Dams can be differentiated from vegetation on thematic imagery by their blue signature compared with the red signature of the vegetation.
Dams can also be identified by the surrounding earth which was disturbed or displaced during the construction of the Dam. This can aid in distinguishing dry dams from depressions.
Spectral response may also indicate the presence of water even in a dry dam. In Figure 2.3.5.1 the SPOT imagery indicates a presence of the water with the light/royal blue signature.
