The ups and downs of a mega-lake

Phys dot org ^ | July 9, 2020 | University of Tubingen

[SunkenCiv]

Together with an international team, researchers of the Senckenberg Center for Human Evolution and Palaeoenvironment at the University of Tübingen reconstructed the 20,000-year-old history of the mega-lake Chew Bahir in a remote valley in Southern Ethiopia. Led by Annett Junginger, the scientists were able to show that the lake underwent rapid water level changes in the course of its history, which had a direct impact on the local population. The study was recently published in the journal Frontiers in Earth Science.

Water is mankind's most important basic resource. From the beginning until today, humans of all cultures sought out settlements not far from the presence of clean drinking water -- as has been the case for 20,000 years at what is now Lake Chew Bahir in Southern Ethiopia.

Currently, this lake is almost completely dry. "However, in the past, the lake often held an enormous volume of water and covered an area five times the size of Lake Constance," explains Markus Fischer, the study's lead author and a doctoral student at the University of Tübingen, and he continues, "Based on hydrological models and the lake's sediments, we were able to document enormous, rapidly changing shifts in the sea level over the course of the lake's history."

The international research team's modeling results and the lake sediments offer impressive evidence that the East African landscape repeatedly fluctuated between desert-like conditions and a gigantic lake; in many cases, the lake would dry out and refill with water within just a few decades. Rainfall during the frequently recurring wet phases was between 20 and 30 percent higher than today. "Those who grew up at a lake and possibly learned to fish there may have been confronted with a dried-out lakebed as adults," adds Fisher.

[SunkenCiv]

Better than its tailwaters. :^)

[JeanLM]

Noyt questioning existence of a wet sahara; just the possibility that early herders made it a desert.

The world population which was in the low millions, had spread to all parts of the planet 11,000 years ago. There weren’t enough to affect the climate anywhere. They were lucky to have survived the 100 year long cold spells that occurred 10,000 and 8,000 years ago.

Killed a lot of mega fauna though. Lucky for us they were a tough group.

[SunkenCiv]

I wholeheartedly agree. While herding has its fans (at least one on FR who believes that grazing *restores* the foliage-supporting landscape), cattle are easier on the flora than are sheep, but cattle also grow slower and larger and require more water; as the natural dessication of the landscape proceeds, sheep tend to predominate.