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Re: E-M:/ Impact of sewer on freshwater, inland lakes?

Wisconsin's Department of Natural Resources is currently using hypolimnetic pumping to remove phosphorus in Devil's Lake, located in Wisconsin's largest state park of the same name.  Hypolimnetic pumping removes water from the hypolimnion that has high levels of phosphorus due to anoxic conditions which create suitable conditions for phosphorus to become water soluble.  Removal of hypolimnetic water via pipes in the summer during periods of strong stratification accelerates removal of phosphorus from sediments and reduces resuspension of phosphorus after inputs are halted.  Resuspension of phosphorus from sediments occurs even after anthropogenic phosphorus sources have been stopped and can lead to eutrophic conditions well after other sources have been removed.
This URL is for the WDNR website on the Devil's lake phosphorus removal project.

Dave Zaber
Remember, Despite the dirty tricks of the Repugs, the truth can win when good citizen's vote.  GO GRANHOLM!
----- Original Message -----
Sent: Sunday, November 03, 2002 7:56 PM
Subject: Re: E-M:/ Impact of sewer on freshwater, inland lakes?

My guess is that the impact will depend a great deal on the flushing rate and configuration of the lake, its inlets, outlets and its participation in regional groundwater flow, etc.  In general, the impact will likely be small, especially at first.  The phosphorus that is in the lake, unlike the N is likely to be tied up in sediments and will not rapidly be removed unless there is some through-put washing it "downstream" if that is part of the "system".  Additionally, the input of homo sapien likely took decades to accumulate and will likely continue to flow to the lake via runoff from the surrounding watershed (depending on the activities, etc,) and via groundwater flow that has already left the tile fields and drywells and are moving toward the lake from lawns, septic systems, etc.
This is just a "quickie" version to get you thinking about the input activities that led to the problem of nutrient enrichment in the first place.  The answers will be very site specific, however.

One of the most knowledgeable people I know is Dr. Wally Fusilier.  He will be happy to talk to you, I would guess.  He studies 75 or more lakes per year and is most likely the one to have seen the effects.  I will send you his phone number under separate email.
Chuck Cubbage