In the end, we will conserve only what we love, we will love only what we understand, and we will understand only what we are taught.“ Baba Dioum ( Senegalese conservationist)

Soil and Water

Unit 13

Flashback-Soil: Foundation for Land Ecosystems • • • • • Types of soil vary due to: geography parent material (rock) climate age presence of soil organisms

FYI: Soil Formation

• • • takes thousands of years to form often transported far from source results from weathering of parent rock: -sedimentary: compacted, cemented sediment -igneous: “fire-formed”, cooled magma, lava -metamorphic: form by heat, pressure in earth

Rock Cycle

Soil Characteristics

• horizon: horizontal layers O- humus, leaf litter A- topsoil: weathered rock and organic matter E- zone of leaching B- subsoil: clay, iron, C- weathered parent

rock:

R- bedrock; regolith (See handout from previous chapter)

Soil Characteristics

• profile: vertical layers

Soil Texture

Classified according to particle size (large to • • • small):

sand silt clay

Soil Triangle

Diagram used to classify soil type

1. Clay side

: extend a line across from the % clay 2. Silt side: extend a line diagonally downward from % silt 3. Sand side: extend a line diagonally upward and to the left from % sand ex. If soil is 30% clay, 30% silt and 40% sand, the texture is clay loam

FYI: Soil Statistics

• • • Soil is produced naturally at a rate of 1mm/ 200-400 years Full soil profile takes 2000-10,000 years to develop Agricultural soil is lost at a rate 10-40 times faster than is natural replaced -global loss is 6 million hectares (ha) per year (I ha = 10,000 m²) from a total of 1200 million ha

Human Impact on Soil

• See notes from Unit 9: Food, Soil and Pest Management

Water: Importance, Availability, and Renewal • • • • •

Essential for chemical reactions within organisms Moderates climate; sculpts the land Removes and dilutes wastes, pollutants

Moves continually through the hydrologic cycle.

≈ 0.02% of the earth’s water is available as liquid freshwater.

Water: Importance, Availability, and Renewal • Comparison of population sizes and shares of the world’s freshwater among the continents.

Figure 14-2

Core Case Study: Water Conflicts in the Middle East - A Preview of the Future

• • Middle East has one of the world’s highest population growth rates Faces water shortages.

Figure 14-1

Water Conflicts in the Middle East: A Preview of the Future

• • • Most water comes from the Nile, Jordan or Tigris rivers.

Countries disagree as to who has water rights.

No cooperative agreements for use of 158 of the world’s 263 water basins shared by two or more countries.

Water is Abundant, But Usable Water is Rare

Location of Water

Main sources:

1. Surface water: bodies of water on surface

2. Groundwater :

accumulated water below the surface; most important source

Surface Water

• • • lakes, rivers, wetlands, estuaries, ocean

recharged from surface runoff :

snow melt, precipitation that doesn’t infiltrate soil watershed (drainage basin): all land that drains into a body of water

Surface Water (cont’d)

• floodplain: land adjacent to rivers; receive nutrient-rich deposits from flooding

FYI World’s Largest Rivers

• • • Amazon in South America (4,000 miles/6,437 km) Congo in Africa ( 2,920 miles/4,700 km) Yangtze in China (3,915 miles/6,300 km) (Civilizations grew along water rivers due to the fertile soil in riparian zones and access to trade)

Lakes

• • Large bodies of freshwater Formed from precipitation, runoff from streams or rivers, seepage from groundwater

Flashback:Lake Classifications

Lake are classified according to nutrients and • PPD:

oligotrophic:

and PPD deep, clear, low plant nutrients

Lake Classifications (cont’d)

• •

eutrophic:

shallow, murky, high plant nutrients and PPD

-cultural eutrophication:

acceleration of lake eutriphication due to human activity (pollution from atmosphere, runoff)

mesotrophic:

falls between nutrient extremes

Groundwater

•

Occurs when precipitation infiltrates the ground, percolates through soil, hits an impermeable rock layer and stops

Groundwater Zones

• • • Zone of aeration: first layers beneath Earth’s surface, filled with air Zone of saturation: subsurface layers, porous,

filled with water Water table: upper limit of saturation zone

-height fluctuates due to drought, over withdrawal (by humans), seasonal rains

Groundwater Zones (cont’d)

• Aquifer: layer of porous rock, sand, silt, clay through which water flows (acts like a sponge for freshwater); holds more water than Earth’s

surface waters -

natural recharge: replenishing aquifer by

precipitation

-lateral recharge: replenishing from side from nearby streams, lakes, etc -nonrenewal aquifers: get little (if any) recharge

Precipitation Confined Recharge Area Runoff Unconfined Aquifer Recharge Area Evaporation and transpiration Evaporation Flowing artesian well Infiltration Water table Recharge Unconfined Aquifer Infiltration Stream Well requiring a pump Lake Fig. 14-3, p. 308

Global Water Usage

• • • • • • 70%: agriculture 20%: industry, manufacturing 10%: cities, residences (more affluent the area, the more water used) Currently humans are using ≈ 50% of globe’s

reliable runoff of surface water

Projected increase by 2050: 70-90%

≈70% of water taken from surface and groundwater is not returned

Case Study: Freshwater Resources in the United States

• by 2025, 17 western states could face intense conflict over scarce water needed for urban growth, irrigation, recreation and wildlife.

Figure 14-5

Wash.

Oregon Idaho Montana Wyoming Nevada Utah Colo.

California N.D.

S.D.

Neb.

Kansas Oak.

N.M.

Highly likely conflict potential Substantial conflict potential Moderate conflict potential Unmet rural water needs Texas Fig. 14-5, p. 310

Average annual precipitation (centimeters) Less than 41 41–81 81–122 More than 122 Fig. 14-4a, p. 309

Acute shortage Shortage Adequate supply Metropolitan regions with population greater than 1 million Fig. 14-4b, p. 309

Water in the United States

• Average precipitation (top) in relation to water deficit regions and their proximity to metropolitan areas (bottom).

Figure 14-4

Freshwater Resources in the United States (cont’d) • • • Shortage of runoff in western states due to drought, high rates of evaporation Water tables are dropping due to depletion of aquifer 2013: 36 states (not just in west) faced shortages due to urban sprawl, water use and

waste- in addition to drought.

Water Shortage Is…

• • • • • Global health issue: 1/3900 children die yearly from waterborne diseases Economic issue: vital for reducing poverty, producing food, energy Gender, child issue: poor women, girls are responsible for daily water supply to family National/global security issue: increasing tensions over access to limited supply Environmental issue: removal of water from environments creates degradation of natural services (reduces biodiversity)

Stress on the World’s River Basins

• Comparison of the amount of water available with the amount used by humans.

Figure 14-6

Case Study: Who Should Own and Manage Freshwater Resources?

• • controversy exists over whether water supplies should be owned and managed by governments or by private corporations.

European-based water companies aim to control 70% of the U.S. water supply by buying up water companies and entering into agreements with

cities to manage water supplies.

How Would You Vote?

• Should private companies own or manage most of the world's water resources?

a. it.

No. Democratically elected governments, which are accountable to the voters, should own and manage water resources.

b. Qualified yes. Governments should own the water, but expert private companies should manage c. Depends. Each case must be decided independently. The record on private versus public ownership is mixed.

d. Yes. Private companies have more expertise and experience in managing water resources than most government bureaucrats.

Increasing Freshwater Supply

• • • • Cities are outbidding farmers for water supplies from rivers and aquifers.

Countries are importing grain as a way to reduce their water use.

More crops are being used to produce biofuels.

Water options are:

–

pump water from aquifers and rivers

–

desalinate ocean water,

–

waste less water.

Trade-Offs Withdrawing Groundwater Advantages Useful for drinking and irrigation Available year-round Exists almost everywhere Renewable if not overpumped or contaminated No evaporation losses Cheaper to extract than most surface waters Disadvantages Sinking of land from overpumping Saltwater intrusion into drinking water supplies near coastal areas (Ga!) Reduced water flows into surface waters Increased cost and contamination from deeper wells

Aquifer Depletion: Land Subsistence

• Sinkholes form when the roof of an underground cavern collapses after being drained of groundwater Figure 14-10

Groundwater Overdrafts: High Moderate Minor or none Fig. 14-8, p. 314

Aquifer Depletion: Saltwater Intrusion • Along the coast, water table is shallow; sea water is drawn into aquifer as too much freshwater is taken out

FYI: Aquifer Depletion in Saudi Arabia (1986 – 2004)

• Irrigation systems from the nonrenewable aquifer appear as green dots. Brown dots are wells that have gone dry.

Figure 14-9

Solutions to Depletion

• • • • •

Subsidize water conservation Raise price of water to discourage waste Do not grow water-intensive crops in dry areas Set and enforce minimum stream flow levels Implement conservation practices in residences

Increasing Water: Dams and

Reservoirs

• • • Dam: structure built across a river to control river flow Reservoir: an artificial lake behind a dam Main goals of damming: hydroelectricity, irrigation for towns/cities

FYI: Hydroelectric Power: Advantages • • • • •

No CO₂ emissions Provides irrigation, drinking water Can provide flood control Provides cheap electricity Reservoir can be used for recreation

Hydroelectric Power: Disadvantages • • • •

Displaces people, wildlife behind/below dam Decreases nutrient-rich silt downstream Loss of water due to evaporation, seepage Disrupts migration of some fish; decreases fish harvest below dam

Major Dams

Colorado River Basin: Colorado River-Gulf of • • • • • California Water flow from Rocky Mtn snowmelt Provides drinking water to L.A., San Diego, Las Vegas (desert, arid regions) Supplies irrigation to 15% of nation’s crops

14 dams; reservoirs- Hoover and Glen Canyon

Excessive withdrawals reduce river flow to Gulf; increased salinity due to farm runoff

The Colorado River Basin

• The area drained by basin more than one-twelfth of the land area of the lower 48 states.

Figure 14-14

The Colorado River Basin

• • Lake Powell, is the second largest reservoir in the U.S.

It hosts one of the hydroelectric plants located on the Colorado River.

Figure 14-15

Major Dams (cont’d)

• • • • • • Three Gorges Dams: Yangtze River in China World’s largest hydroelectric dam Controls flooding (1998 flooding from Yangtze killed 4000) Displaced 1.5 million people Produces same energy as 22 coal-burning plants Reservoir will receive 265 billion gallons of raw sewage normally dumped into ocean Dam is built over seismatic fault and already has small cracks.

Three Gorges Dam

FYI: Lake Lanier

• Above Atlanta; major source of water for that city • Formed by Buford Dam on the

Chattahoochee

• Covers 38,000 sq miles • Water rights are being argued in the Supreme Court for control by Georgia, Alabama, Florida (federal judge ruled against Georgia in water rights fight)

FYI: Dam Removal

• Some dams are being removed for ecological reasons and because they have outlived their usefulness.

– In 1998 the U.S. Army Corps of Engineers announced that it would no longer build large dams and diversion projects in the U.S.

– The Federal Energy Regulatory Commission has approved the removal of nearly 500 dams.

– Removing dams can reestablish ecosystems, but can also re-release toxicants into the environment.

Increasing Water: Water Transfer

Projects

Transferring water can make unproductive areas • • •

more productive

Promotes investment, jobs and strong economy Encourages unsustainable use of water in areas water is not naturally supplied Can cause environmental harm

Water Transfer Projects

California Water Project : northern to southern • • • • Ca.

One of world’s largest transfers Degraded river, lake ecosystems, including Mono Lake, major feeding stop for migratory birds Resulted in water waste Some diversions are now illegal

Case Study: The California Experience

Figure 14-16

Water Transfer Projects (cont’d)

Aral Sea: inland Aral Sea to cotton, rice fields in • • • • Asia (formally Soviet Union) Reduced size of sea; increased its salinity Eliminated ≈ 85% of wetlands; 50% of local birds and mammals Caused extinction of 20/24 fish species Altered climate: hotter in summer; colder in winter

The Aral Sea Disaster

• The Aral Sea was once the world’s fourth largest freshwater lake.

Figure 14-17

Water Transfer Projects (cont’d)

China’s South-North Water Transfer: Yangtze • River basin to populated northern provinces Will provide drinking water to cities such as Beijing (12 million people)

Increasing Water: Desalination

Desalination: removal of dissolved salts from • saltwater: Reverse osmosis/microfiltration: external pressure pushes saltwater through membranes to separate salts from water

Desalination (cont’d)

• Distillation: heats saltwater until evaporation begins, steam is collected and condensed freshwater; salt is left behind

Disadvantages of Desalination

• • • Produces large amounts of briny wastewater Extremely expensive: 10 x cost of aquifer water Not realistic for developing countries

Increasing Water: Water Conservation About two-thirds of the water used is wasted, but • • • waste could be cut to 15% 65-70% of global water used is lost through

evaporation, leaks

Reduce government subsidies for cost of water

Increase government subsidies for water conservation

Water Conservation (cont’d)

• • ≈ 60% of irrigation water does not reach crops Types/effectiveness of irrigation: 1. flood: water flows through fields -60% efficiency (most wasteful) -used on 97% of China’s irrigated land 2. center pivot: pumps move water through

sprinklers

-80-90% efficiency

Water Conservation (cont’d)

3. Drip/micro-irrigation: delivers small amounts of water to roots of plants -90-95% efficiency -reduces salt buildup in soil (used on 1% of global lands- 13% Ca, 66% Israel, 90% Cyprus)

Gravity flow (efficiency 60% and 80% with surge valves) Drip irrigation (efficiency 90–95%) Water usually comes from an aqueduct system or a nearby river.

Above- or below-ground pipes or tubes deliver water to individual plant roots.

Center pivot (efficiency 80%–95%) Water usually pumped from underground and sprayed from mobile boom with sprinklers.

Fig. 14-18, p. 325

Reducing Irrigation Waste

• • • • • • • Line canals bringing water to fields Irrigate at night (reduces evaporation) Add water to soil only when needed Polyculture Organic farming Use treated waste water Import water-intensive crops and meat

Reducing Waste in Business and

Industry

• • • • • • Recycle water (95% of water recycled in steel) Fix leaks- 30-60% of water loss in cities (especially developing countries) Use water meters; raise price of water

Require water conservation

Purify and reuse water for office buildings

Use wastewater as fertilizer for nonfood crops

Reducing Waste in Homes

• • • • • • • Use low-flow toilets, showerheads, faucets 5-7 minute showers (no baths) Wash full loads of clothes, store and use gray water for nonfood plants Xeriscape- replace lawns with native plants

Repair leaks

Use commercial car wash Turn off faucet for while brushing teeth

Bottom Line: Sustainable Water Use • • • • • •

Waste less; subsidize water conservation Don’t deplete aquifers Preserve water quality Protect wetlands, watersheds that store and release water Raise water prices Slow population growth

Too Much Water: Flooding

Causes: Heavy rainfall, rapid snowmelt, removal • of vegetation, destruction of wetlands Floodplains: areas adjacent to rivers -provide flood, erosion control -maintain water quality -recharge groundwater

Flooding

• Comparison of St. Louis, Missouri under normal conditions (1988) and after severe flooding (1993).

Figure 14-22

Flooding Benefits

• • Deposits nutrient-rich silt on floodplain (good farming) Refills wetlands; supports biodiversity

Reducing Flood Risks

• • • • Preserve forests on watersheds Restore wetlands (absorbs excess water) Limit development, use for sustainable farming Build levees, dams

TOO MUCH WATER

• Human activities have contributed to flood deaths and damages.

Figure 14-23

• • • • • • • •

Exam Focus

Main stages of water movement through hydrologic cycle % freshwater on earth (not including glaciers) Location of freshwater Definition of infiltration, zones of aeration and saturation, water table, aquifer Natural forces that effect surface water Greatest global use of water Results of overdrafting aquifer (land subsistence, saltwater intrusion, contamination from toxins, runoff) Sources of excessive nutrients entering surface water/solutions to curb those sources

Exam Focus

• • • • • • • • Solutions to aquifer depletion Specific economic and social benefits of damming Environmental disadvantages of damming Colorado River Basin, Aral Sea disaster Methods to increase freshwater Methods to reduce irrigation waste Greatest use of water in home/ methods to conserve water at home Methods to reduce flooding

FRQ

Ex: Based on total use, how many gallons of water is available to each person total water: 300 billion gallons total population: 100 million people gallons available: 3 x 10¹⁰ = 3 x 10² gal/person 1 x 10⁸ Find % of type of water used: type of water x 100 total water