The hydrological cycle, the movement of water between its different forms; gas liquid and solid.
Infiltation - Movement of water into the soil from the surface
Percolation - Movement of water into underlying rocks
Saturation -When soil is full of water
Interception - The capture of precipitation by vegetation so not making it directly to the ground
Throughflow - Slow movement of water through soil to a river
Surface Runoff - Overland flow
Evapotranspiration- The changing of a liquid into a vapour by heating from the sun
Transpiration - The release of moisture from vegetation into the atmosphere
Water Table - the level at which saturation occur in the soil or ground
Water Stress - occus when the demand for water exceeds the amount available during a period, or when it is not good enough quality to use.
Water Scarcity - physical scarcity (shortages when demand exceeds supply, economic scarcity (when poeple cannot afford water)
Water Wars - conflics between countries for access to and control over water. global warming and populaton surplus increases this as a possibility
What is blue water?
Freshwater runoff (anything not salt water, in the hydrological cylce)
Irrigation - provision of water for crops
Cash crops - crops that can be grown and sld for money
Subsistence farming - growing only enough crops to support your family
Living with chronic Water Shortage
Water scarcity in the Sahel
The Sahel- narrow belt of semi0arid land immeditely south of the sahara. Raifalls in only one or two onths of the year, sometimes this rain is torrential and then lost as surface runoff, causing flooding. In other years there have been several lengthy droughts.
Why is demand for water increasing?
- Lots of cash crops produced - high population needs feed, water is needed for mass irrigation
- The popultion is growing rapidly - Mor water will be needed for domestic purposes (e.g washing, cooking) and there are more poeple who need to be fed (cash crops) so water for irrigation as well as the demand of water for subsistence farming.
- High level power consumption - Power generators need water to propel turbines and reate energy so as people use the power, the demand will become continual
- Many poeple own household appliances like washing machines - Electricity is need to power the appliances, water is used to generate electricity, also sometimes the appliances use water to compete their jobs like dishwashers
Problems of the Sahel
- Sustistence farmers rely on the rain to grow millet and maize
- Drought or flooding could risk loss of food supplies which are critical for a growing population
- Grasses die and soil erosion and desertification follow, due to overgrazing of animals- causing farming of cash crops to become impossible
- Flash flooding can destroy land
- Cash crop infiltration could be over done if there is excessive rainfall
- Drought causes seasonal rvers to dry up and the water table to fall
- Flash floods can destroy land
- Drowning of crops
Eutrophication - depletion of oxygen from the water in rivers. Pollution causes the rapid growth of algea and bacteria. These require oxygen so other plants and animal lie is suffocated.
Siltation - the accumlation of silt. Can have a knock on effect further down stream.
Erosion - the wearing away of land surfaceand removal of rock by rivers, glacirs and sea.
Salinization - the accumulation of salts in the soil. Poisons land (particularly bad for dryland area beause agirculture relies on irrigation).
Irrigation - the artificial watering of crops.
Bilhazia - tropical disease caught by swimming in infested waters.
High Aswan Dam (LEDC)
Social - reliable source of drinking water, protects the community from famine
Economic - agriulturally (increased crop yield, more cash crops), job creation, electricity fro industry, tourism
Social - People forced to resettle, declining water quality because of pollution by fertilizers
Environmental - Increased erosion (loss of agricultural land), reduced silt (reduced fish stocks)
Hoover Dam (MEDC)
- Social - regular all year supply of water for nearby major cities
- Economic - regular all year water supply, less flood risks
- Environment - Less flood risks, flood peaks smoothed out
- Social - tourists lose their use for rafting, loss of land, people have to resettle
- Economic - loss of land flooded by resevoir, expensive to build
- Environment - erosion of sand banks means loss of animall habitats, less energy left to move sediments
Human interference of water quality
Case Study, Aral Sea, over abstraction
Human Causes - cotton farming in the desert lead to the building of large scake irigation systems from the aral sea to the cotton plantation. due to careless water management by farmers, overuse of water and poor decision making about building a cotton factory in the desert, the aral sea was overabstracted.
Physical Causes - half of the water used to irrigae fields is burnt up by the sun on its journey anyway and evaporates.
Social Impacts - the bad water quality is meanin that 83% of children are being born with birth defects, people are having to migrate to find fish, food and money elsewhere, little water per day (25 mins), the spreading of typhoid disease is increasing because of pollueted water from the wells
Economial Impacts - poor crop yield, no tourist attraction, no more fishing villages, only income to the area is through the cotton farms
Environmental Impacts - salt on dried up sea bed drifts with the wind polluting the air, air getting hotter because sea cannot keep things cool, 4/38 fish species left, climate change
Other human activities affecting water quality
- Plant nutrients from fertilisers destroyed in the fields (leads to eutrophication- water deprived of oxygen by the rich nutrients)
- Organisms such as bacteria and viruses (could cause a range of disease eg cholera)
- Radioactive substances could lead to cancer
- Inorganic solid compounds such as toxic material and cyanide from mines (can poison stretches of river completely, killing all life)
Sustainable - meeting the needds of people now and in the future whilst limiting harm to the environment
Appropriate Technology - equipment that the local community is able to use relatively easily and ithout much cost
Intermediate Technology - small scale and practical solutions that local people can apply and maintain themselves
Sustainable solutions to water crisis
- The best schemes... damage the environment as little as possible, are simple and easy to run, are small scale, help the poorest people, use simple technology, help local people develop their own knowledge and skills, change local traditions as little as possible, encourage local people to work together and help themselves.
An Intermediate Technology
- small scale
- practical solution
- available to local people to apply and maintain
- easily built and maintained
- clay and bamboo are an abundant resource
- meets the needs of local people
- minor harm to the environment
- weather dependant, should never run out
- uses simple technology
- cheap - helps the poorest people of the area
- encourages working together
Rainwater Harvesting cont.
- easy water access
- clean, unpolluted water
- saves people time, working, education
helps preseve water for the future
- meets the needs of people now
- in the fture it helps by preventing floods and providing water
- damages the environment
- not small scale
- uses advanced technology
- provides jobs for local people
- all-year water supply to irrigate cash crops
- income to area could improve value of life for people
- clean water
Local water supply
- All year water supply
- prevents floods, more water for locals
- easy soure of irrigation for farmers