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New catchment risk tool boosts water-quality control

Water quality management has received a boost with the development of a new tool for identifying catchment risk.

Outlined in a recent Journal of Water and Health paper, it incorporates a step-by-step survey method and risk calculator to improve on previous tools for identifying risks, said co-author and GHD Principal Consultant Water Resources Danielle Baker.

“The previous WSAA survey is quite dated and it just didn't give practical indication or detail of method,” Baker said.

“It left it to the consultant or the utility to design their own methodology so certainly there was variability and ambiguity.”

Baker said the new method was uniform, repeatable and easy to follow – meaning data could be more regularly updated.

“Because of the electronic data capture tool [tablet and smartphone application], team members who are out in the catchment routinely can just pick new things up whenever they happen to see them. It just prompts you with all the fields and forms to capture data,” she said.

“The information is fairly straightforward. It might be a herd population number or you might estimate the distance from a fence to a waterway – setback distances.

“It's all about things that, with a fairly untrained eye, you could gather the information.”

The survey groups hazards into six types: sewage infrastructure, on-site sewage systems, industrial, stormwater, agriculture and recreational sites. Escherichia coli, protozoan pathogens and chemicals (including fuel and pesticides) are used as index contaminants.

Once data is recorded, an Excel-based tool calculates the risk for individual sites by estimating the likelihood of the site affecting catchment water quality, and the potential consequences.

The risks are then integrated to calculate a cumulative risk for each sub-catchment and the whole catchment.

“The benefit for water utilities is the tool can be used to prioritise catchment works and to understand risks coming to treatment plants – that's important for public health,” Baker said.

“Then for other catchment managers, who might be in it for a natural resources reasons, again it can help you by picking up hotspots in your catchments and working out where you can have some easy victories – easy fixes.

“It can help you prioritise hotspots for catchment works and soft-engineering works for your best water-quality improvements.”

The methodology development was funded by Seqwater and has been directed towards the protection of drinking water supplies and identification of potential hazards to recreational waters.

But Baker said there was no reason it couldn't be applied more broadly.

“It can also be applied to the identification of pollution hotspots in urban and peri-urban areas, to assist in the prioritisation of infrastructure projects such as sewer backlog programs and improvements to the management and design of urban stormwater infrastructure,” the paper concluded.