Often storages are not built accurately to the design and actual volumes can differ by up to 20 per cent. In addition, a build-up of silt and slumping of dam walls can change the dimensions of your storage.

A fact sheet about structural and management techniques to reduce water storage evaporation.

National Program for Sustainable Irrigation Fact sheet 2005/4 As much as 40% of water stored in a farm dam can be lost through evaporation, depending on the depth of the dam and its surface area.