Water World

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  • Created by: Maybury
  • Created on: 08-04-17 20:25

The Hydrological Cycle

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The Hydrological Cycle

The hydrological cycle

  • The movement of water on a global scale.  This is a closed system as the amount of water globally is fixed.

The drainage basin system

  • The area of land drained by a particular river system and is one component part of the hydrological cycle.  The system is an open system so the water level in a drainage basin is not fixed.

The role of the biosphere and lithosphere in regulating the hydrological cycle

  • The earth’s lithosphere stores water in soils and rocks.
  • The biosphere regulates the hydrological cycle as trees slow precipitation from reaching the ground by interception. Trees also input water to the hydrological cycle through transpiration.
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How climate change affecting the water supply in t

The Sahel is located in North Africa, south of the Sahara desert.  It runs from coast to coast through countries such as Sudan, Chad, Niger and Mali.

How is rainfall changing in the Sahel?

  • Rainfall in the Sahel has decreased due to climate change
  • From 1970 to 2005 there have been 22 years with below average rainfall

How are groundwater levels changing in the Sahel?

  • The depth to the water table is increasing over time
  • This shows groundwater levels are decreasing

How else may the hydrological cycle be changing in the Sahel?

  • As temperatures are increasing, there will be more evaporation
  • Lakes and rivers may dry out
  • There may be less interception due to desertification (loss of vegetation) so the area may be prone to flash flooding
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The impacts of unreliable and insufficient water s

Unreliable and insufficient water supply caused by seasonal rainfall and a trend of decreasing rainfall has many consequences on the Sahel region.  Rapid population growth, overgrazing and over-cultivation along with lack of government funding in water projects have all contributed to the problem.  Drought is an ongoing and severe issue in the Sahel.  Recent droughts have occured in 2005, 2010, 2012 and 2016.

  • 2010 - 10 million were affected by drought (mostly in Niger and Chad)
  • 2012 - 26% reduction in crop production in the Sahel with up to 19 million affected by food shortages
  • 2012 - 10-15% rise in child malnutrition in Burkina Faso
  • 2016 - UNICEF has stated that more than 10 million people will need food aid in Ethiopia
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Consequences of human activity on water quality -

  • Water quality decreases with distance downstream as more pollutants are added to the water
  • Throughout the 1900s, water quality in the Rhine decreased as industrial and agricultural pollution increased -> in 1930s last salmon was caught
  • By 1970, river declared ecologically dead
  • 1980s decrease in pollution and increased water purification -> greater water quality
  • 1986  - fire in Sandoz chemical plant -> thousands of gallons of toxic chemicals washed into the Rhine
  • 1987 - Rhine Action Programme -> in 1997 salmon reintroduced into river, by 2000 50% decrease in pollution
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Consequences of human activity on water quality -

Intensive agriculture -> Netherlands and southern Germany

  • Fertilisers cause excessive growth in plants, resulting in deoxygenation (eutrophication)
  • Bacteria use up large amounts of oxygen to break down the waste
  • Lack of oxygen damage fish and other water life

Sewage disposal -> Cologne, Germany

  • Most sewage is sent to treatment works where waste is removed leaving sewage sludge which is discharged into the river
  • Some untreated sewage also reaches the river

Industrial discharge -> Sandoz chemical plant, Switzerland

  • There are many steel and chemical works along the Rhine
  • This waste is harmful to river life, discolours water and gives off an odious smell
  • Power stations extract water for cooling before returning it back to the Rhine at a higher temperature which contains less oxygen
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How human activity disrupts water supply

Over-abstraction e.g. Thames Valley, southern England

  • Water is over-abstracted -> Reduced river flow & some tributaries run dry -> Damage to eco-systems & increased use of groundwater due to drought -> Lowered water table across the Thames basin

Reservoir building e.g. Grafham water, Huntingdon, UK

  • Reservoir built -> Reduced run-off downstream -> increased drought
  • Reservoir built -> Used for water storage -> Add new stores to the water cycle
  • Reservoir built -> Loss of land as villages and farmland flooded -> Vegetation drowned        ->  Methane released as it decays

Deforestation e.g. Amazon rainforest

  • Deforestation occurs -> reduced evapotranspiration so reduction in rainfall and desertification risk
  • Deforestation -> soil exposed and becomes impermeable when exposed to intense heat, increasing surface run off -> increased flood risk
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How human activity disrupts water supply

Over-abstraction e.g. Thames Valley, southern England

  • Water is over-abstracted -> Reduced river flow & some tributaries run dry -> Damage to eco-systems & increased use of groundwater due to drought -> Lowered water table across the Thames basin

Reservoir building e.g. Grafham water, Huntingdon, UK

  • Reservoir built -> Reduced run-off downstream -> increased drought
  • Reservoir built -> Used for water storage -> Add new stores to the water cycle
  • Reservoir built -> Loss of land as villages and farmland flooded -> Vegetation drowned        -> Methane released as it decays

Deforestation e.g. Amazon rainforest

  • Deforestation occurs -> reduced evapotranspiration so reduction in rainfall and desertification risk
  • Deforestation -> soil exposed and becomes impermeable when exposed to intense heat, increasing surface run off -> increased flood risk
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Small scale intermediate technology in the develop

  • Rope pump wells - implemented by WaterAid
  • Advantages - Less polluted water than surface stores, reduce time taken to collect water (improves quality of life), locals can produce and use on their own using basic, accessible and affordable materials

(http://www.wateraid.org/ng/~/media/Images/Global/Grid---302x230/Technology/rope-pump.jpg?la=en-NG)

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Large scale management schemes -developing country

Sardar Sarovar Dam - monsoon means rainfall varies dramatically causing seasonal drought

Benefits

  • 3.5 billion litres of drinking water per day
  • 1,450 megawatts electricity produced
  • 1.8 million hectares farmland irrigated

Costs

  • 234 villages drowned - 320,000 forced to move
  • Good quality farmland submerged
  • Few villages can afford electricity for homes

Overall:

  • The local impacts are negative, the benefits are on a wider scale
  • Large scale farmers benefit from irrigation but subsitence farmers won't
  • People who benefitted the most live in affluent areas like Mumbai
  • Economic benefits outweigh social negatives - dam built to boost economy
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Large scale management schemes - developed country

Colorado Dam - area is semi-desert so limited water supply, population growing, increased wealth so increase in demand for water for domestic and leisure activities

Benefits

  • 800,000 hectares of land irrigated, improving regional food supply - irrigation allows double cropping and food surpluses
  • 200million kW of electricity produced - provides electricty for domestic and industrial use, improving quality of life

Costs

  • Conflict with Mexico as downstream supplies reduced
  • No water has reached the Gulf of California in the last 30 years due to over-abstraction - river ecosystems in the delta destroyed
  • Conflict with Native Americans over reduction in water supply

Overall:

  • Benefits the economy and cities such as Phoenix and Las Vegas
  • Areas downstream are impacted negatively e.g. conflict with Mexico
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