Madison is framed, and often defined by, its lakes.
Whether it means gazing across the 9.842 acres of Lake Mendota from the Union Terrace, fishing in Lake Monona from the bike path or swimming in Lake Wingra, the lakes make the city a unique confluence of water and land. As a city built on an isthmus, Madison's lakes, as part of the Yahara Lake chain, can be, simultaneously, a wonder to behold and a threat to its health.
John Magnuson, professor emeritus of zoology, has an office in the limnology laboratory overlooking Lake Mendota. He sees the lakes as a source of the city's allure and their condition as a consequence of that allure.
\They're beautiful lakes and one of the reasons Madison is here,"" he said. ""One of the reasons we treasure this place so much is the lakes. But, they have been, over the years, badly damaged by human activities.""
The lakes have distinct boundaries and encompass different communities, but are part of a larger system that connects them all. The Yahara River, flowing into the north side of Lake Mendota, exits Lake Monona in the south. Wingra Creek cuts across the city to tie it to Monona. Along with their rivers, they share a common watershed, which means that any changes upstream will have impacts further down the system.
As long as people have been concentrated along the Yahara Lakes, there have been problems in their wake. Ever since the mid-1800s, the ways settlements have upset the natural status of the lakes has waxed and waned as Madisonians have become more aware of their position not only next to, but also between the lakes.
Magnuson said the first species that altered the biodiversity of the lakes was carp introduced from Europe in the late 1800s. Their impact is still being dealt with.
""They have been a nemesis,"" he said. ""In Lake Wingra, the carp continuously stir up the bottom sediments and that lake continues to be quite green partly for that reason.""
From settlement to present times the lakes have gotten quite a bit worse and then somewhat better. Steve Carpenter, professor of zoology, said the current grades of the lakes can be compared to two points, historically.
""[Conditions] are way worse than in the 1850s, and way better than the 1950s,"" he wrote in an e-mail.
One of the reasons the lakes hadgotten so bad is that sewage used to be pumped directly into them. Dick Lathrop, a lake researcher with the Wisconsin Department of Resources, said Monona bore the worst of it for a while.
""All that sewage, going through very primitive sewage treatment, ended up in the lakes,"" he said. ""Most of Madison was draining to Monona.""
In 1936, the city built a distribution plant that drew sewage from most of the city and treated it. This helped clean up Lake Monona at the time, but pushed the problem further downstream. The plant discharged into Nine Springs Creek, which emptied into Lake Waubesa and also contaminated Lake Kegonsa, the southern Yahara Lakes.
At the end of World War II, the focus shifted to the communities on Lake Mendota's north shore. Lathrop said the sewage of outlying communities was affecting the City of Madison.
""The upstream communities of Mendota, like Waunakee and DeForest, were going into the tributaries going into Mendota,"" he said.
In 1971, a network pumped the sewage from those towns into the same plant that handles Madison's waste. Since that time, sewage has been much less of a problem than other maladies.
One of the reasons Memorial Union Terrace has an obnoxious smell in the middle of summer is the presence of algal blooms. Those blooms, which wash up on the south shore in large mats, are a consequence of the chemicals in the lakes. Emily Stanley, professor of zoology, said the algae is part of a broader problem.
""In general, [the lakes] are probably pretty nutrient-rich systems,"" she said. ""Obviously these nutrients are ending up in the Yahara Lake chain and that's why we have algal blooms and problems with eutrophication.""
A lake becomes eutrophic when organisms that feed on chemicals like phosphorus reproduce rapidly. When those organisms, such as algae, decay, they deplete oxygen levels.
It turns out that phosphorus can give a green city green water. Phosphorus, a common ingredient in fertilizer, has made its way from lawns to the lakes. Madison's City Council and the Dane County Board has banned the sale of fertilizers that contain more than a trace of phosphorus.
Stanley sees the prohibition of phosphorus as one part of the move to clean up the lakes.
""Every effort helps and the fertilizer ban is certainly a step in the right direction,"" she said.
Magnuson agreed with the decision. He said there is enough phosphate in the city's soil to last for years.
""At the present time, we have way more phosphate in the soils of the lawns around Madison than we need,"" he said.
Phosphorus is just one example of non-point sources of pollution in the lakes. Non-point sources include the application of fertilizers from yards and farms, construction site runoff, and urban stormwater inputs into a lake.
Jake Vander Zanden, professor of zoology, sees this type of pollution as the most difficult to counter because it is so dispersed.
""This pollution still results from human activities, but is diffuse-it is happening everywhere,"" he wrote in an e-mail.
Jim Lorman, professor of natural science at Edgewood College sees a different set of non-point pollution problems with the shallow waters of the Lake Wingra. Wingra's average depth is around seven feet so wind can easily stir up the sediments at the lake's bottom.
""The sediments are suspended by wind much more than the other lakes,"" he said. ""The lack of water clarity is a little more obvious because of that.""
Lake Wingra is a specific case because its watershed is almost completely urbanized. Meanwhile, its shoreline is undeveloped with the UW Arboretum along its south shore. Lorman said the lake might be more heavily damaged if it weren't for the buffer against the city.
""It would be in worse shape if it wasn't for that,"" he said ""Of course, most of the things that are entering the lake are coming in from the entire watershed, which goes all the way past Westgate [Mall], so there's a large, urban environment that empties into the lake.""
One of the contributors to the lake's status comes from the roads that circle it. Lorman pointed out that it is harder hit by salt because of its size.
""The chloride levels of Lake Wingra have gone up faster in Lake Wingra than in the other lakes,"" he said.
With threats to the lakes coming from many areas, their upkeep requires constant vigilance. Community members, the City of Madison, Dane County and the state of Wisconsin are all working together to improve local lakes.
As the city copes with its present problems, observers of the lakes are aware of upcoming troubles. Ranging from worldwide climate change to statewide concentration of agriculture to invasive species, the Yahara Lakes face an uncertain future.
Magnuson said recent flooding has shown its effects all around Madison.
""We've been very concerned over water quality,"" he said. ""Something that's becoming more apparent to people now is that we have an issue with water quantity.""
Flooding has gotten more severe for two reasons. First of all, Magnuson said, environmental changes are releasing more rain more quickly. Secondly, the continued urbanization of areas around the lakes is making more surfaces impermeable to water.
""So where you might have had a forest that became a cornfield, now it becomes a parking lot for a shopping center or a home division with lots of roofs and streets,"" he said.
Those roofs and streets do not allow water to seep into the soil. Instead of containing heavy runoff, the water flows directly into the lakes and then may overflow their shores.
While flooding is certainly an issue of concern, greater threats may come from zebra mussels and Eurasian watermilfoil. Zebra mussels are freshwater bivalves that kill off other bivalves while milfoil grows densely at the surface and can inhibit water flow. Zebra mussels are directly impacting the lakes by decreasing the populations of native species. Magnuson said the plant is just as disturbing as the zebra mussel.
""The Eurasian watermilfoil is also very disturbing and troubling to the enjoyment of residents around the lake,"" he said.
These species have already taken root and will probably be more difficult to handle in the future. Zebra mussels are currently confined to Lake Monona but will probably spread in the near future. Given the myriad of troubles facing the lakes, optimism is hard to come by. Magnuson sees what they face, but enjoys facing the waters around Madison.
""Very often when we think of all the problems we have with them, what needs to be fixed and how many people want to see it fixed and are involved in it,"" he said. ""At any point in time these are lovely lakes and we're lucky to have them.\
