Geography-Water World

Why sand dams?

Sand dams are alternatives to large scale water management and can be used in developing countries to trap water which provides fluids necessary to survive. Sand dams are also much cheaper and are great alternatives to small communities. However, in some locations they cannot be used due to the geographical area not being adequate. Sometimes they are provided to communities by NGO's (excellent development in this case) in developing countries such as Burkina Faso. The organisation provides the materials necessary to build the dam and then involves the local people in the construction. 

What do sand dams do?

• Water for cooking
• Saves time
• Water for irrigation
• Water for washing
• Water for drinking

They cost around £13,149 which is much cheaper than large scale dams. For small scale water management to work there needs to be a dry river bed, rock near the surface, cement, metal and wood supplied, must also be rocks provided by community. Wall must b built. Takes 1-3 seasons for the dam to be filled with water and sand, this works in harmony with the environment and sustainable. It also lats for ever. 

• The dam cost $22.5 billion and was built in China
• The dam is 1983 meters wide and 185 meters high
• Completed in 2003 and located on the Yangtze river

Why was it built? The dam was built due to floods that wiped out homes and caused mass distress. 

Positive impacts:

Flooding will be prevented

• It will generate hydro-electricity for China
• It will allow for safe navigation along the Yangtze river
• The new settlements will have better housing
• The dam generates jobs for people to fulfil while the dam's being built and after due to tourists

Negative impacts:

• Relocation of around 1.3 million people
• Concern that the dam could break to the sheer weight of the water
• Endangered species such as the Yangtze river dolphin could become extinct
• The project is extremely expensive. 

The Sahel Region & Desertification

Desertification: The process by which land turns into desert due to human activities and climate change and the land turned cannot recover

Drought: A prolonged period without rain after which the land and vegetation are all able to recover. 

The location of the Sahel Region is in North Africa; there are many countries which are in the Sahel region which could lead to major problems for these countries if global warming persists at the current rate: Senegal, Mauritanoa, Mali, Burkina Faso, Niger, Chad, Central African Republic, Sudan, Ethiopia, Somalia.

Jean Marie Sawagogo described when he was a boy his home land had a forest, that it rained all the time and there was plenty of animals. The environment has since changed due to the fact that it no longer rains for long, vegetation has gone and the soil has gotten dryer. Animals have also gone. This has happened due to the fact the land has been overpopulated with people so the land cannot rest and the soil cannot become fetile to make it nutritious. It has also been overfarmed meaning every crop yield is worse than the last. Climate change has also increased the temperature. If the soil is continuously used like this it may very well desertify causing issues for the remaining population. 

Hydrosphere: This item refers to ALL water on the planet. (On the surface, living things and in the atmosphere).

Evaporation: This is when water liquid changes to water vapour

Precipitation: This refers to snow, sleet hail and rain. This can be increased

It's important for suvival. The hydrosphere consits of all the water on the planet - in the seas, oceans, rivers and akes, in rocks and soil, in living things and atmosphere. It exists in three states

• Liquid-Water
• Solid-Ice
• Gas-Water vapour

The 'Closed System': Water flows in a never endin cycle between the atmospheere, land and oceans. The hydrological cycle is a CLOSED SYSTEM. Water goes round and round, none added or lost so Earth never gets wetter or drier. It's conserved. Several different stores of water other than major oceans (accounts for 97.5% of salt water).Other major sources are as follows: Glaciers, groundwater, lakes, soils, atmosphere, rivers, living things. Water flows between stores via transfers such as; runoff(overland flow) infiltration, throughflow and ground water flow. 

Water can change state: Heat energy can change liquid (water) to gas (water vapour) (Evaporation)

Air only holds so much water vapour before becomes saturated as air cools water vapour turns to liquid (condensation)

Water vapour can freeze to a solid (ice) as the temperature cools or melts to form liquid water.

Evaporation from oceans rivers + evapotranspiration from trees condenses to cause precipitation

Precipitation follows a number of routes:

• Some runs off over the surface
• Some seeps into the soil or rock
• Some collects as snow or ice

Transpiration: Water vapour entering the atmosphere from plants

Evapotranspiration: Water vapour released into the atmosphere by plants through evaporation from leaves and transpiration from cells. 

Throughflow: The flow of rainwater sideways through the soil, towards the river

Groundwater flow: When precipitation reaches the ground some it it soaks into the ground (infiltration) if semi/permeable rock/soil is present and then moves downhill under the surface as ground water flow. 

Stream flow: Some groundwater flow and surface runoff will reach rivers and streams where it generally continues its route towards the sea or ocean. 

Surface run off: Rainwater that runs across the surface of the ground and drains into the river (on land)

There's a freshwater crisis. Demand soaring as population increases. May be future water wars. Especially in Middle East. Our use of water is increasing most from agriculture. Moden farming needs irrigation. Uses vast quantities of water. World faces major change due to climate change.                                                                                                               Impact on precipitation: 

• Warmer temperatures likely to lead to more precipitation due to more evaporation.
• More water vapour=increase in amount of precipitation due to moisutrisation. 
• Increased precipitation intensity larger proportion of rain falls shorter time mo' intense storms.

Impacts on evaporation:  Evaporation increase = increase in amount of moisture. Warmer=more evaporation from soil surfaces, drought more likely

Impacts on river flow:

• Warmer climate means earlier Spring. Snows melt earlier increasing river flow reducing river flow in Summer. Results in reduced availability of fresh water in Summer. 

Impacts on Drought

• Increased temperatures+increased evaporation=drought. Most countries suffering experience worse droughts

Drought in the Shael:

Sahel located in a narrow belt of Semi-arid land. Rain falls in only 1 or 2 months of the year (usually 250-450mm) length of season are variable. Sometimes rain comes in torrential downpours and is then lost as surface runoff causing flooding. In others rain fails completely.

• Drought causes seasonal rivers + water holes to dry up and water table to fall.
• Drought=disaster for the nomads who graze animals and for subsistence farmers.
• Grasses die, overgrazing of animals causes soil erosion and desertification

Many countries in Sahel are developing and they have rapidly growing populations. This puts pressure in drought years on failing food supplies. These lands are very fragile - water stress soon causes humanitarian crises and regular famines. 

• Waterborne diseases like cholera, typhoid and dysentery kill one child every second
• Women and chidren spend up to 200 million hours worldwide collecting water, means children cannot go to school. The water supply is often water holes in places such as Africa meaning the water is pulloted. 
• High risk of crop failiure and animal death, crops die due to lack of clean rain water and similar to animals.
• Everyday tasks like cooking and washing are very difficult due to polluted water
• In slums, in developing cities, people have to pay high prices for clean water - so have less to spend on food, education and health. 

• Some regions such as the Sahel, Australia and southern Europe will become drier
• Drought and flood may become more common, and more sever posibly in the same location
• Melting of some water stores, especially mountain glaciers in the Himalayas, Alps and Andes will also lead to thermal expansion

Population growth & climate change:

Climate change and population growth will have an even bigger impact as if there's more people there will be more abstraction. This will then cause the water supply to deplete further, especialy from aquiffers and other underground stores of water. More people also increases the use further depleting the water supply.

Global warming will also have effects:

• Richer countries the cost of water will rise. New reservoirs, pipes and desalination plants keep water flowing, this is will be expensive and will also destroy habitats
• Subsistence farmers in developing world who rely on rainfall become more vulnerable to drought and floods increasing their food insecurity as crops fail
• If precipitation falls, river flow will drop and groundwater will not be recharged as quickly.
• Glaciers will shrink reducing the water supply for some

Different types of pollution:

• Industrial
• Sewage disposal
• Intensive agriculture

Chemicals: From the manufacture of plastics, oil, pesticides and PCBs and inorganic solid compounds (toxic materials) can poison stretches of river completely if deposited in them killing all life due to toxins. 

Radioactive substances: These can be from nuclear waste treatment and can lead to cancers such as leukaemia.

Thermal heat pollution: From power stations pumping hot water into rivers increasing the rate of decomposition of bio-degradable waste, this reduces the river's ability to retain oxygen

Intensive agriculture: Excess fertilisers such as nitrates run into rivers and can cause eutrophication. 

Solids: Somtimes animal manure escapes into streams as slurry, polluting streams with raw sewage. Like eutrophication, slurry dumping deprives ruver water of oxygen killing many organisms. 

Sewage disposal: People in developing countries and slums often ise rivers for washing clothes, these can be badly affected by pollution. Diseases such as cholea, typhoid, dystenery or hepatitis is caused by harmful organisms such as bacteria, viruses, river worms, rats. Domestic sewage consumes oxygen in the water and kills many organisms through oxygen depletion. Suspended solids affect the colour of the water and kills fish/shellfish. 

Human interventions:

• Deforestation and changes in land use, leads to loss of interception capability and possible flooding due to increased surface run off.
• Also reduces evapotranspiration as there are less plants and removes this store of water. Widespread urbanisation (cuts evapotranspiration).
• Overabstraction of groundwater leads to falling water table
• Overabstraction from rivers and lakes leads to conflict between users and loss of evaporation. Building of dams and larger reservoirs (destroys habitats). 
• Melts glaciers due to impacts of global warming

Overabstraction: Too much water is being taken from the river, lake or other water source  Droughts in Souther England have led to increased use of groundwater supplies, this has lowered the water table across the Thames Basin so underground water supplies are not used sustainably. 

Reservoir building: Several types HEP, those used for water storage. Can be useful but also have problems, it can cause a loss of land and habitats. In some countries they can be a source of disease as they are home to insects such as mosquitoes. Vegetation is drowned by the lakes decays and releases methane and carbon dioxide, adds to global warming.

Deforestation: It affects the water cycle: 

• Removes trees reduces evapotranspiration, less green water recycled. Can lead to reduction in rainfall and possibility of desertification. 
• Exposes soil surface to intense heat. Hardens the ground making it impermeable, increases surface runoff. 
• Leads to a loss of soil nutrients due to loss of biomass, nutrients quickly flushed out of the system.
• Cuts out the process of interception. If trees are removed it can increase the siltation in rivers and lead to increased flood risk.

• Removal of trees for firewood leaves soil bare and prone to erosion
• Global warming means increased temperatures. This leads to increased evapotranspiration, reduced condensation and reduced rainfall. 
• Over-cultivation
• Too many animals for the amount of grass available means the protective grass covering is stripped away.
• Crops are grown on marginal land which is more vulnerable to erosion
• Herdsmen have to walk greater distances to find adequate vegetation for their animals
• Seasonal rivers and water holes dry up
• Lack of vegetation leads to starvation and death of animals.
• Crops are grown year after year on the same plot of land, leading to soil exhaustion 
• Poorer soils contain less humus and hold less moisture. The risk of erosion is increased
• Run-off rates are increased as there is no vegetation to soak up precipitation 
• Climate change
• Deforestation
• Non-drought resistant vegetation dies
• Overgrazing
• Loss of vegetation at increasing distances from water holes. 

Causes Effects

Drought: A long period without rainfall that causes crops to die, causes a lack of food

Overgrazing: Too many animals grazing the land eating vegetation. vegetation fails to grow which exposes the soil

Over cultivation: Crops grow on the land year after year, take all nutrients from the soil, therefore, the soil becomes infertile. 

Deforestation: Trees' roots hold the soil together. Once they are lost, the soil becomes loose. After that, the top layer ofthe soil might get washed away or blown with the wind. This top layer contains essential humus and nutrients for plants to grow. If there is no nutrients/humus the soil will become infertile and no plants will grow.

Single crop farming: 

• Plough all the land
• Moisture easil evaporates from all of the land
• One crop planted
• Harvesting done all at once
• If the crop fails, all income is lost - food aid is needed to feed those who might starve due to this.

Conservation farming:

• Plough only where you plant crops
• Moisture evaporates only from parts that have been dug
• Several crops planted mixed together
• Harvesting done over the whole year
• If one crop fails there are others so no one starves.