When glaciers last retreated across the continental US, over 10,000 years ago, meltwater filled river channels and eroded the landscape. This was how the Allegheny, Monongahela, and Ohio Rivers–among many others–were formed; natural corridors for trade and travel that would, eventually, feed the industrial heart of Pittsburgh.

Three Rivers Waterkeeper (3RWK) was founded in 2009 in Pittsburgh, Pennsylvania. 3RWK’s goal is to protect and improve the water quality of the Allegheny, Monongahela, and Ohio Rivers and watersheds, serving as both a scientific and legal advocate for these waterways.

Koa Reitz is the Environmental Scientist at 3RWK–a role that entails a lot of data collection and analysis. Data collection ranges from spot sampling for basic water quality characteristics and PFAS (per- and polyfluoroalkyl substances, commonly known as forever chemicals), to supporting the Swim Guide Program, which tests for E. coli.

Captain Evan Clark is the Three Rivers Waterkeeper. He spends a lot of his time on the water, monitoring for pollution incidents and facilitating trips on the water for interested parties–from politicians to community members and scientists.

Armed with technology, including a recently deployed NexSens buoy, 3RWK is uncovering patterns that were previously not measured—providing deeper insight into pollution events, long-term trends, and a complex story of river recovery.

The buoy measures basic water quality parameters to mirror manual measurements, as well as additional parameters which the team is interested to explore in more depth. (Credit: Koa Reitz / 3RWK)

Layers of Pollution 

Southwest Pennsylvania’s industrial history has strongly impacted fluvial health. Reitz emphasizes that community is at the heart of 3RWK’s work–reconnecting people with waterways that were once exploited and neglected.

“We had dead rivers in the area mostly due to heavy industry, steel, even up until the 70s,” says Clark. “And through that industrial era, we really lost a human connection to rivers. That loss of connection, in some ways, can almost allow the pollution to continue to happen unabated.”

Although in the 21st century, river health has “rebounded massively,” the effects of industrial pollution are still evident.

Reitz notes, “We work a lot in a world where we’re seeing layers upon layers of pollution and we have to figure out how to do the right testing, how to hold polluters accountable.”

Upgrading Monitoring Efforts

To help understand the complex past and present of these three rivers, 3RWK conducts regular monitoring.

Reitz regularly takes spot measurements during river patrols using a YSI ProDSS handheld and Hack Pocket Pro+ that samples for temperature, pH, conductivity, total dissolved solids, and salinity.

However, these only provide a snapshot at “one single moment in time,” and when working across 150 miles of mainstem river, coverage is a challenge.

“We have always been very curious about pollution incidents that are not going to be present 100% of the time. They might happen every once in a while, and we might just not catch them, so we did end up looking for continuous monitoring,” Reitz explains.

In 2023, a Shell-owned plastics production plant along the Ohio River in Beaver County severely violated the Air Pollution Control Act. In addition to a $4.9 million civil penalty, $5 million was also paid to projects to benefit the community, environment, and health.

Part of these funds went towards the purchase of a NexSens XB-200 buoy, which was deployed on the Beaver River in April 2025.

The buoy is equipped with a NexSens X3 data logger with 4G cellular, a Garmin GPS unit for live location, and a YSI EXO2s sonde. The sonde measures temperature, conductivity, specific conductance, pH, dissolved oxygen, turbidity, chlorophyll, BGA-Phycocyanin, salinity, and total dissolved solids.

It is hoped that the buoy will provide insights into long-term trends, with data collected at a frequency not possible with manual sampling. (Credit: Koa Reitz / 3RWK)

Selecting the Right System

When researching what system to purchase, integration with the existing systems 3RWK used–alongside cost and quality–was an important factor. Taken together, Reitz states, NexSens offered a solution that was “high quality in terms of the data and the product that we would get.”

The benefits of the buoy system are threefold. Firstly, it enables 3RWK to track pollution levels in real time. Secondly, the continuous dataset gives the team its first insight into long-term health and cycles of the river. And thirdly, autonomous data collection enables a significant increase in frequency of data collection, enabling identification of moment-to-moment patterns driven by short-term changes, like major rainfall.

Reitz explains that initially, the team wanted a system that could measure the same basic parameters as those assessed in the manual spot sampling–“Things like temperature, pH, conductivity, dissolved oxygen, these things can alert us to a bigger issue.”

However, with additional ports available on the buoy, the team expanded the measured parameters to include turbidity, chlorophyll, salinity, and total dissolved solids. This has exciting possibilities, and Reitz hopes the data will shed light on new, previously unresearched areas, including algal blooms and the possible impact of road salt and fracking brine on river chemistry.

The installation of the new buoy was not without its challenges, and the 3RWK team admits that the learning curve has been “probably a little steeper than expected.” Nonetheless, with the support of the NexSens tech team, the buoy has now been out on the water collecting data for over six months.

Data at a Few Clicks

Data from the buoy is transmitted via 4G cellular to the cloud every 10 minutes, where it can be viewed on WQData LIVE. This makes data collection easy for the team–removing at least a 45-minute drive to the site.

This has another benefit for the team–“Being able to track the buoy’s location and even be able to set alarms if it moves out of its place was a pretty big deciding factor for me,” states Clark, citing concerns about tampering or lost moorings during high water.

So far, though, the buoy has weathered the challenges of the Beaver River, and the team is pleased with its robustness, serviceability and build quality, all while still being “easy enough to get in and out of the water.”

The 3RWK data dashboard is also publicly available. “People are very curious about the water,” Reitz highlights. “Whenever we take a lot of one-time samples, we can still write a report about that and release that data to the public. But being able to have a public dashboard that people can go to–especially in Beaver County–to look at water quality at that moment, that’s really great.”

With a massive increase in data availability, the team is excited to be able to access data in a few clicks via WQData LIVE and share this with the public via an open dashboard. (Credit: Koa Reitz / 3RWK)

Data to Support 3RWK’s Mission

The volume of data generated by the buoy is a big increase from the spot sampling data. A volunteer college student recently performed some initial data analysis, identifying trends that show an interesting rise in conductivity, and peaks in pH that exceed levels stipulated in National Pollutant Discharge Elimination System permits.

Clark says, “It’s going to be really interesting, I think, to see and try to tease apart what could be naturally occurring trends and what could be more influenced by pollutants entering the environment.”

Although permitting challenges mean the buoy will remain in the Beaver River for now, the team is hopeful that it could be relocated outside industrial outfalls to pinpoint pollution events. “Even though we have a lot of sensors, we’re not monitoring for everything.”

Future Possibilities

Acknowledging the limits of monitoring efforts–“Even though we have a lot of sensors, we’re not monitoring for everything”–the team is excited about the future possibilities the buoy could unlock.

“We’re learning, and we’re thinking of all the ways that we can use this tool,” says Reitz.

The buoy is the latest chapter in the 3RWK’s work that spans a decade and a half. Beyond deepening our understanding of these rivers and producing data that can hold polluters accountable, it will help define what a healthy river looks like and highlight the wins as water quality continues to improve.