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Water Chapter 11 Water Cycle Evaporation Condensation Precipitation Transpiration- water released by plants Percolation- water moving through Earth’s surface World’s Water Salt Water 97% Freshwater- 3% Icecaps and Glaciers- 77% Groundwater- 22% Other freshwater- 1% The amount of water in the world does NOT change- it only changes form and where it is located. Surface Water- fresh water on the Earth’s surface Rivers, streams, lakes, wetlands Most cities are built near surface water and many depend on surface water for water needs River System- flowing network of water Streams --> small rivers --> larger rivers Watershed- area of land drained by a river Mississippi watershed drains water from 30 states (40% of land in lower US) Groundwater- water stored beneath the Earth’s surface in sediment and rock formations Water table- a level where rocks and soil are saturated with water. Wetter areas- higher water table and near surface Deserts- hundreds/thousands of feet down Aquifer- an underground formation that contains groundwater Ogallala Aquifer- one of the largest in world 174,000 square miles Under 8 plains states (most of Nebraska) Supplies 1/3 of groundwater used in US The Ogallala Aquifer holds as much water, but spreads over an area seven times the size of Lake Huron. Page 272 Porosity- the amount of space between the particles that make up a rock Permeability- the ability of rock or soil to allow water to flow through it Permeable- allow water flow- gravel, sand Impermeable- stop water flow- clay, granite Low permeability High run-off High permeability Low run-off Aquifers usually form in permeable materials such as limestone, sandstone or layers of gravel and sand There are aquifers in most parts of the world. Most do not take up as much constant area as Ogallala, but do provide a ground water source Recharge Zone- area of the Earth’s surface where water percolates down into the aquifer Well- hole that is dug to reach groundwater Cone-shaped depression in groundwater Must be below water table or will be dry Water Use Section 2 Water Use Agriculture- production of food products 67% world wide (US 45%) Industrial- production of goods and services 19% world wide (US 39%) Residential-home use, cooking, cleaning 8 % world wide (US 10%) Other % is water lost due to evaporation page 277 Water Treatment Potable- water that is safe to drink Free of pollutants and diseases Must remove Contaminants such as heavy metals (mercury, arsenic, lead) can cause major health problems even in low levels Other chemicals- fertilizers, cleaners, runoff Pathogens- organisms that cause illness of disease Bacteria, viruses, parasites Usually contaminated through sewage or animal wastes Drinking Water Treatment 1.First Filtration- removes trash 2.Coagulation- bacteria and impurities form globs that will settle to bottom of tank (usually done with Alum) 3.Sedimentation- solids/sludge settle to bottom of tank to be removed 4.Filtration- layers of sand, gravel and coal filter more impurities 5. Chlorination- chlorine is added to prevent bacteria from growing 6. Aeration- air is forced through water to release dissolved gases 7. Additional treatment- add fluoride (prevent tooth decay), sodium or lime (soften water Open Sewer System Industrial Use 19% of water used in the world Used for…… Most is used to cool power plants To clean ingredients before production and products before shipping To cool metals when cutting As a mixing ingredient Agricultural Use 67% of world water use Plants require large amounts of water, animals even more 80% of the water used evaporates before it is absorbed by plants Irrigation Irrigation- providing plants with water from other sources than direct precipitation Flooding fields Shallow ditches Sprinklers-very inefficient -50%evaporation Drip irrigation Water Management Aqueduct- canals or pipes that move water to a different area Dam- structure built across a river to control the river’s flow Flood control Generate electricity- hydroelectric Create reservoirs Reservoir- artificial lake behind a dam Flood control Drinking water Irrigation Recreation Hoover Dam Hydroelectric Water for irrigation and residential use Three Gorges Dam China Completed in 2008 Produces energy for 4 large cities Flooded large areas Desalination Process of removing salt from salt water. Usually through heating the water and collecting the evaporation (freshwater) Purpose Used in coastal cities and islands without natural freshwater Very expensive Water Conservation What can you do to conserve water? Opener 1/7 Write in your notebook 1.What is the largest watershed in the US? 2.What is an aquifer? What can they be used for? 3.Is sand permeable? Why? 4.How much of the earth’s water is freshwater?