| There
is a double
waterfall above the Rara Avis Complex,
where heavy rainfall causes the river to
overflow
and quickly results in flash flooding. |
|
Nestled
in the Rainforest of Costa Rica, 40 km due North
of the
capital, San José, is the Rara Avis
Lodge and Reserve. Rara Avis, which borders the Braulio
Carrillo National Park and the Zona Protectora La Selva,
is a project that was founded to show that the rainforest
is a valuable economic resource that can produce substantial
economic benefits for the surrounding communities. Rara
Avis is comprised of a several lodges and a biological
station and supports tourism, biological research
and the development of new ways to use the rainforest
without
destroying it. There are several streams high in
the mountains which feed into a double waterfall
above
the Rara Avis
complex. During the construction of this complex,
it was found
that heavy rain that fell high up in the mountains
would cause the river to overflow. Advanced warning
of oncoming flash floods was
needed. With an average rainfall of 335 inches (8500
mm) per year, and as much as 4-8
inches (100-200 mm) possible in a few hours, this
can be both quick and dangerous.
| Above:
Madison's MS8000 Liquid Level Switch
is installed in a rainforest stream to
measure water level and warn of impending
flash floods. This switch operates under
the harshest environmental conditions. |
| Right:
MS800 Liquid Level Switch |
|
Ten
years ago, a Madison MS8000 liquid level switch was
installed
in each of the two main streams feeding the waterfall.
Located about 2600 feet (800
meters)
above the waterfall, each MS8000 is screwed to a Plexiglas strip and set
inside a plastic barrel which is set in concrete. When the water level
rises more
that 10 inches (25 cm), the MS8000 closes, sending a signal by telephone
cable to a relay-operated alarm siren at the waterfall and a second alarm
at the
lodge office. This provides eleven minutes of warning before the river
rises.
 |
The
MS8000 has a 2800 ohm resistor in each circuit and
a milliamp meter to indicate whether
current is flowing in each leg of the circuit.
In addition,
a lighting-protection diode is used to reduce any damage to the circuit
due
to lighting strikes. The power supply is a solar-powered 12-volt automotive
battery. The MS8000 operates under harsh environmental conditions which
involve high water, mud and organic debris, combined with extreme turbulence.
The
water force is enough to move large boulders, and the rainforest's soil
is quite
acidic and highly corrosive. Under these conditions, the MS8000 has proven
to last up to two years in service. Click
here to download this Application Note in printable
PDF format (1.3mb).
Rainforest
photos and data supplied by Amos Bien, President
of Rara Avis Rainforest Lodge and Reserve. |
