Water Resources & Water Pollution

Water Resources & Water Pollution

Chapters 14 & 19Chapters 14 & 19

Importance of WaterImportance of Water• Effects on our planet:

– Helps shape our continents– Moderates our climates– Allows organisms to survive

• Uses of fresh water:– drink it– cook with it– wash with it– travel on it– use it for agriculture– use it for energy production

Water’s Unique PropertiesWater’s Unique Properties

Hydrogen bonding Hydrogen bonding Liquid over wide temperature range Liquid over wide temperature range Changes temperature slowly

(high specific heat)

Changes temperature slowly (high specific heat)

High heat of evaporation High heat of evaporation Great dissolving power Great dissolving power pH – near neutral pH – near neutral Adhesion and cohesion properties Adhesion and cohesion properties Expands when it freezes Expands when it freezes

All water Fresh water Readily accessible fresh water

Oceans andsaline lakes97.4%

Fresh water2.6%

Groundwater0.592%

Ice capsand glaciers1.984%

Lakes0.007%

Soilmoisture0.005%

Biota0.0001%

Rivers0.0001%

Atmosphericwater vapor0.001%

0.014%

97.4% Salt Water (Oceans and salt lakes)

Supply of Water ResourcesSupply of Water Resources

Fig. 14-2 p. 314Fig. 14-2 p. 314

Freshwater 2.6% of all water

on Earth

Freshwater 2.6% of all water

on Earth

Readily accessible freshwaterReadily accessible freshwater

Biota0.0001%

Biota0.0001%

Rivers0.0001%Rivers

0.0001%

Atmosphericwater vapor

0.001%

Atmosphericwater vapor

0.001%

Lakes0.007%

Soilmoisture0.005%

Groundwater0.592%

Groundwater0.592%

Ice capsand glaciers

1.984%

0.014%0.014%

Surface Water:

Fresh water found on Earth’s surface in streams, rivers, lakes, ponds, reservoirs and wetlands.

Surface Water:

Fresh water found on Earth’s surface in streams, rivers, lakes, ponds, reservoirs and wetlands.

• Runoff of precipitation from the land replenishes surface waters– Renewable resource

• Watershed (a.k.a. drainage basin): area of land that is drained by a single river or stream.– Size varies from 1km for a small stream to a huge area of

the continent for major river systems like the Mississippi.

Ground Water: Underground formations that collect and store water in the ground.

Ground Water: Underground formations that collect and store water in the ground.

• Originates as rain or melting snow that seeps into the soil and finds its way down through cracks and spaces in sand, gravel, or rock until it is stopped by an impenetrable layer.

• Flows through permeable sediments or rocks slowly (a couple mm/day) and eventually is discharged into rivers, wetlands, springs or the ocean.

• Aquifers: porous layers of sand, gravel or bedrock that are saturated with water (store ground water).

Evaporation and transpiration

Evaporation

Stream

Infiltration

Water tableInfiltration

Unconfined aquifer

Confined aquifer

Lake

Well requiring a pump

Flowingartesian well

Runoff

Precipitation

ConfinedRecharge Area

Aquifer

Less permeable materialsuch as clay Confirming permeable rock layer

Ground WaterGround Water

Types of AquifersTypes of Aquifers

• Unconfined Aquifers: form when layers of rock above are porous and allow surface water directly above them to seep downward replenishing the aquifer. – The upper limit of an unconfined aquifer, below which

the ground is saturated with water, is the water table.

• Confined Aquifers: layers of rock above and below are impermeable. The water is trapped and often under pressure.– Artesian wells: take advantage of the pressure and tap

confined aquifers (no pumps necessary).

FloodingFlooding• Natural phenomena that renew and replenish water and

nutrients.• Flood damage is exacerbated by

• Deforestation

• Development of flood plains

Floodplain

Levee Floodwall

Dam

Reservoir

Use of Fresh WaterUse of Fresh Water

• Aquifer Depletion: removal of groundwater at a rate higher than it can be recharged by precipitation or melting snow.– Results in

• Subsidence (sinking of the land)• Sinkholes (natural depression of land caused by removal of soil

or bedrock, by water)• Salt water intrusion

• Salinization: results from irrigation with groundwater that is rich in salts. These salts are left behind in the soil and decrease soil fertility.

Salt Water IntrusionSalt Water Intrusion

• Occurs mostly in very sandy areas close to the ocean, islands, spits, etc.

Water ShortagesWater Shortages• Population growth in arid climates within California,

Nevada, Arizona and Florida has placed high demand on limited water supplies.

• To deal with this, water is imported from other areas.– Mono Lake in eastern California had surface water diverted to Los

Angeles, lowering its water level and increasing its salinity.

– Colorado River basin has been over-diverted for human consumption.

– Ogallala Aquifer on the High Plains (S. Dakota, Nebraska) is the largest groundwater deposit in the world. The water table has dropped by 30 feet in some areas.

Transferring Water from One Place to AnotherTransferring Water from One Place to Another

North BayAqueductNorth BayAqueduct

South BayAqueductSouth BayAqueduct

California AqueductCalifornia Aqueduct

CALIFORNIANEVADA UTAH

MEXICO

Central ArizonaProject

Colorado RiverAqueduct

Los AngelesAqueduct

Shasta Lake

Sacramento

Fresno

Phoenix

Tucson

ARIZONA

ColoradoRiver

SacramentoRiverSacramentoRiver

San FranciscoSan Francisco

Los AngelesLos Angeles

San DiegoSan Diego

California Water Project

California Water Project

Central Arizona Project

Central Arizona Project

Water is taken from one watershed and brought to another.

Acute shortage

Adequate supply

Shortage

Metropolitan regions with population greater than 1 million

Use of Water ResourcesUse of Water Resources

Agriculture Agriculture

Power plantsPower plants

Domestic

Industry

Domestic

Industry

United States

Industry 11%

Public 10%

Powercooling

38%

Agriculture38%

Using Dams and Reservoirs to Supply More Water: dams ensure a year round supply of water in areas that have seasonal precipitation or snowmelt

Using Dams and Reservoirs to Supply More Water: dams ensure a year round supply of water in areas that have seasonal precipitation or snowmelt

Large lossesof water throughevaporation

Large lossesof water throughevaporation

Flooded land destroys forests or cropland anddisplaces people

Flooded land destroys forests or cropland anddisplaces people

Downstream flooding is reducedDownstream flooding is reduced

Downstream cropland andestuaries are deprived ofnutrient-rich silt

Downstream cropland andestuaries are deprived ofnutrient-rich silt

Reservoir is useful for recreation and fishing

Can produce cheap electricity (hydropower)

Migration and spawning of some fish are disruptedMigration and spawning of some fish are disrupted

Provides waterfor year-roundirrigation ofcropland

Problems with Using GroundwaterProblems with Using Groundwater

Saltwater intrusion Saltwater intrusion

Chemical contamination Chemical contamination

Reduced stream flows – because of diminished flows of groundwater into streams

Reduced stream flows – because of diminished flows of groundwater into streams

Converting Salt Water to Fresh Water and Making it RainConverting Salt Water to Fresh Water and Making it Rain

• Desalinization: the removal of salt from seawater or salty groundwater.– Distillation: boil water then condense vapor, salt is left

behind (high energy usage).

– Reverse Osmosis: forces saltwater through a membrane that is permeable to water but not to salt (more energy efficient).

– Disadvantages include high expenses and the creation of “brine” which is wastewater with high levels of salts and minerals

• Cloud Seeding: providing particles for water to condense on (like salt crystals) can increase the likelihood of rain fall.

Using Water More EfficientlyUsing Water More Efficiently

Reduce losses due to leakage Reduce losses due to leakage

Reform water laws Reform water laws

Improve irrigation efficiency: Micro irrigation and field leveling can cut agricultural water consumption.

Improve irrigation efficiency: Micro irrigation and field leveling can cut agricultural water consumption.

Water Pollution: any change (physical or chemical) in

water that adversely affects the health of humans and other organisms.

Water Pollution: any change (physical or chemical) in

water that adversely affects the health of humans and other organisms.

• Causes of Water Pollution– Sewage– Disease causing agents– Sediments– Inorganic plant and algal nutrients– Organic compounds– Inorganic compounds– Radioactive substances– Thermal pollution

Point and Nonpoint SourcesPoint and Nonpoint Sources

NONPOINT SOURCES

Urban streets

Suburban development

Wastewater treatment plant

Rural homes

Cropland

Factory

Animal feedlot

POINT SOURCES

SewageSewage

– Microorganisms use the process of cellular respiration to break down sewage into CO2, H2O and other materials.

– Biochemical Oxygen Demand (BOD) is the amount of oxygen needed by microorganisms to decompose sewage and other organic wastes.

•Wastewater carried off by drains or sewers, contributes to enrichment (fertilization of water) and produces oxygen demand as it is decomposed.

Disease Causing AgentsDisease Causing Agents

• Bacteria, viruses, protozoans, and parasitic worms are all transmitted in sewage.

• E. coli (a common intestinal bacteria) are used as an indication of the amount of sewage present in a body of water and as an indirect measure of disease causing organisms.

• The fecal coliform test is used to determine the presence of E. coli in water.

Sediment PollutionSediment Pollution

• Caused by soil erosion• Increases water turbidity• Reduces photosynthetic productivity• Can be measured with a Secchi disk

Inorganic plant and algal nutrientsInorganic plant and algal nutrients

• These include things like nitrogen and phosphorous which will enrich the environment.

• Fertilizer runoff from agricultural and residential land is the major contributor

• Increased levels of nutrients eventually leads to decreasing oxygen levels in the water. This condition is known as hypoxia.

Organic CompoundsOrganic Compounds

• Contain carbon

• Synthetic

• Persistent

• Examples: pesticides, solvents, industrial chemicals

• Generally these are highly toxic (often carcinogenic).

Inorganic ChemicalsInorganic Chemicals• Contaminants that contain elements other than

carbon.• This group includes toxins like lead and mercury.

– Lead: most lead contamination results from human activities. The health consequences of lead poisoning in children include:

• Partial hearing loss, hyperactivity, attention deficit, lowered IQ and learning disabilities.

– Mercury: used in many industrial processes and is released during the combustion of coal. One is a body of water mercury is converted to methyl mercury, which readily enters the food web and accumulates in fish. Methyl mercury compounds are highly toxic.

Radioactive SubstancesRadioactive Substances

• Sources include mining wastes, refining and medical wastes.

• Radioactive substances may concentrate in sewage sludge.

Thermal PollutionThermal Pollution

• Occurs when heated water, produced during many industrial processes is released into waterways.

• Warm water has a lower capacity to hold dissolved gases…

Eutrophication: Nutrient enrichment of oligotrophic lakes, estuaries or slow-moving streams.

Eutrophication: Nutrient enrichment of oligotrophic lakes, estuaries or slow-moving streams.

• Results in high photosynthetic productivity, which supports an overpopulation of algae (algal bloom).

• Eutrophic bodies of water tend to fill in rapidly as dead organisms settle to the bottom.

• Eutrophication kills fishes and causes a decline in water quality as large numbers of algae die and decompose rapidly (high BOD results in a drop in DO, hypoxia).

• Artificial Eutrophication (a.k.a. cultural eutrophication) is the enrichment of an aquatic ecosystem that occurs at an accelerated rate because of human activities such as fertilizer runoff and sewage.

Pollution of StreamsPollution of Streams Oxygen sag curve Oxygen sag curve Oxygen demand in blue and oxygen sag in

orange.

Pollution of LakesPollution of Lakes Eutrophication Eutrophication Slow turnover Slow turnover Thermal

stratification

Thermal stratification

Groundwater PollutionGroundwater Pollution

Coal strip mine runoff

Pumping well

Waste lagoon

Accidental spills

Groundwater flow

Confined aquifer

Discharge

Leakage from faulty casing

Hazardous waste injection well

Pesticides

Gasoline station

Buried gasoline and solvent tank

Sewer

Cesspool septic tank

De-icing road salt

Unconfined freshwater aquifer

Confined freshwater aquifer

Water pumping well

Landfill

Sources include: sanitary landfills, underground storage tanks, agricultural operations

Recovery is slow because temperatures are low and the flow rate is slow.

Groundwater Pollution PreventionGroundwater Pollution Prevention

Monitoring aquifers Monitoring aquifers

Leak detection systems Leak detection systems

Strictly regulating hazardous waste disposal Strictly regulating hazardous waste disposal

Storing hazardous materials above ground Storing hazardous materials above ground

Ocean PollutionOcean Pollution

Oil SpillsOil Spills Sources: offshore wells, tankers, pipelines and

storage tanks

Sources: offshore wells, tankers, pipelines and storage tanks

Effects: death of organisms, loss of animal insulation and buoyancy because of oil coating, smothering

Effects: death of organisms, loss of animal insulation and buoyancy because of oil coating, smothering

Significant economic impacts Takes about 3 years to recover from crude oil spills

and about 10 years for refined oil

Significant economic impacts Takes about 3 years to recover from crude oil spills

and about 10 years for refined oil

Mechanical cleanup methods: skimmers and blotters

Mechanical cleanup methods: skimmers and blotters

Chemical cleanup methods: coagulants and dispersing agents

Chemical cleanup methods: coagulants and dispersing agents

Solutions: Preventing and Reducing Surface Water PollutionSolutions: Preventing and Reducing Surface Water Pollution Reduce runoff Reduce runoff

Buffer zone vegetation Buffer zone vegetation

Reduce soil erosion Reduce soil erosion Clean Water Act (1972): improved number of lakes and

rivers being tested, minimized amount of topsoil lost through agricultural runoff, more sewage treatment plants put into place, and decreased wetland loss - requires the EPA to establish nation emission limitations for wastewater that is discharged into US surface waters.

Clean Water Act (1972): improved number of lakes and rivers being tested, minimized amount of topsoil lost through agricultural runoff, more sewage treatment plants put into place, and decreased wetland loss - requires the EPA to establish nation emission limitations for wastewater that is discharged into US surface waters.

Solutions: Preventing and Reducing Surface Water PollutionSolutions: Preventing and Reducing Surface Water Pollution

• Safe Drinking Water Act (1974): requires the EPA to establish maximum contaminant levels for water pollutants that might affect human health

• Water Quality Act (1987): to control surface water pollution

• It is easier to control point sources than nonpoint sources.

Waste Water TreatmentWaste Water Treatment• Primary treatment: physical settling of solids.

• Secondary treatment: biological degradation of organic wastes.

• Tertiary treatment: removal of special contaminants such as organic chemicals, nitrogen, and phosphorous.

• Sludge: slimy mixture of bacteria-laden solids that settle out during sewage treatment (primary sludge & secondary sludge).– Can be treated and then used as fertilizer if there are not

high levels of toxins.

Technological Approach: Septic SystemsTechnological Approach: Septic Systems

Require suitable soils and maintenance Require suitable soils and maintenance

CAUTION! Do not place too close to wells.

Technological Approach: Sewage TreatmentTechnological Approach: Sewage Treatment

Mechanical and biological treatmentMechanical and biological treatment

Technological Approach: Advanced Sewage Treatment

Technological Approach: Advanced Sewage Treatment

Removes specific pollutants Removes specific pollutants

Often, only 1 or 2 of these processes is used to remove specific pollutants in a particular area. It is very expensive and therefore, not widely used.

Technological Approach: Using Wetlands to Treat SewageTechnological Approach: Using Wetlands to Treat Sewage

Drinking Water QualityDrinking Water Quality

• 1.4 billion people do not have access to safe drinking water.– Contaminated with hazardous chemicals or disease

causing agents.

• 2.9 billion people do not have access to adequate sanitation systems.– Results in contaminated drinking water.– Increased rates of disease.