Amur/Heilong River proper is formed by confluence of Argun and Shilka and has at that point annual flow volume of only 26 km3 or just 7% of its volume of discharge into the ocean 2800 kilometers downstream. On its way the ocean Amur receives countless tributaries, some of which are quite comparable in length and flow volume with the main channel.
The Zeya River is the largest left-bank tributary of the Amur-Heilong. The total length of the Zeya is 1,242 km and the watershed covers 233,000 km2. The Zeya originates at the southern slopes of the Stanovoy (Wai Xing’an) Mountain Range. In its upper reaches the Zeya is a mountain river flowing between high and abrupt mountain slopes, then, blocked by the Tukuringra Range it creates the Upper-Zeya lowlands, now almost flooded by the Zeya Hydropower Plant (HPP) Reservoir built in 1975. After passing the Tukuringra Gorges and its confluence with the Selemzha River, the Zeya flows onto the plains where its current slows, the valley widens, and many tributaries enter the main flow. Average annual discharge is 55 km3.
The Bureya River is the second largest left-bank tributary of the Amur-Heilong. The Bureya originates on the northern slopes of Bureinsky Mountain Range, is 739 km in length, and covers a watershed of about 70,700 km2. In its lower reaches it flows through the Zeya-Bureya Plains where it braids into many side streams and channels. The annual average discharge of the Bureya is 29 km3. The water regime and environment of the Bureya were altered by the Bureya dam built in 2003.
The Songhua River flows from Tianchi (Pool of Heaven) Lake in the Changbai Mountains. The lake is shared with North Korea, therefore about 100 km2 of the Amur-Heilong watershed lies within the the Democratic Peoples Republic of Korea (DPRK). The rest of gigantic Songhua subbasin belongs to China. In the upper reaches the stream is called the Second Songhua River, and at its confluence with the Nen River it becomes the Songhua River for the last 939 km of its journey to join the Amur-Heilong. The Songhua basin covers about 560,000 km2 and annually discharges approximately 82 km3 into Amur River. If the Nen River (northern source) is considered the main source, then the total river length is 2,309 km. In contrast, if the Second Songhua River (the southern source) is taken as the main source, then the total length is shortened to 1,897 km. Both Nen and Second Songhua Rivers are obstructed by hydropower dams, and a new dam is under construction in 2007 on Songhua River downstream from Harbin. Based on its width, some ancient geographers described the Amur (ancient: “Shilkar”) as a tributary of the Songhua River (ancient: “Shungal”) .
The Ussuri-Wusuli River is a Russia-China border river and the second largest right-bank tributary of the Amur-Heilong after the Songhua. Every Russian knows that Ussury originates in the southern Sikhote-Alin Ridge in Russia near Oblachnaya (Cloudy) Mountain. However from Chinese prospective the source of Wusuli is Xinkaihu/Khanka transboundary lake. The Ussury-Wusuli watershed covers 193,000 km2 of which about 30% lies within China with the remainder in Russia. The length of the River is 897 km. Because of its geographic location near the Pacific Ocean and its consequently abundant precipitation, the Ussuri-Wusuli is a water-rich tributary of the Amur-Heilong. Its average annual discharge is approximately 50 km3.
The main stream of the Amur-Heilong River proper is often referred to as a river of three reaches, Upper, Middle, and Lower. Upper Amur shared by Russia and China for 937 km from the confluence of Shilka and Argun Rivers downstream to the mouth of the the Zeya River at the Russian city of Blagoveshensk on the left bank. The Middle Amur-Heilong is also shared by Russia and China along the 950 km reach of the main stream from the mouth of the Zeya River downstream to the confluence of the the Ussuri-Wusuli River near the Russian city of Khabarovsk. The Lower Amur lies completely within Russia and stretches 947 km from the mouth of the Ussuri River to the Amur Estuary (Amursky Liman). The river forms the border between China and Russia for over 3,000 km, making it one of the world’s longest border rivers.
Misty morning in Dragon River Gorges of Small Hinggan
(Photo by E.Simonov)