Twenty-eight countries in Africa could face water stress or scarcity by 2050, according to research led by faculty at Binghamton University, State University of New York.
Binghamton University geographers Emad Hasan and Aondover Tarhule predicted that by 2050, with no change in available water resources, 19 countries in Africa will face water scarcity, while another nine countries will be water-stressed. However, if climate change decreased Africa's water resources by 10 percent, 85 percent of the continent's population would experience a dangerous water scarcity situation.
Africa critically needs accurate information on its water scarcity status. As the second-most populated continent, Africa is projected to have a population of 2.4 billion by 2050, approximately double the current estimated population.
Such rapid population growth will exert considerable stress on the continent's available water resources, worsening the already acute water scarcity situation. So, assessing the potentially available water resources is essential for the future."
Hasan said that it is important to determine whether a region has sufficient water to satisfy the needs of its people, but it is a complicated process.
To estimate water scarcity and availability in a country, hydrologists build a "water budget" which calculates all of the water entering a country, whether it be from rivers, rainfall, groundwater or man-made sources, and then subtract all water leaving the country.
By dividing the available water by the population of a region, hydrologists are able to determine if there is enough water to meet people's daily needs.
From a global perspective, a country will experience water scarcity if it has less than 500,000 liters of water per person per year to meet daily and agricultural needs.
The water budget process only works if there is accurate data for each source of water, and Tarhule said that in developing regions like Africa, data required are either lacking or inadequate, which poses a huge problem.
Using satellites hundreds of miles in space, the researchers measured water scarcity in Africa. They used publicly available data from two satellite missions, the Tropical Rainfall Measuring Mission (TRMM), and the Gravity Recovery and Climate Experiment (GRACE) satellites.
By combining data from these two systems, the researchers calculated the monthly potential available water for each country in Africa. Then, they divided the potential available water storage by each country's population to develop a new measurement of available water storage per capita.
The researchers compared their results with data used by the United Nations Food and Agriculture Organization, which classifies countries into one of four categories: water-sufficient, vulnerable, water-stressed or water-scarce.
Out of 48 African countries studied, their method classified 26 in the same category as the U.N.'s method.
Hasan said that although the accuracy of their new method can be skewed by the size of the country, it still has an edge over other approaches since it accounts for water in aquifers deep underground.
"In general, we think that our method has several advantages over existing methods. It circumvents many of the limitations related to data unavailability and reliability in Africa," he said. "The data are more temporally and spatially continuous, as well as easier for researchers to access. As a result, estimates of water scarcity can be carried out much more rapidly for the entire continent."
Tarhule said he hopes they can improve the new method so it can assess water scarcity on a global scale.
"Satellites will gather new data in the coming years," said Tarhule. "We plan to take advantage of such data improvements as they become available to refine our method in terms of accuracy and water scarcity assessment at the sub-country level, not only in Africa but globally."
Hasan, I. et al. (2019) Assessment of Physical Water Scarcity in Africa Using GRACE and TRMM Satellite Data. Remote Sensing. doi.org/10.3390/rs11080904.