Water as a Resource • Covers 71% of earth’s surface • Important properties • Polar • Moves easily • Changes temperature slowly • Moderates earth’s climate • Protects living things from temperature fluctuations
Available Water • Total = 326 million cubic miles • 97% in oceans • 2.997% is locked up in ice caps and glaciers • 0.003% is easily accessible • Soil moisture • Groundwater • Water vapor • Lakes • Streams
Surface Water • Runoff flows into streams, lakes, wetlands and reservoirs • A watershed or drainage basin www.canaanvi.org/assistance/ watershed.asp
Groundwater • Precipitation infiltrates and percolates • Pores, fractures, crevices, etc. • Zone of aeration - Upper soil layers that hold both air and water. • Zone of saturation is at a depth were ground is filled with water • Top of this zone is water table • Falls and rises with weather
Groundwater • Aquifers - Porous layers of sand, gravel, or rock lying below the water table. • Artesian - Pressurized aquifer intersects the surface. (Water flows without pumping) • Recharge Zones • Recharge rate is often very slow. • groundwater is being faster then it can be replenished
Objectives and Warmup: 12/1/10 • Objectives: • Explain why water is not equally distributed throughout the world. • Warmup: • What makes water not equally distributed throughout the world?
Use of Fresh Water • United States • Agriculture • Power plant cooling • Industry • Public • China • Agriculture • Industry • Public
Water Use Globally • 70% soaked up by agriculture (mostly in the form of irrigation) • Industry accounts for 23% • Domestic use (household, drinking water, sanitation) accounts for about 7%
Water Use • According to the UN, the average person needs a minimum of: • 1.3 gallons of water per day to survive in a moderate climate at an average activity level • 13 gallons for drinking and cooking, bathing and sanitation • The average person in the United States uses between 80-100 gallons per day for drinking, cooking, bathing, and watering their yard.
FRESHWATER SHORTAGES • Estimated 1.5 billion people lack access to an adequate supply of drinking water. • Nearly 3 billion lack acceptable sanitation. • Globally, water supplies are abundant, but, along with capital resources, are unevenly distributed.
Freshwater Shortage Causes • Dry climate • Drought- a period in which precipitation is lower & evaporation is higher than normal • Desiccation- drying of the soil as a result of deforestation & overgrazing • Water stress- more people relying on same amount of water
Global Precipitation Patterns Wright and Nebel, 2002. Michael D. Lee Ph.D. Geography and Environmental Studies
Rainfall Distribution • Rain falls unevenly over the planet • Three factors control rainfall • Global atmospheric circulation-creates regions of high air pressure and low rainfall • Prevailing Winds-bring moisture to land from ocean; areas far from oceans are usually dry • Topography-mountains act as cloud formers and rain catchers
Objectives and Warmup: 12/2/10 • Objectives: • Analyze how national and local water use are distributed and used throughout the US. • Warmup: • Calculate the per capita water use of Montana: • Population 902 in thousands • Water use 8290 in millions
Increasing the Supply of Freshwater • Dams and reservoirs • Tapping groundwater supplies • Desalinization • Towing icebergs • Water conservation
Dams and Reservoirs • Advantages: • Produce electricity • Irrigate land below the dam • Divert water to cities, towns and rural areas • Recreation
Dams and Reservoirs Cons • Environmental Costs • Upsets natural balance of water systems • Croplands downstream are deprived of nutrient rich silt • Evaporation • Ecosystem Losses • Loss of wildlife habitat • Migration and spawning of fish disrupted • Flooded land destroys forests or cropland • Displacement of People
Colorado River Basin • Diversion of water from Colorado River • Disputes between AZ, CA, Mexico • Dams trap silt--- more fertilizer needed • High levels of NaCl- salinization
Three Gorges Dams in China is forcing relocation of 1.2 million people
Tapping Groundwater Supplies • About ½ of the drinking water in the US is pumped from aquifers • Advantages • Year-round use • Renewable if not overpumped or contaminated • No evaporation losses • Often less expensive
Tapping Groundwater Supplies • Disadvantages • Water table lowering • Overpumping • Sinking of land (subsidence) when water removed • Chemical contamination • Saltwater intrusion into drinking water supplies near coastal areas
Ogallala Aquifer • Underlies 8 states from SD to TX • Held more water than all freshwater on Earth • Water shortages
Desalinization • Removing salt from sea water: reverse osmosis • currently 3-4x more expensive
Towing Icebergs • Carry fresh water to places that need it • How can it be done? Would it be economically sound?
Water Efficiency and Conservation • Change in personal habits • Fix leaky pipes • Water–saving toilets, faucets, & shower heads • Plant drought–tolerant vegetation in residential communities located in arid & semi–arid areas • Increase efficiency of irrigation • drip irrigation, computer monitoring, center-pivot • Use recycled water • treat gray water from showers, washing machines for reuse • Education