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Hydrological Changes


Examine the hydrological changes resulting from the construction of dams and reservoirs, as well as the costs and benefits of multi-purpose schemes.

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Hydrological Changes


Examine the hydrological changes resulting from the construction of dams and reservoirs, as well as the costs and benefits of multi-purpose schemes.

 

hydrological changes

  • Reduction of downstream flow > contraction of inland lakes and seas e.g Aral Sea
  • Reduction of nutrients at mouth of river > negative impact on commercial fisheries at coast
  • Nutrients trapped behind dams > loss of mangrove forests in coastal areas 
  • Unnatural flow pattern of the river > riverbank erosion downstream > disruption to riverine species of birds and mammals
  • Fewer floods downstream > increased urbanisation on floodplain
  • Disruption to migratory patterns of river fish

Source

 
 

costs & benefits of multi-purpose schemes

CASE STUDY: GRAND RENAISSANCE DAM / ETHIOPIA

 
 
 
 

CASE STUDY: ASWAN HIGH DAM / EGYPT

 
 

CASE STUDY: MEKONG RIVER / LAOS, CAMBODIA, VIETNAM

THREE GORGES DAM / CHINA

TASK

  1. Access the GeoActive file
  2. Identify and note 5 facts about the Three Gorges Dam
  3. Highlight costs and benefits in two different colours
  4. Transfer these to your notes
 
 

IMPACTS OF HEP ON RIVERS IN SWITZERLAND

TASK

  1. Download and save this document
  2. Create a factfile of information on the Three Gorges Dam with images
  3. Identify and list costs and benefits in two horizontal columns
 
 

exam question

“Dams and reservoirs create as many problems as they solve.” Discuss this statement with reference to multi-purpose schemes. [10 marks]

 

markscheme

At least one example of a multi-purpose scheme should be named and located.

Solutions might include: the benefits of power generation, water supply, irrigation, transport, flood control, recreation and tourism.

These should be balanced against potential problems that could include: loss of land, displacement of population, loss of water through evaporation, silting, seismic problems, cost, diseases such as bilharzia, loss of nutrients due to flood control, salinization.

To access bands E and F, candidates should discuss both solutions and problems using at least one actual scheme.

Marks should be allocated according to the markbands.