The Nile River: a journey from Source to Mouth



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The Nile River: A Journey from Source to Mouth


Thousands of years ago, the Nile River gave rise to one of the world's first civilizations. The ancient Egyptians built great cities, temples, and pyramids along the river. They grew crops on the river's banks. They sailed boats on its waters. They wrote songs and poems in praise of the river. The Nile gave life to ancient Egypt. Today, it is still a key part of Egyptian life.

The Nile is not just an Egyptian river. The river begins its journey in the highlands[highlands: a mountainous part of a country; a climate zone where temperature and precipitation vary with latitude and elevation; a vegetation zone where the mix of plants varies with latitude and elevation; also refers to the type of vegetation in this zone] of East Africa far from Egypt. Along its way to the Mediterranean Sea, it crosses mountains, plateaus[plateau: a raised area of land, such as a hill or mountain, with a flat top], plains, and deserts[desert: a geographic region with too little rainfall to support much plant life; also a vegetation zone]. The river basin[river basin: the area drained by a river and its tributaries. These tributaries are the smaller streams that flow into the main river. Rain falling anywhere in a river basin will eventually flow into the main river.] of this great waterway covers more than 1 million square miles, or about one tenth of the African continent. A river basin is the area drained by a river and the smaller streams that flow into it. The Nile River basin includes parts of 10 African countries. Forty percent of all Africans live in these 10 countries.



In this chapter, you will follow the course of the Nile River. You will discover how the river changes during its long journey from the highlands to the sea. You will read about the origins of the river and the explorers who traced it to its sources. You will also learn about the impact of the river on the people and environment of the Nile River basin.




Two Views of the Nile This satellite image shows the Nile River valley. What patterns of vegetation and landforms do you see? The diagram below shows the change in the Nile’s elevation along its entire length. From its source to the Mediterranean Sea, the river drops more than a mile in elevation.

NASA



Most of Egypt is a barren, sandy desert. The ancient Egyptians could not have survived without the Nile’s life-giving waters. For that reason, the Greek scholar Herodotus called Egypt the “gift of the Nile.” But despite the river’s importance, the ancient Egyptians never knew just where it came from. In fact, the sources of the Nile remained a mystery for thousands of years.

The World’s Longest River The Nile River has two main branches: the White Nile and the Blue Nile. The White Nile is the longest branch. From the White Nile’s most distant tributary[tributary: a stream or river that flows into a larger stream or river] in the highlands of Burundi, the Nile runs north for about 4,160 miles. This is more than twice the distance from Chicago to Los Angeles. At this length, the Nile is the world’s longest river.




Two Branches, Ten Countries The Nile River basin is outlined in dark blue on this...
Two Branches, Ten Countries The Nile River basin is outlined in dark blue on this map. It covers around one tenth of the African continent. The Nile, with its two main branches and many tributaries, travels through ten countries: Congo, Tanzania, Burundi, Rwanda, Uganda, Kenya, Ethiopia, Sudan, Eritrea, and Egypt.

Every year, the waters of the Nile rise and fall with the seasons. These changes in river level are tied to the water cycle that brings rain to the highlands of Africa. The water cycle[water cycle: the movement of water from the surface of Earth to the atmosphere and back again. During this cycle, water evaporates from rivers, lakes, and oceans, rises and condenses into clouds, and then falls back to Earth as rain, hail, sleet, or snow. This process is also known as the hydrologic cycle.] is the constant movement of water from Earth’s surface to the atmosphere[atmosphere: the layer of air that surrounds Earth] and back again. After the rainy season, rising water often floods the land along the Nile’s banks.




The Gifts of Water, Transportation, and Power The Nile has long been essential to the people who live along its banks. They use its water for drinking, washing, and cooking. They also use it for farming. In ancient times, the flooding of the Nile left deposits of rich silt[silt: sand, mud, or clay made up of fine bits of soil and found at the bottom of a river or lake] on farmlands near the river. Farmers planted their crops in this fine, dark soil. They also used the floodwaters to irrigate their fields. Later on, they developed perennial irrigation[perennial irrigation: a system that allows for the year-round watering of crops]. This is a system that distributes water to farm fields year round.

The Nile is also useful for transportation and energy. People along the Nile have long used the river as a water highway. Boats carry goods and people from place to place. The Nile also has great hydroelectric potential[hydroelectric potential: the electrical power that can be generated from flowing water]. That means that the river can be used to generate electrical power. Cities along the Nile depend on hydroelectric power[hydroelectric power: electricity that is generated from the power of moving water] to meet their energy needs.



The ancient Egyptians believed that the Nile sprang forth from an underground lake in southern Egypt. The ancient Romans later tried but failed to find the Nile’s source. It was only in more recent times that explorers finally discovered the origins of the Nile. Like all rivers, however, the Nile really begins with the water cycle.




The Water Cycle This diagram shows how nature recycles water. The water cycle is...
The Water Cycle This diagram shows how nature recycles water. The water cycle is a “closed system.” No water is ever lost. However, some water may collect unseen under the ground. This water can be tapped for human use.

From Rainwater to Rivers: The Water CycleYou have read  that the water cycle recycles water from Earth’s surface to the atmosphere and back again. This never-ending process moves water through the environment. Some water ends up in rivers like the Nile.

The water cycle begins with the evaporation[evaporation: the process by which a liquid, such as water, turns into a vapor, or gas] of water from oceans, lakes, and rivers. This occurs when the sun heats the water. When water evaporates, it becomes water vapor[water vapor: water in the form of a gas, as in steam or moisture in the atmosphere]. Steam is a form of water vapor that you can see.

As water vapor rises into the air, it cools down. The cooling causes the vapor to condense[condense: to lose heat and change from a vapor or gas into a liquid. Moisture, or water vapor, in the air condenses to form rain.] into tiny water droplets. The droplets then come together to form clouds. Under certain conditions, the droplets become too large and heavy to stay in the air. At that point, they fall to Earth as precipitation[precipitation: moisture that falls from the sky as rain, snow, sleet, or hail]. Precipitation can take several forms, including rain, snow, sleet, and hail.

Several things can happen to precipitation after it hits the ground. Some gets stored as snow and ice in glaciers. Some soaks into the ground in a process called infiltration[infiltration: the movement of water from Earth’s surface into the soil]. And some runs off the ground to form streams. In areas with lots of runoff[runoff: water from rainfall that is not absorbed into the soil and instead flows into streams or lakes], streams come together to form rivers. Most rivers eventually flow into the sea. At that point, the water cycle begins again.


Murchison Falls North of Lake Victoria, the White Nile thunders over Murchison Fa...




Murchison Falls North of Lake Victoria, the White Nile thunders over Murchison Falls. This is one of the most dramatic spots on the Nile’s long journey to the sea. Today, these falls are part of a national park in Uganda. Park wildlife includes elephants and giraffes. Hippos and crocodiles are often found in these waters.

Robert Caputo/Aurora



Lake Tana: Source of the Blue Nile Both main branches of the Nile, the Blue and the White, are fed by rainfall and runoff in the East African highlands. In the lush, forested hills of Ethiopia, this runoff flows into Lake Tana. This lake is considered the main source of the Blue Nile. The head-waters[head-waters: the stream or streams that make up the beginnings of a river] of the Blue Nile, however, are found above Lake Tana. Headwaters are the stream or streams that make up the beginnings of a river.

The Blue Nile is a fast and powerful river. Fed by heavy summer rains, it roars down from Lake Tana through deep canyons to the plains below. Along the way, it picks up lots of dark soil. Most of the silt that ends up on flooded farmlands downstream comes from the Blue Nile.

The source of the Blue Nile remained a mystery to outsiders until the 1600s. Around 1615, a Spanish priest named Pedro Páez made his way to Lake Tana. There he found the outlet where the river leaves the lake. In the late 1700s, the Scottish explorer James Bruce also reached the source. He later published a book about his travels and took credit for the discovery.

Lake Victoria: Source of the White NileThe other main branch of the  Nile starts farther to the south. As you may recall, the White Nile’s headwaters consist of a stream flowing out of the mountains of Burundi. But the river’s main source is Lake Victoria, which is a large, shallow lake in Uganda.

For years, however, the origins of the White Nile remained as mysterious as those of the Blue Nile. Various explorers tried to follow the river from Egypt to its source. But they lost their way in swamps or were turned back by river rapids.

Then, in the 1850s, the English explorer John Hanning Speke reached Lake Victoria. Convinced that this was the White Nile’s source, he returned a few years later. In 1862, he found a river flowing out of the north side of the lake. He followed the river for a distance. Then he returned to England to announce that he had discovered the source of the White Nile

At first, many scholars doubted Speke’s claim. They thought he hadn’t explored the area well enough. But later expeditions confirmed that Lake Victoria was the main source of the White Nile. In 1937, a German explorer named Bruckhart Waldekker traced the river’s headwaters farther south into Burundi.

Like the Blue Nile, the White Nile flows out of Lake Victoria as a rushing torrent. It passes through two more lakes and over a large waterfall before reaching the flat plains of Sudan. There it slows down. Along the way, the river takes on a muddy gray color. This gray color gives the White Nile its name.

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