Water Chapter 11, Section 2: Water Use & Management Standards: SCSh2a-b, 3c, 4a, 5a, 6a,d, 9d
How do people use water? • Agricultural Use • Industrial Use • Residential/ Domestic Use
How is water used in residential areas? • 14% of world water use • Varies by country • Average person needs 1.3 gallons to survive • U.S. resident uses 80 gallons per day • India resident uses 10 gallons per day • In U.S. we use it for • Inside sources: drinking, cooking, washing, toilet flushing, etc. • Outside sources: watering lawns, washing cars, etc.
How is water treated to make it potable (drinkable) in residential areas? • Need to remove mercury, lead, arsenic, pathogens (disease causing organisms), etc. • Steps to treat water… • First Filtration • Large materials/trash removed • Coagulation/Sedimentation • Alum is added to clump up large dirt particles into globs called floc. This settles to the bottom of the tank and creates sludge. Sludge can be removed, disinfected & used as fertilizer. • Second Filtration • Water passed through filter of sand, gravel, charcoal to remove impurities • Chlorination • Chlorine is added to prevent bacteria from growing in water. • Aeration • Air is forced thru water to release unwanted gases which reduces odor & improves taste. • Additional Treatment • Fluoride is added to prevent tooth decay • Sodium compounds or lime may be added to soften hard water (hard water will not lather when soap is added) • Storage • Sent to water tower before pumped to homes/businesses
How is water used in industry? • 19% of world water use. • Mostly used to cool power plants • Pump out river water, water boiled, produces steam, turns turbines, water re-condensed and cooled in cooling towers, either reused or returned to river. • Manufacture goods • 1,000L used to produce 1kg of aluminum for cans • 500,000L used to produce a car • Dispose of waste
How is water used in agriculture? • 67% of world water use • Irrigation • Providing plants with water from sources other than direct rainfall. • Traditional • Flood furrows • Lose a lot to evaporation • Modern • Overhead sprinklers • Some evaporates • Drip irrigation • Most efficient but most expensive (replace hoses)
What are water management projects? • Creation of dams, canals, aqueducts, & reservoirs to meet the needs of people. • Ex: • Mono Lake in California • Three Gorges Dam in China
Mono Lake, CA • In 1941, L.A. started diverting Mono Basin streams to add to L.A. Aqueduct. • Mono Lake’s volume halved while salinity doubled. The simple ecosystem began to fail and threatened migrating birds and nesting gulls. • The state and courts now mandate raising the level of the lake 17 feet. It will take about 20 years. • Should make more habitable for birds & fish
Pros & Cons of Dams • Pros: • Creates reservoir- artificial lake behind dam • Collect and store water from rain and snow • Produce electricity • Irrigate farm land • Control flooding • Provide drinking water to cities, towns and rural areas • Provide recreational activities such as swimming, boating, fishing • Cons: • Enormous loss of water due to evaporation • Flooded land destroys forests or cropland and displaces people • Danger of Dam collapse • Downstream areas deprived of nutrient-rich soil, which will eventually clog the reservoir • Migration and spawning of fish disrupted • Causes water wars between states & countries • Expensive to build
What are some ways to conserve water? • As water becomes depleted, water becomes more expensive. • Dig deeper wells • Send water through pipes a greater distance • Clean polluted water • Conservation is best method of solving water shortage problems.
What are some ways to conserve water? • Agriculture • Most problems with evaporation, seepage, and runoff • Drip irrigation systems deliver water directly to roots via perforated tubing- less evaporation • Industry • Recycle cooling water • Residential • Low flow toilets/shower heads • Turn off water while brushing teeth. • Xeriscaping- using drought tolerant plants in landscaping so you don’t have to water them too much. • Water lawn at night
What are some solutions to the water depletion problem? • Desalination • Removing salt from ocean water • Two methods: • Distillation- heat & evaporate fresh water, leaving salts behind • Reverse osmosis- pass water through membranes that trap salt • Expensive • Ex: Middle East, coastal communities
What are some solutions to the water depletion problem? • Transporting Fresh Water • Melt water at source, bag it and transport it to areas in need. • Towing icebergs- efficient technology not developed yet.
You should be able to… • Describe the patterns of global water use for each continent shown in the bar graph in Figure 5. • Describe the drinking water treatment process in your own words. • Describe the benefits and costs of dams and water diversion projects. • List at least three things you would do to help conserve the world’s water supply.