Yalu River ecosystem

• Category: Inland Aquatic Biomes.
• Geographic Location: Asia.
• Summary: The Yalu River is the border river between China and North Korea, an area rich in biodiversity and vital to migrating raptors and waterfowl.

The Yalu River is located on the border between China and North Korea. It was known in ancient times as Mazishui (Ma Zi River) and Paesu during early Chinese historical periods. Starting in the Tang Dynasty, it became known as the Yalu River. The word yalu in Chinese means “duck green.” It is believed it was so named because the clear waters of the river appear to be the same color as the feathers on a duck’s head. Another possible source of the name is the combination of two river names, the Ya River and Lu River, which do come together to form the Yalu.

The Yalu River originates in the Changbai Mountains in northeastern China, then flows southwest through the cities of Changbai, Linjiang, Kuandian, and Dandong along the border between China and North Korea. As the various tributary branches of the Yalu combine, the river’s southward flow takes it into the Yellow Sea. Approximately 493 miles (795 kilometers) long, the Yalu covers an area of over 12,260 square miles (31,750 square kilometers). The river ranges 459–1,279 feet (140–390 meters) wide in various sections; at its estuary, the Yalu is 3 miles (5 kilometers) wide.

Except for small areas of basalt in the upper portions, the entire riverbed is mostly Precambrian rock formations; the river flows through deep river valleys in rugged mountainous terrain in most places. There are many waterfalls and hidden reefs. The lower part of the Yalu has slow-running water; it is often used for timber transportation. Alluvial sediment is plentiful in this segment, and the water is very shallow in winter. In some places, even a raft cannot float downriver easily.

South of Ji’an City, the river opens onto a coastal plain; the water runs deep and swiftly in this area. It is a spot conducive to hydroelectric plants, and several have been built there. The water then slows once more, depositing more alluvial sediment to form many large deltas and islands along the estuary to the Yellow Sea. The rate of sedimentation ensures that the delta grows and that the alluvial area of the river becomes shallower, with mudflats and reed islands growing.

The annual precipitation in the Yalu River area is 34–43 inches (870–1,100 millimeters) and is higher in the downstream region than upstream. Summer floods occur annually starting in mid-June, and the monthly flow reaches its highest point in August. The summer water flow makes up about 60 percent of the total water flow in an entire year, with the average annual flow rate at around 3,038 cubic feet (926 cubic meters) per second. The water volume decreases in the fall, and the river enters its dry season in October. A series of reservoirs has changed the character of these natural seasonal flows to a great extent, however.

Biodiversity

The Yalu River area is considered a humid, temperate continental climate zone. The winter is very cold, and the summer is warm. There are vast differences in terms of natural conditions between the upper and lower parts of the Yalu River. The river surface is usually frozen from November to February.

The ample precipitation encourages the growth of conifer and deciduous trees, and vast forests cover much of the landscape. Forests provide ideal habitats for various wildlife; commonly found mammals along the riverbanks include the wild boar, wolves, tigers, leopards, bears, and foxes. Birds such as the pheasant and many others are found here. In Liaoning Province, a major migration route and resting place for waterfowl and raptors, at least 163 species of waterbirds and 46 species of shorebirds have been recorded among the more than 418 total avian species cataloged here. Surveys indicate that some migratory shorebird populations using the estuary have declined, including bar-tailed godwit and great knot.

Some 90 fish species in the Yalu River give proof of a fairly robust riparian habitat. Most are native species, including types of carp and eel. They must contend, however, with a number of introduced fish species, such as silver carp, bighead carp, grass carp, Changchun bream, and triangular bream. Each of these is considered a favorable type for subsistence or commercial fisheries.

Threats

Threats to the Yalu River include human-induced changes, such as the addition of hydroelectric plants that change the nature of the river and destroy habitable areas, as well as the increased pressure upon farmlands to produce more and more food. Climate change threats include greater chance of floods. A 2020 study published in the journal Hydrology and Earth System Sciences found that flooding on the river steadily increased from the year 1000 to 1940. Following a decrease during the latter half of the twentieth century, flooding on the Yalu once again rose in the 2010s. The 2020s also saw the Yalu receiving significant rains, with the river region flooding in 2020, 2023, and 2024. The 2024 floors were severe, with heavy rains causing the Yalu to flood, significantly damaging some areas along the river, according to Daily NK. Combined atmospheric changes and direct human intervention, in the forms of logging and land clearance for more cropland, are degrading the capacity of some ecosystems along the Yalu River to keep pace. Flora and fauna that cannot adapt must move to higher ground and, in some cases, find shelter and sustenance in the expanding estuary area in others.

Bibliography

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Gao, Jian-hua, Shu Gao, Yan Cheng, Li-xian Dong and Jing Zhang. “Sediment Transport in Yalu River Estuary.” Chinese Geographical Science 13, no. 2 (2002).

"Green Fish Farming: Fishermen in NE China Protecting Yalu's Water Quality." CGTN, 5 Apr. 2021, news.cgtn.com/news/2021-04-05/VHJhbnNjcmlwdDUzNDYz/index.html. Accessed 13 Mar. 2026.

Liu, Y. "Population Changes of Migratory Shorebirds at Yalu Jiang Estuary Wetland, a Critical Refuelling Sites along the East Asian-Australasian Flyway." J Biomed Res Environ Sci, vol. 6, no. 3, 17 Mar. 2025, pp. 256-265, doi:10.37871/jbres2080, www.jelsciences.com/abstracts/1898.[1] Accessed 13 Mar. 2026.

Sheng, Hui, et al. “Frequency and Magnitude Variability of Yalu River Flooding: Numerical Analyses for the Last 1000 Years.” Hydrology and Earth System Sciences, vol. 24, 2020, pp. 4743–4761, doi.org/10.5194/hess-24-4743-2020. Accessed 13 Mar. 2026.

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