chap 13/14

Chapter 13: Water resources

Case study: The Colorado River Story 

• The Colorado River

  • Flows through 7 states

  • 14 dams and reservoirs

  • Water supplied mostly from the Rocky Mountains

  • Supplies water and electricity for about 40 million people

  • Irrigates crops that help feed America

• Issues

  • Very little water is reaching the Gulf of California

  • System has experienced severe drought

  • Lake Mead at record low water level

Will we have enough usable water?

• Freshwater

  • One of the earth’s most important natural capital

  • Used inefficiently and polluted

  • Low cost encourages waste

  • Not accessible to many people

Freshwater is an irreplaceable resource that we are managing poorly

• Access to freshwater global health issue

  • 4,000 people die everyday because they don’t have access to safe drinking water

• Economic issue

  • Water vital for producing food and energy

• National and global security issue

• Environmental issue

  • Excessive withdrawal

Most of earth’s freshwater is not available to us

• Freshwater Availability:0.024% of water supply

• Hydrologic cycle

  • Movement of water in seas, land, and air

  • Distributed unevenly

• Humans alter the hydrologic cycle

  • Withdrawing and polluting water, and causing climate change 

Groundwater and surface water are critical resources

• Zone of saturation

  • Spaces in soil below a certain depth are filled with water 

• Water table

  • Top of zone of saturation

• Aquifers

  • Underground reservoirs

  • Recharged naturally by precipitation or by nearby lakes, rivers, and streams

• Surface water

  • Surface runoff

  • Watershed (drainage) basin

We are using increasing amounts of the world’s reliable runoff

• ⅔ of surface runoff lost to seasonal floods

• Reliable runoff

  • Remaining ⅓ reliable source of freshwater

• Worldwide averages

  • Irrigation for crops and livestock: 70%

  • Industrial use: 20%

  • Cities and residences: 10%

• Virtual water

  • Water used to produce food and other products 

Case Study: Freshwater resources in the U.S. 

• More than enough renewable freshwater

  • Unevenly distributed and polluted

Critical Concept: Your water footprint

• Rough measure of all the water an individual uses

• Virtual water is water used indirectly to produce products and food, but is considered part of a person’s water footprint depending on what they consume

Freshwater shortages will grow

• Many of the world’s major river systems are highly stressed

• More than 30 countries face freshwater scarcity

• 30% of the earth’s land area experiences severe drought

  • Research predicts this will worsen 

Is groundwater a sustainable resource?

• Groundwater used to supply cities and grow food is being pumped from many aquifers faster than it is being replenished by precipitation

Groundwater withdrawals are unsustainable in some areas

• Aquifers are renewable resources for fresh water unless they are contaminated

• Widespread drilling of wells by farmers

  • Accelerated aquifer pumping

  • Water tables falling

• In 2008, Saudi Arabia announced it had depleted its major deep aquifer

Case Study: Overpumping the Ogallala Aquifer

• Ogallala Aquifer-largest known aquifer

  • Irrigates the Great Plains

  • Very slow recharge

  • Water table dropping

    • Water pumped 10-40 times faster than recharge rate

  • Government farm subsidies result in further depletion

  • Biodiversity threatened in some areas

Over Pumping aquifers can have harmful effects 

• Limits food production and raises prices

• Widens gap between rich and poor

• Land subsidence

• Groundwater overdrafts near coastal areas

  • Contamination of groundwater with saltwater

The ground sunk or subsidized this much of a distance because water being pulled out of an aquifer causing the ground to sink (the number of top is 1925 and the number on the bottom is 1977-- the line at 1925 is where the base of the land was)

How can we increase freshwater supplies?

• Large dam-and-reservoir systems

  • Greatly expanded water supplies in some areas

  • Disrupted ecosystems and displaced people

Large dams provide benefits and create problems

• Main goal of a dam and reservoir system 

  • Capture and store runoff

  • Release runoff as need for:

    • Flood control

    • Generating electricity

    • Supplying irrigation water

    • Recreation (reservoirs)

• Reservoirs

  • Increase the reliable runoff available for use 

  • Displaced people

  • Impair ecological services of rivers

  • Endangered plant and animal species

  • Fill up with sediment within 50 years

• Oroville dam in California was compromised by extremely heavy rainfall after a severe drought 

• Main spillway was damaged which almost caused the weir to collapse

• 180,000 people were evacuated with only an hour’s notice

• Climate change intensifies weather extremes

  • Mountain snowpack will be reduced, making less freshwater available downstream

  • When water levels drop, hydroelectric dams cannot function

  • Colorado River will most likely not be able to meet water needs in Arizona, New Mexico, and California 

How can dams kill an estuary?

• Only a small amount of Colorado River water reaches the Gulf of America

  • Threatens aquatic species in river and species that live in the estuary 

• Current rate of river withdrawal is not sustainable

• Inefficient use of irrigation water for agriculture

• Proposed actions for state using the Colorado River

  • Enact strict conservation measures

  • Phase out agriculture subsidies

  • Shift water-their crops to less arid areas

  • Raise the price of freshwater 

• 2014: Morelos dam near Yuma, AZ opened for two months to release water through the delta to the Gulf of California

  • Dramatic short-term results

Critical concept: NEPA and Environmental impact statements

• National Environmental Policy Act requires that an environmental impact statement be developed for every federal project likely to have an effect of environmental quality 

• Impact on water, soils, air quality, wildlife habitat, etc

Removing salt from seawater to provide freshwater

• Desalination methods

  • Distillation- heating the seawater, only the freshwater turns into water vapor when evaporated, then that freshwater is condensed and can be used for many purposes

  • Reverse osmosis-- applying high pressure to force seawater from one chamber into another chamber through a semipermeable membrane

• More than 17,000 desalination plants currently operating in 150 countries

• Issues: high cost, high energy use, and large amounts of salty wastewater

Can water transfers expand water supplies?

• Transferring water from one place to another has greatly increased water supplies in some areas

  • Has also disrupted ecosystems

Water transfers have benefits and drawbacks

• China

  • South-North Water Diversion Project

    • Diverts six trillion gallons of water per year

• California central valley

  • Aqueducts

• Water loss through evaporation and leaks

• Ecosystem degradation

Case study: the aral sea disaster

• Large-scale water transfers in dry central Asia java led to:

  • Water destruction

    • Desertification 

  • Greatly increased salinity 

  • Fish extinctions and decline of fishing 

  • Blowing salt and dust destroying wildlife and crops

  • Increased glacial melting in the Himalayas

• Shrinkage of the Aral Sea has altered local climate

  • Hot, dry summers, colder winters, and shortened growing season

• Restoration efforts

  • Cooperation of neighboring countries

  • More efficient irrigation

  • Dike construction raised level of Northern Sea

How can we use freshwater more sustainably?

• Ways to use freshwater more sustainably

  • Cut water waste

  • Raise water prices

  • Slow population growth

  • Protect aquifers, forests, and other ecosystems that store and release freshwater

Cutting water waste would have many benefits

• ½ to ⅔ of water is wasted

  • Evaporation, leaks,and inefficient use

• The cost of water to users is low

  • Government subsidies mask the true cost of water

    • No subsidies for improved efficiency

• Raising prices could hurt lower-income farmers and city dwellers

  • Solution: establish lifeline rates

We can improve efficiency in irrigation

• Flood irrigation

  • 45% of water lost

• More efficient techniques

  • Center pivot, low pressure sprinkler

  • Low-energy, precision application sprinklers

  • Drip or trickle irrigation, micro irrigation

    • Cotly

    • Less water waste

Poor farmers conserve water using low-tech methods

• Human-powered treadle pumps being water into irrigation ditches

• Harvest and store rainwater

• Capture water from fog

• Use polyculture to create canopy vegetation

  • Reduces evaporation

Cutting freshwater losses in industry and homes

• Recycle water used in industry

• Use low-flow toilets, shower heads, and front-loading washing machines

• Fix leaks in the plumbing systems 

• Use native plants in landscaping

• Use gray water

• Water meters reduce water use

Using less water to remove wastes

• Large amounts of freshwater used to flush away wastes

• Reuse wastewater 

  • Only about 7% of wastewater is currently recycled

• Use waterless composting toilets

Using water more sustainably

• Protect water supplies

• Apply strategies at local, regional, national, and international levels

• Appy strategies at a personal level

  • Use less freshwater and use it more efficiently

How can we reduce the threat of flooding?

• We can lessen the threat of flooding by:

  • Protecting more wetlands and natural vegetation in watersheds

  • Not building in areas subject to frequent flooding

Some areas get too much water from flooding

• Floodplain

  • Area flooded when a stream overflows its channel

  • Fertile soils for farming

  • Recharge groundwater and refill wetlands

• Human activities that damage floodplains

  • Vegetation removal

  • Draining of wetlands

• Rising sea levels from global warming means more coastal flooding

Case study: Living dangerously in floodplains in Bangladesh

• Dense population on coastal floodplain

• Moderate floods maintain fertile soil

• Recent increased frequency of severe floods

• Destruction of coastal wetlands 

  • Mangrove forests cleared

  • Increased storm damage

• Adapting: using more flood-tolerant crops 

Reducing flood risks

• Rely more on nature’s systems

  • Wetlands

  • Natural vegetation in watersheds

• Rely less on engineering devices

  • Dams 

  • Levees

  • Channelized streams 

Chapter 14: Nonrenewable energy

Core case study: using hydrofracking to produce oil and natural gas 

• OIl and natural gas trapped between compressed layers of shale rock formations

• New technologies allowed access

  • Horizontal drilling

  • Hydraulic fracturing (hydrofracking)

    • Pump water, sand, and chemicals into cracks

    • Produces hazardous waste slurry

What types of energy resources do we use?

• 90% of the commercial energy used in the world comes from nonrenewable resources

  • Oil, natural gas, and coal

• Energy resources vary greatly in their net energy

  • Amount of energy available from a resource minus the amount of energy needed to make it available 

Where does the energy come from?

• Energy that heats the earth comes from the sun

• Commercial energy is sold in the marketplace

  • Non Renewable

    • Oil, coal, natural gas, and nuclear energy

  • Renewable

    • Solar, hydropower, biomass, geothermal, and wind

Net energy: It takes energy to get energy

• Each step in making energy available uses high-quality energy

  • Example: oil must be found, pumped, transferred to a refinery, converted to gasoline, and delivered to consumers

• Net energy yield

  • Amount of high-quality energy available from a resource minus the high-quality energy needed to make the energy available

• Net energy ratio

  • Also called energy returned on investment

  • Energy obtained per unit energy used to obtain it

• Energy efficiency

  • Getting more useful work using less energy; heating buildings, producing electricity, driving more efficient cars 

  • Want a high net energy → getting more energy out of the product then put in to create the product 

What are the advantages and disadvantages of using oil?

• Conventional crude oil is abundant

  • Medium net energy yield

  • Causes air and water pollution 

  • Releases Carbon Dioxide into the atmosphere

• Unconventional heavy oil from oil shale rock and oil sands

  • Potentially large supplies

  • Low net energy yield

  • Higher environmental impact

We depend heavily on oil

• Crude oil (petroleum)

  • Contains combustible hydrocarbons

• Peak production

  • Time after which production from a well declines

• Crude oil cannot be used as it comes out of the ground

  • Must be refined using high-quality energy

  • Petrochemicals-byproducts 

Is the world running out of crude oil?

• Proven oil reserves-available deposits

  • 12 OPEC countries have 81% of the world’s proven crude oil reserves

    • These countries play a role in regulating global prices by agreeing to increase or decrease the amount produced

• Increasing shortage of cheap oil

  • Easy-to-reach deposits are quickly being depleted

 Case study: oil production and consumption in the U.S.

• U.S. commercial energy sources

  • 82% from fossil fuels

    • Largest portion comes from crude oil

• U.S. oil consumption exceeds domestic production

  • Must import oil

• Recent rise in domestic production of tight oil from shale rock

  • Likely to peak around 2020 and then decline

Use of heavy oil has a high environmental impact

• Shale oil 

  • Oil that is integrated within bodies of shale rock

    • As opposed to being trapped between layers of rock

  • Production involves mining, crushing, and heating the rock

    • Extracts kerogen that can be distilled

• Oil sands (tar sands) another source of heavy oil

  • Contains bitumen

  • Extensive deposits in Canada

• Extraction 

  • Clear-cutting forests and strip-mining the land

  • Low net energy yield

  • Requires much water

  • Emits pollutants 

What are the advantages and disadvantages of using natural gas?

• Natural gas

  • Mostly methane

    • Propane, butane, and hydrogen sulfide in smaller amounts

  • Has a medium net energy yield and a fairly low production cost

  • Burns cleaner than oil and coal

  • Extracted through horizontal drilling and fracking

Natural gas is a versatile and widely used fuel

• Liquefied petroleum gas (LPG)

  • Stored in pressurized tanks for use in rural areas

• Liquefied natural gas (LNG)

  • Can be transported across oceans

  • Low net energy yield

  • The U.S. currently exports to other nations

Environmental effects of natural gas production and fracking in the U.S.

• Fracking has several harmful environmental effects

  • Requires enormous volumes of water

  • Produces hazardous wastewater

    • Earthquakes could release into groundwater

  • Failure of well-casting cement causes contaminated groundwater

• Natural gas fracking was excluded from EPA regulations in 2005

Can natural gas help to slow climate change?

• Emits less Carbon Dioxide per unit of energy than coal

• Low price could slow shift to other renewable energy sources

• Methane a much more potent greenhouse gas than Carbon Dioxide

  • Drilling, production, and distribution of natural gas releases large quantities of methane

What are the advantages and disadvantages of coal?

• Conventional coal is plentiful 

  • High net energy yield

  • Low cost

  • Using it has a high environmental impact

• We can produce gaseous and liquid fuels from coal

  • Lower net energy yields

  • Higher environmental impacts than conventional coal

Coal is a plentiful but dirty fuel

• Coal

  • Solid fossil fuel formed from the remains of land plants

• Burned in power plants

  • Generated 40% of the world’s electricity in 2015

• Largest consumers of coal

  • China, U.S and India

• Environmental costs of burning coal

  • Mining coal severely degrades land

  • Water and air pollution

    • Soot and Carbon Dioxide

    • Produces trace amounts of mercury and radioactive materials

  • Scrubbers remove some pollutants before they leave smokestacks

    • Produces coal ash that must be safely stored

We are not paying the full cost of using coal

• Harmful environmental and health costs

  • Not included in market price of coal-generated electricity

• Ways to implement full-cost pricing

  • Phase out subsidies and tax breaks

  • Require stricter air pollution controls

  • Tax Carbon Dioxide emissions

  • Regulated coal ash as a hazardous waste

The future of coal

• U.S. coal use dropped 18% between 2007 and 2013 

  • Increased competition from natural gas, wind, and solar power

  • Grassroots political opposition

• Natural gas should overtake coal as the largest electricity source by the 2030s

• U.S. coal producers are exporting coal

  • Use is expanding in India, Africa, and Asia 

We can convert coal into gaseous and liquid fuels

• Conversion of solid coal to synfuels

  • Synthetic natural gas (SNG) by coal gasification

  • Methanol or synthetic gasoline by coal liquefaction

•  Producing synfuels requires mining of 50% more coal

  • Lower net energy and cost more to produce than coal

• Lose-Lose situation causing more environmental degradation because there is more mining being done (probably not the way to go to reduce coal)

What are the advantages and disadvantages of using nuclear power?

• Nuclear power has a low environmental impact and a very low accident risk

• Drawbacks

  • Low net energy yield

  • High costs

  • Fear of accidents

  • Long-lived radioactive wastes

  • Role in spread of nuclear weapons technology

How does a nuclear fission reactor work?

• Controlled nuclear fission (heavier element is ripped apart into 2 lighter elements- a lot of energy is released) reaction in a reactor 

  • Light-water reactors

  • Boil water to produce steam to spin a turbine

  • Fueled by uranium ore mined from the earth’s crust

    • Enriched uranium packed as pellets in fuel rods and fuel assemblies

  • Control rods absorb neutrons

• Water is the usual coolant

• Containment shell around the core for protection

• Emergency core cooling system

• Typical cost to construct

  • $9-11 billion

• U.S., France, and Russia

  • Leading producers of nuclear power in 2014

• A nuclear fission reactor is a device that controls a nuclear chain reaction that splits atoms to produce heat

What is the nuclear fuel cycle?

• Mining the uranium 

• Processing and enriching the uranium to make fuel

• Using it in a reactor 

• Safely storing the radioactive waste

• Retiring the worn-out plant

  • Storing its high and moderate-level radioactive parts safely 

Dealing with radioactive nuclear wastes

• Fuel rods must be replaced every three to four hours

• Stored in water--filled pools for several years to cool

• Transferred to dry casks

• Can be processed to remove plutonium 

  • Reprocessing reduces storage time from 240,000 years to about 10,000 years

  • Costly and produces weapons material

• No permanent, secure repository exists today

  • Nevada Yucca Mountain site plan abandoned

• Retiring nuclear plants

  • Enormous costs

Can nuclear power slow climate change?

• Nuclear power plants- no Carbon Dioxide emission

• Nuclear fuel cycle- emits Carbon Dioxide

• Cutting global Carbon Dioxide emissions in half between 2015 and 2040 and meeting energy needs would require building 12,000 nuclear power reactors

  • According to Mark Lynas, climate change author 

• Nuclear power is not cost effective 

Controversy about the future of nuclear power?

• Nuclear reactors produced 19% of the U.S. energy in 2014

• 67 new nuclear reactors under construction worldwide in 2015

• U.S. government provides subsidies, tax breaks, and insurance for the nuclear industry

• Accidents have dampened public confidence in nuclear power

• New technologies

  • Advanced light-water reactors

    • Built-in safety features

  • Smaller, modular light water reactors

    • Not yet built and evaluated

  • Thorium-based reactors

    • Less costly and safer

• Solutions 

  • Reactors must be built so that a runaway chain reaction is impossible 

  • The reactor fuel and methods of fuel enrichment and fuel reprocessing must be such that they cannot be used to make nuclear weapons

  • Spent fuel and dismantled plants must be easy to dispose of without burdening future generations with harmful radioactive waste

  • Taking its entire fuel cycle into account, nuclear power must generate a net energy high enough so that it does not need government subsidies, tax breaks, or loan guarantees to compete in the open marketplace

  • Its entire fuel cycle must generate fewer greenhouse gases than other energy alternatives 

Case study: The Fukushima Daiichi nuclear power plant accident in Japan

• March 11, 2011 accident 

  • Triggered by major offshore earthquake and resulting tsunami

• Important effects

  • Increased fear about nuclear power

  • Revealed single accident can cost $500 billion

  • Some countries announced phasing out nuclear power

  • Spurred Japan to reduce energy use 

Is nuclear fusion the answer?

• Fusion

  • Two isotopes fused together to form a heavier nucleus

  • Releases energy

  • Technology used by the sun to release energy

• Technology is very difficult to develop

  • No approach has produced more energy than it has used 

Big ideas

• Net energy 

  • Key factor in evaluating the long-term usefulness of any energy resource

• Conventional oil, natural gas, and coal

  • Plentiful with moderate to high net energy yields

  • Use has a high environmental impact

• Nuclear power fuel cycle

  • Low environmental impact

  • Very low accident risk

  • Downsides

    • High costs

    • Low net energy

    • Long-lived radioactive wastes

    • Role in spreading nuclear weapons technology

Tying it all together: fracking, nonrenewable energy, and sustainability

• Horizontal drilling and fracking have greatly increased oil and natural gas production in the U.S.

• Long-term usefulness of an energy resource depends on net energy

• Challenge: find ways to reduce harmful environmental impacts of fossil fuels and nuclear energy

  • Option: shift to renewable energy resources