water resources & water pollution chapters 14 & 19
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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.
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