Cheryl Nenn
A Voice for the River
“If we strategically put beavers back in the landscape and really encourage ponding and overflow of that water into floodplains, could we reduce those big peak flows that we see from these really intense heavy wet weather events that we’re seeing increasingly often?”
Meet Cheryl. Cheryl Nenn is Milwaukee’s Riverkeeper.
“As Riverkeeper one of my big jobs is to be a voice for the river, because the river obviously doesn’t have a voice,” she says.
Milwaukee Riverkeeper is a science-based advocacy organization. Cheryl’s job title there since 2003 has been, literally, Riverkeeper for the waters of the Milwaukee River basin, which encompass the Milwaukee, Menomonee, and Kinnickinnic River watersheds. Her role is dynamic: senior scientist, policy advocate, educator, communicator—Cheryl is a trusted critical node in the local water nonprofit sphere. Her accomplishments are legion and her reputation sterling. What does not show up in her credentials or many-hats job description is Cheryl’s extemporaneous humor and warm wit.
In 2022, Cheryl shared her time and expertise to partner with WaterMarks artist David Najib Kasir to provide the water’s perspective for a public walk along the Beerline Trail. She also shared her time for a wide-ranging interview—from beavers to road salt—conducted at the midpoint of the walking trail spanning the Milwaukee River at the site of the former North Avenue Dam.
It is a symbolic location. Connecting the East Side and Riverwest, the bridge over the sluicing rapids of the Milwaukee River below knots together the Beerline Trail on the west and Oak Leaf Trail on the east, encompassing the Milwaukee River Greenway. The former dam—a dam had been in place here since before the city’s 1846 founding—was removed in 1997, ushering in a new era of improved water quality, increased fish passage, and restored riparian habitat that brought on its coattails economic and recreational development.
This footbridge of concrete and steel also spans the river just upstream of the outlet pipe from the former flushing tunnel. (The tunnel connects underground a half mile to the east with what is now the lakefront Colectivo Cafe in the 1888 pumphouse building, stately clad in Cream City Brick. Some 130 years ago, this engineering solution diluted polluted river water with a blast of Lake Michigan water powered by what was then the world’s largest pump. Historian John Gurda has compared the effect to flushing a giant toilet tank.) The flushing tunnel is no longer used but you can still spot the 12-foot diameter pipe. Its presence is a reminder of how far we’ve come over the last century, and also how bad things got for the water due to human activity and neglect.
Standing midway over the bridge also suggests a precarious if tenacious optimism—to acknowledge that progress is not guaranteed but must be continually chosen, sometimes fought for. We entrust people like Cheryl to keep the river due to the very real possibility that even something so vital could yet be lost.
Today the river offers fishing, canoeing, and kayaking opportunities in the heart of a major American city, water-facing recreational development, the expansion of the RiverWalk, designation of riverside public access points known as the Milwaukee Urban Water Trail, a place for people of all ages and walks of life to gather or explore.
The bridge opened in 2004 and represents one fulcrum in Milwaukee’s water story. There’s no question that since her arrival here in 2002, Cheryl has had her hands on that story’s lever.
Whether it’s collaborating with the lab of UW-Milwaukee’s Dr. Sandra McLellan to use PCR testing to identify the source of bacterial contaminants finding their way into our rivers, filing lawsuits like those that led to the 2018 removal of the Estabrook Dam, serving on myriad boards and committees, marshalling an army of volunteers who perform water quality tests throughout the watershed, advocating to uphold the integrity of the Great Lakes Compact, testifying on issues ranging from emerging contaminants and climate change to single-use plastics and PFAS, or patrolling waterways to investigate river pollution like the 2022 Komatsu oil spill on the Menomonee River, Cheryl’s has not only has been a voice for our river—hers is a leading voice.
Cheryl puts the mission simply. “We’re doing this work to protect the rivers, but we’re also doing this to protect ourselves, to protect the health of our communities.”
Inspirations & Influences
A biologist by training, when she was young Cheryl thought she would grow up to become a doctor. Young-Cheryl aimed to be a pediatrician and even enrolled in pre-med. A study-abroad experience in Australia opened Cheryl’s eyes to the wider world and made her realize that she could apply the same passion for healing to the biological world in which humans are naturally enmeshed. She returned from Australia with a refined focus on natural resource management and hasn’t looked back.
Growing up on the South Side of Chicago did not offer many opportunities for connecting with nature, but Cheryl’s family would take trips to a cottage on a lake in central Illinois. Exposure to wild and wet places here nurtured the curiosity of the budding scientist, who would explore fish and other critters. It also fostered a sense of self-reliance. “Growing up, the big thing was they would take us out to the middle of the lake and throw us off the boat, and if we could swim back then we were good enough to be down by the water on our own.”
Water remains a central part of Cheryl’s personal life. She loves to sail. She does boat races most Wednesday and Friday nights in the summer. She also kayaks, hikes, skis, and snowshoes. “My time off, generally I’m on the river, walking along a river, enjoying all the beautiful natural areas that we have in Wisconsin.”
Water and nature also flow through other interests. In 2022 she enjoyed the Beyond Monet: The Immersive Experience at the Wisconsin Center, and counts the famous water lily artist and his Impressionist fellows among her favorite artists. Cheryl also points to the art of Andy Goldsworthy and his often ephemeral site-specific installations using natural materials like stones, ice, or flower petals as an inspiration. Conversations with artist David Najib Kasir about possible themes for his art including refugees fleeing water-scarce, war-torn regions like Syria—crossing the Mediterranean Sea in lifeboats wearing life jackets—suggested a comparison with Milwaukee’s own water safety challenges.
“We’re lucky in a lot of ways here. We don’t have water scarcity. We have 20% of the world’s fresh surface water sitting at our door. But water safety is still a huge issue everywhere. Unfortunately in 2020, the year of the pandemic, we had four people die in Milwaukee because a lot of folks aren’t being taught to swim anymore in schools and aren’t being taught to learn about hazards like rip currents.”
Since the pandemic, Cheryl says Milwaukee Riverkeeper has worked with partners to develop a beach ambassador program in an effort to save lives due to Milwaukee County Parks’ difficulties putting lifeguards at the beaches.
Bringing back the Beavers?
Ask Cheryl about beavers and you will get an education that reveals fascinating interactions among humans, animals, land, and water.
Milwaukee, as historian John Gurda has noted, was “built on water” at the confluence of three rivers that met in a marshy wetland before draining into a protected bay. “These cities popped up along these rivers because they really were the highways of their day. They gave early settlers access to all of the amazing abundance of what the land had,” Cheryl says. “In that process, we deepened rivers, we straightened them, we polluted them certainly, but we also drained all the wetlands. And I think back when we had beavers—beavers are these amazing ecosystem engineers—they’re amazing wetland creators. We really lost that.”
Land and water neither are nor were static elements. Beavers are a species described as “ecosystem engineers” because they build dams that dramatically alter the flow of rivers in ways that transform habitats and change how nutrients, life, and resources move. By extirpating local beaver populations humans displaced beavers’ keystone influence on the watershed.
It’s worth slowing the flow to consider the underappreciated significance of beavers on the history of our civilization. The economic value of selling beaver pelts to continental Europeans for fashionable hats attracted fur traders to the Great Lakes and drove westward expansion. Indeed, Milwaukee city father Solomon Juneau and first mayor was a fur trader. The sheer volume of commoditized pelts was big business and this commerce shaped relationships between European Americans and Native Americans who trapped beavers. The eventual decline in beaver populations in the 1800s also dramatically affected the water.
“If you look at the original maps of Milwaukee, it was all wetland and marsh and wild rice marshes,” Cheryl says. “It was very productive, which is why a lot of people moved here. And why a lot of Native Americans obviously lived here for eons. It was just a very abundant, wonderful place to live. It still is. Obviously, we’ve changed it a lot. But I am heartened that a lot of the beavers are coming back.”
In recent years, beavers—and their downed trees—have again been observed along the Milwaukee River. Cheryl notes that it would be pretty hard for beavers to dam the Milwaukee River and these beavers are likely migrants from farther upstream, where beaver colonies are once again damming smaller creeks into oxbows and wetland habitat.
Encouraging beavers to thrive in the upper watershed could actually help us deal with two big water challenges: flood management and pollution abatement. Wet habits beavers create allow for water to slow down and pollutants to settle.
It’s more than mere thought experiment. Cheryl points to a first-of-its-kind collaborative research project between Riverkeeper, UW-Milwaukee, and MMSD in 2020 that took a watershed-scale approach to analyze how and where reintroducing beavers in the Milwaukee River Basin could help reduce flood risk during heavy storms. The study identified 14 targets of opportunity, mainly in Washington and Ozaukee Counties.
“If we strategically put basically beavers back in the landscape and really encourage ponding and overflow of that water into floodplains, could we really reduce those big peak flows that we see from these really intense heavy wet weather events that we’re seeing increasingly often?” Cheryl says of the 2020 study. “And the answer is yes. I think even just picking a few dozen locations in very strategic points, we can dramatically reduce these peak flows.”
Cheryl says resource managers out West are already encouraging beavers to create homes in waterways where they were historically more numerous. “They put these boards in the rivers. They’re called beaver boards. They’re kind of like telling the beavers, ‘start here: build a dam here, please.’”
Beavers are actually controversial because many people consider them a nuisance. It’s not just downing trees. Beavers can dam intakes or culverts and get blamed for flooding fields or foundations.
Acknowledging the need to pay careful attention to local hydrology, Cheryl points to innovations like the “Beaver Deceivers” that allow for coexistence and still protect human infrastructure. She thinks there still is a role for beavers to play in watershed management.
“They do very excellent wetland creation. They’re very cheap. They work very hard. I think we really could encourage them to come back into strategic parts of the watershed, really help us with flood management, help us capture this rainwater and slowly soak it in and slow it down, so it’s not rushing into our city so quickly and causing damage.”
Salty Waters
Since the 1950s the application of road salt and its impact on local waterways has grown exponentially. Milwaukee Riverkeeper has been monitoring chloride in local streams since 2010. The results are alarming.
“We’ve had about [117] miles of river listed as impaired with chloride,” Cheryl says. “That means that the levels are so high of chloride in some of our rivers they can be instantly toxic to fish or toxic to fish at lower levels over a prolonged period of time. It’s a real concern.” (The 108 stream miles from the video interview was updated to 117 miles with new data since the November 2022 interview.)
There are both process and behavioral changes that can make a difference.
Municipal fleets are switching to brine application of a liquid salt mix sprayed onto roadways. In some cases this has allowed for significantly less salt to be used—with up to 40% reductions, Cheryl says, which saves money. The salt brine also sticks to the road surface so it’s more effective at preventing ice than rock salt chunks that scatter off the roads.
Cheryl guides a 2022 green infrastructure tour
But private contractors face different incentives, Cheryl observes. Public entities want to save money by applying the minimum amount of salt that will be effective at keeping roads and walks safe. Private property owners don’t want to get sued for slips and falls and their contractors are paid for their de-icing visits, so there is an incentive to overapply salt onto walks and parking lots. Cheryl says advocates are pushing for a private liability exemption to remove this incentive, but this policy change has seen pushback from lobbies for litigators who fear losing slip-and-fall cases.
Education about the temperatures at which salt works is also needed. “I still see people applying road salt under 15 degrees when it completely doesn’t work,” Cheryl says.
Increasing public awareness leaves room for optimism, Cheryl says, but salt in our water remains a big problem. We cannot easily remove dissolved ions that are slowly making our fresh water saltier. Every winter, we are essentially loading salt into our streams and ultimately the rivers and Lake Michigan. The levels are especially notable in creeks draining the interstate freeways.
“We see very severe impacts to Honey Creek, Underwood Creek, Ulao Creek, Indian Creek,” Cheryl says. “These small creeks that are draining the roads are being really, really heavily impacted, which is a concern. In addition to these winter months, we’re starting to see some salt spikes even in summer months.”
She says the summer spikes are “a little befuddling.” There is a question whether salty groundwater could be the source. Another question is if green infrastructure is facilitating the transmission of salt into our groundwater. She points to the comprehensive Southeastern Wisconsin Regional Planning Commission (SEWRPC) study underway that could provide answers.
The city of Madison is already a poster child for salty groundwater. “A lot of their wells are so salty that it’s starting to affect the taste of the water,” Cheryl says. “They’ve really dramatically cut back on salt and are using a lot of sand. Sand doesn’t melt ice but it provides a lot of traction.”
Cheryl offers this rule of thumb for applying salt to your walk or driveway: one coffee cup is generally enough for a driveway or 20 sidewalk squares.
Milwaukee Riverkeeper also offers a free program to contractors to get certified in smart salt application.
Getting Involved
Cheryl expresses appreciation for the hundreds of amazing volunteers who test water and monitor aquatic organisms throughout the river basin, for the many groups who have adopted a stretch of river, and the thousands who come out each April to the annual river cleanup.
Milwaukee’s Riverkeeper encourages people looking to make a difference to dive in and volunteer, whether with her organization or another group. “As much as you’re giving to the community by doing that, you also get a lot.”