Lake Chala
Lake Chala, also known as Lake Challa, is a crater lake that straddles the border between Kenya and Tanzania. The lake formed approximately 250,000 years ago. The lake is east of Mount Kilimanjaro, north of Taveta, Kenya, and east of Rombo District. The lake is surrounded by a steep crater rim with a maximum height of . Lake Chala's average annual rainfall is about . The lake surface has an average annual evaporation of near . Approximately 80 percent of the lake's inflow comes from groundwater, which is derived mostly from rainfall in the montane forest zone of Mount  Kilimanjaro at an elevation of . It takes about 3 months for groundwater to reach the lake. The groundwater flowed into the lake at an estimated annual volume of from 1964 through 1977. Ecology. The only native fish in this lake is the Lake Chala tilapia ("Oreochromis hunteri"), which is found nowhere else in the world. It is considered critically endangered by the IUCN, and now greatly outnumbered by other tilapia species that have been introduced to Lake Chala. An 18 year old British woman was killed in 2002 by a relatively small Nile crocodile while swimming at night in the  lake. A few days later, the Kenya Police Service said that the lake was "infested" with crocodiles, while the Kenya Wildlife Service said, "Crocodiles are found in Lake Chala and it is not regarded as safe to swim at all."