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Explore the scarcity of usable water on Earth, including aquifers, groundwater recharge, surface water, and human impact on water availability. Discover methods like desalination and dams to manage water resources effectively.
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Chapter 9 Water Resources
Usable Water is Rare • Figure 9.1 Fresh water represents less than 3% of all water on Earth, and only about three-fourths of that fresh water is surface water. Most of the surface water is frozen as ice and in glaciers. Less than 1% of all water on the planet is accessible for use by humans.
Groundwater • Aquifers- small spaces found within permeable layers of rock and sediment where water is found. • Unconfined aquifers- an aquifer that is simply porous rock covered by soil. Unconfined aquifers are rapidly recharged by water that percolates downward from the land surface. • Confined aquifers- an aquifer capped by an impermeable layer of rock or clay, which can cause water pressure to build up underground.
Groundwater • Figure 9.2 Aquifers are sources of usable groundwater.
Groundwater • Water table- the uppermost level at which the water in an area fully saturates the rock or soil. • Groundwater Recharge- the input process of water percolating into an aquifer. • Springs- water from an aquifer that naturally percolates up to the surface. • Artesian well- when a hole is drilled into a confined aquifer releasing the pressure on the water, allowing it to burst out of the aquifer and rise up in the well. No pump needed to get the water to the surface.
Groundwater • Figure 9.4 (a) shows the Ogallala aquifer. It is the largest aquifer in the U.S. • In this figure, red and orange represent the water-level change in meters. Some areas in Texas have had a 45 meter decline in the aquifer due to irrigation.
Groundwater • Cone of depression- an area where there is no longer any groundwater due to rapid pumping. • Figure 9.5 (a) shows a area where the deep well is used at a sustainable rate. (b) shows a deep well pumping water from an aquifer more rapidly and recharge cannot occur.
Groundwater • Saltwater intrusion- when the pumping of fresh water out of a well is faster than the recharge. Near coastal areas this can cause salt water to infiltrate the aquifer. • Figure 9.6 (b) shows the lowering of the water table reduces water pressure in the aquifer.
Surface Water • Surface water is the fresh water that exists above the ground. Examples include streams, rivers, ponds, lakes and wetlands. • Figure 9.7 shows statistical measurements of the seven largest lakes in the world. (surface area, depth, and volume)
Surface Water • Lakes are classified by their level of primary productivity. There are three levels. • Oligotrophic- low amounts of nutrients such as phosphorous and nitrogen. • Mesotrophic- a moderate level of productivity • Eutrophic- high levels of productivity
Atmospheric Water • Although the atmosphere contains only a very small percentage of the water on Earth, that atmospheric water is essential to global water distribution. • Figure 9.8 shows the dust bowl. Poor agricultural practices combined with prolonged drought can produce severe dust storms.
Humans can altering the availability of water • Levees- an enlarged bank built up on each side of the river. • Dikes- similar to a levee but built to prevent ocean waters from flooding adjacent land. • Figure 9.9 shows a levee which broke near St. Louis, Missouri in 2008.
Humans can altering the availability of water • Dams- a barrier that runs across a river or stream to control the flow of water. • Reservoir- the area where water is stored behind the dam. • Figure 9.10 shows Three Gorges Dam, the largest dam in the world. It is used for both flood control and electricity generation.
Humans can altering the availability of water • Fish ladders- a set of stairs with water flowing over them that have been added to some dams to help migrating fish such as salmon get upstream. • Figure 9.11 shows a fish ladder in New Brunswick, Canada, which help native fish reach their traditional breeding grounds.
Humans can altering the availability of water • Aqueducts- canals or ditches used to carry water from one location to another. • Figure 9.12 shows a section of the Colorado River Aqueduct, which diverts water from the Colorado River to Los Angeles, and passes through the Mojave Desert.
Humans can altering the availability of water • Desalination- removing the salt from salt water to obtain fresh water. • Figure 9.14 (a) shows how distillation uses heat to convert pure water into steam that is later condensed, leaving the salt behind. • (b) Reverse osmosis uses pressure to force pure water through a semi impermeable membrane, leaving the salt behind.
Humans can altering the availability of water • Figure 19.5 shows water availability per capita The amount of water available per person varies tremendously around the world. North Africa and the Middle East are the regions with the lowest amounts of available fresh water.
Agriculture, Industry and Household Needs • The daily use of water per capita varies dramatically among the nations of the world. • Figure 9.16 shows the total water use per person for agriculture, industry and household use varies tremendously by country. • The top three countries are U.S., Spain, and Canada.
Agriculture, Industry and Household Needs • Agriculture- the largest user of water around the world.
Agriculture, Industry and Household Needs • Five Irrigation techniques- • Furrow irrigation- a trench that is flooded with water. • Flood irrigation- the entire field is flooded with water. • Spray irrigation- an apparatus that sprays water across a field. • Drip irrigation- using a slow dripping hose that is laid on or buried beneath the soil. • Hydroponic agriculture- crops grown in fertilized water and no soil.
Agriculture, Industry and Household Needs • Industry- the second largest user of water worldwide. Industry uses water for generating electricity, cooling machinery, and refining metals and paper. • Figure 9.19 shows a nuclear power plant in Germany. Here the heated water is changed to steam and a great deal of water vapor is released into the atmosphere.
Agriculture, Industry and Household Needs • Households- the third largest user of water worldwide. About 10% of all water used in the U.S. is used in homes. • Figure 9.20 shows household per capita water use per day. The figure shows Australians, Canada's, and Americans use the most per day.
Agriculture, Industry and Household Needs • Indoor water use focuses on toilet flushing, bathing, laundry, and cooking and drinking. • Figure 9.21 shows that most Americans indoor use focuses on flushing toilets at 41%.
The Future of Water Availability • Water ownership- people can have rights to water use, but they do not own the water. • Water conservation- using techniques such as more efficient water fixtures, faucets and washing machines. • Figure 9.23 shows that homeowners in Arizona can use native plants to reduce water consumption.
The Future of Water Availability • Grey Water is defined as the wastewater from baths, showers, bathroom sinks, and washing machines. • Figure 9.25 Reusing gray water. A Turkish inventor has designed a washing machine that pipes the relatively clean water left over from a washing machine, termed gray water, to a toilet, where it can be reused for flushing.
