It used to flow to the north and drain into the Nile until around 12,000 years ago, lavas flows from the Virunga volcanoes dammed this outflow, reversing the direction of its waters and also causing the depth to increase. Around 5,000 years ago when local volcanism and hydrothermal activities began to affect the lake, it became very stratified with different layers that hardly interact with each other. 

This stable stratification is the secret to it’s huge resource, more than any other lake in the world, it has vast quantities of trapped methane at depths of over 200m so there are projects near to Gisenyi and Kibuye that are beginning to extract this reserve.

The surface water temperature is about 24 °C, however, at depth, unlike almost every other (non-frozen) lake in the world that becomes cooler with increasing depth geothermal activity keeps the temperature in the lower layers of Lake Kivu warmer, at 26 °C.

With very steep sides river run offs and most pollutants from the towns around the lake descend quickly to the depths. The surface layer therefore comprises very clean, fresh water, in which some 31 species of fish live, many of which are caught by local fishing cooperatives using their unique fishing boats. However, there are no large animals such as hippopotamus or crocodiles. Furthermore, with few habitats for the host snails to live in and almost no human habitation close to the water (due to a law banning all dwellings within 50m of the shore), Lake Kivu has one of the lowest instances of Schistosomiasis (bilharzia) in any African body of water.

If it is not removed by – such as by the methane extraction process that is being used to generate electricity – the dissolved methane and carbon dioxide in the deep layers, will (when the partial pressures of these gasses become more than the pressure of water from above), eventually cause a limnic eruption. However, the scientific analysis indicates that this is many decades away, so for now, we are free to enjoy the beauty and tranquillity of Lake Kivu.

Containing relatively high concentrations of dissolved minerals, with a pH of 8.6, the surface water in Lake Kivu is also slightly alkaline. As a result rocks around the shores are generally covered in a mineral scale, similar to limescale in a home kettle or stalagmite in a cave. Also, on occasions when the water temperature naturally fluctuates, the amount of these minerals that can stay dissolved reduces, making the water appear milky in patches or even over a widespread area – as occurred extensively in 2016. Such colouration is harmless however, sometimes local people (and media) erroneously confuse the change of colour with the methane.

As the largest lake in Africa that does not have a single hippo or crocodile, and it’s safe clean water, Lake Kivu is a special place for the local people who live around its shores and fish on its water as well as all kinds of tourism activity.