Climate change could cause the world’s largest tropical lake – Lake Victoria, located in eastern Africa o dry up in the next 500 years, the White Nile (one of the two main tributaries of the Nile) could lose its source waters in just a decade.
Largest tropical lake in the globe
Lake Victoria (LV), located in Eastern Africa is the second-largest freshwater lake in the world, second only to Lake Superior (USA). Lake Victoria. English explorer – John H. Speke named the lake after Queen Victoria.
LV is a part of the African Great Lakes and is a source of the White Nile. The lake’s drainage basin is located in Tanzania (49% area), Kenya (6%) and Uganda (45%). Resources (water, fishes, electricity, biodiversity) from Lake Victoria supports the livelihood of millions of Africans. Several environmental issues have plagued the lake, including; invasive plant species, invasive fishes, pollution, water level decline, and climate change.
Lake Victoria and Climate Variability
Ecosystems and communities in Africa are highly sensitive to changes in climate, especially variation in rainfall. In 2010-11 eastern African countries experienced a severe drought which affected 10 million people. in Kenya, Somalia, and Ethiopia. Future climatic forecasts have shown that East Africa will experience a rise in temperatures. Despite an increase in drought and a decrease in rainfall observed between March and May, climatic models predict an increase in rainfall. The disconnect between observed and modeled precipitation trends is called the East African climate paradox. Therefore, It is unknown if East Africa will become wetter in the future due to human-induced climate change or not.
Several regional and global factors contribute to climatic variability in Africa; orbital forcing, sea surface temperatures, position, and intensity of Inter-tropical convergence zone, Congo air boundary, and high-latitude processes. Researchers do not completely complex the interplay of these regional and global factors due to unavailability of data. A team of researchers led by Dr. Emily J. Beverly from the University of Houston studied the impact of changing climate on Lake Victoria. The results of the study were published in the journal – Earth and Planetary Science Letters.
The researchers generated a water-budget model using ancient sediments to study the impact of climate change on water levels and the rate of water level change in LV. This water-budget model included precipitation, basin area, temperature, net radiation, wind speed, dam, and run-off ration as input variables. The calculated variables included; catchment (area, interception, runoff) and lake (area, interception, elevation, flow).
Water models in the past have shown that Lake Victoria would be reduced to less than 10% of its current surface area. “These models did not account for evaporation, temperature change, insolation, and did not estimate the rate of surface area lost,” said Dr. Emily J. Beverly. Furthermore, Dr. Emily said that “we developed a new water-budget model and coupled it with previously published data on paleosols based paleoprecipiation proxies to understand Lake Victoria’s water levels in Pleistocene Epoch“.
This research study involved analysis of lake depth, geometric changes in the lake, past lake discharge, and modeling the present, past & future lake levels.
Rain is the major source of water for Lake Victoria, approximately 55 inches of rain falls on the lake annually. Analysis of sediments found along Lake Victoria showed that rainfall levels 35,000 to 100,000 years ago were about 28 inches (half of what they are today). The water-budget model used in the present study demonstrates that low amounts of rainfall caused the lake to dry up at least three times in the past 100,000 years, and it could happen again.
Results showed that significant changes in the size and volume of Lake Victoria are possible due to changing precipitation, temperature, and orbital forcing. The study revealed that the lake can transform back and forth between modern lake levels. Complete desiccation of Lake Victoria can occur in centuries or a few millennia same as previously observed desiccation events between 14,000 to 18,000 years ago, during which the lake drained and refilled twice. Hydrological modeling and paleohydrologic estimates show that Lake Victoria desiccated between 36,000 to 94,000 years ago. This desiccation was probably a result of eccentricity-enhanced precession and high latitude forcing that affected Congo air boundary convergence.
“Our model predicts that at current rates of temperature change and previous rates of lake level fall, Lake Victoria could have no outlet to the White Nile in as little as 10 years. Every major port in Lake Victoria could be landlocked within a century, and Kenya could lose access to the lake in less than 400 years,” Dr. Emily explained.
Climatic changes will affect the socio-economic conditions of approximately 40 million people living in the Lake Victoria basin. Kenya and Tanzania’s fishing industry, Uganda’s electricity sector, Rwanda and Burundi’s livestock and agriculture sector will be affected by these changes.
Global Climate Change Concerns for Africa’s Lake Victoria
Sara Tubbs | November 14, 2019 | University of Houston, USA.
Rapid Pleistocene desiccation and the future of Africa’s Lake Victoria
Earth and Planetary Science Letters