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.
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
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.
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.