6.5.1
Interpreting Evaporation Data
The following (annotated) graph is an example of typical data from a period,
and how it can be interpreted. Three sets of data are logged. The pan water
level trace is a full record of all level changes. You can analyse this and
extract the evaporation and rainfall data you require. However this has
already been done for you, and logged as the evaporation and rainfall data.
The derived evaporation and rainfall data is the accumulated total since the
logger was last reset. It may contain corrupting events if there has been any
artificial water level changes. There are two shown in the above example.
These can be removed by editing the data in a spreadsheet or with one of a
range of commercial editing systems.
Automatic Evaporation System
OPERATING THE SITE 39
Derived evaporation
Rainfall
Pan water level
(evaporation reset at 0100 each day)
Derived rainfall
Level reset after rainfall
Manual intervention to be
removed from data
No reset required
This page intentionally left blank.
UNIDATA
40 OPERATING THE SITE
