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© 2011 Pearson Education, Inc. SWBAT Problems of water supply and solutions.

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Presentation on theme: "© 2011 Pearson Education, Inc. SWBAT Problems of water supply and solutions."— Presentation transcript:

1 © 2011 Pearson Education, Inc. SWBAT Problems of water supply and solutions

2 © 2011 Pearson Education, Inc. Solutions can address supply or demand We can either increase supply or reduce demand Increasing supply through intensive extraction -Diversions increase supply in one area but decrease it elsewhere Reducing demand is harder politically in the short term -International aid agencies are funding demand-based solutions over supply-based solutions -Offers better economic returns -Causes less ecological and social damage

3 © 2011 Pearson Education, Inc. Desalinization “makes” more water Desalination (desalinization) = the removal of salt from seawater or other water of marginal quality -Distilling = evaporates and condenses ocean water -Reverse osmosis = forces water through membranes to filter out salts Desalinization facilities operate mostly in the arid Middle East -It is expensive, requires fossil fuels, kills aquatic life, and produces salty waste seawater-desalination-facility

4 © 2011 Pearson Education, Inc. The largest seawater desalination facility in the US, it produces an initial 25 million gallons per day (mgd) of drinking water, to help reduce the growing demand on the area's aquifers. The plant now provides 10% of the region’s drinking water supply. Tampa Bay Seawater Desalination Plant, United States of America

5 © 2011 Pearson Education, Inc. Some desalination facts It is estimated that some 30% of the world's irrigated areas suffers from salinity problems and remediation is seen to be very costly. In 2002 there were about 12,500 desalination plants around the world in 120 countries. They produce some 14 million m3/day of freshwater, which is less than 1% of total world consumption. The most important users of desalinated water are in the Middle East, (mainly Saudi Arabia, Kuwait, the United Arab Emirates, Qatar and Bahrain), which uses about 70% of worldwide capacity; and in North Africa (mainly Libya and Algeria), which uses about 6% of worldwide capacity. Among industrialized countries, the United States is one of the most important users of desalinated water (6.5%), specially in California and parts of Florida.

6 © 2011 Pearson Education, Inc. The world’s largest reverse osmosis plant Near Yuma, Arizona Intended to remove salt from irrigation runoff Too expensive to operate and closed after 8 months -Engineers are trying to re-open it in a cost- effective way

7 © 2011 Pearson Education, Inc. Lake Worth, Florida Reverse Osmosis Plant A reverse osmosis plant is a manufacturing plant where the process of reverse osmosis takes place. An average modern reverse osmosis plant needs six kilowatt-hours of electricity to desalinate one cubic meter of water. The process also results in an amount of salty briny waste. The challenge for these plants is to find ways to reduce energy consumption, use sustainable energy sources, improve the process of desalination and to innovate in the area of waste management to deal with the waste.

8 © 2011 Pearson Education, Inc. Agricultural demand can be reduced Line irrigation canals Level fields to reduce runoff Use efficient irrigation methods -Low-pressure spray irrigation sprays water downward -Drip irrigation systems target individual plants Match crops to land and climate Eliminate water subsidies Selective breeding and genetic modification to produce crops that require less water Eat less meat

9 © 2011 Pearson Education, Inc. Line irrigation canals Unlined irrigation canals

10 © 2011 Pearson Education, Inc. Skidmark Geomembrane™ Skidmark Geomembrane™ is a blend of recycled tire rubber and thermoplastic. It is used to line irrigation canals, primarily to save water but it can also prevent erosion and vegetation growth in canals. Future applications may include reservoir liners and secondary containment lining under hazardous liquid storage. This product was not developed to find a use for recycled tire rubber, but rather because of its ideal physical characteristics and the cost advantages it provides as a canal lining membrane. However, because Skidmark Geomembrane™ does use recycled tire rubber, it is an environmentally GREEN/GREEN product. How Much Water Can Be Saved This is an impossible question to answer but the opportunities are enormous. By conservative estimates, there can be from 30 to 50 percent water loss due to seepage during transport in unlined canals. Further, it has been estimated that there are 12,000 miles of unlined canals in the western United States.

11 © 2011 Pearson Education, Inc. Drip irrigation systems

12 © 2011 Pearson Education, Inc. Drip Irrigation or Microirrigation The bushes in this picture are being irrigated using the "drip irrigation" method, which is the most common type of "microirrigation." If you look closely you'll see the small horizontal pipes that are slowly dripping water running just above the ground. Drip irrigation is one of the more advanced techniques being used today because, for certain crops, it is much more efficient than traditional spray irrigation, where a larger portion of the water is lost to evaporation. In drip irrigation, water is run through pipes (with holes in them) either buried or lying slightly above the ground next to the crops. Water slowly drips onto the crop roots and stems. Unlike spray irrigation, very little is lost to evaporation and the water can be directed only to the plants that need it, cutting back on water waste. Advantages of microirrigation Microirrigation has gained attention during recent years because of its potential to increase yields and decrease water, fertilizer, and labor requirements if managed properly. Microirrigation systems can apply water and fertilizer directly to individual plants or trees, reducing the wetted area by wetting only a fraction of the soil surface; thus, water is applied directly to the root zone. Microirrigation is a low pressure, low volume irrigation system suitable for high-return value Crops such as fruit and vegetable crops. If managed properly, microirrigation can increase yields and decrease water, fertilizer and labor requirements. Microirrigation applies the water only to the plant's root zone and saves water because of the high application efficiency and high water distribution uniformity. Microirrigation can irrigate sloping or irregularly-shaped land areas that cannot be flood irrigated. Any water-soluble fertilizer may be injected through a microirrigation system.

13 © 2011 Pearson Education, Inc. Low-energy spray irrigation This is a picture of a type of center-pivot irrigation system that does not spray water through the air onto crops, though. It is called a Low Energy Precision Application (LEPA) center-pivot system. Instead of high-power spray units, this system has small water sprayers hanging down from a large water-carrying pipe above. At the bottom of each pipe, very close to the ground, is a nozzle that gently sprays water onto the crops. Because the nozzle is so close to the ground, you lose a lot less water to evaporation than you would with a traditional spray-irrigation system. Plus, electricity is saved because it takes less to use these low-powered systems. These systems allow more than 90-percent of the water pumped to be used by the crop -- pretty efficient! Typical sprinkler (spray) irrigation

14 © 2011 Pearson Education, Inc. Residential demand can be reduced Install low-flow faucets, showerheads, washing machines, and toilets Rainwater harvesting = capturing rain from roofs Gray water = wastewater from showers and sinks Water lawns at night We can save hundreds or thousands of gallons/day Xeriscaping uses plants adapted to arid conditions

15 © 2011 Pearson Education, Inc. Install low-flow faucets, showerheads, washing machines, and toilets

16 © 2011 Pearson Education, Inc. Industrial demand can be reduced Shift to processes that use less water -Wastewater recycling Use excess surface water runoff to recharge aquifersrecharge aquifers Patch leaky pipes and retrofit homes with efficient plumbing Audit industries Promote conservation/education

17 © 2011 Pearson Education, Inc. Market-based approaches to conservation End government subsidies of inefficient practices -Let the price of water reflect its true cost of extraction -But since industrial uses are more profitable than agricultural uses, poorer, less developed countries suffer Privatize water supplies: construction, maintenance, management, and ownership -May improve efficiency -There is little incentive to provide access to the poor Decentralization of water control may conserve water -Shift control to the local level


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