The cutting-edge tool that identifies catchment risk in real-time

The cutting-edge tool that identifies catchment risk in real-time

Drinking water, compromised.

It’s something that you wouldn’t expect to hit a developed nation like New Zealand.

But in 2016, over 5,500 people fell ill, four lives were lost and many more affected with long-term illness when a Campylobacter outbreak contaminated Havelock North’s drinking water.

In response, the Government introduced the Water Services Bill.

Expected to be passed in mid-late 2021, the Water Services Bill requires action on six fundamental principles of drinking water safety based on recommendations from the Inquiry into the contamination event.

Moving forward, source waters are to be identified, managed, and monitored with measures to manage any risks published on a regular basis.

But what’s the best way to do so, not just consistently, but accurately?

An innovative Dynamic Catchment Risk Assessment tool can make the process a whole lot easier.

Developed by Tonkin + Taylor hydrogeologist Chris Shanks and Senior Geospatial Specialist Andy Thomas in conjunction with Hastings District Council (HDC), the tool uses available GIS data and an understanding of catchment processes to quickly identify and prioritise contamination risks.

“Havelock North was a real circuit breaker for our organisation in terms of what we used to do and what we do now”, says HDC Three Waters Manager Brett Chapman. “In our efforts to rebuild, we’ve put the past behind us, but we haven’t forgotten the learnings that have come from Havelock North”.

Learning from the past to build a more resilient future lies at the heart of the DCRA tool, and the cutting-edge use of live GIS data is what can help to prevent a future outbreak from happening.

As Andy Thomas explains, “Because the input GIS data is live and often hosted by regulatory authorities or the water suppliers themselves, this tool responds in real-time to changes in the catchment, identifies new potential contaminant sources, and shows ways to reduce risk”.

The typical method adopted for delivering safe drinking water is via a multiple barrier approach. The trouble is that catchments can contain thousands of contaminant sources within highly complex and dynamic systems.

Identifying them all and prioritising which ones to focus on first is not easy.

Rather than looking for “needles in haystacks”, the DCRA tool enables a water supplier or decision-maker to identify, prioritise and respond to source risks in real-time and as they emerge. Drawing on several new innovative approaches, the tool is at the cutting-edge of catchment risk management in New Zealand.

“We wanted to provide water supply managers and decision-makers with something that would enable them to maintain an updated understanding of potential risk even when catchments are highly complex and dynamic”, reflects Chris Shanks.

When it comes to catchment risk, there are two key components to identify - a source of contamination and pathways for it to reach a receptor, like a water supply bore or supply intake.

The DCRA tool utilises GIS data to identify potential sources of contamination and assesses these in terms of aquifer vulnerability and transport mechanisms to where water is abstracted.

GIS data is also used to identify contaminants associated with land-use activities, drawing from an understanding of spatial trends in the aquifer’s vulnerability, in relation to surface contamination and groundwater flow within the catchment.

There are several GIS data sources available in New Zealand that assist in identifying potential contamination, including contaminated land databases, together with district and regional land-use and surface water mapping. Further bolstering this, there are also hazardous substance registries, discharge consenting and wastewater infrastructure data, and data showing the location, age and construction material of wastewater infrastructure, or areas of historical quarrying, mining and landfilling.

Using Feature Manipulation Engine (FME) software, risk scores are extracted from this collective data and calculated. They are then shown as a “heat map” on an interactive GIS viewer which displays the results and allows a user to assess the risk. Even if information is sparse, conservative scoring can be revised on a case-by-case basis as more data is gathered.

For instance, detailed GIS data is often held by wastewater asset owners including age, condition, depth, pipe size, pressure and material type. These can all be used to refine risk calculations based on factors like age, material and condition.

Simply put, the DCRA tool makes life easier for asset owners and managers. A water supplier can maintain an up-to-date understanding of source-risks and identify new risks as they emerge. A water manager can prioritise resources to address the highest risks, then measure value in terms of risk reduction.

“Using the DCRA tool, we’ve tried to take care of the initial heavy lifting associated with screening large amounts of data to find potential contaminant sources” Chris says. “The tool enables a new level of responsive and proactive decision-making which is a much-needed step forward in catchment risk management.”