Climate change could drastically increase Nile flow variability

People have relied on the fertile soils and constant flow of fresh water in the Nile river basin for millennia. Today, this river fills water bottles, irrigates crops and creates hydroelectricity. Climate change threatens to disrupt the delicate balance between the Nile and the people it sustains.

A recent prediction of climate models is an increased occurrence of the climate oscillation responsible for El Nino and La Nina. Scientists at MIT are suggesting this very ability is also likely to be reflected in the flow of the Nile river, resulting in more floods and droughts, especially in the Eastern Nile region. With tributaries running through almost a dozen countries, the Nile river serves as the main water artery for Eastern Africa and a vital resource for the 400 million people living along its shores. Unfortunately, the Nile basin is already an ecosystem under significant stress.

Considering climate model simulations of rainfall and stream inflow, the MIT research team projected future river flow patterns. Observational data were used to document recent trends, while global climate models were employed to estimate future runoff. These models use mathematical formulas that take into account greenhouse gas emissions and how they affect climate, allowing scientists to make future projections under the ‘business-as-usual’ scenario of emission levels. From these data, a troubling trend emerged.

The coming years and decades are likely to see an increase in the variability of river water levels, attributed to increases in future occurrences of El Nino and La Nina events. For people living in the Nile basin and relying on the resources it provides, this translates into more frequent fluctuations manifested in extreme floods and droughts the effects of which are already being felt.

In 2015, regions along the Nile saw the worst droughts in half a century, causing crops to fail and food prices to skyrocket and leaving millions hungry. A year later, hundreds of thousands of people were displaced and houses destroyed by floods along the river’s banks.

Scenes such as these are likely to continue as climate change progresses, threatening environmental sustainability, local cultures and food security in this already fragile region. With the population in the Nile river basin expected to double by the year 2050 – primarily in Egypt, Sudan, and Ethiopia- reaching nearly 1 billion, the demand for water is growing stronger everyday.

While the data suggest ongoing climate change will likely increase overall average water flow in the river, this additional water comes at a prices. Increased interannual variability will require building dams to store water surplus during flood years for use in drought years. This combination of projected population growth and climate change impacts presents the Nile basin a microcosm of Africa in the 21st century. The projected changes in Nile river flow predicted in this study highlight the need for careful future planning regarding the protection and utilization of this essential resource.

The study, published in the journal Nature Climate Change, was carried out by professor of civil and environmental engineering Elfatih Eltahir and postdoc Mohamed Siam.