The Lakes of Ounianga

A worldwide unique phenomenon

Green, flourishing and rich in life-giving water - that was the Sahara during the Humid Period thousands of years ago. Lakes, rivers and savanna landscapes offered ideal living conditions. Through changes in the climate, the savanna transformed into a dry desert. Almost every lake disappeared over the course of millennia. Except, that is, for the Lakes of Ounianga. To this day they provide a liveable habitat for people and animals in the middle of the most extreme of deserts. The history of climate change over the last 10,500 years can be seen in the sediments of the lake bed.

In 2012 UNESCO declared the Lakes of Ounianga the first World Heritage Site of Chad.

A landscape of lakes in a sea of desert

The Lakes of Ounianga are home to the biggest and deepest lakes of the Sahara. They extend over an area of 20 square kilometres, spanning from Ounianga Kebir (meaning large) in the west, through to Ounianga Serir (small) in the east. The surface area of the largest lake, Lake Teli in Ounianga Serir, is that of 600 football pitches. The major lake in Ounianga Kebir is Lake Yoa. It's the deepest of the Sahara, as well as the one with the biggest volume of water.

Stefan KröpelinUniversity of Cologne

One who doesn't know the Lakes of Ounianga, doesn't know the Sahara.

Die Seen von Ounianga, Lac Teli, Felsen im Wasser, Explore Chad

How they formed

5,000-10,000 years ago - during the last Humid Period of the Sahara - it rained a lot more than nowadays and rivers that formed in the highlands were plentiful. They flowed into geological basins of various sizes, where the waters accumulated. This gave rise to huge ground water reserves and many lakes.

Over time the climate changed. It became ever drier. The lakes retreated and eventually disappeared – except for a very few. The major ones remaining are the Lakes of Ounianga

Wandering sand dunes

The Ounianga region is dominated by very strong north-easterly trade winds. For thousands of years the winds have been creating "wandering" sand dunes, some of which have driven themselves into the lakes. Some of these then splinter off into tongues of sand that year by year creep ever further into the lake water. At some point the lakes become divided by these, and eventually completely separated.

From the once single, connected fresh water lake of Ounianga Serir, such a landscape came into being. Today it consists of 16 lakes of varying sizes. Most of these are covered by a floating layer of reeds, and are no longer recognisable as lakes.

Salt and fresh water lakes

Lake Yoa is evaporating at a rate of 6,000 millimetres a year. That's equivalent to around 2,000 times the current rainfall there, or to that of the German city of Cologne's annual water consumption.

A unique geological mechanism holds the answer as to why most of the lakes of Ounianga do not increase in salt concentrations as a result of the evaporation. The sand tongues play a crucial role in this.

There are salt water lakes here too - the most central of the Lakes of Ounianga and the Lake Yoa are among these. The concentration here is about 6 times higher than that of the oceans. As good as no life survives here. Some species of birds have adapted to the conditions, feeding off the layer of algae which forms at the water's surface. In the evening they fly to the fresh water lakes to clean their feathers of the salt.

Oasis in Ounianga

Hot sand - cool water

The Lakes of Ounianga remain at a refreshing 17 degrees Celsius, as well as a constant depth of up to 26m in Lake Yoa. They don't dry up despite temperatures of 50 degrees in the shade. How can this be?

Below the surface the lakes are connected to huge groundwater reserves. They feed into the lakes, compensating for and protecting them against the enormous loss of water through evaporation. A floating forest of reeds also form on the lakes' surface, to such an extent that the majority of the lakes' surfaces are covered up.

Winds also help the evaporation to contribute to the constant cooling effect from the inflow of ground water. These factors all work together to keep the water at this remarkably cool temperature.

Die Seen von Ounianga, Blick auf den See, Explore Chad

A fragile habitat

As the deserts spread and the savanna dried up in northern Chad over 3,000 years ago, the Lakes of Ounianga - along with the rivers of the Ennedi Massif - became one of the only places in the Sahara where life was still possible. Separated from fellow members of their species and shielded by the desert, fish, shellfish and plants developed and evolved over thousands of years in an isolated ecosystem.

Maintaining this fragile habitat is of utmost importance.

A gift of nature

Archaeological findings have shown that early man had already settled in this region. Digs and other research help us to learn more about the life and times of these people.

To this day, people still like to live on the shores of the life-giving lakes. They farm fruit and vegetables and keep livestock. The algae and minerals of the lakes are thought to have therapeutic qualities. Skin conditions in particular are treated using the mud from the sea beds.

Stefan KröpelinUniversity of Cologne

There, where no puddle survives more than a few hours, the Lakes of Ounianga have survived for thousands of years. With no intake from rivers or the sea. That is unique!

The secrets of Lake Yoa

How has the climate changed over the last 11,000 years? Were there volcanic eruptions, earthquakes or fires? What plants grew here and what animals came to the shores of the lakes?

Samples, in the form of long sediment cores extracted from the seabed, hold answers these questions. They give us a picture of how the climate in North Africa has changed over millennia. This information also gives us clues as to what the future of climate change might have in store.

Die Seen von Ounianga, Lac Yoa, Bohrplattform, Sedimentbohrungen, Explore Chad

UNESCO World Heritage Site since 2012

Through many years of research, we know today that the Lakes of Ounianga are a worldwide unique phenomenon. Preserving this fragile ecosystem is for the good of humanity.

Some of the main features

exquisitely beautiful landscapes
largest and deepest lakes of the Sahara
worldwide unique ecosystem
isolated development of plant and animal life
map of the history of climate change over the last 10,500 years
unique presence of fresh water in extreme desert conditions

Die Seen von Ounianga, UNESCO Welterbestätte, Urkunde, 2012, Explore Chad

Research projects
in Ounianga

Objectives

Gaining deeper insights into and gathering new information on the topics of

how the lakes were formed
climate change
hydrogeology (e.g. the presence of fresh water)
history of human settlement

Expeditions

Since 1999, the scientist Stefan Kröpelin has been travelling to Ounianga on a regular basis. The aims are

gathering research data
basic research for the World Heritage project

Research work

A wide range of investigations are carried out during and after each visit

mapping and seismological research
sediment core drilling and collecting of samples
archaeology, geology, botanics, ethnology, zoology