4
SITE REQUIREMENTS AND LAYOUT
4.1
Site Requirements For All US Class A Evaporation Pans
Site requirements are frequently a compromise. The following features are
desirable when selecting a site. They are listed in order of importance.
·
If the site is near a water body or a spray irrigation or reticulation system,
it should be at least fifty metres away and on the prevailing upwind side.
·
The site should be secure from unauthorised interference and easy to
access and service.
·
Select a level, open site, free from obstructions such as trees, bushes and
buildings that will shade or shelter the site from wind. The evaporation pan
should be in the full sun.
·
Any obstruction should be at a distance from the pan of at least 4 times the
height above the pan rim.
·
Select an area six metres square. If necessary fence the area using an open
fencing system with minimum wind resistance.
·
Maintain the ground cover within the fenced compound in a similar
condition to the natural surroundings. Keep vegetation trimmed to below
the pan rim height.
Automatic Evaporation System
SITE REQUIREMENTS AND LAYOUT 15
4.1.1
Water Supply
The evaporation pan is refilled each day by the level control system. The
automated refill is controlled by a solenoid switched on by the datalogger in
response to the level registered on the water level transducer.
The instrument must be permanently connected to a reliable supply of potable
water. Some typical examples are shown in the following sections. Solenoids
and pumps can be supplied to suit all applications.
4.1.2
High Pressure Supply
The simplest method is to connect to a reticulated water supply of potable
water. A pipeline is required to the site, terminating in a tap or shut-off valve.
A short length of m12.5 hose can be used to connect to the solenoid filter.
A high pressure solenoid with a range of 10-100kPa is available as an option.
UNIDATA
16 SITE REQUIREMENTS AND LAYOUT
Optional Model
6529B Water
Temperature
Instrument
Water Supply
Model 6529E Water
Level Control System
Optional Model
6506A Rain
Gauge
Mounting
Pole
Model 6529A Water
Level Monitoring
System
Model 6529C
Evaporation
Pan on Pallet
6m x 6m fenced enclosure located in full sun with free air flow
To Equator
Water Drain
to waste or
recycling
Level monitoring
flow
