Nile River ecosystem

• Category: Inland Aquatic Biomes.
• Geographic Location: Africa.
• Summary: The world’s longest river offers its ecoregion amazing gifts—but 11 countries contend over the disposition of these hydrological and ecological riches.

The Nile River is the longest river in the world, extending some 4,040 miles (6,500 kilometers) across the northeast sector of the African continent. The Nile River basin comprises 1.3 million square miles (3.4 million square kilometers), watering at least part of 11 countries: Burundi, Democratic Republic of the Congo, Egypt, Eritrea, Ethiopia, Kenya, Rwanda, Republic of Sudan, South Sudan, Tanzania, and Uganda. Major lakes account for about 2.4 percent of the basin, while swamps cover another 2 percent.

Located in high-altitude swampland, the most upstream tributary to the Nile is the Kagera River, an important feeder to Lake Victoria, the largest of Africa’s Great Lakes. North of the Great Lakes region, the river is referred to as the Upper White Nile where it flows through a hot, arid area with high evaporation losses in South Sudan. The White Nile stretches from the Sobat River to Khartoum, capital of the Republic of Sudan. Here, the river combines with the Blue Nile, which is comprised of flows from Lake Tana and other pools on the Ethiopian Plateau. Once the Blue and White Nile merge in Khartoum, the last remaining major Nile River tributary is the Atbara River, a seasonally dry stream flowing down from Ethiopia that meets the Nile in Egypt.

The Nile flows into the vast storage reservoir in Aswan, Egypt, known as Lake Nasser. From here, water is released into a narrow, sinuous stream, which ultimately passes through the Egyptian capital, Cairo. Approximately 14 miles (23 kilometers) north of Cairo, the Nile breaks into two branches, the Rosetta and the Damietta. These branches form the main bulk of the Nile Delta, where the river flows into the Mediterranean Sea.

The majority of the Nile River basin flows are highly seasonal and affected by rainfall variability. As much as 30 percent of the rainwater is lost to evapotranspiration. As the Blue Nile passes through eastern Sudan during the hot summer months, it can lose up to half its flow to evaporation. During the June-to-November rainy season in the Ethiopian highlands, however, surges in flow can cause major soil loss, streambed erosion, and flooding. The Blue Nile provides 20 percent of the total Nile volume, the White Nile roughly 80 percent, on average.

Several major dams are located on the Nile River basin to reduce flooding, generate electric power, and store water. Major dam construction began in 1902 with the Old Aswan Dam. It was followed in 1925 by the Sennar Dam in Sudan on the Blue Nile, then in 1937 by Sudan’s Jebel Aulia Dam on the White Nile, and then others.

Although damming the Nile has helped some geographic areas, it has caused detrimental effects in others. Since the construction of the Aswan High Dam in the mid-twentieth century, the lower Nile basin and Nile Delta have received very little of the fertile sediment previously accumulated during floods. Now, most of this sediment settles out upstream in Lake Nasser. The dam decreased the Nile’s flow rate, depressed water oxygen levels, and increased the salinity of large parts of the ecosystem.

Further upstream, Lake Victoria’s only outflow, the White Nile, was dammed in 1952 by British colonial engineers. The goal was to utilize the flow to provide power for the region. In 2002, Uganda constructed the Kiiva Power Station along the White Nile, and by 2006, Lake Victoria’s water level was at an 80-year low. The Grand Ethiopian Renaissance Dam (GERD), which opened in 2020, has caused great concern for Egypt and Sudan, who have opposed Ethiopia filling the reservoir behind the dam. Researchers believe the dam will impact soil salinity, ground and surface water, and crops in Egypt.

Climate

The climate of the River Nile basin varies greatly throughout its long run. The temperature is generally around 100 degrees F (40 degrees C) during daylight hours in the summer’s hot, dry season. The winters are generally mild. Temperatures are hottest in the northern reaches of the river (mainly in Sudan and Egypt), but also quite warm in the rainforest wetlands in central and eastern Africa.

The northern region of the biome is affected by a year-round high-pressure system; as the temperature increases, southern khamsin winds cause heat waves.

In contrast to the north region, the southern basin has significantly more rainfall, especially during summer, and is affected by sea surface temperatures and summer monsoon winds. Significantly less rainfall occurs in winter.

Biodiversity

The flora of the tropical forests found in the Great Lakes region of the upper Nile River basin comprise many diverse plant species including ebony, banana, rubber, bamboo, and coffee shrub. Further north, there is an area of unique dryland biodiversity. On the Sudanese plains, papyrus, reed mace, ambatch, turor, and the South American water hyacinth can be found. On the Ethiopian Plateau, mixed woodlands and savannas dominate; in the Sahel and Sahara zones, deserts predominate and very little vegetation exists except along the river edges. There are more than 95 species of aquatic plants belonging to 33 families along the Nile.

The Nile River basin is home to reptiles, birds, and fish, including the Nile crocodile and hippopotamus, which are found mainly in the wetter southern region. Other reptiles, such as soft-shelled turtles, monitor lizards, and more than 30 types of snakes, also are found in the basin.

Currently, some 800 fish species are in the Nile, the majority of them from the Cichlidea, Cyprinidae, Mormyridae, and Mochokidae families.

Since the early twentieth century, the Nile River system has experienced a significant decrease in fish population diversity. The native fish Haplochromis are small, bony fish that were not very profitable for the local fishing industry, but were very prevalent. In the mid-1900s, the Nile perch, which can weigh over 175 pounds (80 kilograms), was introduced into the river, and by the end of the century, Nile perch was so successful that it ranked as Uganda’s second-biggest export (behind coffee). Although the fisheries increased up to four times their yield, the carnivorous fish preyed on smaller native fish. This has caused as many as 150 native Nile River fish to become extirpated, or wiped out in the river.

In the Nile River Basin, there are both cosmopolitan and endemic—found only here—bird species. The most common of these include the osprey (Pandion haliaetus) and the moorhen (Gallinula chloropus). The blue-winged goose (Cyanochen cyanopterus) is among the most abundant of all the endemic species.

Environmental Issues

Besides the variety and always-shifting nature of its climate zones and hydrology, the Nile River basin faces many sociocultural challenges. Population growth is predicted to contribute to water scarcity in half of the river basin’s countries during the 2020s. Major challenges face the 11 countries, chiefly finding a way to work together to better manage their shared water resources, complicated by the region’s high rates of poverty and famine, and the frequency of drought. Experts worry that water disputes could destabilize the region. These nations also are challenged within the parameters of past Nile River treaties, specifically the 1959 Egypt-Sudan treaty that allocates the Nile’s water annual flow and largely excludes other upstream countries.

The socioeconomic issues not only affect the allotment of water resources, but also the pollution along the river. Industrial waste is released directly into the Nile and associated irrigational canals. In Egypt, about 85 percent of the water available is used for agriculture, but the runoff carries pollutants such as pesticides, manure, salts, and wastewater. Agricultural drains and household waste also is directly discharged into the Nile. In some of the major drainage points, referred to as black zones, the water exceeds the European Community Standard of fecal contamination.

The lack of education, government planning, and enforcement continues to undermine Nile River cleanup efforts. Climate change poses other obstacles. Rising water temperatures could lead to even higher evaporation—and shore erosion from violent storm flooding. Evidence shows the Nile already shrinking at a rate of 3 to 5 millimeters per year. Unpredictable precipitation and river flow, land degradation, siltation, waterweed infestation, droughts, deforestation, species loss, increased soil salinity, and possible increased incidences of disease are all projected potential outcomes of global warming here. Improving education and better-coordinated regional water management schemes will be needed to form part of the answer to these daunting challenges.

Bibliography

Aziz, Sherien Abdel, Martina Zelenakova, Peter Mesaros, Pavol Purcz, and Hany F. Abd-Elhamid. "Assessing the Potential Impacts of the Grand Ethiopian Renaissance Dam on Water Resources and Soil Salinity in the Nile Delta." Sustainability, vol. 11, no. 24, 2021. DOI: 10.3390/su11247050. Accessed 14 Jan. 2025.

Beyene, Tazebe, et al. “Hydrological Impacts of Climate Change on the Nile River Basin: Implications of the 2007 IPCC Climate Scenarios.” Seattle: University of Washington; and Wageningen, Netherlands: Wageningen University and Research Centre, 2008.

Dumont, Henri J., ed. The Nile: Origin, Environments, Limnology and Human Use. Dordrecht, Netherlands: Springer Science and Business Media, 2011.

Hamzawy, Amr, Mohammad Al-Mailam, and and Joy Arkeh. "Climate Change in Egypt: Opportunities and Obstacles." Carnegie Endowment For International Peace, 26 Oct. 2023, carnegieendowment.org/research/2023/10/climate-change-in-egypt-opportunities-and-obstacles?lang=en. Accessed 14 Jan. 2025.

Osman, M. M. Ali. “Aquatic Plants of the Sudan.” In Henri J. Dumont, ed. The Nile: Origin, Environments, Limnology and Human Use. Dordrecht, Netherlands: Springer Science and Business Media, 2011.

Polakovic, Gary. "Water Dispute on the Nile River Could Destabilize the Region." University of Southern California, 13 July 2021, today.usc.edu/nile-river-water-dispute-filling-dam-egypt-ethiopia-usc-study/#:~:text=The%20study%20projects%20that%20economic,crops%20and%20improving%20irrigation%20systems. Accessed 14 Jan. 2025.

Yassin, Fatma Elzahraa. "Protecting the Nile Delta." United Nations Egypt, 13 June 2021, egypt.un.org/en/131231-protecting-nile-delta. Accessed 14 Jan. 2025.

Zane, Damian. "River Nile Dam: Why Ethiopia Can't Stop It Being Filled." BBC, 8 July 2021, www.bbc.com/news/world-africa-53432948. Accessed 14 Jan. 2025.