When Stable Source Water Isn’t Stable Anymore

This is part three of a three-part series on climate change. Part one shared an overview of how climate change is impacting water quality. Part two and this story share solutions to climate-driven water quality challenges from the perspectives of our utility partners.

The Challenge: New Extremes, Higher Organic Matter, and Treatment Plants Designed for Neither

In July 2023, in just about 12 hours, roughly ten inches (about 25 centimeters) of torrential rain pounded down on the Halifax region of Nova Scotia, Canada. The area hadn’t seen that kind of precipitation since a hurricane in the early ‘70s.

Drainage systems overflowed and rivers burst their banks. The normally clear waters of Lake Major and Pockwock Lake—which supply most of Halifax's drinking water—turned dark brown from floodwaters laden with organic matter.

Just a few weeks earlier, Krkosek’s team had been monitoring intense wildfires that crept close to, but thankfully didn’t reach, the lakes’ watersheds. “We went from forest fire risk to flood risk in two months,” she said.

Water Quality Risks from Extreme Storms

Click on each icon to learn more.

The lakes’ baseline water quality has also been changing in slower, more gradual ways. Historically, Halifax Water never had issues with geosmin—a harmless taste and odor compound that can make water taste or smell unpleasant—or with the cyanobacteria that can produce it. Then, in 2012, her team detected it. Krkosek said it’s showed up in the water ever since.

She said the geosmin was one of the first indicators that the lakes’ levels of natural organic matter (NOM) have been gradually increasing, partly due to warmer temperatures and more intense rainfall events from climate change. Lindsay Anderson, who manages water quality for Halifax Water, said lake recovery from acid rain has also played a role.

“Our water treatment plants were built a long time ago, when the lakes were very impacted by acid rain,” Anderson said. “As the lakes are recovering, the filter run times are getting shorter, we have to use more chemicals to maintain finished water quality, and there’s direct strain on the infrastructure, because the plants are starting to receive this water they weren’t designed to treat.”

Anderson said the higher organic load has also increased the risk of biological changes in the watershed and lakes and elevated disinfection byproduct (DBP) formation in the distribution system. To stay resilient amid these compounding challenges, Halifax Water needed a new path forward. 

Tools for Navigating Deep Uncertainty

Halifax Water knew it might need to upgrade its drinking water plants to add clarification systems that could handle higher organic loads. But Hazen Director of Water Resources Innovations Josh Weiss said the utility wanted two things to guide its treatment decisions: hard data and a comprehensive approach to capital improvements.

“Our industry is shifting to looking at these things holistically,” Weiss said. “There’s a renewed focus on managing the source water, managing the watershed, not just relying on treatment to fix all of our issues, because that can be really expensive.”

Utilities also face more contingencies than they used to. “Historically, we had very stable water supplies,” Krkosek said. “Now, with both the discrete weather events and this longer-term, more gradual lake recovery, planning for multiple futures becomes the direction we need to take, because that uncertainty is so much greater than it has been in the past.”

This flexible tool would power faster, more robust water quality management decisions through:

• Streamlining data storage

• Turning data into actionable insights through Power BI dashboards

• Transforming key water quality management strategies into adaptable, easy-to-use decision trees

Climate Change Amplifies Existing Water Quality Risks

Climate change often exacerbates weather events that already posed water quality risks. It can also drive back-to-back events that compound each other. Here are a few examples of those risks—wildfires, storms, and algal blooms—and the impacts they can trigger. Click on each icon to learn more.

Connecting and Assembling

The project began with a series of workshops designed to highlight existing synergies—and to look for new ones—between Halifax Water’s different teams and processes. Hazen then did a deep dive into the utility’s many data streams: where the information went, what it contained, and what gaps and siloes needed addressing.  

“Halifax Water is a very forward-looking utility, so they were doing better than average in connecting the dots,” Weiss said. “Even so, there were challenges. Their watershed and tributary data lived in an Excel database, their lab monitoring went to a lab data system. There were these different warehouses of data that weren’t talking to each other.”

After identifying how to better sync Halifax Water’s data, the team got to work turning all the qualitative and quantitative information they’d collected into a Power BI dashboard and a set of decision trees that were both ready for Halifax to use and flexible enough for other utilities to adapt.  

Clarity and Confidence

Krkosek said one of the biggest takeaways from the decision support tool was hard data confirming what they’d suspected: Halifax Water’s water treatment plant, which currently uses direct filtration, would benefit from adding a clarification system. “It was very clear that the water quality trends we saw were resulting in us being outside the design parameters of the facility that we have,” she said.  

Krkosek and Anderson said that Halifax Water is now exploring dissolved air flotation (DAF) as a potential clarification system to see whether it could meet treatment goals while addressing other long-term needs they’re also considering.

Anderson said her team relies heavily on some of the key dashboards from the tool, which they’ve continued adapting for their own system. She clicked through a series of maps and charts in a DBP risk dashboard, explaining that it allows her team to “trend back in time to be able to understand, is this an event, or is this just a seasonal change that we shouldn’t be surprised by. It would take hours—a day, even—to manually get that information without these dashboards.”

The decision trees from the framework have also become embedded in the utility’s operations. Before this project, Anderson explained, the requirement for monitoring and responding to algal blooms was more observational: “Look at the intake, and if you see pea soup, take a sample and report it.” Now, thanks to an algae decision tree and monitoring program the utility developed based on the decision support tool, “we would see a change before an operator would ever see something growing in the lake.”

She said the more robust data management and tools Halifax Water established with Hazen will empower her team to face the next big water quality event—whether it’s a flood or an algal bloom—with more information and more confidence.