Landscape architects who understand the relationships
between microbes and nutrients in water can create water features that will
stay clean without artificial treatment.
By Bruce Kania
Floating Island International
For a long time, Iíve studied a small lake that formed long
ago in a natural bowl in northern Wisconsin. It has about 20 acres of surface
area and is now surrounded by a cow pasture and a cornfield.
Holsteins graze right up to the waterís edge and at times
step into the lake to drink. Sometimes, cows being cows, their waste ends up in
the water as well. On the opposite shore, the cornfield has an unusual
configuration, with its furrows running straight down the slope and into the
lake. When it rains or the fields are irrigated, some fertilizer inevitably
washes into the lake.
The stage is set for aquatic misery: Viscous, pea-soup mats
of green algae and foul odors are the common results of this sort of nutrient
loading. Indeed, few life forms other than algae survive in such water, and
such situations are far from uncommon. Almost any waterway connected in these
ways with human activity can experience profound nutrient surges, and the
results tend not to be pretty.
While common sense would tell us its water should be a mess,
the fact of the matter is, beyond a slight tannic tinge, the water in this
Wisconsin lake is crystal clear. And when you scoop up a sample in a clear
glass, you see itís teeming with lifeótiny critters enjoying a swim in water
that smells fresh and doesnít have anything more than the slightest trace of
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