Large Lakes of the Sahara

Who knew?  In the literal middle of nowhere in Chad several large lakes still provide fresh water to the few animals and people who live there.  Salt water lakes reside in many deserts worldwide, but not freshwater lakes.  The May/June 2014 issue of Saudi Aramco World both astonished and enlightened me.  These lakes are not mere oases, but really large lakes, the Lakes of Ounianga.  In 2012, all eighteen of them became part of World Heritage sites.

Each lake remains different, some interconnected, some fresh water, some saline.  They are 500 miles from the nearest large body of water, Lake Chad.  To get there, you must use four wheel drive or ride a camel.  In 2001 and 2002 not far from these lakes, the fossils of extremely ancient hominids were found, hominids who lived seven million years ago, potential precursors to modern humans and chimpanzees.  Here and there camels graze in sand nearly devoid of vegetation. Near these lakes lush foliage grows, green gems in the middle of miles of varying shades of endless brown.  One of the lakes’ water is red from the algae growing in it sometimes several inches thick.  Frogs croak.

Once upon a time long ago, this Sahara grew savanna grass where the wildlife we associate with other parts of Africa lived–elephants, giraffe, hippos, antelopes, and the now extinct auroch.  Lake Boukou holds fresh water, crystalline, pure.  Around this lake one can find ancient stone hammers and scrapers dating from half a million years ago.  Because of evaporation in the dry heat, one would expect these lakes to become increasingly saline.  Only one of the eleven lakes in this area is saline. How is this possible?

Under the Sahara lies the world’s largest fossil-water aquifer beneath the countries of Chad, Sudan, Egypt, and Libya.  The maximum depth is 12,800 feet. This acquifer supplies the Lakes of Ounianga.  The mats of reeds and algae on top of the fresh water lakes keep their evaporation rate low and their water fresh.  Once these lakes covered vast distances.  Researchers use diatomic soil to study the changes in the lakes over centuries.  Diatoms are the remains of microscopic sea creatures that turn into ivory or white soil.  Studying these soils enable scientists to date the age of the lakes to approximately 6000 years ago.  Once researchers thought the Sahara suddenly became a desert about 5000 years ago, but new data reveal a more gradual change to desert taking thousands of years and only becoming the desert we know more recently.  Research around the lakes will prove important to understanding climate change and its causes.

Currently fifteen clans live in Ounianga.  These people believe their ancestors came out of the lakes when they were one giant lake surrounded with date palms.  Core studies (scientists take a core sample of the soil–in this case 16 meters) indicate that date palms came rather late in the area’s millennial history.  They have also found the roots of reeds and even trees dating back to approximately 8000 years ago.  Their goal is to drill even deeper.  Heat (122 degrees F) make this a long, torrid task, but the scientists dedicated to learning the story of these incredible lakes and the Sahara press on.



Notes:  Saudi Aramco World is one of my favorite magazines, filled with fabulous photos, historical articles, recipes, and endless fascinating information.  This issue also included an article about the Muslim Tartars who live in Poland today.  You can subscribe  by adding your name to their free subscription list.

Diatomaceous earth is found in many places.  I feed it to my horses to prevent parasites.  It is used in cleaners and even tooth paste.