Question: who created the country borders in the continent with the river that the Tekezé River turns into?

full_context: Document 1: Yangtze: The river originates from several tributaries in the eastern part of the Tibetan Plateau, two of which are commonly referred to as the ``source ''. Traditionally, the Chinese government has recognized the source as the Tuotuo tributary at the base of a glacier lying on the west of Geladandong Mountain in the Tanggula Mountains. This source is found at 33 ° 25 ′ 44'' N 91 ° 10 ′ 57 ''E ﻿ / ﻿ 33.42889 ° N 91.18250 ° E ﻿ / 33.42889; 91.18250 and while not the furthest source of the Yangtze, it is the highest source at 5,342 m (17,526 ft) above sea level. The true source of the Yangtze, hydrologically the longest river distance from the sea, is at Jari Hill at the head of the Dam Qu tributary, approximately 325 km (202 mi) southeast of Geladandong. This source was only discovered in the late 20th century and lies in wetlands at 32 ° 36 ′ 14'' N 94 ° 30 ′ 44 ''E ﻿ / ﻿ 32.60389 ° N 94.51222 ° E ﻿ / 32.60389; 94.51222 and 5,170 m (16,960 ft) above sea level just southeast of Chadan Township in Zadoi County, Yushu Prefecture, Qinghai. As the historical spiritual source of the Yangtze, the Geladandong source is still commonly referred to as the source of the Yangtze since the discovery of the Jari Hill source.
Document 2: Africa: In the late 19th century, the European imperial powers engaged in a major territorial scramble and occupied most of the continent, creating many colonial territories, and leaving only two fully independent states: Ethiopia (known to Europeans as ``Abyssinia ''), and Liberia. Egypt and Sudan were never formally incorporated into any European colonial empire; however, after the British occupation of 1882, Egypt was effectively under British administration until 1922.
Document 3: Sahara: The desert comprises much of North Africa, excluding the fertile region on the Mediterranean Sea coast, the Atlas Mountains of the Maghreb, and the Nile Valley in Egypt and Sudan. It stretches from the Red Sea in the east and the Mediterranean in the north to the Atlantic Ocean in the west, where the landscape gradually changes from desert to coastal plains. To the south, it is bounded by the Sahel, a belt of semi-arid tropical savanna around the Niger River valley and the Sudan Region of Sub-Saharan Africa.
Document 4: Modern history: At the time of the Berlin Conference, Africa contained one-fifth of the world’s population living in one-quarter of the world’s land area. However, from Europe's perspective, they were dividing an unknown continent. European countries established a few coastal colonies in Africa by the mid-nineteenth century, which included Cape Colony (Great Britain), Angola (Portugal), and Algeria (France), but until the late nineteenth century Europe largely traded with free African states without feeling the need for territorial possession. Until the 1880s most of Africa remained unchartered, with western maps from the period generally showing blank spaces for the continent’s interior.
Document 5: Modern history: From the 1880s to 1914, the European powers expanded their control across the African continent, competing with each other for Africa’s land and resources. Great Britain controlled various colonial holdings in East Africa that spanned the length of the African continent from Egypt in the north to South Africa. The French gained major ground in West Africa, and the Portuguese held colonies in southern Africa. Germany, Italy, and Spain established a small number of colonies at various points throughout the continent, which included German East Africa (Tanganyika) and German Southwest Africa for Germany, Eritrea and Libya for Italy, and the Canary Islands and Rio de Oro in northwestern Africa for Spain. Finally, for King Leopold (ruled from 1865–1909), there was the large “piece of that great African cake” known as the Congo, which, unfortunately for the native Congolese, became his personal fiefdom to do with as he pleased in Central Africa. By 1914, almost the entire continent was under European control. Liberia, which was settled by freed American slaves in the 1820s, and Abyssinia (Ethiopia) in eastern Africa were the last remaining independent African states. (John Merriman, A History of Modern Europe, Volume Two: From the French Revolution to the Present, Third Edition (New York: W. W. Norton & Company, 2010), pp. 819–859).
Document 6: Tekezé River: The Tekezé River rises in the central Ethiopian Highlands near Mount Qachen within Lasta, from where it flows west, north, then west again, forming the westernmost border of Ethiopia and Eritrea from the confluence of the Tomsa with the Tekezé at to the tripoint between the two countries and Sudan at . After entering northeastern Sudan at the tripoint it joins the Atbarah River, which is a tributary of the Nile. The Tekezé is perhaps the true upper course of the Atbarah, as the former follows the longer course prior to the confluence of the two rivers.
Document 7: Birbir River: The Birbir River of southwestern Ethiopia is a tributary of the Baro River, which it creates when it joins the Gebba at latitude and longitude . It is politically important because its course defines part of the boundary between the Mirab Welega and Illubabor Zones of the Oromia Region.
Document 8: Flooding of the Nile: The flooding of the Nile is the result of the yearly monsoon between May and August causing enormous precipitations on the Ethiopian Highlands whose summits reach heights of up to 4550 m (14,928 ft). Most of this rainwater is taken by the Blue Nile and by the Atbarah River into the Nile, a less important amount is flowing through the Sobat and the White Nile into the Nile. During this short period, those rivers contribute up to ninety percent of the water of the Nile and most of the sedimentation carried by it, but after the rainy season, dwindle to minor rivers.
Document 9: Walaqa River: The Walaqa River, a tributary of the Blue Nile, is river in the Amhara Region of Ethiopia. Wegde is located to its north. Mida Woremo and Dera are to the south, while Kelala is to the northeast. The Walaqa River may have been the northern boundary of the historical province of Walaqa.
Document 10: Scramble for Africa: The ``Scramble for Africa ''was the occupation, division, and colonisation of African territory by European powers during the period of New Imperialism, between 1881 and 1914. It is also called the Partition of Africa and by some the Conquest of Africa. In 1870, only 10 percent of Africa was under European control; by 1914 it had increased to almost 90 percent of the continent, with only Ethiopia (Abyssinia), the Dervish state (a portion of present - day Somalia) and Liberia still being independent.
Document 11: Atbarah River: The Atbarah River (; transliterated: Nahr 'Atbarah) in northeast Africa rises in northwest Ethiopia, approximately 50 km north of Lake Tana and 30 km west of Gondar. It flows about 805 km (500 mi) to the Nile in north-central Sudan, joining it at the city of Atbarah (). The river's tributary, the Tekezé (Setit) River, is perhaps the true upper course of the Atbarah, as the Tekezé follows the longer course prior to the confluence of the two rivers (at 14° 10' N, 36° E) in northeastern Sudan. The Atbarah is the last tributary of the Nile before it reaches the Mediterranean.
Document 12: Sobat River: The Sobat River is a river of the Greater Upper Nile region in northeastern South Sudan, Africa. It is the most southerly of the great eastern tributaries of the White Nile, before the confluence with the Blue Nile.
Document 13: Medjerda River: The Medjerda River (), the classical Bagrada, is a river in North Africa flowing from northeast Algeria through Tunisia before emptying into the Gulf of Tunis and Lake of Tunis. With a length of , it is the longest river of Tunisia. It is also known as the Wadi Majardah or Mejerha ().
Document 14: Nile: The Nile (Arabic: النيل‎, written as al-Nīl; pronounced as an-Nīl) is a major north-flowing river in northeastern Africa, and is the longest river in Africa and the disputed longest river in the world (Brazilian government claims that the Amazon River is longer than the Nile). The Nile, which is about 6,650 km (4,130 mi) long, is an "international" river as its drainage basin covers eleven countries, namely, Tanzania, Uganda, Rwanda, Burundi, the Democratic Republic of the Congo, Kenya, Ethiopia, Eritrea, South Sudan, Republic of the Sudan and Egypt. In particular, the Nile is the primary water source of Egypt and Sudan.The river Nile has two major tributaries, the White Nile and Blue Nile. The White Nile is considered to be the headwaters and primary stream of the Nile itself. The Blue Nile, however, is the source of most of the water and silt. The White Nile is longer and rises in the Great Lakes region of central Africa, with the most distant source still undetermined but located in either Rwanda or Burundi. It flows north through Tanzania, Lake Victoria, Uganda and South Sudan.  The Blue Nile begins at Lake Tana in Ethiopia and flows into Sudan from the southeast. The two rivers meet just north of the Sudanese capital of Khartoum.The northern section of the river flows north almost entirely through the Sudanese desert to Egypt, then ends in a large delta and flows into the Mediterranean Sea. Egyptian civilization and Sudanese kingdoms have depended on the river since ancient times. Most of the population and cities of Egypt lie along those parts of the Nile valley north of Aswan, and nearly all the cultural and historical sites of Ancient Egypt are found along river banks.
Document 15: Modern history: The major European powers laid claim to the areas of Africa where they could exhibit a sphere of influence over the area. These claims did not have to have any substantial land holdings or treaties to be legitimate. The European power that demonstrated its control over a territory accepted the mandate to rule that region as a national colony. The European nation that held the claim developed and benefited from their colony’s commercial interests without having to fear rival European competition. With the colonial claim came the underlying assumption that the European power that exerted control would use its mandate to offer protection and provide welfare for its colonial peoples, however, this principle remained more theory than practice. There were many documented instances of material and moral conditions deteriorating for native Africans in the late nineteenth and early twentieth centuries under European colonial rule, to the point where the colonial experience for them has been described as "hell on earth."
ground_truth: European imperial powers
sub_queries: What river does Tekezé River turn into? Answer: Atbarah River
Atbarah River >> continent Answer: Africa
who created the borders of Africa 's countries Answer: European imperial powers