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Dam Building

Examine the costs and benefits of increased dam building for multipurpose water schemes


Dam Building

Examine the costs and benefits of increased dam building for multipurpose water schemes

What impacts do dams have on the hydrology (properties of water and its movement) of rivers?


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



costs & benefits of multi-purpose schemes




  • Less irrigation water in Egypt > reduced agricultural output

  • Possible 10% decrease in energy production of Egypt's S1 Dam

  • Increased channel erosion downstream as water level falls

  • Deposition of nutrients behind the dam reduces nutrient levels in the water downstream

  • Fewer nutrients in Nile river water reduces the amount of deposition of nutrients during river floods, reducing the fertility of agricultural lands around the Nile

  • Lake water behind the dam may increase the reproduction of mosquitos, increasing rates of malaria

  • Local communities will be displaced as the lake forms behind the dam

  • The weight of water behind the dam may contribute to seismic stress and the increased probability of earthquakes








exam question

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



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.

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Drainage Basin Management

Examine the growing importance of integrated drainage basin management (IDBM) plans, and the costs and benefits they bring

Drainage Basin Management

Examine the growing importance of integrated drainage basin management (IDBM) plans, and the costs and benefits they bring


Groundwater Tax to Conserve Water in Colorado

Click to read article

Click to read article


Describe the strategy used in Colorado and comment on its effectiveness.


evaluation of management strategies

Watch and note information about the Colorado river. What strategies have been used to conserve water and how effective have they been? How have different people reacted to this?


Exam Practice

Evaluate the strategies that have been used to resolve competing demands for water in one named river basin [10 marks]



Responses will depend on the river basin chosen. The river basin should be named and located.

The competing demands should be outlined and could include:

  • farming

  • industry

  • domestic supplies

  • recreation

  • power supply.

Strategies depend on the river basin selected but could include:

  • customer metering of water,

  • dams and reservoirs,

  • transfer of water,

  • zoning,

  • water use restriction (temporary or permanent),

  • customer advisory services,

  • the use of incentives for installation and/or retrofitting of water efficient equipment,

  • reduction of water use by the water utility,

  • leakage detection and repair programmes and pressure reduction,

  • regulation of the efficiency of water using appliances, especially in new buildings, and

  • use of reclaimed water (eg waste water/grey water) to reduce the need for fresh water supplies.

Good answers may discuss the varying power and/or perspectives of different user groups in relation to how a resolution is arrived at (commercial/human need for water may ultimately take precedence over the needs of ecosystems/wetlands, for instance) Another approach might be to evaluate the importance/success of strategies/actions.

Answers that do not refer to a named river basin and focus on demands only should not move beyond band C.

At band D, expect description of some strategies used to tackle water demand problems in a recognizable river basin.

At Band E, expect either more in-depth explanation of strategies, or some critical evaluation of how successful the strategies have been.

At band F, expect both.



Growing pressures on major wetlands and efforts to protect them, such as the Ramsar Convention


Growing pressures on major wetlands and efforts to protect them, such as the Ramsar Convention

  1. Watch the above video and make notes on:

  • the importance of wetlands

  • the consequences of wetland destruction

  2. Research and outline the objectives of the Ramsar Convention 


Areas that are regularly saturated by surface water or groundwater, including freshwater marshes, swamps and bogs. [IB Guide]

Areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres. [Article 1.1 of the Ramsar Convention text].



1. Read "Why Manage Wetlands" in the article above.


case study: stung treng ramsar site, cambodia

Stung Treng Ramsar Site is situated on the Mekong River between the Lao border and Stung Treng town in Cambodia.


It was designated as a Ramsar Site in 1999 because it contains a unique seasonally flooded riverine forest habitat, and is also home to the Irrawady Dolphin Orcaella brevirostris and the Mekong Giant Catfish Pangasianodon gigas.

More than 10,000 people live in or close to the Ramsar Site, and most of them rely on the Mekong for their food and livelihoods. Fish is the major source of protein and is also harvested to be sold. Many other species are also used, such as snails, crabs and frogs for food, and various plants for fuel wood, building, crafts and medicine. The regular flooding of the river supports rice farming using paddies.

The area is subject to a number of threats. Immigration is resulting in increased pressure on the wetland, with the clearance of land for agriculture and increased use of the natural resources. Upstream developments, such as hydro-electric dams and increasing water use by agriculture, are likely to change the river's flow regime, which will affect populations of fish and other aquatic biodiversity. Illegal harvesting activities such as fishing with explosives and collecting turtles and lizards are also having impacts. These pressures not only threaten the area's biodiversity, but also the livelihoods of the people who depend on it. (Source)


stung treng management plan

Click to open

Click to open


  • Collaboration with Mekong Wetlands Biodiversity Programme

  • Documenting value of wetland biodiversity

  • Sharing information about value with local communities

  • Mapping of data collected to show value of wetland biodiversity

  • Providing information to local decision makers to allow then to take this into consideration when planning in the region

  • Community fisheries committee set up in each of the 21 villages

  • Restricting fishing in deep pools and creating fish conservation zones



  • High rates of immigration to the area raise pressure on local wetlands and natural resources such as clean water, fish, wild fruit, wood

  • The Don Sahong dam in Laos on the Cambodia border (scheduled for completion in 2019) will greatly affect downstream discharge and the river’s flow regime - blocking the only channel for fish migration in the area, negatively impacting fisheries

  • 13% of the Cambodian population live in poverty, with 90% of the poor living in the countryside (source)

  • Limited funding and logistical support for wetland conservation and patrols

  • Local communities that rely on fishing may not view controls on fishing as beneficial


Note strategies and the obstacles to management presented in the video above.


exam practice

“Wetland management strategies are never a complete success.” Discuss this statement, with reference to one named major wetland. [10 marks]


mark scheme

Responses should clearly name, describe and locate one relevant major wetland. If more than one wetland is referred to, credit only the first.

Strategies (there should be at least two included) should be clearly outlined with respect to why they were needed and what their aims were. Strategies can then be evaluated in terms of how successful they have been (or not). Good answers may approach the strategies from different perspectives (eg biodiversity, human water security, tourism, etc).

Answers that do not refer to a specific wetland should not proceed further than band C.

At band D, responses should describe one or more strategies for a major named wetland, and may assert success/failure.

For band E, there should be either greater detail of the strengths and weaknesses of a range of (at least two) strategies, or a more sophisticated discussion of the veracity of statement (but with less factual support).

At band F, expect both elements.