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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

© Matt Catalano
Tagging and releasing a sturgeon on the Baraboo River. Now that free-flowing conditions have been restored to the Baraboo, sturgeon and other fish species use more of the river each year. © Matt Catalano

August 2004

Loosening a knotty hold on rivers

The Baraboo provides a national model for removing obsolete dams and measuring the natural recovery of free-flowing rivers.

Matt Catalano

Appreciating the lay of the land | Harnessing power
Ecological consequences of damming
What went up, comes down
The research flows forward

To look at the number of aging, weathered dams, you'd think Wisconsin rivers had been impounded forever, but "forever" isn't what it used to be. State rivers have only been "tamed" with dams for about 150 years – a single lifetime for the venerated lake sturgeon. For thousands of years lake sturgeon came back to the Baraboo River each year to spawn in an ancient ritual of renewal and rebirth. This southwestern Wisconsin river was impounded over time with 11 dams, denying sturgeon the opportunity to reach spawning grounds they had used for centuries. Now the last dam on the Baraboo has been removed, and biologists are researching whether sturgeon and other fish will reclaim their traditional haunts.

A team of fisheries reseachers from the Department of Natural Resources and the University of Wisconsin recently concluded a six-year project to measure change in the Baraboo River after the final four dams were removed. As a UW graduate student and later a DNR researcher, I was part of the team evaluating those changes. I'm happy to report the restoration efforts have been fruitful: Habitat, aquatic insect life and fish communities dramatically and quickly recovered. As more old dams become obsolete, we believe the financial strategies and approaches used on the Baraboo River can serve as a model for future dam removals.

Appreciating the lay of the land

From its headwaters near Kendall and Hillsboro to its confluence with the Wisconsin River at Portage, the Baraboo River drains a rich, 650-square-mile basin. For much of its 120-mile length, the Baraboo flows between the majestic ridges of the Baraboo Bluffs, quartzite outcroppings of hard rock thought to be more than 1.5 billion years old.

In more recent times, glaciers shaped the Baraboo River basin. During the last Ice Age, the Wisconsin Ice Sheet, the last glacial lobe that once covered most of Wisconsin, advanced toward the southwest to the present day location of the City of Baraboo, carrying eroded rocks, gravel and sand. About 12,000 years ago, the glacier retreated, leaving a terminal moraine oriented north to south and bisecting the Baraboo River basin. The rock and gravel deposited along the moraine created the Baraboo Rapids – fast-flowing, rocky riffles in the otherwise sluggish, silty river.

The rapids tumbled and oxygenated the water, and provided vital fish spawning habitat by preventing the build-up of silt. Many fish species must lay their eggs in clean gravel or cobble, where eggs can fall into crevices and spaces in a gravel bottom to develop for several days to a couple of weeks. Clean gravel bottoms protect the eggs and allow water to flow through, carrying vital oxygen to developing embryos. Eggs covered with silt can suffocate.

Before European settlement, the Baraboo landscape was dominated by open grassy areas and scattered oaks with little or no underbrush. Historians believe the region was kept in open grasslands by the Winnebago (Ho Chunk) people, who set fires to drive game and maintain grazing lands for wildlife.

Harnessing power

The rich Baraboo landscape and the river's clear rapids attracted European settlers in the early 1800s. The dams they built provided inexpensive mechanical power, deepened river channels for navigation, provided flood control and created backwater pools for recreation.

Up to 11 dams were constructed on the Baraboo, the first in 1840. Settlers Eban Peck and James Alban seized on an ideal location that took advantage of a natural steep gradient to turn a water wheel just below the dam. Peck and Alban's handiwork, later known as the Waterworks Dam, was a rock and timber structure fitted with a sawmill. A local entrepreneur, George McArthur, built two other dams along the Baraboo Rapids in 1844 and 1898 later called the Oak Street and Linen Mill Dams. The dams powered sawmills, grist mills, textile factories, and, later, electrical generators. A fourth dam, constructed about 50 miles upstream of the lower three, was known as the La Valle Dam. All of the Baraboo River dams were about 6-10 feet high – lowhead, run-of-the-river structures. Each dam created millponds with small storage capacities that overflowed and did not alter river flow.

Ecological consequences of damming

Although no official fish surveys survive from the days before the river was dammed, one can assume migrating sturgeon and other species could not move far upstream. The six- to 10-foot-high dams formed a physical barrier, converting the Baraboo Rapids from a free-flowing complex of riffles to a series of sluggish millponds. After the river was dammed, historical accounts cease to refer to species like lake sturgeon or smallmouth bass upstream.

Today scientists generally agree that dams do more harm than good to aquatic river life. Aside from blocking fish migrations, dams disrupt natural river processes. Emily Stanley, a UW-Madison limnologist, studied how dams block the downstream flow of sediment and nutrients. When water flows more slowly, sediments settle and eventually cover up rocky bottoms. Aquatic organisms that need rocky habitats to survive are especially hard hit.

Fish surveys on the Baraboo river indicate more than 25 species of fish are using more and more of the free-flowing river each year. A tube of blood from a bird sent for analysis. Last year birds in 65 of Wisconsin's 72 counties tested positive for WNV. © Matt Catalano
Fish surveys on the Baraboo indicate more than 25 species of fish thrive in the free-flowing river.

© Matt Catalano

The changes damming brings occur in stages. First, dams create lake-like impoundments just upstream with sluggish waters that favor lake-dwelling species. As sediments build up behind the dam, aquatic species able to tolerate heavier siltation, low dissolved oxygen levels and more extreme temperature fluctuations start to predominate. For instance, common carp might replace bass, walleye or lake sturgeon.

Dams block fish migrations. Engineers managing larger dams can add fish ladders or fishways to help fish migrate around the dam. Similar designs for lowhead dams have been developed only during the last 15 years or so, and most aging dams have not been retrofitted as such work is costly.

Finally, dams can strand aquatic species and cause their extirpation when they can no longer reach upstream habitats. A review of salmon found in the Pacific Northwest found that 101 of the 214 separate salmon stocks evaluated were under immediate threat of extinction, mainly due to the dams blocking their migrations. In another example, Matthew Winston with the University of Oklahoma found that four fish species were extirpated upstream of an impoundment on a prairie stream in Southwest Oklahoma. He cited loss of access to seasonal habitat and negative interactions with other fish found in reservoirs as two reasons for the extirpations.

Fewer scientific studies have looked for signs of river recovery after dams are removed. The most well-known study, conducted by the Wisconsin Department of Natural Resources on the Milwaukee River following removal of the Woolen Mills Dam, found common carp numbers declined 80 percent while smallmouth bass populations increased ten-fold in the former millpond – a complete reversal in the fish community composition. The amount of rocky habitat increased by about 50 percent after the dam came out.

What went up, comes down

Creative management and creative financing certainly helped remove the Baraboo River dams more quickly, but bottom-line economics played the biggest role: It was simply much cheaper to remove the Baraboo River dams than to repair them.

In their heyday, the dams and mills were the most important industrial operations in their communities, providing jobs for many residents. However, the years eroded their importance. Construction of coal-fired power plants and large hydroelectric projects at Wisconsin Dells and Prairie du Sac decreased reliance on smaller dams for industrial and domestic power.

Time and the relentless forces of flowing water also took their toll on the aging dams. In the early 1990s safety inspectors found several structural problems with the dams. The Linen Mill Dam was missing several timber buttresses. The Oak Street Dam lost a large piece of concrete from the dam face after a flood in 1993.

Repair costs were prohibitive for the dam owners. The City of Baraboo owned the Waterworks Dam and was eager to explore other options after receiving a $650,000 repair estimate. Dam removal was an enticing option because the community would incur one-time costs, while a repaired dam would need periodic maintenance and upkeep. The McArthur family, owners of the Oak Street and Linen Mill dams in Baraboo, was also more open to the idea of dam removal after weighing repair costs.

As the City of Baraboo considered removing the Waterworks Dam to save taxpayer dollars, the Department of Natural Resources and two nonprofit environmental advocacy groups offered options. DNR staff began formulating a plan to restore the entire length of the Baraboo River to free-flowing conditions, removing all four remaining dams. To alleviate costs, DNR helped secure state funds through the Municipal Dam Repair and Removal Program, and federal funds through the Federal Aid in Sport Fish Restoration program. The nonprofit Sand County Foundation purchased the La Valle Dam from its private owners for about $100,000 and allowed the state to remove that dam with federal Sport Fish Restoration funds.

In each case, dam removal was far less costly than dam repair: at the Oak Street Dam, repair estimates ran over $300,000 while actual removal costs were only $30,000 (of which $23,000 would be provided by the River Alliance of Wisconsin via a grant from the National Fish and Wildlife Foundation). Similar savings were realized for the other two dams.

Despite the financial incentives, stiff opposition to the removal plan arose in Baraboo and the Town of La Valle, where the dams were viewed as aesthetic, historic community fixtures that provided a sense of identity.

One holdout in Baraboo was Circus World Museum, which owned property on both sides of the river along the millpond created by the Waterworks Dam. The museum's mission to preserve the look and feel of the historic grounds of the Ringling Brothers Circus put it in an odd bind – costs to repair the old dam were prohibitive, yet the structure was clearly unstable. A survey revealed the community's greatest concerns with dam removal were the loss of wildlife habitat (42 percent), the fate of the millpond (16 percent), aesthetics (14 percent), and other historical/community values (12 percent).

Concerns about the river's aquatic life were only raised by 11 percent of the respondents. Even anglers had mixed feelings: Some had fished the millponds since childhood and did not want to lose their fishing holes. Other anglers were excited about the potential return of spawning runs of game fish like walleye, sauger and lake sturgeon. Groups including the Baraboo River Canoe Club supported restoring the free-flowing river to enhance recreation.

The aesthetic and historical values of the dams were preserved wherever possible. For example, the La Valle mill and turbines were preserved and eventually sold to a local businessman who started an antiques store and gave tours of the old mill facilities. The Linen Mill building was preserved and is used as a canoe livery to provide daily trips along the Baraboo Rapids. La Valle residents didn't want to lose the peaceful feel of a millpond; their concerns were helped a bit when an artificial wetland was constructed in the floodplain adjacent to the river.

The research flows forward

As historical preservation and financial issues were resolved, the dam removal plans proceeded, and so did our fisheries research.

A year before removals began, we started surveying fish communities above and below each dam to determine which species inhabited the millponds and tailwaters. We also collected fish throughout the river to determine population ranges for each species. We measured habitat features such as current speed, depth and bottom type (sand, gravel, rock, sediment). We used electrofishing to stun fish, then quickly net, identify, count, weigh and measure them before releasing them back to the water.

Removal work started in April 1998 with the Waterworks Dam, followed by the Oak Street Dam in January 2000, and the La Valle Dam in January 2001. According to the River Alliance of Wisconsin, after the last of the four dams – the Linen Mill Dam – was removed in the fall of 2001, the Baraboo became the longest river in North America (120 miles) entirely restored through dam removal.

Fish and environmental sampling continued through fall of 2003. Fish proved to be useful indicators of changing environmental quality and river health. If pollution-tolerant species like carp were abundant and few other species were present in a section, then we knew the environmental quality was probably poor. Where sensitive species like smallmouth bass were abundant, we knew that the environment and the fish community were getting healthier. We also looked at the total number of species collected at any given location. Generally speaking, the more species inhabiting a river section, the better its environmental quality.

Other interesting patterns emerged. Habitat in the former impoundments quickly became more river-like. Faster moving currents scoured sediments and exposed rocky areas along the Baraboo Rapids within a year. Within two years we saw dramatic changes in the fish community. At the former Waterworks Dam site, 26 fish species now inhabit water that formerly held 11 species. Before the dam was removed, pollution-tolerant species made up about 45 percent of the fish community; now they comprise only 2-10 percent of the fish found here. Results were similar at the Linen Mill and Oak Street dams, but not at La Valle about 50 miles upstream. Even in its natural state, the river is much smaller and slower at La Valle; it's also subject to eroding sediments from intensive agriculture in the area.

After free-flowing conditions were restored, eight of 16 migratory species like sauger, spotted sucker, and walleye have moved upstream to spawn. Most remarkably, the emerald shiner, a small minnow species, repopulated the river up to 75 miles upstream of the lower dam site within the first year. Anglers are pleased that walleye are clearly moving upstream. Before the Linen Mill Dam was removed, we did not collect a single walleye from the Baraboo Rapids area. A year after the dam was taken out, we netted three walleye, and last year netted 15, a substantial increase. Knowledgeable anglers are now beginning to catch a few walleye from the rapids during the spring run.

Past researchers looking at dam removals anticipated problems with downstream sedimentation once dams were removed, but our findings did not support these concerns. Species diversity dipped a bit in the tailwaters, but within two years these fish communities recovered. Our research shows the negative downstream effects of removing small, lowhead dams are short-lived. However, this may not hold true for larger dams that have retained more sediment.

Matt Catalano is a DNR fisheries biologist and researcher stationed in Monona.