Sep 11, 2007, 1:11 AM
Post #5 of 5
Just a couple of thoughts to add to your excellent summary, Eileen: First, if left alone, nature can do an amazing job in a short time of restoring what humans have messed up for decades. There's a large lake just west of Minneapolis, Minnesota that had suffered mightily from municipal sewage inflows, farm and lakeshore home septic system and fertilizer runoff, as well as other pollutants. After installing area-wide trunk sewer lines & service to homes (diverting the black water to a remote regional treatment facility) - building catch basins & settling ponds - discouraging excessive lawn fertilizer use by waterfront home owners - and banning the further removal of marshes at the lakes' edges, it took less than 5 years for noticeable improvement in water clarity and elimination of algae blooms, and another 5 for the lake to look as good as it did in the 1940's. BUT what nature was not able to do was remove the pollutants that had been "washed" out of the water by rain & gravity and into the lake bottom. Any agitation of that sediment in shallow areas released the pollutants (which were "locked" in the lake bottom) back into the water. So your comment about the shoreline is well taken. There can be anoher source of agitation than normal wave action, however: powerboats running at high speed. One solution is to post "no wake" zones in shallow areas(including near the shore) (which require policing), another is to restrict water use to canoes, sailboats, small fishing boats and/or boats with small electric motors only.
While running water analysis tests can produce important information, a cheap (but labor-intensive) way to monitor water clarity is via the use of setchi (sp? - pronounced "set-chee") disks. These are simple and easy to make: take a (roughly) pie pan-sized disk, divide it into quarters, and paint each alternate section black and white. attach a line with depth markers along its' length, and add a weight on the bottom, if needed. The disc is lowered into the water and the depth at which the black & white disc disappears from view is noted. This could be done at the end of a pier, or by boat (which may require use of a GPS). Periodic readings over time will give a measurement of improvment or lessening water clarity. Another lake with the desired water clarity could be checked with the disk for comparison purposes.
The $64,000 question is: who would do the secci-disk work? In Minneapolis, public employees. At Lake Chapala, I suspect it would have to be volunteers, or, if it could be made part of an ongoing school program with adequate supervision & control(s), perhaps students. Like the wonderful Ajijic Limpio program, it could raise environmental awareness and serve an educational purpose.
BTW, if anyone runs across a depth chart of Chapala Laguna, no matter how old, I'd love to have a copy of it...8^). Buena suerte al Amigos del Lago.