Wednesday, October 17, 2007

Loving our lakes a lot more

Madison is known for its lakes. We're the only state capitol situated on an isthmus. We host the Wisconsin Ironman competition, 1/3 of which relies on one of our lakes. There's a long tradition of recreation and use of the lakes here.

And yet, algae blooms and beach closures become more frequent, surface visibility is decreasing dramatically, and the overall health of the lakes is growing worse and worse. The main culprit is run-off from area farms, coupled with a whole slew of smaller issues. The city (with the help of the Dane County Office of Lakes and Watersheds) took a step in the right direction when it banned the use of phosphorous lawn fertilizer and coal tar sealants, and I certainly applaud their efforts.

But there's a lot still to be done if we want our lakes to be usable not only by future generations, but by our generation, too.

Rob Zaleski wrote a great article in the Capital Times about this issue (and a hat tip to Paul Soglin's blog for bringing it to my attention) and how we can look to Minneapolis' recent efforts to clean up their lakes as an example of how to get it right. Many of the techniques and suggestions offered by the Minneapolis story sound great to me, and I'm hoping that Madison gets on the ball and begins to more exactly pinpoint our own unique problem areas and then to act accordingly to fix them. Public involvement is key. Hiring the best scholars and scientists in related fields is key.

But there's one thing, and it seems like it was a major part of the Minneapolis clean-up effort, that doesn't quite sit right with me: the use of aluminum sulfate in the lakes.

In theory, it sounds good: bind up all that phosphorous and other solids and get 'em out of the way. But what are the long-term environmental effects of pouring all that aluminum into the water?

So far, I've found this:

"However, the use of aluminum sulfate as an additive has inherent problems when employed in lake water having low alkalinity and low pH, as aluminum sulfate tends to further depress the pH of the entire lake. For example, one mg/liter of aluminum sulfate consumes about 0.5 mg/liter of alkalinity from lake water, thereby depressing the pH of the lake. Lake pH is of particular importance because at a pH of 6.0 or less, free aluminum becomes soluble and enters the lake water. Toxicity tests have indicated that aluminum concentrations in water which are greater than about 50 µg/liter are detrimental to aquatic life." (

And then: "However, in eutrophic lakes algal blooms often raise the pH to 9 or above, and a significant fraction of the ammonia is thus present as volatile NH3. The pH of the Lake Mendota surface water is generally 8.9 to 9.0 during the summer. However, ammonia is depleted to trace concentrations (0.01 to 0.05 mg. of N per liter) by algal assimilation in early spring and remains low in concentration until late fall. During periods when the surface water ammonia content is high (0.3 to 0.4 mg. of N per liter) the pH is near 8.0, and during much of the period of high ammonia values, the lake is ice covered." (

Which would indicate that at this time, with the lake pH level being as high as it is, likely due to all that algae, adding the aluminum sulphate would be relatively safe. But what about if/when we reach the goal of cleaner lakes, resulting in fewer algae blooms and, presumably, lower pH levels? Would the aluminum then be released into the water?

I would hope that any task force created to study and make recommendations for the cleaning up of the lakes would seriously address this issue before using the technique. Who knows, maybe I'm completely off-base with this (I kind of hope so, because frankly I suspect that it'd be easier to use this process than not). I wonder what the Minnesota planner's knew about the process?

I realize this makes me geeky and picky, but it seems important to know.

One thing's for sure, though: we need to take drastic and sustained action to clean up our watershed. In addition to its recreational uses, the viability of the watershed is crucial in maintaining a healthy ecosystem--something that benefits each and every one of us, from the water we drink to the air we breathe. So what's next? What petitions do we have to start, which politicians need to be hassled, committees formed, etc? We can't leave everything to the officials. We have to let them know that we care, and that we care right now.

1 comment:

Cant Sit Still said...

Great blog. I appreciate you posting that article, which I found really intriguing, as well.

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