G4: GEOGRAPHY REVISION Theme 2: Sustainable Water Supply

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1 G4: GEOGRAPHY REVISION Theme 2: Sustainable Water Supply What physical factors determine the supply of water? Water supply in the UK Plentiful supply of surface run-off and precipitation in the North and West of the UK - Mountains - Relief rainfall: provides stores such as reservoirs and lakes - Prevailing winds - Weather from the West, over the ocean = rain (Golf Stream) The South and East are abstracting between 41-72% of groundwater - Drier, more continental climate - Doesn t receive Westerly winds - Flatter - Relief = less favourable for dam building - Exploiting permeable rock (such as chalk, limestone and sandstone) to reach artesian wells and aquifers - Kent = bread basket of the UK More than 20% of rainfall is abstracted in South East England = water stress South and East England are massively over-extracting water How do human activities influence supply and demand in South East England? Environmental Agency Responsible for the environment in England and Wales Monitor water levels in rivers and lakes Government department responsible for the Environment Background to water levels Significant pressures on water resources across the UK Severe across South East and Eastern England - Highest population density - Highest domestic water use - Highest irrigation in Eastern England = Increased pressure on limited resources Available Water The annual average rainfall across England and Wales is 890mm This is reduced to an effective rainfall average of 465mm the rest is lost to evaporation Rainfall not evenly distributed across Britain - Far more rain falling in parts of Wales and the Lake District Usually sufficient rainfall to meet the needs of people and wildlife except in extreme periods of dry weather

2 Using Water The Water Exploitation Index (compare the volume of water used with the volume of effective rainfall) Water resources are considered to be under stress if this index is more than 20% The average for England and Wales is about 10% = below acceptable levels South East and Eastern England 22% = under stress CAMS Catchment Abstraction Management Strategies - Developed by the Environment Agency - Sees how much water is available and how much is currently being used - Results show that pressures on water resources exist across England and Wales and are not just confined to the South East and Eastern regions Abstraction Uses: The total amount abstracted from all sources in 2006/07 averaged 60,000 megalitres per day This figure has changed very little in the previous five years but the source of abstraction has changed over that time Groundwater abstraction = stable - used only for public water supply In East Anglia, up to 20% of the water abstracted in a typical summer can be for spray irrigation (can rise to 50% on dry days) Supplying People with Water: Less water per person in South East England than in much hotter and drier countries such as Morocco and Egypt House hold usage varies Households with meters use less water than those that are unmetered - Metered properties = use 13% less - Over 30% of households now have a meter Only paying for water they use Not uniform - Less than 20% of households have a meter in North East England - 50%, in areas such as Cornwall, Devon and East Anglia

3 Supply Demand Balance: Total volume of water put into supply = stable over the last 8 years Amount used by industry and business has slowly declined In a dry year, there is enough water to meet demand across the whole of England and Wales Future Pressures: Population increase (an extra 10 million people expected by 2031) Further metering across the country needed - By % of households in water stressed areas are expected to have a water meter Climate change 2012: Drought? - Higher river flows - Water temperature - Reduce recharge of aquifers Much of Southern and Eastern England in a state of drought Groundwater levels are lower than in the dry summer of 1976 Hosepipe bans from early spring The firms have agreed measures to reduce the environmental impact of dry conditions - Reducing water losses - Improving leak detection - Encouraging customers to save water The Environment Agency will also take steps such as monitoring the impact of the dry weather on fisheries and wildlife Measures at an individual level (Thames Water's sustainability director) - Turn off taps while cleaning their teeth

4 - Take shorter showers - Fix leaks - Only wash laundry with a full load Drought contrasts with Scotland, where reservoirs were between 95% full Ms Spelman - wanted water companies to connect pipe networks to transfer water from wetter areas Severn Trent's water director said each water company had tended to focus on its own area Causes - Two dry winters - Lack of rain continued - South-east England received just two-thirds of the long-term average rainfall for January - Rainfall below average The Colorado River The River Colorado (not the longest in the US) is the most dramatic, most used and closer than most basins in the US to using the last drop of available water for man s needs. Things have only worsened Great American desert The Colorado doesn t reach the ocean Multiple dams Multiple states are dependent on the water from the river 2025 Water Plan National Academy of Science, 1978

5 Background to the Colorado South West America 2,300km long 20 dams (storage and electricity) 500ml per year of precipitation in the Rocky Mountains (source) 26 th largest river in the US Cities rely on the river (including Las Vegas, Phoenix, Touson, California and LA) Last 600km = hardly any natural river (used to reach the sea) Large part of river runs through the desert (high evaporation levels) Large amounts of snow melt fuels and feeds the river Cut the Grand Canyon Used as a water source for over 2000 years Supplies the demand of 40 million people Major dams in 7 US states Produces 120 million kw of electricity Irrigates 800,000 hectares of farmland 1928: First dam site chosen (Hoover Dam completed in 1936) Upper basin - Wyoming - Colorado - Utah - Arizona - Nevada - California Lower basin - New Mexico Lowest flow = 1917 (4.9 km 3 ) Maxest flow = 1984 (25.3km 3 ) Varying discharge Value of water = very unreliable How much water can be taken out?