Chapter 15

Transcript Chapter 15

Lecture Outlines Chapter 15

Environment: The Science behind the Stories 4th Edition

This lecture will help you understand:

• • • • • • Water’s importance to people and ecosystems Water’s distribution Use and alteration of freshwater systems Problems of water supply and solutions Problems of water quality and solutions How wastewater is treated © 2011 Pearson Education, Inc.

Gambling with water in the Colorado River basin

• • • • • • 7 states share the Colorado river Droughts and overuse are threatening supplies Las Vegas, Nevada, needs more water than it is allotted Other states will let Las Vegas drill for underground water Drilling threatens the area’s ecology and people This issue will end up in Nevada’s Supreme Court © 2011 Pearson Education, Inc.

The Colorado River

• • • The Colorado River originates in the Rocky Mountains Draining into the Gulf of California Its waters chiseled the Grand Canyon But it has been reduced to a mere trickle Dams provide flood control, recreation, and hydroelectric power 30 million people use the water © 2011 Pearson Education, Inc.

Freshwater systems

• • Water may seem abundant, but drinkable water is rare

Freshwater

Water is renewed and recycled

• • • • • As water is cycled it redistributes heat, erodes mountains, builds river deltas, maintains ecosystems and organisms It also shapes civilizations and political conflicts

Surface water

= on Earth’s surface 1% of freshwater

Runoff

= water that flows over land Water merges in rivers and ends up in a lake or ocean

Tributary

= a smaller river slowing into a larger one

Watershed

(

drainage basin

) = the area of land drained by a

river system

Water is renewed and recycled as it moves through the hydrologic cycle

Water Cycle Scramble

Rivers and streams wind through landscapes

• • • Rivers shape the landscape

Braided river

= an interconnected series of watercourses that run through steep slopes

Meandering river

Rivers shape the landscape

• • Oxbows = areas where river bends become exaggerated

Oxbow lake

A river may shift course over time

• • •

Floodplain

= areas nearest to the river’s course that are flooded periodically Frequent deposition of silt makes floodplain soils fertile Good areas for agriculture

Riparian

= riverside areas that are productive and species-rich Rivers and streams hosts diverse ecological communities Algae, insects, fish, amphibians, birds, etc.

Lakes and ponds are ecologically diverse

• • • • • Lakes and ponds = bodies of open, standing water

Littoral zone

= region ringing the edge of a water body Rooted aquatic plants grow in this shallow part

Benthic zone

= extends along the bottom of the water body Home to many invertebrates

Limnetic zone

= open portion of the lake or pond where sunlight allows photosynthesis

Profundal zone

A typical lake

Lakes vary in their nutrients and oxygen

• • • •

Oligotrophic

lakes and ponds = have low nutrient and high oxygen conditions

Eutrophic

lakes and ponds = have high nutrient and low oxygen conditions Eventually, water bodies fill completely in through the process of succession The largest lakes are known as inland seas Great Lakes, The Caspian Sea © 2011 Pearson Education, Inc.

Wetlands include marshes, swamps, bogs, and seasonal pools

• • • •

Wetlands

= the soil is saturated with shallow standing water

Freshwater marshes

= shallow water Plants grow above the surface

Swamps

= shallow water in forested areas Can be made by beavers

Bogs

Species in vernal pools are adapted to seasonal drying

Wetlands are valuable

• • • Wetlands are extremely valuable for wildlife They slow runoff, reduce flooding, recharge aquifers, and filter pollutants People have drained wetlands, mostly for agriculture Southern Canada and the U.S. have lost over half of their wetlands In 2006 the Supreme Court told the Army Corps of Engineers it must create guidelines to determine when wetlands are valuable enough to protect by law © 2011 Pearson Education, Inc.

Groundwater plays a key role

• • •

Groundwater

= water beneath the surface held in pores in soil or rock 20% of the Earth’s freshwater supply

Aquifers

= porous, sponge-like formations of rock, sand, or gravel that hold water -

Zone of aeration

water = pore spaces are partly filled with -

Zone of saturation

= spaces are filled with water -

Water table

= boundary between the two zones

Recharge zone

A typical aquifer

There are two categories of aquifers

• • • •

Confined (artesian) aquifer

= water-bearing, porous rocks are trapped between less permeable substrate (clay) layers Is under great pressure

Unconfined aquifer

= no upper layer to confine it Readily recharged by surface water Groundwater’s average age is 1,400 years It may be tens of thousands of years old Groundwater becomes surface water through springs or human-drilled wells © 2011 Pearson Education, Inc.

The Ogallala Aquifer

• • The world’s largest known aquifer Underlies the Great Plains of the U.S.

Its water has allowed farmers to create the most bountiful grain-producing region in the world

Water is unequally distributed across Earth

• Water is unevenly distributed in space and time Different areas possess different amounts of water People erect dams to store water

Many densely populated areas are water-poor and face serious water shortages

Climate change may bring shortages

• Climate change will cause Altered precipitation patterns Melting glaciers Early season runoff Intensified droughts Flooding

Lake Mead is already hurting from drought

How we use water

• • We have achieved impressive engineering accomplishments to harness fresh water 60% of the world’s largest 227 rivers have been strongly or moderately affected Dams, dikes, and diversions Consumption of water in most of the world is unsustainable We are depleting many sources of surface water and groundwater © 2011 Pearson Education, Inc.

Water supplies houses, agriculture, and industry

• • • Proportions of these three types of use vary dramatically among nations Arid countries use water for agriculture Developed countries use water for industry

Consumptive use

= water is removed from an aquifer or surface water body and is not returned Irrigation = the provision of water to crops

Nonconsumptive use

Why does agriculture use so much water?

• • • • • Rapid population growth requires more food and clothes The Green Revolution uses irrigation We use 70% more irrigation water than 50 years ago Irrigation can double crop yields 18% of land is irrigated but produces 40% of our crops Irrigation is highly inefficient Water evaporates in “flood and furrow” irrigation Overirrigation leads to waterlogging and salinization Reducing world farm income by $11 billion © 2011 Pearson Education, Inc.

Governments subsidize irrigation

• • Irrigation subsidies promote food self-sufficiency But irrigation uses up huge amounts of groundwater for little gain Water in the Colorado River Valley is diverted for cotton and other crops grown in the desert

Farmers in California’s Imperial Valley pay only 1 penny for 220 gallons of water

We divert surface water for our needs

• People divert water to farm fields, homes, and cities

The once mighty Colorado River has been extensively diverted and used

Water-poor regions take water from others

• • • • Politically strong, water-poor areas forcibly take water from weaker communities Los Angeles commandeered water from rural areas Turning the environment into desert, creating dustbowls, and destroying the economy In 1941, L.A. diverted streams that fed Lake Mono Lake levels fell, salt concentrations doubled Las Vegas wants to import water from sparsely populated eastern Nevada An ecologically sensitive area © 2011 Pearson Education, Inc.

We build dikes and levees to control floods

• • • •

Flooding

= a normal, natural process where water spills over a river’s banks Spreading nutrient-rich sediments over large areas In the short term, floods damage property

Dikes

and

levees

(long, raised mounds of earth) along the banks of rivers hold water in channels Levees make floods worse by forcing water to stay in channels and then overflow Dams prevent flooding and change a river’s nature Releasing water periodically simulates flooding © 2011 Pearson Education, Inc.

Levees increase flooding

We have erected thousands of dams

• • •

Dam

= any obstruction placed in a river or stream to block the flow of water to prevent floods, provide drinking water, allow irrigation, and generate electricity 45,000 large dams have been erected in more than 140 nations Only a few major rivers remain undammed In remote regions of Canada, Alaska, and Russia Dams are great engineering feats Many stand hundreds of feet tall © 2011 Pearson Education, Inc.

A typical dam

China’s Three Gorges Dam

• The dam, on the Yangtze River, is the largest in the world 186 m (610 feet) high, 2.3 km (1.4 mi) wide Its reservoir stretches for 616 km (385 mi) Provides flood control, passage for boats, and electricity © 2011 Pearson Education, Inc.

Drawbacks of the Three Gorges Dam

• • • • • • Cost $39 billion to build Flooded 22 cities and the homes of 1.24 million people Submerged 10,000-year-old archaeological sites Drowned farmland and wildlife habitat Tidal marshes at the Yangtze’s mouth are eroding Pollutants will be trapped

It will cost $5 billion to build sewage treatment plants to treat water

Some dams are being removed

• • • Some people feel that the costs of dams outweigh their benefits They are pushing to dismantle dams The Federal Energy Regulatory Commission (FERC) renews licenses for dams If dam costs exceed benefits, the license may not be renewed 400 dams have been removed in the U.S.

We are depleting surface water

• In many places, we are withdrawing water at unsustainable rates Reduced flow drastically changes the river’s ecology, plant community, and destroys fish and invertebrates

The Colorado River often does not reach the Gulf of California

The Aral Sea

• • • • • Once the fourth-largest lake on Earth It lost 80% of its volume in 45 years The two rivers leading into the Aral Sea were diverted to irrigate cotton fields 60,000 fishing jobs are gone Pesticide-laden dust from the lake bed is blown into the air Cotton cannot save the region’s economy © 2011 Pearson Education, Inc.

Can the Aral Sea be saved?

People have begun saving the northern part of the Aral Sea

Irrigation wastes water

• 15–35% of water withdrawals for irrigation are unsustainable •

Water mining

The world is losing wetlands

• • • • Wetlands are being lost as we divert and withdraw water Channelize rivers, build dams, etc.

As wetlands disappear, we lose ecosystem services Filtering pollutants, wildlife habitat, flood control, etc.

Many are trying to protect and restore them The

Ramsar Convention on Wetlands of International Importance

We are depleting groundwater

• • • • Groundwater is easily depleted Aquifers recharge slowly Used by one-third of all people As aquifers are mined, water tables drop Salt water intrudes in coastal areas

Sinkholes

Can we quench our thirst for bottled water?

• • • Groundwater is being withdrawn for bottled water An average American drinks 29 gallons/year People drink bottled water for portability, convenience They think it tastes better or is healthier Bottled water is no better than tap water It is heavily packaged and travels long distances using fossil fuels Bottles are not recycled Corporations move in, deplete water, and move away © 2011 Pearson Education, Inc.

Bottled water is popular but problematic

• Bottled water is popular but it has several problems

Energy costs of bottled water are 1,000–2,000 times greater than those of tap water

Will we see a future of water wars?

• • • Freshwater depletion leads to shortages, which can lead to conflict 261 major rivers cross national borders Water is a key element in hostilities among Israel, Palestinians, and neighboring countries Many nations have cooperated with neighbors to resolve disputes They sign water-sharing treaties © 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

filter out salts = forces water through membranes to Desalinization facilities operate mostly in the arid Middle East It is expensive, requires fossil fuels, kills aquatic life, and produces salty waste © 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.

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.

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

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 © 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 © 2011 Pearson Education, Inc.

Freshwater pollution and its control

• • • Water for human consumption and other organisms needs to be: Disease-free Nontoxic Half of the world’s major rivers are seriously depleted and polluted They poison surrounding ecosystems Threatening the health and livelihood of people The invisible pollution of groundwater has been called a “covert crisis” © 2011 Pearson Education, Inc.

Point and nonpoint sources of pollution

• • • Pollution = the release of matter or energy that causes undesirable impacts on the health and well-being of humans or other organisms

Point sources

= discrete locations of water pollution Factories, sewer pipes Addressed by the U.S. Clean Water Act

Nonpoint sources

Freshwater pollution sources

Nutrient pollution

• • Nutrient pollution from fertilizers, farms, sewage, lawns, golf courses leads to eutrophication Fertilizers add phosphorus to water, which boosts algal and aquatic plant growth Spreading algae cover the surface, decreasing sunlight Bacteria eat dead algae, reducing dissolved oxygen Fish and shellfish die Solutions include treating wastewater Reducing fertilizer application Using phosphate-free detergents Planting vegetation to increase nutrient uptake © 2011 Pearson Education, Inc.

Eutrophication is a natural process, but…

Pathogens and waterborne diseases

• • • Enter water supplies through inadequately treated human waste and animal waste from feedlots Fecal coliform bacteria indicate fecal contamination They are not pathogenic organisms But the water may also hold other disease-causing pathogens (e.g., giardiasis, typhoid, hepatitis A) Bacterial pollution causes more human health problems than any other type of water pollution Conditions are improving 86% of people now have safe water © 2011 Pearson Education, Inc.

Pathogens cause human health problems

• • • • 1 billion are still without safe water 2.6 billion have inadequate sewer or sanitary facilities Mostly rural Asians and Africans Health impacts kill 5 million people per year Solutions: Disinfect drinking water Treat sewage Public education to encourage personal hygiene Government enforcement of regulations protecting food © 2011 Pearson Education, Inc.

Toxic chemicals

• • • Pesticides, petroleum products, synthetic chemicals Arsenic, lead, mercury, acid rain, acid drainage from mines Effects include poisoned animals and plants, altered aquatic ecosystems, and decreased human health Solutions: Issue and enforce more stringent regulations of industry Modify industrial processes Modify our purchasing decisions © 2011 Pearson Education, Inc.

Sediment pollution

• • • • Sediment in rivers can impair aquatic ecosystems Clear-cutting, mining, clearing land for housing, and cultivating farm fields expose soil to erosion It dramatically changes aquatic habitats Fish may not survive Solutions: Better management of farms and forests Avoid large-scale disturbance of vegetation © 2011 Pearson Education, Inc.

Thermal pollution

• • Water that is too warm causes problems Warmer water holds less oxygen Dissolved oxygen decreases as temperature increases Industrial cooling heats water Removing streamside cover raises water temperature Water that is too cold also causes problems Water at the bottom of reservoirs behind dams is colder When water is released, downstream water temperatures drop suddenly, killing aquatic organisms © 2011 Pearson Education, Inc.

Indicators of water quality

• Scientists measure properties of water to characterize its quality Biological indicators: presence of fecal coliform bacteria, disease-causing organisms, algae, etc.

Groundwater pollution is a difficult problem

• • Groundwater is increasingly contaminated But is hidden from view and difficult to monitor “Out of sight, out of mind” Groundwater pollution is hard to address It retains contaminants for decades and longer It takes longer for contaminants to break down because of lower sunlight, microbes, and dissolved oxygen © 2011 Pearson Education, Inc.

Sources of groundwater pollution

• • Some toxic chemicals occur naturally Aluminum, fluoride, sulfates Pollution from human causes wastes leach through soils Pathogens enter through improperly designed wells Leaking underground storage and septic tanks

So far, the EPA has cleaned up 388,000 leaking tanks

Agriculture and industry pollute groundwater

• • Agricultural pollution comes from several sources Pesticides are in most of the shallow aquifers tested Nitrates from fertilizers have caused cancer, miscarriages, and “blue-baby” syndrome Pathogens like

Escherichia coli

(

E. coli

) Manufacturing industries and military sites have been heavy polluters By-products seep into water from miles around Radioactive wastes will contaminate water for 750,000 years © 2011 Pearson Education, Inc.

It is best to prevent pollution

• • • It is far better to prevent pollution than use “end-of-pipe” treatment and cleanup Other options are not as good: Removing just one herbicide from water in the U.S. Midwest costs $400 million/year Pumping, treating, and re-injecting it takes too long Consumers can purchase sustainably made products Become involved in local “riverwatch” projects Urge government to pursue policies to fight pollution © 2011 Pearson Education, Inc.

Legislative efforts reduce pollution

• • Water pollution was worse decades ago Citizen activism and government response resulted in legislation during the 1960s and 1970s The situation is much better now The Federal Water Pollution Control Act (1972) Renamed the Clean Water Act in 1977 It is illegal to discharge pollution without a permit Sets standards for industrial wastewater Funded sewage treatment plants © 2011 Pearson Education, Inc.

Enforcement of water quality is decreasing

• • • Underfunded and understaffed state and federal regulatory agencies were pressured by industries and politicians Violations of the Clean Water Act have risen to over 100,000 documented violations/year 10% of Americans are unknowingly exposed to unsafe drinking water The new EPA administrator has promised to improve Citizens pushed politicians to improve the Great Lakes The water quality of the lakes has dramatically improved © 2011 Pearson Education, Inc.

We treat our drinking water

• • • Technology and government regulation have improved our pollution control Treated drinking water is widespread and successful in developed nations Before water reaches the user, it is chemically treated, filtered, and disinfected The EPA sets standards for over 90 drinking water contaminants Local governments and private water suppliers must meet these standards © 2011 Pearson Education, Inc.

We treat our wastewater

• •

Wastewater

= water people have used in some way Household, manufacturing, stormwater runoff, etc.

It is treated before being released into the environment

Septic systems

= the most popular method of wastewater disposal in rural areas Underground septic tanks separate solids and oils from wastewater The water drains into a drain field, where microbes decompose the pollutants Solid waste is periodically pumped out and landfilled © 2011 Pearson Education, Inc.

Municipal sewer systems

• • • • In populated areas, sewer systems carry wastewater to treatment locations

Primary treatment

= physically removes contaminants in settling tanks (clarifiers)

Secondary treatment

= water is stirred and aerated Aerobic bacteria degrade organic pollutants Water treated with chlorine (and/or ultraviolet light) is piped into rivers or the ocean Reclaimed water is used for lawns, irrigation, or industry © 2011 Pearson Education, Inc.

A typical wastewater treatment facility

• •

Sludge

= solid material resulting from treatment Is decomposed microbially Then landfilled, incinerated, or used as fertilizer on cropland Methane-rich gas created by decomposition can be burned to generate electricity © 2011 Pearson Education, Inc.

Artificial wetlands clean wastewater

• • • After primary treatment at a conventional facility Water is pumped into the wetland Microbes decompose the remaining pollutants Cleansed water is released into waterways Or percolates underground They are havens for wildlife and areas for human recreation

The U.S. has over 500 artificially constructed or restored wetlands

Conclusion

• • • • Obtaining future supplies of freshwater requires citizen action, legislation and regulation, technology, economic incentives, and education With expanding population and increasing water usage, we are approaching conditions of widespread scarcity Water pollution is already harming health, economies, and societies of both rich and poor nations Better regulation has improved water quality in the U.S. and other developed nations © 2011 Pearson Education, Inc.

QUESTION: Review

The area of a lake that rings the edge and contains rooted plants is called the _______ zone.

QUESTION: Review

An unconfined aquifer is defined as: a) An aquifer that traps porous rocks between layers of less permeable substrate b) An aquifer that traps porous rocks under one layer of less permeable substrate c) An aquifer with porous rocks resting on bedrock d) An aquifer with no upper layer © 2011 Pearson Education, Inc.

QUESTION: Review

Why do governments subsidize irrigation?

a) It promotes food self-sufficiency.

b) Governments have to or food could not be grown.

c) Governments want to lower water tables.

d) Governments do not subsidize irrigation.

QUESTION: Review

Which of the following statements is NOT true about dams?

a) They change habitat.

b) They generate electrical power.

c) They have created more farmland upstream.

d) Pollutants are trapped in reservoirs.

QUESTION: Review

Which of the following is a point source of water pollution?

QUESTION: Review

Which of the following type of water pollution causes the most severe human health problems?

QUESTION: Review

Which statement is NOT correct regarding using artificial wetlands to treat wastewater?

a) Water first undergoes primary treatment.

b) Microbes decompose pollutants.

c) Cleansed water cannot be released into waterways.

d) They are good areas for wildlife.

QUESTION: Interpreting Graphs and Data

In this figure of a wastewater treatment facility, what is the first step in treatment?

QUESTION: Viewpoints

During times of drought, conflicts erupt between farmers (who need water for irrigation) and ecologists (who want water left in rivers to protect wildlife). Who should have the highest priority?

a) Farmers - they need the water for their crops.

b) Wildlife - animals will die without water.

c) Farmers should be paid subsidies to withdraw water from other places.

d) Farmers should be paid to plant different crops that do not require so much water.

QUESTION: Weighing the Issues

Should cities in dry areas, such as Las Vegas, be allowed to increase their populations, so that they will require more water?

a) Yes; it’s un-American to limit what cities can do.

b) Yes; but make the people pay the true cost of water.

c) Yes; but only if the people are required to use drastic conservation measures.

d) No; enough is enough, and cities in arid environments simply cannot continue growing.