Huang River

The Huang (Yellow) River, at 5,400 kilometers in length, is China's second-longest river. It originates in Qinghai Province and flows northeast and then east across the top of its great bend. At Hekouzhen in Inner Mongolia the river turns south for 800 kilometers before again turning northeast to cross the North China plain and reach the sea at its delta at the Bohai Gulf.

The river's drainage area of 745,000 square kilometers ranks it twenty-ninth among the world's rivers, but its discharge of 1,365 cubic meters per second is far less than that of many rivers of comparable drainage area. The Mekong River, for example, has a similar drainage area but more than ten times the flow of the Yellow River.

In spite of its small flow, the Huang River has been infamously difficult to control, repeatedly flooding and changing course throughout history. Two main factors contribute to the river's tendency to flood. The first is a seasonal rainfall pattern that causes extreme and often sudden variations in water levels, particularly in summer and fall.

The second factor is the river's massive silt burden. As the river travels south between Sanxi and Shaanxi Provinces it crosses the highly eroded loess plateau. Loess is a fine-grain, nutrient-rich but easily eroded soil that gives the river its characteristic yellow color. In the rainy season, sudden downpours in the barren erosion gullies of the loess plateau send streams of mud cascading into the river.

This results in a silt content that has been measured as high as 37 kilograms of silt per cubic meter of water. When the river leaves the mountains and turns east to cross the relatively flat North China plain, perhaps one-third of this silt settles out, causing the river channel to fill and rise. Eventually the river breaks out of its elevated bed and finds a new, lower course to the sea.

All of China's early dynasties emerged on or near the Huang River, and river control played an important part in imperial politics from earliest times. Emperor Yu, the legendary founder of China's first dynasty, the Hsia (2207-1766 все), supposedly established his right to the throne by subduing the Huang River. The Yuan (1279-1368) dynasty marked the beginning of a more active approach to control of the river.

The Yuan constructed the Grand Canal to allow the shipment of grain from the Yangtze River valley to the capital at Beijing. Because the canal incorporated part of the Huang River, controlling the river became a central concern of the imperial state. The Ming (1368-1644) and Qing (1644-1911) dynasties created an extensive and growing system of dikes, locks, spillways, and revetments (embankment facings) to keep the river in its bed and the grain flowing north.

By the middle of the nineteenth century, the Huang River control system was one of the largest and most expensive projects of imperial administration, but devastating floods continued to be a problem.

Beginning in the 1950s, the People's Republic of China attempted to use both reforestation of the loess plateau and the construction of dams to reduce silting and regulate the flow of the Huang River. Initial efforts at reforestation failed, and silting behind Huang River dams has severely limited or eliminated their hydroelectric potential.

Since the early 1990s soil conservation efforts in the loess plateau have reduced the silt burden carried by the river, but extensive agricultural use of water in the upper reaches has so reduced flow that the downstream bed has gone dry for extended periods. The Huang River valley is also troubled by air pollution, water pollution, and a growing demand for water resources that will only increase as China continues to industrialize.