World Multipurpose River Projects

Lessons

Senior 6 · Geography

World Multipurpose River Projects

4 lessons

Lesson 4 of 4

Case Studies: the Huang He Project and the Tennessee Valley Authority

45 min

China's Sorrow

The Huang He (Yellow River) is about 5,464 km long, the second-longest river in China, with a basin of 795,000 km². Its middle course crosses the Loess Plateau, a vast area of fine, wind-blown soil that washes easily into the river: where the river leaves the plateau it has carried about 1.6 billion tonnes of silt a year, more than any other river in the world, and the middle reaches supply 92% of it. On the North China Plain the river slows and drops much of that silt on its bed. Over centuries people built the levees higher, the bed rose with them, and the river came to flow above the surrounding plain (Figure 1).

Figure 1. Cross-section of the lower Huang He as a raised river (not to scale). Drawn by Ganzaa.

When such a river breaks its levees, it pours down onto farms and towns. The flood of 1887 killed an estimated 900,000 to 2 million people and that of 1931 between 1 and 4 million, among the deadliest disasters in history. In 1938 Nationalist troops deliberately broke the levees near Huayuankou to slow the Japanese advance, killing some 500,000 to 900,000 people. No wonder the river was called "China's Sorrow".

Definition

Loess: fine, yellowish, wind-deposited silt that is fertile but very easily eroded by water.

Levee (dyke): a raised bank along a river, natural or built, that keeps the river in its channel.

Raised (suspended) river: a river whose bed has been built up by deposition until it lies above the level of the surrounding floodplain, held in only by its levees.

Check dam: a small dam built across a gully to trap soil and slow runoff.

Case study 1: the Huang He project

In 1955 China adopted a comprehensive plan to control the Yellow River and use its water, prepared with the help of Soviet engineers. It combined three ideas: a "staircase" of dams on the main river, soil and water conservation on the Loess Plateau, and irrigation and flood control on the plain.

Part of the project	What was done
Sanmenxia Dam (1957–1960)	The first great dam on the river, for flood control and power. About 400,000 people were moved. Its reservoir filled with silt so quickly that floods backed up into the Wei valley upstream; it had to be rebuilt with extra tunnels to pass sediment through, and its power and storage were cut.
Upper-river dams	A series of power dams in the gorges of the upper river, where there is little silt: Longyangxia, Lijiaxia, Liujiaxia and others, with a combined capacity of about 5,600 MW (reported in 2000).
Xiaolangdi Dam (completed 2001)	154 m high, six 306 MW turbines (1,836 MW). Besides power, irrigation and flood control, it releases planned surges of water each year that scour silt out of the lower channel and carry it to the sea.
Loess Plateau conservation	Terracing hillsides, building check dams in gullies, planting trees and grass, and banning grazing on steep slopes, so that less soil reaches the river.
Lower river	Strengthened and raised levees, flood-diversion areas, and irrigation canals that water the wheat and maize of the North China Plain.

Achievements: there has been no catastrophic levee breach on the lower river since the project began; the plain has become one of China's main grain-producing regions; the dams supply electricity to the cities of north China; and the silt reaching the river has fallen sharply.

Problems: reservoir sedimentation (Sanmenxia); people displaced; demand for water from farms, cities and industry grew so fast that in the 1990s the lower river often ran dry, and in 1997 it failed to reach the sea for 226 days; pollution from industry and towns; and the bed of the lower river still lies above the plain, so the danger has been reduced, not removed.

Worked example 1: how fast does the river bed rise?

Problem. In an illustrative model, 300 million tonnes of silt settle each year in the lower Huang He, in a channel 700 km long and 5 km wide between the levees. Deposited silt has a density of 1.4 tonnes per m³. How much does the bed rise each year, and in 50 years?

Solution.

V = \frac{3.0 \times 10^{8}\,\mathrm{t}}{1.4\,\mathrm{t\,m^{-3}}} \approx 2.14 \times 10^{8}\,\mathrm{m^3} \qquad A = 700\,000 \times 5000 = 3.5 \times 10^{9}\,\mathrm{m^2}

\text{Rise per year} = \frac{2.14 \times 10^{8}}{3.5 \times 10^{9}} \approx 0.061\,\mathrm{m} \approx 6\,\mathrm{cm}; \qquad \text{in 50 years} \approx 3\,\mathrm{m}

Interpretation. A few centimetres a year becomes metres within a lifetime, so levees must be raised again and again. That is why the long-term answer is to stop the silt at its source on the Loess Plateau and to flush it through to the sea, as Xiaolangdi does.

Case study 2: the Tennessee Valley Authority, USA

In 1933, during the Great Depression, the Tennessee Valley in the south-eastern United States was one of the poorest parts of the country. Rural incomes averaged US$ 639 a year, forests had been cut, soils were eroded, floods were frequent and about 30% of the people suffered from malaria. On 18 May 1933 the US Congress created the Tennessee Valley Authority (TVA), part of President Franklin D. Roosevelt's New Deal, to develop the whole river basin as one unit. Its first dam, Norris Dam on the Clinch River, was begun in October 1933 and finished in 1936; in its first 11 years TVA built 16 hydroelectric dams.

Aim	What TVA did	Figures (TVA, 2026)
Flood control	Reservoirs store floodwater and release it slowly	49 dams on the river system
Navigation	Dams and locks turned the river into a deep, year-round channel	14 navigation locks; the 652-mile (1,049 km) river carries more than 50 million tons of cargo a year
Electricity	Cheap power for farms, homes and industry	29 conventional hydroelectric sites; power for about 10 million people in parts of seven states
Agriculture and soil	Developed fertilisers, taught crop rotation, contour ploughing and terracing	Restored eroded farmland
Forestry and health	Planted trees on eroded slopes; drained breeding sites to eliminate malaria	Malaria was wiped out in the valley
Regional development	Jobs for the unemployed; new industries; lakes for recreation	Chattanooga, Knoxville and other cities grew

Problems and criticisms: more than 125,000 valley residents (about 15,000 families) were moved, and farms, cemeteries and small towns were flooded; the best valley-floor farmland was lost under reservoirs; as demand grew, TVA built coal and nuclear power stations, with their own pollution and risks, such as the failure of a coal-ash pond at the Kingston plant in December 2008; and critics argued that a government agency should not compete with private companies.

Worked example 2: why rivers matter for freight

Problem. The Tennessee River carries more than 50 million tons of cargo a year (TVA, 2026). If a road truck carries 25 tons, how many truck journeys would be needed to move the same cargo? What does this suggest about the value of navigation?

Solution.

\frac{50\,000\,000}{25} = 2\,000\,000 \text{ truck journeys a year}

Interpretation. About 5,500 trucks a day would be needed. Barges on a regulated river move bulky goods such as coal, grain, gravel and chemicals cheaply, with less fuel per tonne and less road damage. This is one reason why the TVA's locks and deep channel helped industry to grow in the valley.

Comparing the two projects

	Huang He project	Tennessee Valley Authority
Main problem to solve	Silt and catastrophic floods	Poverty, floods, erosion and disease
Approach	Staircase of dams plus conservation of the Loess Plateau	Whole-basin authority: dams, power, navigation, farming, forests, health
Key lesson	Treat the cause (soil erosion upstream), not only the symptom (floods)	One authority planning a whole basin can drive regional development
Main cost	Sedimentation, displacement, water shortage downstream	Displacement, loss of farmland, later pollution from thermal power

Warning

Common mistakes

Describing the TVA as "a dam". It is an authority that manages a whole river system, including 49 dams.
Saying the Huang He floods because of heavy rain alone. The deeper cause is silt from the Loess Plateau raising the bed above the plain.
Forgetting the lessons for Africa. The best answers apply them: catchment conservation for the Nile and Kagera basins, and basin-wide authorities such as the Nile Basin Initiative.

Encyclopaedia Britannica: "How the TVA Changed Rural Life". As you watch, list the changes the TVA brought to farm families, and decide which of them a river basin authority could bring to rural Rwanda.

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Practice

Explain why the Huang He is called "China's Sorrow".
Using Figure 1, explain how a river comes to flow above its floodplain.
Explain why the Sanmenxia Dam had to be rebuilt.
State four methods used to reduce soil erosion on the Loess Plateau.
In an illustrative model, 200 million tonnes of silt (density 1.25 t per m³) settle each year on a channel bed 800 km long and 4 km wide. Calculate the yearly rise of the bed in centimetres.
Describe five aims of the Tennessee Valley Authority and how each was achieved.
"The Tennessee Valley Authority is a better model for Rwanda than the Huang He project." Discuss.

Show answersHide answers

Its floods have killed millions of people (1887, 1931, 1938) because silt raises its bed above the plain, so levee breaches are catastrophic.
The river slows on the plain and deposits silt on its bed; people raise the levees to hold the river in; the bed keeps rising inside them until it lies above the plain.
Its reservoir filled rapidly with silt, which backed floods up into the Wei valley; it was rebuilt with tunnels to pass sediment through, and its storage and power output were reduced.
Any four: terracing; check dams in gullies; planting trees and grass; banning grazing on steep slopes; contour ploughing.
V = 200,000,000 ÷ 1.25 = 1.6 × 10⁸ m³; area = 800,000 × 4,000 = 3.2 × 10⁹ m²; rise = 1.6 × 10⁸ ÷ 3.2 × 10⁹ = 0.05 m = 5 cm.
Flood control (reservoirs at 49 dams); navigation (locks and a deep channel); electricity (hydro dams, then other power stations); soil conservation (fertilisers, contour ploughing, terracing); forestry (tree planting); health (malaria control); regional development (jobs, industry, recreation).
For the TVA: Rwanda's needs, like the Tennessee Valley's in 1933, are rural development, electricity, erosion control and jobs, and the TVA treated a whole basin. For the Huang He: Rwanda's steep, eroding hills feed silt into the Nyabarongo and Akagera, so conservation of the catchment, central to the Huang He project, is vital. Rwanda's rivers are small and shared with neighbours, so basin cooperation (Nile Basin Initiative, Rusumo) matters. A balanced answer takes lessons from both.

1China's Sorrow

2Case study 1: the Huang He project

3Case study 2: the Tennessee Valley Authority, USA

4Comparing the two projects

China's Sorrow

Case study 1: the Huang He project

Case study 2: the Tennessee Valley Authority, USA

Comparing the two projects