Global Warming Fact: Lake Victoria Could Dry Up

Emily J. Beverly

Security, Africa

It's happened before.

Lake Victoria, in East Africa, is the world’s largest tropical freshwater lake. At 68,800km², it’s also the second largest freshwater lake in the world after Lake Superior in North America. On a clear day you cannot see the other side of Lake Victoria, yet this vast body of water has dried up several times in the past – and it could happen again.

Over the past 100,000 years, the lake has completely dried up at least three times. Each time it was probably replaced by a vast grassland.

My colleagues and I found that the lake could dry up again in as little as 500 years because of changes in temperature, rainfall and orbital forcing – the effect on climate of slow changes in the tilt of the Earth’s axis. Our predictions are based on historical and geologic data from the last 100,000 years.

Inadequate and conflicting data on long term weather trends make it hard to be conclusive. And we can’t be sure of how climate will change in the future due to human actions without more data. Over the past few decades, the frequency of drought in East Africa has increased but climate models project an overall increase in rainfall over the next century for this area.

Previous studies on Lake Victoria’s future water levels have been done, but didn’t have evidence for past changes in rainfall or include orbital forcing.

Based on historical and geologic observations, our findings show that Lake Victoria can dry up very quickly with small decreases in annual rainfall. Knowing whether rainfall is going to increase or decrease over the next 100 years becomes very important.