Environmental Studies

Covering unit 2 of AS environmental studies

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  • Created by: Kathy
  • Created on: 14-01-12 12:58

The atmosphere

Composition of the atmosphere! 

  • Nitrogen - 78% - used in proteins
  • Oxygen - 21% - used in aerobic respiration 
  • Co2 - 0.038% - used in photsynthesis
  • Rare gasses - 1%
  • Methane - 0.00017% - important for early life and deep oceans
  • Ozone - 0.000007% - Absorbs uv light in stratosphere 
  • Water vapour - Very variable, up to 4 - Water in the water cycle is distributed in the atmosphere

DYNAMIC EQILIBRIUM - Is ver important! The processes must balance each other out e.g. photosynthesis and respiration. 

The concentration of gases e.g. carbon dioxide changes over a 24 hour cycle - rises at night (respiration) and falls during the day (photsynthesis is much more rapid than respiration) and Water vapour varies due to the transpiration and evaporation rates. Long term changes are due to activity of the sun, geological processes and human activity. 

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Atmosphere 2

Changes with altitude - 

  • More ozone naturally occurs in the stratosphere where UV interacts with o2. 
  • Temp declines with increasing altitude in the troposphere due to heating by infrared from the ground, but it increases with altitude in the stratosphere due to uv heating from sun. Pressure decreases with increasing altitude. 
  • These changes combined with the energy from the earth and sun produce a sequence of layers in the atmosphere

The layers of the atmosphere (in order from closest to earth to further away) 

  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere

The boundaries between them are the tropopause, stratopause and mesopause. 

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The consequences of global climate change

Temperature change - quite small but with serious consequences =

Sea level rise due to -

  • Thermal expansion, the warmer atmosphere causes the sea to warm up and expand. Very slow process as water has a high specific heat capacity. 
  • Melting land ice, ice floating on sea causes no rise  but glaciers and antartic ice shelves will. The rate of rise over last 100 years has been 1.7 mm.

Changes in climate lead to - 

  • Wind patterns change in velocity, frequency and direction. Cause storm damage , rain fall in different areas ect. 
  • Precipitation - higher temperatures lead to increased evaporation results in more precipitation. Areas where it rained less, it will get to warm to condense. Where it rained rained more it could be carried further and fall on them. 
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The consequences of global climate change 2

Ocean current changes 

  • More wind = more movement = more evaporation = water flows to balance the water levels = change in density of surface water caused by heating and cooling =  change in the surface water sinking = change in salinity also effects water density. All of this leads to a change in currents. 
  • El nino - under normal surfaces wind blows westward across the pacific ocean. This causes cold deep water to be drawn up near the coast of south america and due to its richness in nutrients causes massive algal blooms which is important for fish and therefore humans. The current continues west and warms as it goes and eventually recahes australia. The current also affectsrainfall patterns, if it is a cold costal current then rain will condense and fall. If its warm then winds retain water. In some years the winds create a reverse of this and prevents the algal blooms - food web collaspses. 
  • El nino - spanish term meaning 'christ child' - its the name given to these events as they normally occur at chrimstmas time. They seems ti be happening more frequently. 
  • La nina means girl child and this is when the normal currents flow strongly. 
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More on ocean currents

THE NORTH ATLANIC CONVEYER. 

Warm water from tropical atlantic ocean travels north east - the current is driven by  2 processes - prevailing winds and sinking of water near the artic ocean as it cools and becomes denser. 

Warming of the atmosphere is causing land ice on greenland to melt and flow into the sea. This dilutes salty surface water and makes it less dense so the colder water doesnt sink as eaily - current slows down. 

The current transfers heat energy from the tropics and produces a much warmer than what would be expected for area so far north. If the current slows down then northwest england will become veeeerrry chilly. 

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More consequences of global warming -

Ecological changes - 

  • temperature rise may cause plants to grow fater. This provides more food for herbivoires. But toxins can build up in plants and kill insects ect. 
  • Plants will shallow roots may cope less with drier periods 
  • Species that hibernate may benefit by able to feed for more of the year, or suffer as they are disturbed more frequently. 
  • Precipitation changes may cause wetland habitats to enlarge or shrink. 
  • The timing of ecolofical events such as flowering, migration and nesting may change. Survival of independant species may be reduced.

Distrubution of species may also change 

  • They may colonise new areas more slowly 
  • Sutible new areas may not be avaliable. 
  • Human land use may block movement
  • Species live in independant communitys or species. 
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Predicting Global Climate change - why is it hard?

  • Some of the likely changes might occur naturally so it is difficult to tell whether an event is caused by human actions or not. The change may be the frequency with which events such as floods or storms or droughts occur. This is often only detectable after many years when the trend is clear; Individual storms or even several do not indicate a trend. 
  • Its difficult to identify trends as there may be limited historical data on factors such as rainfall patterns, extent of sea ice or wind velocity. Some historical data cannot be trusted. Temperature records from towns may show that the increase is from the heat island effect not global climate change. Historical data is from indirect sources, and it can be difficult to interpret these to accurately estimate past climates. 
  • Many natural processes are interconnected so one change may have unexpected changes. 
  • Some changes, such as sea level rise are very slow. The cause of the change could of been happening long before the change was noticed.
  • Different changes may occur is different locations at different times. The climate will vary is different places so simple questions are hard to answer.
  • We do not understand how the earths climate works so prediction is hard.
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Feedback mechanisms - Positive

=A change in one environmental factor may cause other features to change. These may have an effect on the original change, increasing or reducing it. 

A positive feedback mechanism occurs when an environmental change causes other changes that increase the rate or amount of the original change and therefore increase its effect. These may increase temperatures directly or increase the concentrations of the gases that will cause further temperature rise . Raised temperatures cause the following - 

  • Warming may increase the rate of decomposition, causing more co2 to be released and therefore more warming. 
  • Warming reduces the area of ice and snow on the ground or floating ice on sea. Reduced albedo means heating is increased and temperatures rise further. 
  • Warming on sea - methane released from methane hydrate in marine sediments. This leads to further warming 
  • Melting permafrost in arctic releases methane. 
  • Forest fires more frequent adding co2. 
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Feedback mechanisms - Negative

A negative feedback mechanism occurs where an environmental change causes other changes that decrease the rate or amount of the initial change and therefore reduce its effect and help to re-establish the original equilibrium. 

  • Higher temperatures may cause increased rates of photosynthesis, which would store more carbon in biomass. Levels of Co2 in the atmosphere would be lowered, which would cause cooling. 
  • Warming would increase evaporation and cause formation of clouds, this increases the earths albedo and more sunlight is reflected. This reduces the temperature. 

Definition of - 

Positive FB mechanism - a situation where the initial change causes a reaction that increases the original change. 

Negative FB mechanism - a situation where the initial change causes a reaction that reduces the original change. 

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Methods of reducing greenhouse gas levels

Carbon dioxide  

  •  Energy conversations to reduce use of fossil fuels 
  • Use of alternative energy resources 
  • Carbon sequestration by planting more trees or storage of co2 from sources
  • Kyoto protocol

Methane

  • Reduced dumping of waste in landfill sites 
  • Reduced live stock production. 
  • Better collection of gas from coal mines and gas and oil facilities. 

Oxides of Nitrogen 

  • Reduced use of internal combustion, use public transport 
  • Catalytic converters in vehicle exhaust 
  • Addition of urea to power station effluents or diesel engine exhausts.  
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Methods of reducing greenhouse gas levels continue

Chlorofluorocarbons 

  • Use of alternative materials such as:
  • Butane or propane in aerosol cans
  • HFCs and HCFC's in fridges
  • alcohol as solvent for cleaning electronic equipment
  • OR use of alternative processes such as:
  • trigger and pump action spray cleaners instead of aerosols 
  • stick deodorants instead of aerosols.  

Tropospheric ozone 

  • Methods that reduce NOx emissions reduce the formation of Tropospheric ozone. 
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The Kyoto Protocol (1997)

MEDC's that signed up to the treaty were legally bound to reduce their emissions of six greenhouse gases by an average of 5.2 %  below their 1990 levels by 2008 -12. Failure to achieve this leads to their permitted emissions for the next period being cut by a further 30 %. 

Each country has developed its own method to meet its target. The EU has identified 12,000 factories and power stations that have been given a CO2 quota. If they exceed it they can purchase extra allowances or pay a finance penalty. If they fall below they can sell the extra quota. 

LEDCS do not have legally binding emission limits as this would unfairly hinder their development.

Agreements such as the Kyoto protocol do not reduce emissions themselves, but encourage the use of methods that will.  

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Strategies to cope with climate change

Agriculture 

  • Cultivate warmer climate crops
  • Cultivate drought resistant crops
  • Abandon areas where irrigation is unsustainable
  • Increase soil organic matter to increase water retention 
  • Water storage in times of water surplus for later irrigation use

Building Design

  • Better ventilation and cooling systems to reduce the use of air conditioning
  • Paler materials to reduce heat absorption 

Flooding 

  • Riverbank defenses 
  • River barrages to protect against high tides
  • Less building on flood plains
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Strategies to cope with climate change continued

  • Reduce runoff rates, for example, by reducing paved areas to increase infiltration 
  • River regulation dams

Coastal erosion 

  • Improved coastal defenses 
  • Managed retreat - abandon lower value areas that are difficult to defend

Storm damge

  • Design of stronger buildings
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Ozone depletion

Since the 1970's a reduction is atmospheric ozone has been observed in two different ways 

  • a general reduction of about 4 per cent per decade over the whole planet 
  • So called 'ozone holes' in polar regions where there is an annual drop in stratospheric ozone concentrations . Concentrations over Antarctica have dropped by up to 2/3 while over the arctic the drop has been up by one third.  

Why is there concern about ozone depletion?

If UVB is not absorbed in the atmosphere then it will reach the earths surface and may be absorbed by living cells. The energy of the UVB is absorbed and some is converted to chemical energy as it breaks up biological molecules and causing damage to the DNA in exposed cells, skin cancer, cataracts and damage to plant tissue and marine plankton.

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UV light absorption

Type      Wavelength       Characteristics 

UV A -   320 - 400 nm      Not absorbed by ozone
UV B     280 - 320 nm      Almost fully absorbed by ozone
UV C    <280 nm              Completely absorbed by ozone and normal oxygen

The effects of UVB light on the gases in the atnosphere

UVB is involves in a number of chemical reactions. It is absorbed in providing the energy for the reactions so very little reaches the Earths surface. 

UVB is absorbed by both diatomic and triatomic oxygen in photolytic reactions where the molecules are split. The product of these reactions are involved in further reactions. 

O3 --------> O2 + O                                                                                                         <--------- 

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Chlorine and ozone depletion

Halogens, especially chlorine in the stratosphere, cause ozone depletion in a range of reactions. 

A single chlorine atom is a chlorine radical because it has a unpaired electron which makes it very reactive. 

A chlorine radical can react with oxygen molecules, it breaks them down to leave an oxygen molecule and chlorine monoxide. Cl + O3 ---> ClO + O2

The ClO2 can then break down to release chlorine again which may repeat these reactions thousands of times Cl02 ----> Cl + O2

SO the reactions start and end with a free chlorine radical 

The important summary of the reaction is: Cl + O2 + O ---> 2O2 +Cl

This therefore removes the important starting materials for both parts of the reaction in the dynamic equilibrium that maintains the ozone layer. 

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Pollution by CFC's

CFC's contain only chlorine, fluorine and carbon. They were used in fridges and aerosols. They have properties making them useful for many things, they are usually very stable and can be liquefied with pressure, they are not flammable or toxic. 

Their chemical stability and low solubility in water mean they can remain in the atmosphere for years and may get carried up to the stratosphere . They are broken down by UV and release chloine which causes damage. 

How are they reduced?

The Montreal Protocol (1987) is an international agreement which phased out the manufacture and use of CFC'S and other ozone depleting substances such as the bromine in fire extinguishers. 

A range of alternative materials have been used to phase CFC's out like HCFC's and alcohols. 

HCFC's have replaces CFC's in fridges they are less chemically stable so break down before reaching the stratosphere. 

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Ozone depletion

Why is ozone depletion greatest in the polar regions? 

The chemical reactions involving chlorine and ozone require UV  B but occur most easily at very low temperatures when ice crystals form that provide catalytic surfaces. During the Polar winter the temperatures drop and allow ice crystals to form, there is no sunlight so when spring comes the crystals are still there and the sunlight causes ozone depleting reactions to take place. 

Do other gases cause ozone depletion? 

Oxides of nitrogen have been identified as possible causes of ozone depletion but releases in the troposphere do not reach the stratosphere as they dissolve in rain or react with other substances. High flying aircraft do release Nox into the stratosphere , but there are relatively very few so no obvious damage is caused. 

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The properties of water

Changes of state

 

The shape of a water molecule and the way the electrons are arranged allows the negative parts of one molecule to form weak bonds with the positive parts of others.

These bonds produce groups of up to four molecules that behave like a larger molecule with a higher boiling point. So, water is a liquid at temperatures when its low molecular mass would normally make it a gas. The bonds are continually forming and being broken. Individual water molecules at the water surface may escape as a gas: evaporation. At 100°C and one atmosphere pressure all hydrogen bonds are broken and the water turns into gas as it boils.

The narrow temperature range within which water changes state between solid, liquid and gas allows the hydrological cycle to occur.

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The properties of water 2

Anomalous Expansion

 

The water molecules are less densely packed than when they are in liquid form so solid ice floats on liquid water.

In an area that has cold winters, the water in a lake will be cooled by the cold air above. As the water is cooled below 4°C, the water molecules start to take up arrangement they will have as a solid. This lowers the density as the water expands and the cold water will float. This expansion on cooling is unusual and is known as anomalous expansion.

The deeper, warmer, water is unaffected as further cooling produces floating solid ice. This floating layer of cold water and ice prevents the water below from freezing and allows most of the water in the lake to remain unfrozen even if the air above is very cold.

If cooling water became denser until it frozen, hen ice would sink, more water would be exposed to the cold air, this would also sink and eventually the whole lake would freeze, killing most aquatic life.

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The properties of water 3

Solvent properties

 

Water is an excellent solvent is called the 'general physiological solvent'  because most biological reactions occur with solutes dissolved in water. Plant nutrients can only be absorbed if they are dissolved in water and most materials transported in blood and sap are dissolved in water.

 

High heat capacity

 

Water heats up and cools down slowly. This helps to maintain climatic stability by moderating temperature changes.

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he hydrological cycle

The hydrological cycle is driven by solar power, it causes water to evaporate. The evaporated water is transferred into gravatational potential energy in the atmosphere and kinetic energy as it falls as rain.

The transfer of water between resevoirs -

Water is a renewable resource but human actions can alter the rates of water movement in the cycle so that resources become depleted. An understanding of residence times can help with the sustainable management of water resources.

Aquifer depletetion -

The amount of water in an aquifer may be a poor guide to how it can be exploited. Aquifers in the Uk are rapidly recharged with rainwater so they are reliable. Aquifers in some hot dry countries contain alot of water but it takes a long time to accumulate. Any explotation is unsustainable unless the aquifer is extensive or recharged in a differnent way.

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Residence time!

Residence time = Volume / average transfer rate in/ out of resevoir.

The residence time in each resecoir is different.

Oceans - 4000 years

Land ice - 20 - 100 years

Ground Water - 100 - 10000 years

Lakes/ rivers - 2 months - 100 years

Soil moisture -  1 - 2 months

Atmosphere - 10 days

Living Organisms - 1 week

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The main processes in the hydrological cycle

  • INPUTS
  • Precipitation - where water vapour condenses and falls back to earth. Causes changes in temperature. Human impacts on precipitation - any impacts with have on global temperature.
  • THROUGH FLOW
  • Interception, when precipitation is stopped by rocks/ trees ect. Deforestation, afforestation urbanisation ect. affects this
  • Infiltratration - flow of water through ground surface into soil or rock below. Soil compaction, urbanisation affect this,
  • Percolation  - flow of water through soil or rock. Soil compaction affects this
  • Groundwater flow - movement of water through pores in rock. Groundwater abstration  and articficial aquifer recgarge effect this, 
  • OUT PUTS
  • Evaporation - affected by resevoirs, increased temperature ect.
  • Transpiration - affected by vegetation changes.
  • River channel discgarge (volume of water carried by river) affected by abstraction, and flood drainage.
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Water as a resource

Abstractive uses -

Domestic - Washing, flushing, food prep, drinking,watering plants, recreation. MEDCS shortages dont restrict use. LEDCS shortages lead to serious problems

Industrial - Many industrys need large amounts of water - (chemical industry, mining and mineral processing industries) - needed for cooling, heating, washing, steam generation, transport and as a solvent.

Approximately half the water used in the UK is used in power stations to condense steam.

Agricultural uses -

Irrigation - biggest single agricultual use of water. Crops need water for growth, to stop them from dying and to keep them reducing CO2.

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Water quality requirements

  • Turbidity - suspended solids must be removed as they give water an unpleasant apperance and taste. And solids can block pipes.
  • PH - acidic water can dissolve pipes, also tastes unpleasant.
  • Calcium content - disolved calcium ions make water 'harder' which means its better for health. BUT it produces limescale and scum.
  • Pestcide concentration - all our toxic and virtually all should be removed.
  • Heavy metal concentration - e.g. lead and mercury - these damage health.
  • Dissolved o2 - cause a musty bad smell
  • Chlorine retention - chlorine is added to keep water sterile -
  • E coli abundance - sewage contamination of water can cause spread of serious diseases such as cholera and typhoid. Testing for E coli lets you know whether it is contaminated water. The coliform count is the number of bacteria present in a litre of water.
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Water requirements for specified uses

Potable water for public water supply - water that looks, smells and tastes good and contains no harmful chemicals. If requirements not meant public health is at risk

Spray irrigation  - low turbidity and no toxins, sediment would block pipes and toxins can harm plants and humans.

Power station condenser water - no gross solids - as pipes would block

Power station boiler steam water - absolutely pure water as mineral deposits would build up in pipes and reduce water flow and heat exchange,

Textile washing - soft water with low dissolved calcium content so no scum forms during washing.

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Conflict of interest case study

The Syr Dahra River flows through 4 countries in asia. A resevoir in Krygystan is used to generate electricity and government want to reduce summer flow to increase winter electricity generation.

The countries downstream use water for crop irrigation and want more flow in summer.

Similar disputes have occured all over the world.

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Sources of water

RIVERS - river water is often the most convineant source. They are accesible over a large land area. The short residence time means they self clean quickly . The main features that affect the usefullness of water are -

  • total annual water flow
  • flow fluctuations
  • level of natural contaminants
  • human pollution
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Sources of water 2

RESEVOIRS - Many factors must be considered in choosing a site for a dam and a resevoir -

  • Topography - needs to be able to hold alot of water. Ideal would be a large deep basin and narrow exit so alot of water can be held by small dam.
  • Geology - rock must be impermable and strongw without seismic activity.
  • Catchment area - larger catchment area = more water to supply
  • Water supply - regular rainfall with no losses through evaporation
  • Existing land use - nothing important lost
  • Pollution risk - toxic pollutants and pesticides not wanted
  • Sedimentation - soil erosion makes it turbid and sedimentation reduces the amount of water the resevoir can hold.
  • Infrastructure - convineant site near area of demand.
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Environmental effects of resevoirs

Habitat change - obviously the habitat is flooded but new  and possibly valuable habitats are formed. BUT the dam acts as a barrier to some wildlife (salmon) that migrate along the river.

Changes in river flow - A change in flow can wash away sediments, and sedimentation can occur. Also fish eggs may not be able to survive.

Sedimentation - the sediments will not be carried further down stream, they are important in fertilisation of flood plain.

Resevoir microclimate - large body of water = high heat capacity = less temperature fluctuations, wind speeds higher, increased humidity. Also more cloud cover and precipitation downwind of the resevoir.

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Aquifers

Main features of aquifers

  • Porosity (measure of the proportion of rock which holds water)
  • Permeability (measure of the ease in which fluids flow through rock)
  • Geology - rock below water bearing rock must be impermable to prevent escape of water. Rock above must be pemable to allow recharge.

Consequences of aquifer overuse

  • Reduced supply (unsustainable)
  • Subsidence ( causes seriosu damage)
  • Changes in surface hydrology (water table will lower - springs ect dry up)
  • Ecological impacts - if water table is lowered plants die and other species are affected .
  • Salt water incursion - sea water replaces the reduced fresh water and water makes aquifer unsuitable.

Desalination is very expensive so cant really be used.

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Water treatment

Fresh water treatment

  • Screens (remove floating debris)
  • Sedimentation (solids and silt settle)
  • Aeration (ensure high oxygen levels, toxins can be removed)
  • Flocculation (clumps remaining sediment)
  • Activated carbon filters (removes organic chemicals like pesticides)
  • Sterilisation (kills pathogens)
  • Fluoridation (improve dental health).

Sea water treatment

  • Reverse osmosis (alot of energy is needed to create the pressure)
  • Distillation (Water is boiled by heating and steam is collected
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Demand for water

  • change is population size
  • change in living standards- rich people use more water in modern appliances
  • industrialisation - agriculture and industry use large amounts of water
  •  changes in attitude - people with problems concerning water supply are likely to be more careful about how they use it.

Global water supplies

The avaliability of water, affluence and development are interconnected issues. LEDCs cant afford to purify water and water bourne diseases are common. Dry periods destroy crops and kill people.

Affluent societys can afford to exploit water and develop more comfortable life styles and industries.

Over explotation by rich leads to problems with poor.

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Water conservation and management

Better use of water resources can be achieved in several ways -

  • increase the total amount of water avaliable to use
  • distrubute more effectively
  • use water more effectively

Increasing avalibility of water

  • increased abstraction
  • Catchment management - resevoirs can be used to maintain river water levels and the prevention of pollution upstream reduces the amount downstream which is too polluted to use.
  • Aquifer recharge e.g water from river thames pumped into aquifer.

Better distrubution of water

  • reducing distribution losses
  • Interbasin transfer
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Most efficient use of water

Case study for better distrubution of water -

Water transferred from Elan valley in wales to Birmingham. This is a 80 mile distance.

Ways to reduce water use -

  • Metering
  • Low water - use appliances
  • Recycling ' grey water use' - water in baths can be used to flush toilet.
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Aquifers

Main features of aquifers

  • Porosity (measure of the proportion of rock which holds water)
  • Permeability (measure of the ease in which fluids flow through rock)
  • Geology - rock below water bearing rock must be impermable to prevent escape of water. Rock above must be pemable to allow recharge.

Consequences of aquifer overuse

  • Reduced supply (unsustainable)
  • Subsidence ( causes seriosu damage)
  • Changes in surface hydrology (water table will lower - springs ect dry up)
  • Ecological impacts - if water table is lowered plants die and other species are affected .
  • Salt water incursion - sea water replaces the reduced fresh water and water makes aquifer unsuitable.

Desalination is very expensive so cant really be used.

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Water treatment

Fresh water treatment

  • Screens (remove floating debris)
  • Sedimentation (solids and silt settle)
  • Aeration (ensure high oxygen levels, toxins can be removed)
  • Flocculation (clumps remaining sediment)
  • Activated carbon filters (removes organic chemicals like pesticides)
  • Sterilisation (kills pathogens)
  • Fluoridation (improve dental health).

Sea water treatment

  • Reverse osmosis (alot of energy is needed to create the pressure)
  • Distillation (Water is boiled by heating and steam is collected
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Demand for water

  • change is population size
  • change in living standards- rich people use more water in modern appliances
  • industrialisation - agriculture and industry use large amounts of water
  •  changes in attitude - people with problems concerning water supply are likely to be more careful about how they use it.

Global water supplies

The avaliability of water, affluence and development are interconnected issues. LEDCs cant afford to purify water and water bourne diseases are common. Dry periods destroy crops and kill people.

Affluent societys can afford to exploit water and develop more comfortable life styles and industries.

Over explotation by rich leads to problems with poor.

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Water conservation and management

Better use of water resources can be achieved in several ways -

  • increase the total amount of water avaliable to use
  • distrubute more effectively
  • use water more effectively

Increasing avalibility of water

  • increased abstraction
  • Catchment management - resevoirs can be used to maintain river water levels and the prevention of pollution upstream reduces the amount downstream which is too polluted to use.
  • Aquifer recharge e.g water from river thames pumped into aquifer.

Better distrubution of water

  • reducing distribution losses
  • Interbasin transfer
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Most efficient use of water

Case study for better distrubution of water -

Water transferred from Elan valley in wales to Birmingham. This is a 80 mile distance.

Ways to reduce water use -

  • Metering
  • Low water - use appliances
  • Recycling ' grey water use' - water in baths can be used to flush toilet.
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Comments

Kathy

Not finished yet. 

meganbevan

these are perfect thanks!

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