Koerner (1997) stated that a cover is required for many of liquid containment structures for one of the following reasons: loses due to evaporation (up to 80% per year),savings on chlorine treatment for water reservoirs, savings on algae control chemicals for water reservoirs, reduced air pollution from reservoirs holding chemicals, reduced need for drainage and cleaning, increased safety against accidental drowning, protection from natural polluting entering the reservoirs, e.g. animal excretion, and protection from intentional pollution, i.e. sabotage.
 Obviously, a rigid roof structure could be constructed over the reservoirs, but the costs involved are usually prohibitively high (Koerner,1997). At a far lower cost, is the use of an inperneable HDPE liner with superior ultraviolet an exposed weathering resistance. Ususlly,