By Laurie Allmann
I stand on one of my favorite spots in the St. Croix valley, a high oak-strewn bluff overlooking the river near Bayport. The river below flows sedately, almost imperceptibly, a far cry from the raging torrent of glacial meltwater that scoured this broad valley some 10,000 years ago. From this vantage the water appears blue, though its true color is tea-brown, a marker of its passage through the tannin-rich peatlands of the north.
A jewel among rivers, the St. Croix runs approximately 165 miles from its origins near Solon Springs, Wis., to its confluence with the Mississippi at Prescott. For most of these miles, it serves as the border between Minnesota and Wisconsin.
Celebrated as a national scenic river, the St. Croix is distinguished by the place it holds in the hearts of local residents and the million people who visit it each year. Anglers pull 15-inch walleyes from these waters and catch trout in its tributaries. Tourists marvel at the dalles at Interstate State Park, where basalt from ancient lava flows is "piled in savage grandeur" (in the lavish language of 19th century travel writer Elizabeth Ellet).
Interactive Map of the St. Croix River
Children swim at beaches along the wide lower river known as Lake St. Croix, playing in the ever- present rollers from the wakes of passing boats. Day-trippers from the Twin Cities swell the populations of river towns on weekends when the weather is fine.
I've kept company with the St. Croix for nearly 25 years. Often, I've come to the river alone. In retrospect, the dozens of mornings are like one. Check the wind. Slip my old cedar-strip solo canoe into the water at a quiet landing. Feel the pull of the current, then watch as the forested riverbanks slowly reel out from their point of convergence at the horizon. Here, the familiar is not tiresome but consoling: the looping flight of a kingfisher, the sharp mineral scent of a breeze coming off a rock face wet with spring water, a white pine rising with unruly grace above the canopy. Such are the gifts of the St. Croix. Not wilderness, no. Respite.
Today, from my blufftop perch, I watch as the shadow of a cloud glides like a boat across the surface of the water. It is tempting to look no further than this lovely view and believe that the job of protecting the St. Croix is done. But it is not.
Nearly 40 years ago, in 1968, President Lyndon Johnson signed the Wild and Scenic Rivers Act into law, designating the upper St. Croix among the first eight rivers in the country to be protected under the act. (The lower river was added in 1972.) The legislation led to creation of the St. Croix National Scenic Riverway, a 78,000-acre unit of the National Park Service. It sounds like—and is—a large area; but it constitutes less than 2 percent of the river's watershed.
"If we are serious about safeguarding the ecological integrity of the St. Croix, we need to direct conservation efforts to the entire watershed," says Daniel Engstrom, director of the St. Croix Watershed Research Station.
Engstrom and other scientists with public agencies, universities, and private research facilities are uncovering startling new information about the status of the waterway. They're counting on the public to look beyond its picture-postcard beauty and embrace the broader issues of ecosystem health. And those issues are many.
"The St. Croix has a reputation for good water quality, in part because it compares favorably to other large rivers in the region, such as the Minnesota and Mississippi," says National Park Service aquatic ecologist Brenda Moraska Lafrancois. "But in reality, recent studies show some very troubling trends."
The chief threat to the river's water quality is excess nutrients. Scientists from the St. Croix Watershed Research Station and the University of Minnesota have analyzed core samples of riverbed sediments to track changes during the past 200 years. Essentially capturing layers of time in a tube, the scientists were able to read the sediments and determine that the river is impacted by phosphorus levels nearly two-and-a-half times greater than baseline (pre-European settlement) conditions. Phosphorous fuels algae growth, which can negatively impact the habitat and food base of many native species, including popular game fish such as smallmouth bass.
"We've documented a fivefold increase in diatom (a type of algae) production in Lake St. Croix, and a distinct shift from a prevalence of bottom-dwelling species to a prevalence of species suspended in the water column," says research station scientist Mark Edlund. "That's a shift generally associated with poorer water quality."
Likely sources of phosphorous include livestock waste, fertilizer, leaking septic tanks, wastewater treatment plants, and sediment-laden runoff from construction sites and urban areas.
The river faces other water-quality threats as well. Since 1999 the Minnesota Pollution Control Agency has classified the St. Croix as an impaired waterway for mercury. In 2006 the PCA recommended the St. Croix be classified as impaired for polychlorinated biphenyls too. Final approval by the Environmental Protection Agency is pending.
PCBs were once a component of electrical transformers. They were banned in the 1970s but persist in the environment today. As for mercury, it poses an ever-increasing threat to aquatic ecosystems and public health worldwide. Coal-fired power plants, waste incinerators, and mining release mercury into the environment. The exact source of mercury in the St. Croix is not known. Because airborne mercury can travel long distances, some of the St. Croix's burden likely comes from distant sources such as power plants throughout the United States and even as far away as China. Local facilities, such as the King Power Plant at Bayport, also contribute.
To help reduce human exposure to mercury, the Minnesota Department of Health has issued fish consumption guidelines for the St. Croix. For instance, it recommends that women who are or may become pregnant and children younger than age 15 eat no more than one meal of walleye from the St. Croix per month. For the general population, the recommendation is one walleye per week (except walleyes measuring more than 25 inches, which also have the once-per-month guideline).
"We see something exciting every time we go out," says Bernard Sietman of the DNR Stream Habitat Program, speaking of mussel surveys conducted near Interstate State Park. He, DNR colleague Mike Davis, and University of Minnesota researcher Mark Hove routinely do night dives to shoot video footage of the river's mussel communities while studying the reproductive biology of rare mussels.
Though the idea of mussel movies might not inspire a run to the box office, unraveling the mysteries of mussel reproduction is vital. "The St. Croix is among the most important refuges on the continent—on the planet, in fact—for this imperiled group of animals," says researcher Dan Hornbach of Macalester College in St. Paul.
The St. Croix harbors at least 40 mussel species, including one of only two known reproducing populations of the federally endangered winged mapleleaf mussel. The endangered Higgins' eye mussel also takes refuge in the river. Because mussels are relatively intolerant of poor water quality, the presence of such a diverse assemblage speaks well of the St. Croix. However, recent studies raise some cautionary flags.
In 2005 Hornbach and Hove reported overall declines in the health of the mussel communities. Of particular note were reduced densities of younger age classes. "We haven't pinpointed a cause," says Hornbach, "but the trend is concerning, since these younger age classes represent the future."
One pressing threat is no mystery: invasive zebra mussels. Notorious for decimating native mussel populations in other river systems, this nonnative species has been found as far north as Stillwater in the St. Croix. Zebra mussels can attach to native mussels, thus impeding their burrowing activities and competing with them for food.
The St. Croix basin is undergoing unprecedented population growth: The Metropolitan Council and U.S. Census Office project a 39 percent increase in residents by 2020. The associated land-use changes could dramatically increase stress on the river ecosystem by bringing higher volume and toxicity of runoff, accelerating loss of natural communities, and increasing recreation pressure on sensitive areas. As a result, public agencies on both sides of the river, dozens of nonprofit groups, and many research scientists are rallying on behalf of the St. Croix.
In April 2006, Wisconsin DNR deputy secretary Bill Smith and Minnesota PCA commissioner Sheryl Corrigan signed an agreement to jointly work to reduce phosphorous loading to the St. Croix. The goal: 20 percent reduction by 2020. Actions include nutrient management plans for farms and installation of water filtration basins to intercept stormwater runoff from nearby housing developments.
The Wisconsin DNR and Xcel Energy also reached an agreement in April 2006. It calls for Xcel to operate its St. Croix Falls hydroelectric dam to mimic natural water flow conditions. During a three-year trial period, Xcel will regulate flow to avoid rapid changes in water levels and extreme low-water conditions that threaten the health of aquatic life downstream.
And in the most recent Minnesota legislative session, the Minnesota Environmental Partnership—a coalition of 90 nonprofit groups—realized the culmination of its many years of work toward mercury reduction. In May Gov. Tim Pawlenty put his signature on a new deal between the state, Xcel Energy, and Minnesota Power to reduce mercury emissions from the state's three largest coal-fired power plants by 90 percent by 2014. That's much faster than the federal mercury reduction plan for power plants nationwide, which calls for 70 percent reduction by 2018.
Other river-health initiatives include an effort to propagate and restock winged mapleleaf mussels. Also, in the fall of 2006, Washington County residents will have a chance to vote in favor of bonds to raise public money for the "preservation of water quality, woodlands, and other natural areas." The county has one of the highest projected growth rates in the river basin, with population expected to increase by 41 percent between 1998 and 2020.
"Call it a healthy start," says former Vice President Walter Mondale. "The passage of the Wild and Scenic Rivers Act was one of the proudest moments of my political life.
"Still, I've always recognized the designation as a starting point for protection of the St. Croix," says Mondale, who co-authored the bill when he was a U.S. senator. "It bought us some time, perhaps. But sustaining the values of the St. Croix will require that each generation make a renewed commitment to the cause. We will need to be most vigilant on the local level, making land-use decisions carefully and responding to threats to the riverway as they arise."
Wading through knee-high prairie grasses as I descend the steep slope of the bluff, I feel both intimidated and exhilarated by the idea that something so important as the fate of the St. Croix rests in our hands. Below, a gust of wind riffles the surface of the water. To my left, some hundred miles to the north, is the river's origin. To my right, the river flows south toward its confluence with the Mississippi and, ultimately, the sea. I am poised, as are we all, somewhere between where this river has been and the future that awaits it.
Based in Marine on St. Croix, the private nonprofit St. Croix Watershed Research Station is part of the Science Museum of Minnesota. It has a core team of staff scientists, four on-site laboratories, and an ever-changing cadre of visiting researchers. The station serves as a lively nexus for scientific inquiry in the basin. Informed by their studies of watersheds worldwide, the scientists investigate mercury pollution, water quality, biodiversity, and other issues affecting the St. Croix. The station is one of 10 organizations on the St. Croix Basin Team, which is leading the effort to reduce nutrient loading to the river.
Laurie Allmann, recipient of a Minnesota Book Award for her collection of essays Far From Tame (1997, University of Minnesota Press), has written widely on environmental themes for public radio, television documentary, theater, and print media. She lives in the St. Croix valley.