By Ronald A. Wood, Worthington
After reading several Facebook posts about the algae and the recurring blooms, I thought there should be some food for thought on the green lake we see. A reminder is that the lake has turned green each year for longer than anyone can remember, and will continue to turn green unless it dries up. It is a shallow prairie lake.
While we need to control the water entering the lake, it will not change the fact that our lake will continue to have bouts of algae. Agriculture seems to bear the brunt of blame, but it is only a small part of the story. We should realize from an economic perspective we do not exist without our agriculture partners in Nobles County. The algae saga is much more complex.
In the last century, we have seen a slow but certain rise in the air temperature. It is now making a difference with respect to water bodies across the globe. As we warm the water bodies, the bacteria known as algae increases dramatically. During the last decade of living on the lake, I have seen the change predicted globally by the EPA.
As the air temperature has gone higher we see weather patterns changing. Bigger storms followed by longer periods of dry weather is changing our lake like so many other bodies of water. Over the last few decades, our lake has suffered through a slow but certain drop in its normal water level. It has been exacerbated by the global change in rain. Even with rainfalls double normal in August, the lake has not reached any high water mark. The shallower the lake the faster the water temperature rises, resulting in bigger algae blooms. The issues do not stop at this point. With the level of carbon dioxide in the atmosphere rising we add another major fuel to the growth of algae.
The natural growth of a problem has been worsened by nutrients that accelerate the algae growth.
Phosphates and nitrogen enter from agriculture, business, residential development and the city parks.
So what has the watershed board, the city and the DNR (maybe) done to at least control that part we can control at our level? We have sloughs north of the Prairie View property, we have the Prairie View property, we have a retention pond on the Minnesota West campus, and we sort of have a retention pond in Sunset Bay (Mudhole Bay). But the bloom has worsened each year.
The best example of control comes from the Prairie View property. It’s too bad the recent studies did not take the time to actually come to the property and analyze its property maintenance and operation protocol. The property distributes over 24 million gallons of bad water onto the property, filtering out phosphates and nitrogen back to the soil. Additionally, over 10 million gallons of clean well water is pumped into the ponds further diluting the phosphates and nitrogen. Understand that phosphorous attaches to our clay base as it moves in water and does not sink to the bottom. Thus, no matter what you do to dam bad water during rain events, the phosphorous will ultimately move with the water to its next location. It’s interesting that the Prairie View ponds do not have the algae blooms close to the level found in the lake.
Further actions are possible but will take dedication by all the agencies. Nineteen percent of the sub watershed south of Palm Ave is allowed to flow towards Whiskey Ditch unfiltered. This needs to be corrected. The best correction is to place a diversion dam to Whiskey Ditch at Oxford Street culvert to be closed during major rain events, with the diversion dam to County Ditch 12 being opened much more quickly. A second action would be to ask all those with riparian rights to the lake, including the city, to cut the amount drawn from the lake drastically. We lose 1 inch of surface water from the lake with every 20 million gallons drawn from the lake. In the evaporation formula, this will cause several inches to be lost unnecessarily due to lake temperature. A third, and what seems like a wild solution: we should drill wells along the old rail line and pump the clean water into the storm water system that enters the lake. We used to have city wells before we opened the Bella well field. These wells would not impact Bella, since the city is naturally in the Des Moines River basin and Bella is in the Missouri River basin. Well water would be clean and cold, reducing the lake temperature and rising the lake level depending on the amount of water pumped. Also, anecdotally it would reduce wet basements during rain periods to those in Post Office/Atrium area. One last solution would be to turn our aerators on. While it would not alleviate the algae, it would increase the oxygen in the water which inhibits the algae and has the side effect of benefiting our fish base.
Lots more but space is limited. Hope this offers food for thought and something to ask agencies.
