Environmental Engineering Reference
In-Depth Information
THE IMPORTANCE OF PLANTS
IN THE WATER CYCLE
Plants play a vital role in Earth's water cycle because they transpire
or, in effect, exhale water vapor into the air. To see this clearly, place
a plastic bag over part of an ordinary houseplant or one outdoors,
seal it, and leave it overnight. In the morning, you'll see the condensa-
tion (water droplets) on the inside of the bag, which are the result of
the plant “exhaling” water vapor.
TODAY'S REALITY
This self-perpetuating water cycle has worked well for millions of
years. But the cycle today is severely threatened globally and across
North America. As climates change, populations grow and move,
pollution increases, and needs and demands shift, the scarcity of
Earth's essential resource—especially in a safe, clean state—has
become a real threat. Let's look at reality in the United States.
All Dried Up
Reservoirs, rivers, and streams are drying up. We talked about
what's happening along the once-mighty Rio Grande and the over-
used Colorado. But beyond the major rivers of North America, the
little streams and “washes” that once fed the land and the people
have dried up, and many smaller rivers are being drained way
down, too.
Historically one of the most important rivers in Massachusetts,
the Ipswich, which meanders through the northeast portion of the
state then out to sea, is a prime example of what can happen with
overpumping. The river is only 45 miles long, but it's what Kerry
Mackin calls the “lifeblood of the central part of Essex County not
only because of its importance as a water supply but as the fl uid
that keeps everything alive here.” Mackin is an environmentalist
and executive director of the Ipswich River Watershed Association
(http://ipswichriver.org). She's also been involved in water issues in
the area for more than 15 years. “The river has been overallocated
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