EP Class A Evaporation Pan

The Class A Evaporation Pan is a standard device for manual measurement of evaporation (Australian Bureau of Meteorology Class A type). The pan represents an open body of water: It is filled with water and exposed on a flat plateau. The evaporation rate is calculated by the change in level of the free water surface (daily manual readings) and the recorded rainfall (in millimetres). Data can be calculated for any period required for estimation of evaporation and evapotranspiration rates.

Installation

The pan is normally installed above the ground level on a wooden pallet set (provided) on flat ground to ensure air can freely circulate under the pan. The location should not be adversely affected by shade and free from surrounding obstructions such as trees, buildings, shrubs or instrument shelters. The pan should not be placed directly upon a concrete slab or asphalt. Above that it has to be ensured that water does not enter the pan from the surrounding ground during wet weather events.
A fix point gauge (a cylinder with a base that sits in the pan) helps to fill the pan to the required water level which is indicated by a stainless steel pointer (part of the gauge).