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1. General Introduction
The Yellow River is an important water source for the northwestern and northern areas. It is the second longest river in China. It rises on the Yueguzonglie Basin of the northern slopes of the Bayankela Mountain of the Qinghai Plateau and flows east through the Loess Plateau and Huang-Huai-Hai Plain and empties into the Bohai Sea. The total length of the mainstream is 5,464 km with a river fall of 4,480m and a draining area of 795,000 km2. Its annual natural runoff is 58 billion m3.
The mainstream of the Yellow River traverses North China from the west to the east covering nine provinces and autonomous regions: Qinghai, Sichuan, Gansu, Ningxia, Inner Mongolia, Shaanxi, Shanxi, Henan and Shandong. The nationalities living within the river basin include the Han, Hui, Zang and Mongol, with a total population of 107,000,000, accounting for 8.6% of the national population.
The GDP of the Yellow River basin is 484 billion Yuan; the gross industrial output value is 601.5 billion Yuan, accounting for 5.3% of the national value; the gross agricultural output value is 150.9 billion Yuan, accounting for 6.1% of the national value (data of 1997).
2. Physical Geography
The Yellow River basin connects with the Bayankela Mountain on its west, the Yinshan Mountain on its north and the Qinling Mountain on its south, and runs east to the Bohai Sea. The contour of the basin goes from being high in the west to low in the east with a height difference that forms a three-level ladder from the west to the east and from the high to the low. This comprises the Qinghai Plateau - the riverhead; the Loess Plateau, and the low North China Plain - the plains.
Because the mainstream of the Yellow River has many bends, the actual flow of the river is 2.6 times that of a straight-line distance from river head to the estuary. The river course can be divided into the upper, middle, and lower reaches with 11 river stretches.
2.1 The upper reach
The upper reach is from the river head to Hekou Town of Tuoketuo County of the Inner Mongolia Autonomous Region, with a total length of water course of 3471.6 km and a catchment area of 428,000 km2 accounting for 53.8% of the catchment area of the river.
The basin above Duoshixia of Maduo County in the upper reach of the Yellow River is called the riverhead area. The total length of the water course from Maduo to the lower rivers is 2211.4 km with a river fall of 2,985m being the resource area of water power of the Yellow River. The total length of the water course from the lower river to Hekou Town is 990km with a catchment area of 174,000 km2 and a river fall of 246m.
2.2 The middle reach
The middle reach of the Yellow River goes from Hekou Town to Taohuayu of Zhengzhou City of Henan Province. The total length of the middle reach is 1206.4 km with a catchment area of 344,000 km2 accounting for 43.3% of the total catchment area, and with a river fall of 890m.
The Yellow River from Hekou Town to Yumenkou is the canyon stretch of the Jinxia Canyon with a total length of 725 km and a river fall of 607m. The vast Loess Plateau is on both banks of the canyon with loosen earth, which leads to severe water and soil erosion; the Hukou Fall on the downstream of the canyon is the only fall in the mainstream of the Yellow River. The total length of river course of stretch from Yumenkou to Tongguan is 125km with a river fall of 52m and frequent course changes of the river. The total length of the stretch from Tongguan to Taohuayu of Zhengzhou City is 356km with a river fall of 231m, including Loess Canyon and Jinyu Canyon, it is an important sources for water supply in the lower reaches of the Yellow River.
2.3 The lower reach
The Yellow River from Taohuayu to the sea entrance is part of the lower reach. It has a catchment area of 23,000 km2 which accounts for 3% of the total catchment area. The river course is 785.6 km long with a river fall of 94m. The main river stretch includes Taohuayu-Gaocun Stretch, Gaocun-Taochengpu Stretch, Taochengpu-Lijun Stretch and estuary stretch below Lijun.
The river course in the lower reach transverses the North China Plain and is restricted by embankments. The total area of the river course is 4,240km. The river course increases annually. The present riverbed is 3-5m higher than the adjacent land and some of the river sections like Caogang, at Fengqiu of Henan is 10m higher, which is the world-famous "suspended river" because of great sedimentation of mud and sand.
The estuary of the Yellow River lies between the Bohai Bay and the Laizhou Bay. The Yellow River transports a lot of sediments, most of it silt, to the estuary areas, in the coastal region. This deposit settles in the sea and creates the land - the Yellow River Delta.
2.4 Distributaries of the water system
The Yellow River has many tributaries of which 76 tributaries drain an area over 1000 km2. The drainage area reaches 580,000 km2, accounting for 77% of the flow collection area of the whole river. The main tributaries are the Baihe, Heihe, Taohe, Huangshui, Daheihe, Kuyehe, Wudinghe, Fenhe, Weihe, Luohe, Qinhe, Jindihe and Dawenhe River, in addition to the lakes: Zhaling, Eling and Dongping.
3. Society and Economy
The Yellow River basin covers 9 provinces or autonomous regions as Qinghai, Sichuang, Gansu, Ningxia, Inner Mongolia, Shaanxi, Shanxi, Henan and Shandong, 8 capital cities, 25 prefecture-level cities and 33 county-level cities. The total population of the basin is 107,000,000, accounting for 8.6% of the national population; among which the urban population is 25,060,000; the population of ethnic groups as Hui, Tibetan, Mongol, Dongxiang, Tu, Salar, Bao'an and Man is over 6,000,000, accounting for 10% of the total population of the basin. The urbanization rate is 23.45%, lower than the national urbanization rate of 30%.
The main cities within the basin are Xining, Lanzhou, Yinchuan, Xi'an, TaiYuan, Zhengzhou, Huhehaote, Jinan, Shizuishan, Baotou, Wuhai, Yan'an, Sanmenxia, Luoyang, Kaifeng and Dongying, which are important regions with dense population and modern social and economic system.
The cultivated land area of the Yellow River basin is 189,000,000 mu, accounting for 13.3% of the nation's land among which 75,900,000 mu is irrigated; 153,000,000 mu consist of the forest; and 419,000,000 of pasture and grass land. The moderate climate and solar energy are sufficient in most areas and provide great potential for the development of farming, forestry and animal husbandry.
Energy resources, a growing industrial base, and new booming cities are providing the foundation for the developing economy of the valley. The energy industry includes coal, electric power, oil and natural gas: the coal yield accounts for over half of the national yield, the oil yield accounts for about 1/4 of the national yield. This has become the largest industrial sector within the basin. The smelting industry of nonferrous metals such as lead, zinc, aluminum, copper, platinum, tungsten and gold and rare-earth industry has great potential.
4. Harnessing and Exploitation
Harnessing of the Yellow River has always been a great challenge for the Chinese people. Flood prevention was necessary for the prosperity of the nation and livelihood of the people in the Yellow River Valley.
Historically, the upper, middle and lower reaches of the Yellow River have been hit by continuous flood disasters. The most damaging feature of this disaster is the break-off water discharge in the lower reach of the river.
Since the establishment of the People's Republic of China (PRC), the strategies of harnessing the Yellow River have been developed and improved. Different strategies and technologies have been adopted in different periods: "keeping a broad flood plain with solid embankment" was implemented in the early days of the PRC; "disaster relief and water conservancy rejuvenating; water storage and sediment control" was implemented in the 1950s and 1960s; "trapping in the upper reach and discharging in the lower reach, separate detention on both banks" was implemented during the 1970s.
The utilization and protection of water supplies stimulated the need for water resource exploration and conservation. The strategy for water and soil conservation is to combine prevention and control; make areas receiving the most sediment the focus; and take the small valley as the basic unit. In addition, by using comprehensive methods from engineering, biology, and agriculture, careful attention was paid to the construction of the backbone for ditch control.
The development and improvement of harnessing strategies of the Yellow River plays a guiding role in controlling and exploring the Yellow River.
The dike is the main engineering solution created to prevent floods on the Yellow River.
Dikes have been built to control the river's flood runoff for millennia. Around 200 A.D. an effort was made to link up all the dike sections into a complete system. It was indeed a marvel in civil engineering, comparable in grandeur to the building of the Great Wall.
The dikes successfully protected the river's lower reach for eight centuries, with only relatively infrequent dike breaches. However it is not a simple matter to interrupt nature's plain-building process. The heavy sediment load brought down with the flood water started to accumulate in the flood plain between the dikes, raising the riverbed to such an elevation that it would be many meters above that of the surrounding land, turning it into a "suspended river."
The core focus for control of the river is the prevention of floods. Attention to clean river water irrigation and the safety of people living in the alluvial plain is also a part of flood prevention. These last several years have seen hundreds of million Yuan in local funds invested to regulate shoal protection works, groyne, battlement, bank revetment and other river improvement works.
Finally, water resources are abundant in the basin; as a result, a series of hydropower plants were built or are under construction - the Longyangxia, Liujiaxia, Bapanxia, Lijiaxia, Daxia, Sanmenxia, and Xiaolangdi Hydropower Plant.
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