Deficiency in rainfall is reflected in an absence of permanent rivers or streams, and the approximately twenty perennial lakes are brackish or salty.
Libya is a large country with a relatively small population, but the population is concentrated very narrowly along the coast. Population density is about 50 persons per km² (130/sq. mi.) in the two northern regions of Tripolitania and Cyrenaica, but falls to less than one person per km² (2.6/sq. mi.) elsewhere.
Within Libya as many as five different climatic zones have been recognized, but the dominant climatic influences are Mediterranean and Saharan.