Satellite data provide up-to-date information on the amount of water in the Nile basin



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The Nile River, which flows through 11 African countries, plays an important role in the lives of more than 24% of the African population. For both upstream and downstream countries, the waters of the Nile are crucial in planning development, food and energy production.

As countries compete for these resources, there has been immense tension. In particular, Egypt and Sudan have challenged Ethiopia’s decision to build and fill the Great Ethiopian Renaissance Dam. This is a large project on one of the main tributaries of the Nile, the Blue Nile, which supplies more than 80% of the water that reaches Egypt.

Read more: Colonial-era treaties to blame for the unresolved dispute over the Ethiopian dam

Treaties are needed to regulate the allocation of water resources in the region. For this to happen, it is essential to have accurate data on the amount of water there is. But the world’s water scarcity data is based on insufficient ground-based observations. They are very out of date and do not cover enough of the main transboundary river basins. This is due to financing, maintenance cost, terrain, and topography. In the Nile basin, the number of hydrological monitoring stations has decreased significantly in the last 30 years.

But this is changing. Recent advances in hydrological satellite observations are allowing the frequent collection of much more reliable information. This has opened the door for new research efforts to update global water availability.

Hydrological satellite observations occur when a satellite, hundreds of miles from the Earth’s surface, observes and makes periodic visits to the same site several times a month. One of them, which allows a better evaluation of the total changes in the volume of water, is the joint NASA satellite mission, Gravity Recovery and Climate Experiment.

Our research team is one of the first to use data from this satellite mission to assess water scarcity in Africa. We have used the data in several studies of the Nile Basin. This includes assessments of how water levels in the Nile Basin are affected by climate and people.

The data has allowed us to perform precise calculations that were not possible before. For example, we have been able to assess how much surface water there is and what is the soil moisture and groundwater levels. Previous studies focused primarily on one or a few of these variables, such as river flow water.

Our study shows that a water crisis is looming in the Nile basin. This calls for an urgent regional basin initiative on sustainable management of water resources.

Monitoring from space

Launched in 2002, the Climate Experiment and Gravity Recovery satellites monitor changes in the world’s water resources in all their forms. Data is available monthly.

We use these observations to determine the total available water storage in the Nile basin between 2002 and 2020. Overall, the data revealed that the total available water storage in the basin, from all sources, could average 180 thousand million cubic meters per year. This estimate is roughly double the current estimated storage of 88 billion cubic meters per year. Having data like this would inform how much water is allocated in the watershed’s water distribution agreements.

We also use satellite data to estimate the total water storage available for two main water tower regions (the source of the river), Lake Victoria and the Blue Nile basin, and two main water sink regions (where water slowly flowing is lost to evaporation) – the Sudd wetlands in South Sudan and the main Nile area in Egypt.

From what was previously reported, recent satellite observations from the Climate and Gravity Recovery Experiment showed that the Lake Victoria Water Tower receives approximately twice the volume of water that the Blue Nile Basin receives during the rainy season. And the Sudd basin (the southern water sink) loses roughly twice as much water compared to the northern main Nile region.

These updated figures call for progressive planning of water resources to save additional water resources for the future development of the region.

Satellite observations also confirmed that between 2002 and 2020, the Nile River basin experienced more humid conditions. In 2020, the Nile River basin had about eight times more water storage than in 2002. These wetter conditions require more planning to obtain more volumes of water during flood seasons.

Despite this, our conclusion confirms previous assessments that the basin is under water stress.

Water stress

A region is said to experience water stress if the water available to use per person per year – for indoor, agricultural and industrial needs – is less than 1000 cubic meters per year, about 1,000,000 liters per person per year.

For basic daily needs, a person uses about 150 liters a day. In Egypt (one of the main receivers of water from the Nile), a person consumes about 200 liters on average for domestic water needs per day. However, agricultural needs, such as food production, require between 2000 and 5000 liters of water per day.

If the water available for use is less than 500 cubic meters per year (about 500,000 liters of water per person per year) to meet all water demands, a region is in conditions of absolute water scarcity.

Due to current and booming population projections (the basin’s population is projected to reach 800 million by 2050), the basin is under severe water stress conditions.

To estimate the annual available water per capita, we need to divide the total available water in the region, which we find at 180 billion cubic meters per year, by the total population. Therefore, we estimate that the water available for use per capita is approximately 450 cubic meters per year, or approximately 1,230 liters per person per day. But there is an important caveat; the total amount of available water cannot be fully extracted and used due to technological and economic limitations. Therefore, the actual amount of usable water is probably considerably less than 1,230 liters per person per day.

More than ever before, riparian nations must strengthen agreements on future water planning and new policies for sharing water.

Data to the rescue

It will not be easy to get the 11 countries in the basin to agree on a plan to share water to avoid chronic water shortages in the future. But the key to ensuring cooperation is good information exchange and technical cooperation among the riparian states.

Having accurate information on available water will improve understanding of common water resources and promote trust between basin states.

The authors do not work, consult, own shares or receive funding from any company or organization that benefits from this article, and they have not disclosed relevant affiliations beyond their academic appointment.

By Emad Hasan, Postdoctoral Researcher in Remote Sensing Hydrology, Binghamton University, State University of New York and

Aondover Tarhule, Professor, Vice President for Academic Affairs, and Chancellor of Illinois State University, Illinois State University

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