Drought

Drought, excessively dry climatic conditions, generally due to absence of rainfall. Permanent drought conditions prevail over approximately one-third of the world's land surface, the sand deserts alone covering a total area more than twice as large as the United States. A region is classed as arid or drought-stricken when the annual precipitation is below 10 in (25.4 cm). Under such conditions, farming becomes extremely difficult. Recently, however, progress has been made in dry land reclamation by means of new irrigation schemes. Experiments for inducing artificial rainfall through cloud-seeding techniques have also been promising.

See also: Climate.