Lake Naivasha is a freshwater lake and part of the Great Rift Valley. The name derives from the local Maasai name Nai'posha, meaning "rough water" because of the sudden storms which can arise. The lake has a surface area of 160 square kilometres, but this can vary largely depending on rainfall. It is situated at an altitude of 1,890 metres / 5900 ft. The lake has an average depth of 5 metres. The lake is home to a variety of wildlife; over 400 different species of bird have been reported. It is particularly famous for its flamingos. There are two smaller lakes in the vicinity of Lake Naivasaha: Oloiden and Sonachi (a green crater lake).