The lake is surrounded by a steep crater rim with a maximum height of 170 metres (560 ft).

[2] 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 1,800 to 2,800 metres (5,900 to 9,200 ft).

[2]: 221  The groundwater flowed into the lake at an estimated annual volume of 8,390,000 cubic metres (296,000,000 cu ft) from 1964 through 1977.

[7][8] It is considered critically endangered by the IUCN,[9] and now greatly outnumbered by other tilapia species that have been introduced to Lake Chala.

[10][11] An 18 year old British woman was killed in 2002 by a relatively small Nile crocodile while swimming at night in the lake.