Question: Battle of the Barrier Forts was fought along the river that has what total length?

full_context: Document 1: Battle of the Yalu River (1894): The Battle of the Yalu River (; Japanese:Kōkai-kaisen (黄海海戦 , "Naval Battle of the Yellow Sea") ) was the largest naval engagement of the First Sino-Japanese War, and took place on 17 September 1894, the day after the Japanese victory at the land Battle of Pyongyang. It involved ships from the Imperial Japanese Navy and the Chinese Beiyang Fleet. The battle is also known by a variety of names: Battle of Haiyang Island, Battle of Dadonggou, Battle of the Yellow Sea and Battle of Yalu, after the geographic location of the battle, which was in the Yellow Sea off the mouth of the Yalu River and not in the river itself. There is also no agreement among contemporary sources on the exact numbers and composition of each fleet.
Document 2: Pearl River (China): The Pearl River, also known by its Chinese name Zhujiang and formerly often known as the Canton River , is an extensive river system in southern China. The name "Pearl River" is also often used as a catch-all for the watersheds of the Xi ("West"), Bei ("North"), and Dong ("East") rivers of Guangdong. These rivers are all considered tributaries of the Pearl River because they share a common delta, the Pearl River Delta. Measured from the farthest reaches of the Xi River, the Pearl River system is China's third-longest river, 2400 km , after the Yangtze River and the Yellow River, and second largest by volume, after the Yangtze. The 409480 km2 Pearl River Basin (珠江流域 ) drains the majority of Liangguang (Guangdong and Guangxi provinces), as well as parts of Yunnan, Guizhou, Hunan and Jiangxi in China; it also drains northern parts of Vietnam's Northeast Cao Bằng and Lạng Sơn provinces.
Document 3: Qian River: The Qian River () is the name of a short section of the Xi River system and, thus, the greater Pearl River system in Guangxi, China. It is formed by where the Liu Jiang meets the larger Hongshui He east of Laibin, then flows southeast through Wuxuan. At Guiping it is joined by the more southerly Yu Jiang to form the Xun branch of the Xi Jiang. The Qian, for most of its length, winds between the Dayao and Lianhua Mountains, before entering the valley just below Xishan Mountain west of Guiping.
Document 4: Yu River (Guangxi): The Yu River (郁江 or 鬱江) (also called the Siang River) is a river in the south of China. It rises in two branches - the Zuo River (左江) and the You River (右江). The You flows roughly south-east from its source close to Baise City in Guangxi. The Zuo flows north-east from its sources in Vietnam: Peng River (Vietnamese: Bằng Giang) and Kỳ Cùng River (totally in Vietnam). They meet just west of Nanning. From here, it is known as the Yong Jiang (邕江) as it flows through Nanning before becoming the Yu . The Yu itself runs roughly northeast before joining the Qian River (黔江) at Guiping to form the Xun River.
Document 5: Battle of Nanyang: The Battle of Nanyang took place in 1641 and 1642 in Nanyang, an important city in Henan Province. This city is an ancient original place of the Silk Road. At the end of Ming Dynasty, many battles took place in Nanyang. In 1641, a person named Li Zicheng "(李自成)" attacked Nanyang and finally took control of the west of this city. In 1642, he attacked Nanyang again and took control of the whole city. And that war was called Battle of Nanyang, which lasted nearly a year.
Document 6: Xun River: The Xun River (Chinese: 浔江, pinyin: Xún Jiāng, jyutping: "Cham Gong") is a short section of the main branch of the Pearl River system upstream from the Xi Jiang in China. Although less than 150 km long, it is of considerable importance in Guangxi Province as it drains the majority of the province. The Xun River in name is formed by the Yu and Qian rivers, with the Qian being the greater of the two tributaries. The Xun then flows out of Guiping and through Pingnan, finally joining with the Gui Jiang in Wuzhou to form the Xi Jiang. The Xun is also a section of the Pearl's longest tributary.
Document 7: Battle of Macau: The Battle of Macau in 1622 was a conflict of the Dutch-Portuguese War fought in the Portuguese settlement of Macau, in southeastern China. The Portuguese, outnumbered and without adequate fortification, managed to repel the Dutch in a much-celebrated victory on 24 June after a three-day battle. To date, the battle remains the only major engagement that was fought between two European powers on the Chinese mainland.
Document 8: Battle of the Barrier: The Battle of the Barrier was fought between British and Chinese forces at the boundary separating Macau from the Chinese mainland on 19August 1840 during the First Opium War. Located in modern-day Portas do Cerco, Macau was connected to China by a narrow isthmus about 100 m wide and 1.2 km long. A wall called the "Barrier" was built across the isthmus in 1573, and it served as Macau's border.
Document 9: Lianjiang River: The Lianjiang River (), anciently kown as Huang River (), is a right-bank and the largest tributary of the North River in Guangdong. The river rises in Momianshi (磨面石) of Xingzi Town (星子镇) in Lianzhou county, and it runs generally northwest to southeast through Lianzhou, Yangshan and Yingde counties. It joins the Bei River at Jiangkouzui of Lianjiangkou Town (连江口镇), Yingde. The Lianjiang River has a length of 275 km , with its tributaries; it has a drainage basin area of 10,061 km2 .
Document 10: Xi River: The Xi River () is the western tributary of the Pearl River in China. It is formed by the confluence of the Gui and Xun Rivers in Wuzhou, Guangxi. It then flows east through Guangdong, and enters the Pearl River Delta just east of the Lingyang Gorge in Zhaoqing. The main branch of the Xi River flows southeast through the delta entering the South China Sea at Modao Men, just west of Macau. The major cities along the Xi include Wuzhou, Zhaoqing, and Jiangmen.
Document 11: Second Phase Campaign: The Second Phase Campaign of the Korean War was an extended military offensive by the Chinese People's Volunteer Army during the last week of November, 1950, and the first two weeks of December. The two major engagements were battles near the Ch'ongch'on River in the Chinese-designated Western Sector and Chosin Reservoir in their Eastern Sector. The Chinese opposed United Nations-authorized forces composed of American military and various allied forces.
Document 12: First Opium War: The First Opium War (第一次鴉片戰爭), also known as the Opium War or the Anglo-Chinese War, was a series of military engagements fought between the United Kingdom and the Qing dynasty over conflicting viewpoints on diplomatic relations, trade, and the administration of justice in China.
Document 13: Battle of Chinkiang: The Battle of Chinkiang was fought between British and Chinese forces in Chinkiang (Zhenjiang), Jiangsu province, China, on 21July 1842 during the First Opium War. It was the last major battle of the war. The Chinese force consisted of a garrison of Manchu and Mongol Bannermen. In command of the British forces was Sir Hugh Gough. Leading one brigade was future British field marshal Sir Colin Campbell. The British capture of this stronghold allowed them to proceed to Nanking. Fought near the confluence of the Grand Canal and Yangtze River, the battle effectively blocked operation of the Caoyun system, a transport network vital for the movement of grain throughout the empire. As a result, the Daoguang Emperor decided to sue for peace and agreed to sign the Treaty of Nanking, which brought hostilities to an end. Mass suicide was committed by the Manchu Bannermen who were defending the city.
Document 14: Battle of the Barrier Forts: The Battle of the Barrier Forts (also known as the Battle of the Pearl River Forts) was fought between American and Chinese forces in the Pearl River, Guangdong, China in November 1856 during the Second Opium War. The United States Navy launched an amphibious assault against a series of four forts known as the Barrier Forts near the city of Canton (modern-day Guangzhou). It was considered an important battle by the British whose interest lay in capturing Canton.
Document 15: Red River system: The Red River system is a network of rivers surrounding the main river - Red River in North Vietnam. These branches of the system contribute to or receive water from Red River. Red River system, joining with the Thái Bình river system in the northeast, creates the Red River Delta - the second largest delta in Vietnam. Because of the close relation between Red River system and Thái Bình river system, the two system are known as the common name "Red and Thai Binh rivers system". Alluvium of the Red River system creates the central and south Red River Delta. Two banks of the rivers are protected by a great dyke system.
ground_truth: 2400 km