Topic 4: Water World

1. What is the hydrological cycle?

  • What exists on Earth in three states: liquid, solid and gas
  • The hydrological cycle is a closed system (neither gains nor loses anything)
  • Water is either in stores (rocks, soil, lakes and oceans) or moving in transfers/flows (such as evaporation, precipitation etc.)

KEYWORD: Hydrosphere - consists of all water on planet

2. How can changes to the hydrological cycle affect human and ecosystem health?

  • Biosphere interacts with the hydrosphere e.g. trees intercepting rain; it then evaporates or continues to ground level. Plants store water and purify it.
  • Interactions with lithosphere include when water flows through and between layers of rock beneath the ground. This filters water and stores it for human use.

KEYWORDS: Biosphere - part of the earth and atmosphere in which living organisms exist

Lithosphere –rock layers of Earth’s surface (crust & upper mantle)

3. How do humans affect the quality of rivers (quantity and quality)?

  • Decline in water availability: population growth; agricultural demand; urbanisation, industrial development; climate change; tourism; energy
  • Decline in water quality: industry pollutes water with heavy metals; non-organic farming uses pesticides and herbicides which damage the environment and poison other living things

KEYWORDS: physical water scarcity - shortages occur when demand exceeds supply

economic water scarcity - when people simply cannot afford water, even if it is readily available

4.How does deforestation affect water supply?

  • Climate change is worsening the lack of water that is already a problem in many parts of the world (e.g. unpredictable rainfall; loss of trees that store water and keep it from evaporating)
  • Case Study: The Sahel - narrow belt of semi-arid land immediately south of Sahara Desert. Drought causes seasonal rivers and water holes to dry up and water table to fall; nomads with grazing animals and crops suffer; grass dies, and soil is eroded (or blown away) and cannot be used to farm = DESERTIFICATION (areas that become desert because of human actions)

5.How does over-abstraction of groundwater affect water supply?

  • Water quality threatened by: deforestation; disposal of hazardous waste; landfill; industrial discharge; crop spraying. Impacts vary but one significant threat is eutrophication where there is a lack of oxygen in the water and this causes natural life to die. Also, radioactive substances that find their way into water can cause cancer.
  • The least developed countries (e.g. Bangladesh) and most developed countries (e.g. UK) tend to have lower levels of pollution in their water. The countries that are beginning to develop (China and India) with factories and manufacturing tend to have the worst water quality.

6. How do reservoirs affect water supply?

  • Loss of land; in warmer countries they can cause disease (e.g. Malaria); drowns vegetation and creates methane gas (polluting)
  • Humans also interfere in the water cycle by cloud seeding (making it rain); deforestation; urbanisation; overabstraction; dam building; global warming.

KEYWORD: overabstraction - means too much water is being taken from the river, lake or other waste source

7. What are the costs and benefits of large scale water management projects?

  • Large-scale solutions to managing water supplies often involve dams - dams have many advantages such as reliable supply of water, generation of electricity and the creation of recreation areas; there are also disadvantages, such as loss of farmland and villages (flooded), increased humidity, sedimentation in lake, damage to wildlife routines (e.g. Salmon).
  • Case study: Three Gorges Dam - (see Moodle for your presentation) Basics - completed in 2009; 26 generators capable of creating 84.7 billion kWh of electricity a year; the impact on biodiversity has been devastating; 1.4 million people lost their homes (1200 villages destroyed!); water quality has deteriorated.
  1. What are the costs and benefits of small scale water management projects?
  • Small-scale sustainable solutions to managing water supply involve the work of NGOs such as WaterAid and Practical Action in assisting small communities. NOGs often use appropriate or intermediate technology that is simple, effective and can be maintained, repaired and renewed by local people using the water service (think of the basic guttering and tank made of bamboo - a local resource that is easily grown and harvested).
  • Several case studies were used based on the WaterAid DVD… (Remember to name countries: Bangladesh (Asia) and Bukino Faso (Africa)
  • KEYWORD: tube wells - are built where the water table is too deep to be reached by a hand-dug well