My question...What are some permaculturey ways to control algae on a 30-40 acre lake?
This lake was created by a man-made damn, and until several years ago, worked GREAT. But then, someone built a damn upstream and screwed the whole thing up. Now the rate at which water flows through the lake has slowed considerably and this allows an abundance of algae and plants to grow. I am not so concerned about the underwater plants, but algae makes the pond unusable for fishing/swimming and takes away that pretty "On Golden Pond" look.
What we (the HOA) have done in the past is to dump Cutrine+ or some diluted Copper Sulfate in there but I cringe every time we do it. There has to be a better, more sustainable, and more natural way to get control of the algae. Here are some methods we have considered. I would appreciate any more ideas you all may have.
Another possible approach would be to look at the algae as the result of excess Nitrogen in the water. (That's one of those things I learned in that failed attempt to get a Masters in Environmental Engineering )
High carbon items such as straw and wood require lots of nitrogen to compost (errr. decompose). It might be that keeping algae in check is as easy as adding enough wood chips into the water to eat up the nitrogren.
Denise wrote: Another idea is a floating wet-lands full of pretty water-loving plants to use up the Nitrogen for you.
I second that. You could also introduce a species that eats algae, such as tilapia. Blue tilapia are currently used in some areas as I form of bioclean up. Tilapia fry have been marketed to golf courses as alternative means to chemicals for cleaning up their "scum ponds" The tilapia grow through the warm season and eat the algae, they then die off once the water temp reaches below 50 deg. Depending on your area it might work as a seasonal control.
SE, MI, Zone 5b "Opportunity is missed by most people because it is dressed in overalls and looks like work."
I'm dealing with this issue now. The previous owner used copper sulfate, and encouraged me to do so, by even leaving a bunch of it in the barn. Other non-permies seem to encourage it.
I love all the ideas listed in this thread. Thought I'd bump it back up.
Along with some of the ideas mentioned, I was thinking of digging a step around parts of the bond with a shallower water depth, and planting more growies. I imagine they will aerate and help eat up Nitrogen.
Anyone know how to tell if the algae is growing due to excessive Nitrogen levels? Or is that always the case, making carbon always appropriate to add.
There is a lot information about DIY testing for nitrogen on the net. To get and accurate idea of what you are dealing with, I would take several water samples and send them off to a lab. That would let you know exactly what you are dealing with in your water.