The Model 3590 Evaporation Station is a standard U.S.
National Weather Service Class A Station used to measure
the amount of water lost each day through evaporation.
There are two commonly used procedures for making these
measurements. In both, a pan 10 inches deep and 47.5
inches in diameter is used to hold the water. This U.S.
Class A pan is normally installed on a wooden platform set
on the ground in a grassy location.
One method for measuring evaporation loss is to use a
graduated hook gage set on a stillwell to determine the
water level in the pan. The hook gage is adjusted until
the point just breaks the water surface, and a reading is
taken from the attached scale.
The second method uses a stillwell with a fixed point.
Each time a measurement is taken, the pan is refilled to
the level of the point using a calibrated graduate. The
graduate has a surface area of 1/100 that of the pan so
that the amount of water added is the equivalent
evaporation.
The choice between these alternatives is generally made
on a practical basis, such as the availability of daily
replacement water.
The amount of evaporation is a function of temperature,
humidity, wind and other ambient conditions. In order to
relate the evaporation to current or expected conditions,
the maximum and minimum temperatures of the water and the
amount of air passage are normally recorded along with the
evaporation.
A bird guard constructed of wire mesh on a cylindrical
frame is used when evaporation measurements may be
affected by birds or animals having access to the water in
the pan. The Evaporation Station includes evaporation pan,
hook gage, stillwell, submersible min/max thermometer,
cable and totalizing anemometer and necessary hardware for
installation. Specify English or metric units.
1002-001
Evaporation Station, complete
125 lbs.
1002-006
Evaporation pan
80 lbs.
1002-007
Hook Gage
3 lbs.
1002-008
Stillwell
10 lbs.
1002-009
Sub. Min/Max Thermometer
5 lbs.
1002-010
Totalizing Anemometer, miles
9 lbs.
1002-011
Totalizing Anemometer, km
9 lbs.
1002-012
Birdguard
46 lbs.
1002-013
Pan Platform
50 lbs.
