Dams and Reservoirs

You are to:

  • Examine the hydrological changes resulting from the construction of dams and reservoirs.

  • Examine the costs and benefits of dams and reservoirs as part of multipurpose river management schemes.

Key terms

  • Dam: a barrier constructed to hold back water and raise its level, forming a reservoir used to generate electricity or as a water supply.
  • Reservoir: a large natural or artificial lake used as a source of water supply.

  • Multipurpose scheme: a scheme or project built for more than one purpose. For example to prevent flooding as well as irrigate the land and also generate HEP

Background: Dams and Reservoirs.

What are they for? How do they affect the hydrological cycle?

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The problems with dams.

Complete this worksheet dams_and_reservoirs_worksheet.docxusing all of the information above. You should also refer to pages 118 &119 in your course companion.

Now read the Geofile below and make notes on the impact of big dams using the SEEP acronym (Social, Economic, Environmental and Political).
Geofile 410 – Big Dams.pdf

We will now look at the environmental impacts in more detail.
First of all read this article from the BBC and then the Geofile below. Use both documents to make notes on the environmental impact of big dams. Make sure you pay attention to the hydrological changes as well.
399 River management scheme – blessing or curse.pdf

Restoring the River: The Grand Canyon Releases.

Use this page to explain what can be done to reduce some of the damage that dams do to the river downstream.

Case Study: The Three Gorges Dam

What is a multi-purpose scheme? Can you give named examples?

What are the different ‘purposes’ of the Three Gorges Dam?

Create a table to outline the advantages and disadvantages of the dam. You may wish to think about its implications in the following areas:

Positives: agriculture, irrigation, energy, navigation, fishing, flood control, employment.

Negatives: culture, religion, settlement, hydrology (erosion and deposition), pollution, river ecology, economic cost, geological instability.

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Since 1985, International Rivers has been at the heart of the global struggle to protect rivers and the rights of communities that depend on them.

Rising from the waters of the Yangtze River, the Three Gorges Dam stands more than 40 storeys high. The scale and scope of the project is stunning.

The dam stretches for over 2km (1.25 miles), took tens of thousands of workers over a decade to build and cost more than $40bn (£25bn).

Designed to control the flooding of the mighty river, the dam produces vast amounts of electricity – the equivalent of 11 nuclear power stations.

It is one of the most impressive feats of civil engineering anywhere in the world and stands as a symbol of China’s progress over the last 20 years.

Unsurprisingly, the Communist Party has hailed the mega-project as a triumph. But the dam has come at an enormous environmental and human cost. (Martin Patience, 2 November 2012, www.bbc.co.uk/asia)

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Three Gorges dam faces major flood test

China’s massive Three Gorges dam faces the biggest test so far of its flood control as torrential rains swell the rivers that feed it

China’s gargantuan Three Gorges dam passed its toughest test yet as it controlled and released the flood waters that filled its reservoirs following recent torrential rains. Wednesday 21 July 2010 15.24 BST

Three Gorges Dam has caused urgent problems, says China

The hydroelectric project requires action to curb pollution, counter risks of natural disasters and improve living standards

Yangtze river dolphin driven to extinction


The Yangtze river dolphin, until recently one of the most endangered species on the planet, has been declared officially extinct following an intensive survey of its natural habitat.

China admits problems with Three Gorges Dam

Drought forces State Council to confront downstream water-supply problems.

China Rivers at the Brink of Collapse

“China’s rulers have traditionally derived their legitimacy from controlling water. The country ranks only sixth in terms of annual river runoff, but counts half the planet’s large dams within its borders. A new report warns that dam building has brought China’s river ecosystems to the point of collapse.

Exam Question:

“Multi-purpose schemes result in more benefits than problems.” Discuss this statement, referring to both physical and human impacts. (10 marks)

Mark scheme

Multi-purpose scheme (MPS) should be named and located.

Dams and reservoirs likely to be included, built for a range of purposes eg water supply, electricity, irrigation.

MPSs may also incorporate navigation, recreation, climate regulation or may have other purposes. However, solutions may not always have been fully realized in practice ie problems only partially solved.

Physical and human problems often associated with MPSs include: forced migration, loss of farmland and historic features/settlements, transport interruption, biodiversity loss, increased siltation, changing river load downstream (and water temperature change with ecosystem impacts), increased evaporation, seismic activity.

To access band D, some benefits and/or problems associated with a MPS should be described. For bands E and F, discussion is provided or a conclusion arrived at.

Marks should be allocated according to the markbands.