Presentation on theme: "Chapter 5: Water “All is born of water, all is sustained by water.”"— Presentation transcript:
1Chapter 5: Water “All is born of water, all is sustained by water.” Johann Wolfgang von GoetheGerman Poet and DramatistPowerpoint Templates
25.1: Our Water ResourcesMuch of our water we drink today has been around since water first formed on Earth millions of years agoClean, fresh water is essential to life and is critical to human healthPeople can survive for more than a month without food; can only life for a few days without waterPeople live longer today because we have clean water (to drink, to bathe in, to wash with, to irrigate crops and to flush away sewage)Water is renewable; endlessly circulated through the water cycle
3Water, Water Everywhere, but… Earth is called the water planetAbout 70% of Earth’s surface is covered by water97% of that water is salt water3% is fresh water; 77% of that is frozen in the polar icecaps; leaving only a fraction of the freshwater for human useThe water we require for our everyday needs (agriculture and drinking) comes from two sources: surface water and groundwater
4Surface WaterMost large cities depend on surface water (fresh water that is above ground in lakes, ponds, rivers and steams)All rivers are a result of precipitation; rain falls, snow melts; it all drains into rivers (ex: Mississippi)Area of land that is drained by a river is its watershed; amount of water that falls on a watershed varies from year to yearLakes provide a more stable water source
5Rivers of ControversyRiver water is in high demand; disputes over who have rights to it occur (ex: Colorado River) oftenColorado River flows 1450 miles; passes through the Grand Canyon to Gulf of California; by the time it reaches the Gulf there is very little water left because so much has been removed along the way40% of world’s people rely on water that originates in another country; conflicts over water rights, especially when dams are built restricting flow to other countries downstream are commonDisputes over water rights is likely to become more common as populations increase and demand for fresh water increases
6DamsStructures built across a river to restrict the flow of water downstream and form a reservoir (artificial lake)Water is used drinking, irrigation, manufacturing, flood control, electricityMixed blessing: artificial lake destroys existing ecosystems when they are formed and disrupts ecosystems downstream when they get less waterNo additional dams being built in US but other countries will probably continue to build
7GroundwaterNot all rain flows into rivers and streams, some soaks into the groundPlants use some of the water, most seeps undergroundLarge amounts of water is found underground in rock formations called aquifers (consist of rocks, sand, gravel with lots of air space where water can accumulate)Aquifers continuously receive water that percolates down from the surface (very slow process)Area of land from which groundwater originates is called it recharge zoneDeep: wells; close to surface: springs
8Aquifers Are Running Low Problem: People are pumping out water faster than it can be replaced naturally; consequently, water levels are dropping rapidlyOgallala Aquifer (western US) is being depleted rapidlySome communities who once depended on aquifers are now using other sources of fresh water
9Solutions to Water Shortages Many potential solutions to water shortages:Develop new sources of fresh waterUse less by practicing conservationMinimize pollution
10Desalting the SeaSome coastal countries and communities are trying to resolve water shortages by removing salt from salt water (desalinization)Two main methods of desalinization are distillation and reverse osmosis (pressure is used to push the water through a semi-permeable membrane that does not allow salt to pass through)Very expensive
11Towing Water Considered towing water from one place to another Ex: towing icebergs; problem with this? They melt, hard to towAlaska considered sending fresh water in huge plastic bags and selling it!
12Water Conservation Fresh water is a precious and limited resource It takes time for water to move through the water cycle, so people need to do whatever they can to use water wisely- install low flow faucets and showerheads- turn off tap while brushing teeth or shaving- water lawns at night- put filled water bottles in toilet tanks
135.2: Freshwater Pollution Over the past 20 years, developed countries have been working to clean up polluted waters.Less developed countries continue to have polluted water from industrial and agricultural waste. (Soviet bloc countries and Poland are among the worst)In poor countries, industry is NOT the problem but population has outgrown the water supply; only supply of drinking water is polluted with sewage and agriculture runoff, causing sickness and death from waterborne diseases.
14Freshwater Pollution…continued Water pollution – chemical, physical or biological agents introduced into the water supply degrading the quality and affecting the organisms depending on it.Two underlying causes: industrialization and human population explosions
15Point PollutionPollution that is discharged from a single source (ex: factory, waste treatment plant, oil tanker)Relatively easy to regulate and control because it is easily identified and tracedHard to enforce clean-up
16Nonpoint PollutionComes from many sources rather than from a single specific site; reaches bodies of water via streets and storm sewers (ex: homes, lawns, farms, highways, also from pesticides, fertilizers, animal feces)Extremely difficult to regulate and controlSmall amounts add up to a huge pollution problem; 96% of polluted bodies of water come from nonpoint pollution contaminationPublic awareness and education will probably be the most effective way of reducing nonpoint pollution
17Wastewater Treatment Plants Water that goes down a drain ends up in a wastewater treatment plant; then returned to a river or lakeCannot always remove all the harmful substances; home wastewater is biodegradable and can be purified; industrial and storm runoff may contain toxic substances that interfere with treatmentBy-product of wastewater treatment is sludge; many contain toxic chemicals; incinerated and then buriedNon-toxic sludge can be used as fertilizer (contain plant nutrients) if it is free of toxins; can be made into bricks when combined with clay
18PathogensDisease causing organisms (bacteria, viruses, parasitic worms)Can enter water supplies in untreated wastewater or animal fecesCholera, hepatitis, typhoid are diseases people can get from drinking water containing these pathogensPublic water supplies are constantly monitored for the presence of these pathogens.
19How Water Pollution affects Ecosystems Biological magnification – starts at the level where a toxin enters the ecosystem; bottom dwelling organisms enter their bodies-> eaten by small fish -> eaten by large fish -> eagleThe toxin increases in concentration from one tropic level to the nextPolluted water may also cause an immediate change in the ecosystem; killing nearly all things for miles downstreamHarmful to humans; harmful to fish (cancers, scale rot, fin rot) or accumulate in fish tissue making them dangerous for humans to consume (birth defects, reproductive, nervous system, liver, kidney damage)
20Artificial Eutrophication Eutrophication occurs naturally over time; however, the addition of inorganic plant nutrients (phosphorous and nitrogen) from fertilizer runoff and sewage causes excessive growth of algae (algal blooms) which die and when they decompose use large amounts of dissolved oxygen in the water; fish suffocate and dieSome states are now banning phosphate detergents; others have limited the amount of phosphates in the detergents
21Thermal PollutionExcess amount of heat added to the water creates thermal pollution; from power plants and industries use the cool water to circulate in their engines and then return the warmed water to the lake or riverCan kill large quantities of fish when it is too warm; warm water holds less oxygen – depriving organisms of oxygen; constant influx of warm water disrupts the ecosystemCitizens are usually opposed to new construction of power plants
22Cleaning Up Water Pollution Congress has passed several laws designed to improve water quality in the US1972 – Clean Water ActMarine Protection, Research and Sanctuaries Act1975 – Safe Drinking Water Act1980 Comprehensive Environmental Response Compensation and Liability Act1987 Water Quality ActThey were able to succeed in curbing point pollution, but non-point pollution continues to be a problem
23The Special Problem of Groundwater Pollution Likely to plague us for centuries to come (pesticides, fertilizers, agricultural chemicals are common pollutants)EPA has detected at least 200 hazardous chemicals that can seep through the soil and into groundwaterGroundwater recharges very slowly so it is very difficult to decontaminate the aquifers
24Bottled WaterMany people have opted to drink more bottled water than tap because they feel it is safer to drinkMost bottled water comes from the tap that is filtered and treated with various chemicalsBottled water is regulated by the government but is NOT tested for pollutants as often as the public water supply is tested
255.3: Ocean PollutionHow much pollution can the oceans absorb? Sailors have reported a “river of polystyrene” that stretches across the ocean from Bermuda to the African coast.How long will it take to decompose?Where does it come from?
26How Pollution Gets Into Oceans At least 85% of ocean pollution (mostly oil) comes from activities on the land (most occurring near the coastline); harms sensitive coastal ecosystems like coral reefs and estuaries the mostPollution entering rivers flows to the oceanPollutants are dumped directly into the oceans (sludge from wastewater treatment and garbage)Accidental oil spills, only 5% (Exxon Valdez, 1989); plastic (six pack rings, bags, fishing line)
27Preventing Ocean Pollution MARPOL – prohibits the discharge of oil and disposal or abandonment of plastic in oceans or coastal water1974 Helsinki Convention – seeks to control land-based sources of ocean pollution (toxic dumping – DDT, cadmium, mercury); and raw wastewaterUS is strengthening its laws: 1990 (Marine Mammal Protection Act) requiring ships have double hullsProblem: It is difficult to monitor every ship in the ocean
28Who Owns the Oceans?Who has jurisdiction over the oceans? In the past, international law allowed nations to control the water extending out 3 miles from the coast; rest of the ocean was high seas and open to everyoneNow, Law of Sea Treaty – extends out 12 nautical miles (22 km) or its territorial sea and then another 370 km (200 nautical mi) or its exclusive economic zone (environmental preservation and research); the rest is communalUS did not sign treaty (didn’t like restrictions on seabed mineral mining)