22
© 2011 Pearson Education, Inc. SWBAT Problems of water supply and solutions

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

Embed Size (px)

Citation preview

© 2011 Pearson Education, Inc.

SWBAT

• Problems of water supply and solutions

© 2011 Pearson Education, Inc.

Groundwater & Groundwater Depletion

• Where surface water, such as lakes and rivers, are scarce or inaccessible, groundwater supplies many of the hydrologic needs of people everywhere.

• In the United States, it is the source of drinking water for about half the total population and nearly all of the rural population, and it provides over 50 billion gallons per day for agricultural needs.

• Groundwater depletion, a term often defined as long-term water-level declines caused by sustained groundwater pumping, is a key issue associated with groundwater use. Many areas of the United States are experiencing groundwater depletion.

© 2011 Pearson Education, Inc.

Some of the negative effects of groundwater depletion:

• drying up of wells• reduction of water in streams and lakes• deterioration of water quality• increased pumping costs• land subsidence

© 2011 Pearson Education, Inc.

Where does land subsidence occur in the United States?

© 2011 Pearson Education, Inc.

Industrial water useIndustrial withdrawals were about 4 percent of Nation's total withdrawals

• The industries that produce metals, wood and paper products, chemicals, gasoline and oils are major users of water.

• Industrial water use includes water used for such purposes as fabricating, processing, washing, diluting, cooling, or transporting a product; incorporating water into a product; or for sanitation needs within the manufacturing facility.

• Some industries that use large amounts of water produce such commodities as food, paper, chemicals, refined petroleum, or primary metals.

© 2011 Pearson Education, Inc.

Industrial Water

• Louisiana used the most water for industrial purposes, mainly in the chemical and paper industries.

• Louisiana, Indiana, and Texas accounted for almost 38 percent of total industrial withdrawals, while Louisiana and Indiana accounted for 32 percent of the total fresh surface-water withdrawals.

• The largest fresh groundwater withdrawals were in Georgia, Louisiana, and Texas, which together accounted for 23 percent of the total fresh groundwater withdrawals.

• Texas accounted for 71 percent of the saline surface-water withdrawals for industry.

© 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

© 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

http://hbfreshwater.com/your-seawater-desalination-facility

© 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

© 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.

© 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

© 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.

© 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

© 2011 Pearson Education, Inc.

Line irrigation canals

Unlined irrigation canals

© 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.

© 2011 Pearson Education, Inc.

Drip irrigation systems

© 2011 Pearson Education, Inc.

Drip Irrigation or MicroirrigationThe 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 microirrigationMicroirrigation 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.

© 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

© 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/dayXeriscaping uses plants adapted to arid conditions

© 2011 Pearson Education, Inc.

Install low-flow faucets, showerheads, washing machines, and toilets

© 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 aquifers• Patch leaky pipes and retrofit homes with efficient

plumbing• Audit industries• Promote conservation/education

http://water.epa.gov/polwaste/nps/chap3.cfm

© 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