48 hours) to culture and count bacteria in a laboratory and then publish the results on beach notice boards or online. Heavy rains and strong winds can also change pollution levels overnight. And sampling is costly,” says Dr Justin Pringle, senior lecturer, University of KwaZulu-Natal (UKZN).

Computer model

These problems are addressed using a computer model to predict pathogen levels at beaches between sampling periods to manage exposure risks effectively.

Pringle notes that the model is based upon the original UKZN fluid dynamics computer model that was developed (sadly for the same problem) by Derek Stretch and Dave Mardon about 20 years ago.

It has now been repurposed to provide real-time information to the public and predicts E. coli concentrations in the nearshore zone using real-time and forecast winds, rain, river and stormwater/ river drain flows.

“The model captures a variety of data that influences the mixing and dispersion of pathogenic bacteria pollution close inshore (including rainfall and wind). It also estimates the amount of pollution moving offshore, as well as the decomposition rates of bacteria when exposed to seawater and sunlight.”

The pollution comes from freshwater sources (like rivers and stormwater drains). Fresh water has a lower density than salt water, so it is concentrated within the top layer when it enters the sea. Therefore, when the wind blows, the fresh water (where the pollution is) is easily ‘swirled around’.

By factoring in a range of rainfall data, the computer model can predict the amount of water from stormwater drains and the Umgeni River entering the sea. A wind field is used to calculate where the pollution will travel and how much pollution is present.

“We also use old observational data from eThekwini Municipality (when they used to do sampling every two weeks) to build a statistical distribution of E. coli. An event mean concentration and flow rate will indicate how much pollution is entering the sea and the wind field will tell us where the pollution will travel,” explains Pringle.

To guard against rolling blackout hitches, Pringle has taken the precaution of using a server in the USA. Global model outputs from the National Centre for Environmental Protection (in the USA) are also used to make forecasts.

Other information is extracted daily from:

• global earth observation systems

• a weather station at uShaka Beach

• test results from Talbot Laboratories.

Talbot

Talbot (at their own cost) have been testing the water quality of eThekwini beaches and rivers. Weekly sampling is done at various points and the test results are made public.

“Paddling used to be one of my most favourite sports, but I sadly stopped due to the poor water quality of the Umgeni River. Talbot sponsors testing to firstly make people aware of high levels of pollution in our rivers. We hope that our water quality results will prompt more action in looking after and valuing our water resources. The river and marine environment are being used as a dumping ground for sewage, which is easy to treat. It is important for community members to be aware of the quality of the water that they are using for recreation so that they can make more informed decisions. In Gauteng, Talbot have also been sponsoring regular water quality testing for the Hennops River Revival in Tshwane,” adds Carl Haycock, CEO, Talbot.

“As a scientist I want to ensure that information gets to people and I hope that the new website will also help to stimulate new conversations about and potential solutions to the problem of sewage flows that have dented the city’s tourism image. We are also looking for funding to help finance the tests done by Talbot as the model relies on these test results,” says Pringle.

Future plans

The University of KwaZulu Natal recently launched a website – Woz’Olwandle –that will provide real-time and forecast guidance to people who want to swim at six of Durban’s beaches

The project is part of a broader UKZN academic collaboration that may help the municipality to pinpoint the major sewage pollution problem areas for priority attention and repairs.

For example, there are plans to enlist the help of cellular biologists to study the genetic structure of bacteria to help determine the source of sewage pollution at individual wastewater treatment works, stormwater outlets or rivers across the municipal area.

The research team will include cellular biology and genomics researcher Dr Angus Macdonald, marine geologist Professor Andy Green, ecotoxicologist Dr Dalene Vosloo, and environmental fluid dynamics expert Professor Derek Stretch.

Pringle hopes the system can be expanded to cover other beaches, such as uMhlanga, with support from the tourism and hospitality sector and research grants. There is the potential to expand the project to the entire South African coastline.