WATER
WATER
Universal Solvent
Water is the solvent of Life
Solute – substance dissolved in a solvent to form a solution
Solvent – fluid that dissolves solutes
Solute – substance dissolved in a solvent to form a solution
Solvent – fluid that dissolves solutes
cohesion = water attracted to other water
molecules because of polar properties adhesion = water attracted to other materials surface tension = water is pulled together creating the smallest surface area possible |
Capillary Action
Capillary Action = water’s adhesive property is the cause of capillary action. Water is attracted to some other material and then through cohesion, other water molecules move too as a result of the original adhesion. Because water has both adhesive and cohesive properties, capillary action is present. |
High Heat Capacity
|
The ocean moderates coastal temperatures
Average seawater salinity = 35‰
|
Water has high heat capacity, so it can absorb (or release) large quantities of heat without changing temperature.
Moderates coastal temperatures. Salinity-total amount of solid material dissolved in water. Can be determined by measuring water conductivity. Processes affecting seawater salinityProcesses that decrease seawater salinity:
Processes that increase seawater salinity:
Pattern of surface salinity: Lowest in high latitudes Highest in the tropics Dips at the Equator Surface processes help explain pattern High latitudes have low surface salinity High precipitation and runoff Low evaporation Tropics have high surface salinity High evaporation Low precipitation Equator has a dip in surface salinity High precipitation partially offsets high evaporation Seawater density Factors affecting seawater density: Temperature, Density (inverse relationship) Salinity, Density Pressure, Density Temperature has the greatest influence on surface seawater density |
All freshwater comes from two sources
SURFACE WATER GROUND WATER
Lakes, ponds, rivers, and streams…ALL water above ground Water that seeps below ground
Most urban areas rely on surface water Some is taken up and used by plants
Supply resources and allow for travel/trade Large amounts found in underground rock formations called aquifers
Lakes, ponds, rivers, and streams…ALL water above ground Water that seeps below ground
Most urban areas rely on surface water Some is taken up and used by plants
Supply resources and allow for travel/trade Large amounts found in underground rock formations called aquifers
Surface water movement: Water Cycle
Earths water supply is constantly recycled
Surface Water Movement
1) Runoff
Water flowing down slope along Earth’s surface or seep into the ground
Run off speed determined by slope of the hill
Ends up in a stream or lake, evaporate, or accumulate into puddles
Movement
Seep into ground
Ground must have large enough pores – loose soil
Evaporate
Fate of water: Run off or Seep
Certain characteristics will determine whether not water will either seep into or become runoff
1) Vegetation
Vegetation allows for loose soil
Loose soil allows water to enter ground
Gardeners do not pack their soil
l2) Rate of precipitation
Heavy:
soil clumps together closing pores
Fills up ground to quickly and water becomes runoff
Light:
allows water to gently slide through
Less erosion
3) Soil Composition
Effects the waters holding capacity
Decayed organic matter (humus)
Creates the pores in soil – Increases retain ability
Minerals
Clay – fine mineral which clump together
Few Spaces
Sand – large pores
4) Slopes
Steep: allows for high runoff & little absorption
Little: low runoff and high absorption
Formation of Stream systems
Runoff
Surface water flows in thin sheets and eventually collects in small channels
Runoff increases, channels widen and become deeper and longer
Channels fill up again each time with rain
Channel can become a stream
Water flowing down slope along Earth’s surface or seep into the ground
Run off speed determined by slope of the hill
Ends up in a stream or lake, evaporate, or accumulate into puddles
Movement
Seep into ground
Ground must have large enough pores – loose soil
Evaporate
Fate of water: Run off or Seep
Certain characteristics will determine whether not water will either seep into or become runoff
1) Vegetation
Vegetation allows for loose soil
Loose soil allows water to enter ground
Gardeners do not pack their soil
l2) Rate of precipitation
Heavy:
soil clumps together closing pores
Fills up ground to quickly and water becomes runoff
Light:
allows water to gently slide through
Less erosion
3) Soil Composition
Effects the waters holding capacity
Decayed organic matter (humus)
Creates the pores in soil – Increases retain ability
Minerals
Clay – fine mineral which clump together
Few Spaces
Sand – large pores
4) Slopes
Steep: allows for high runoff & little absorption
Little: low runoff and high absorption
Formation of Stream systems
Runoff
Surface water flows in thin sheets and eventually collects in small channels
Runoff increases, channels widen and become deeper and longer
Channels fill up again each time with rain
Channel can become a stream
Water sheds
DRAINAGE BASIN
LAND WHERE ALL WATER DRAINS INTO
DIVIDE:
HIGH LAND AREA THAT SEPARATES WATERSHEDS
Stream Load
Suspension
Small particles held up by the turbulence of stream
Clay, silt, sand
Depends on volume and velocity of water
Bed Load
Turbulence of water pushes heavy things
Pebbles and cobbles
Larger velocity – large objects
B/c of abrasion, rocks are smooth
Floods
Water fills over the sides of a stream banks
Floodplain: broad flat area of land that extends out from streams for excess flooding
LAND WHERE ALL WATER DRAINS INTO
DIVIDE:
HIGH LAND AREA THAT SEPARATES WATERSHEDS
Stream Load
Suspension
Small particles held up by the turbulence of stream
Clay, silt, sand
Depends on volume and velocity of water
Bed Load
Turbulence of water pushes heavy things
Pebbles and cobbles
Larger velocity – large objects
B/c of abrasion, rocks are smooth
Floods
Water fills over the sides of a stream banks
Floodplain: broad flat area of land that extends out from streams for excess flooding
Freshwater Ecosystems
Characteristics of a Freshwater Ecosystem
Slow moving waters
Low dissolved salt
Plant and animal life depends on depth of water, rate of flow, and amounts of nutrients, sunlight, and oxygen
Include lakes, ponds, rivers, and wetlands
Rivers
START in mountainous regions
Cold
Shallow beds
Highly oxygenated
A river’s characteristics changes with geography, climate, and the runoff from nearby developments
Wetlands
Covered in water at least part of the year
Trap and fix carbon
Control flooding and absorb extra water when other bodies overflow
Produce commercial products like seafood and berries (bogs)
Lakes and Ponds
An inland body of standing water that is smaller than a lake. Natural ponds form in small depressions and are usually shallow enough to support rooted vegetation across most or all of their areas.
Slow moving waters
Low dissolved salt
Plant and animal life depends on depth of water, rate of flow, and amounts of nutrients, sunlight, and oxygen
Include lakes, ponds, rivers, and wetlands
Rivers
START in mountainous regions
Cold
Shallow beds
Highly oxygenated
A river’s characteristics changes with geography, climate, and the runoff from nearby developments
Wetlands
Covered in water at least part of the year
Trap and fix carbon
Control flooding and absorb extra water when other bodies overflow
Produce commercial products like seafood and berries (bogs)
Lakes and Ponds
An inland body of standing water that is smaller than a lake. Natural ponds form in small depressions and are usually shallow enough to support rooted vegetation across most or all of their areas.
ground water
Water Beneath the Surface
Much of the water in soil seeps downward until it reaches the zone of saturation
The zone of saturation is the area where water fills all of the open spaces in sediment and rock
Groundwater is the water within this zone
The water table is the upper level of the saturation zone of groundwater
Movement
The groundwater moves more slowly when the pore spaces are smaller
Groundwater moves by twisting and turning through interconnected small openings
Porosity
- Determines how much groundwater can be stored
- The percentage of pore spaces
Permeability
- Aquifers are permeable rock layers or sediments that transmit groundwater freely
- Ability to transmit water through connected pore spaces
Much of the water in soil seeps downward until it reaches the zone of saturation
The zone of saturation is the area where water fills all of the open spaces in sediment and rock
Groundwater is the water within this zone
The water table is the upper level of the saturation zone of groundwater
Movement
The groundwater moves more slowly when the pore spaces are smaller
Groundwater moves by twisting and turning through interconnected small openings
Porosity
- Determines how much groundwater can be stored
- The percentage of pore spaces
Permeability
- Aquifers are permeable rock layers or sediments that transmit groundwater freely
- Ability to transmit water through connected pore spaces
Springs
A spring forms whenever the water table intersects the ground surface.
Hot Springs
Water is heated by cooling of igneous rock
Water is 6–9ºC warmer than the mean air temperature of the locality.
Geysers
Water turns to steam and erupts
Intermittent hot springs
A spring forms whenever the water table intersects the ground surface.
Hot Springs
Water is heated by cooling of igneous rock
Water is 6–9ºC warmer than the mean air temperature of the locality.
Geysers
Water turns to steam and erupts
Intermittent hot springs
Geyser Eruption Cycle
Wells
A well is a hole bored into the zone of saturation
An artesian well is any formation in which groundwater rises on its own under pressure
Pumping can cause a draw down (lowering) of the water table or pumping can form a cone of depression in the water table
Cone of Depression
A well is a hole bored into the zone of saturation
An artesian well is any formation in which groundwater rises on its own under pressure
Pumping can cause a draw down (lowering) of the water table or pumping can form a cone of depression in the water table
Cone of Depression
Environmental Problems Associated with Groundwater
Overuse and contamination threatens groundwater supplies in some areas
-Treating it as a nonrenewable resource
-Contamination
-Land subsidence caused by its withdrawal
Groundwater Contamination
Overuse and contamination threatens groundwater supplies in some areas
-Treating it as a nonrenewable resource
-Contamination
-Land subsidence caused by its withdrawal
Groundwater Contamination
Caverns
A cavern is a naturally formed underground chamber
Erosion forms most caverns at or below the water table in the zone of saturation
Travertine is a form of limestone that is deposited by hot springs or as a cave deposit
Characteristics of features found within caverns
-Common features include stalactites (hanging from the ceiling) and stalagmites (growing upward from the floor).
-Formed from calcite deposited as dripping water evaporates
-Composed of drip stone
-Formed in the zone of aeration
Karst Topography
Formed by dissolving rock at, or near, Earth's surface
Common features
Sinkholes—surface depressions
-Sinkholes form when bedrock dissolves and caverns collapse
Caves and caverns
Area lacks good surface drainage
A cavern is a naturally formed underground chamber
Erosion forms most caverns at or below the water table in the zone of saturation
Travertine is a form of limestone that is deposited by hot springs or as a cave deposit
Characteristics of features found within caverns
-Common features include stalactites (hanging from the ceiling) and stalagmites (growing upward from the floor).
-Formed from calcite deposited as dripping water evaporates
-Composed of drip stone
-Formed in the zone of aeration
Karst Topography
Formed by dissolving rock at, or near, Earth's surface
Common features
Sinkholes—surface depressions
-Sinkholes form when bedrock dissolves and caverns collapse
Caves and caverns
Area lacks good surface drainage
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human impacts on water
WATER POLLUTION
What’s the difference?
Point Source Pollution vs. Non-point Source Pollution
Point Source Pollution- comes from a specific source/factories, industry, municipal treatment plants/can be monitored and controlled by a permit system
Non-Point Source Pollution- Non-point Source pollution is pollution associated with storm-water or runoff/ cannot be traced to a direct discharge point such as a waste water treatment facility.
Examples of Non-Point Source Pollution
oil & grease from cars
fertilizers
animal waste
grass clippings
septic systems
sewage & cleaners from boats
household cleaning products
litter
Pollutant Transport Mechanisms
•N-P-S pollutants build up on land surfaces during dry weather
Atmospheric deposition
Fertilizer applications
Animal waste
Automotive exhaust/fluid leaks
•Pollutants are washed off land surfaces during precipitation events (stormwater runoff)
•Storm-water runoff will flow to lakes and streams
Point or Non-Point Source?
Eroding soil from construction sites-NON-POINT
Leachate from landfill-POINT
Overflowing hog lagoon-POINT
Pesticides-NON-POINT
Septic tank leak-POINT
Storm water run-off from city streets-NON-POINT
Pollutant build-up and wash off are affected by land use.
Impervious increases runoff /More Impervious = More Water
Land use changes impact build up
What is impervious cover?
roads, rooftops, parking lots, and other hard surfaces that do not allow stormwater to soak into the ground
“predominant American vegetation”
•provides a surface for accumulation of pollutants
•leads to increased polluted runoff and flooding
•inhibits recharge of groundwater
Impact of Non-point Source Pollution
fish and wildlife
recreational water activities
commercial fishing
tourism
drinking water quality
Pollutants Found in Runoff
Sediment
Soil particles transported from their source
Toxins
● Pesticides
Herbicides
Fungicides
Insecticides
● Metals (naturally occurring in soil, automotive emissions/ tires)
Lead
Zinc
Mercury
● Petroleum Hydrocarbons(automotive exhaust and fuel/oil)
Debris
Litter and illegal dumping
Biochemical Oxygen Demand (BOD)
● Oxygen depleting material
Leaves
Organic material
Nutrients
● Various types of materials that become dissolved and suspended in water (commonly found in fertilizer and plant material):
Nitrogen (N)
Phosphorus (P)
Bacteria/ Pathogens
Originating from:
● Pets
● Waterfowl
● Failing septic systems
Thermal Stress
Heated runoff, removal of stream side vegetation
Potential Sources of Pollutants Found in Residential Areas
Nutrients: Fertilizers and septic systems
Pathogens: Pet waste and septic systems
Sediment: Construction, road sand, soil erosion
Toxic: Pesticides, household products
Debris: Litter and illegal dumping
Thermal: heated runoff, removal of streamside vegetation
Pollutants from Agriculture
Sediment reduces light penetration in stream, clogs gills of fish and aquatic invertebrates.
Nutrients act as fertilizer for algae & aquatic plants which can cause highly varying dissolved oxygen levels. At low DO levels, the aquatic life has the potential to be harmed.
Toxics can impact life and contaminate drinking water supplies.
Bacteria/Pathogens are an indicator of possible viruses present in the system.
Inefficient Irrigation
Worldwide, the amount of land under irrigation has been increasing.
Whether from aquifers or surface bodies of water, the majority of the freshwater we use for irrigation is lost before it ever reaches the crops.
-Inefficient “flood and furrow” irrigation, in which fields are liberally flooded with water that may evaporate from shallow standing pools, accounts for 90% of irrigation worldwide.
-Over-irrigation leads to water logging and salinization, which affects 1/5 of farmland today and reduces world farming income by $11 billion.
-Unfortunately, huge amounts of groundwater are being used up for little gain; because of the dry climate and inefficient irrigation methods.
Eutrophication
Most nutrients in water come from organic matter (leaves, waste, etc.)
Nutrients are an essential part of any aquatic ecosystem, but when slow-moving waters contain too much, they are eutrophic.
Eutrophication= build-up of organic matter in water causing algal blooms
Outcomes:
•Decreased sunlight
•Decaying matter uses oxygen
•Suffocation/Fish Kills
Artificial Eutrophication
-Humans act as a catalyst by adding excess nutrients to the soil
-Main culprits= phosphates from fertilizers and cleaning agents
-Human activity can also cause thermal pollution
Pollution of Groundwater
It can take hundreds to thousand of years for contaminated groundwater to cleanse itself of degradable wastes.
Non-degradable wastes (toxic lead, arsenic, fluoride) are there permanently.
Slowly degradable wastes (such as DDT) are there for decades.
Groundwater has low flow rates, few bacteria, & cold temps - all slow down recovery time
Avg. recycling time for groundwater = 1400 years
What’s the difference?
Point Source Pollution vs. Non-point Source Pollution
Point Source Pollution- comes from a specific source/factories, industry, municipal treatment plants/can be monitored and controlled by a permit system
Non-Point Source Pollution- Non-point Source pollution is pollution associated with storm-water or runoff/ cannot be traced to a direct discharge point such as a waste water treatment facility.
Examples of Non-Point Source Pollution
oil & grease from cars
fertilizers
animal waste
grass clippings
septic systems
sewage & cleaners from boats
household cleaning products
litter
Pollutant Transport Mechanisms
•N-P-S pollutants build up on land surfaces during dry weather
Atmospheric deposition
Fertilizer applications
Animal waste
Automotive exhaust/fluid leaks
•Pollutants are washed off land surfaces during precipitation events (stormwater runoff)
•Storm-water runoff will flow to lakes and streams
Point or Non-Point Source?
Eroding soil from construction sites-NON-POINT
Leachate from landfill-POINT
Overflowing hog lagoon-POINT
Pesticides-NON-POINT
Septic tank leak-POINT
Storm water run-off from city streets-NON-POINT
Pollutant build-up and wash off are affected by land use.
Impervious increases runoff /More Impervious = More Water
Land use changes impact build up
What is impervious cover?
roads, rooftops, parking lots, and other hard surfaces that do not allow stormwater to soak into the ground
“predominant American vegetation”
•provides a surface for accumulation of pollutants
•leads to increased polluted runoff and flooding
•inhibits recharge of groundwater
Impact of Non-point Source Pollution
fish and wildlife
recreational water activities
commercial fishing
tourism
drinking water quality
Pollutants Found in Runoff
Sediment
Soil particles transported from their source
Toxins
● Pesticides
Herbicides
Fungicides
Insecticides
● Metals (naturally occurring in soil, automotive emissions/ tires)
Lead
Zinc
Mercury
● Petroleum Hydrocarbons(automotive exhaust and fuel/oil)
Debris
Litter and illegal dumping
Biochemical Oxygen Demand (BOD)
● Oxygen depleting material
Leaves
Organic material
Nutrients
● Various types of materials that become dissolved and suspended in water (commonly found in fertilizer and plant material):
Nitrogen (N)
Phosphorus (P)
Bacteria/ Pathogens
Originating from:
● Pets
● Waterfowl
● Failing septic systems
Thermal Stress
Heated runoff, removal of stream side vegetation
Potential Sources of Pollutants Found in Residential Areas
Nutrients: Fertilizers and septic systems
Pathogens: Pet waste and septic systems
Sediment: Construction, road sand, soil erosion
Toxic: Pesticides, household products
Debris: Litter and illegal dumping
Thermal: heated runoff, removal of streamside vegetation
Pollutants from Agriculture
Sediment reduces light penetration in stream, clogs gills of fish and aquatic invertebrates.
Nutrients act as fertilizer for algae & aquatic plants which can cause highly varying dissolved oxygen levels. At low DO levels, the aquatic life has the potential to be harmed.
Toxics can impact life and contaminate drinking water supplies.
Bacteria/Pathogens are an indicator of possible viruses present in the system.
Inefficient Irrigation
Worldwide, the amount of land under irrigation has been increasing.
Whether from aquifers or surface bodies of water, the majority of the freshwater we use for irrigation is lost before it ever reaches the crops.
-Inefficient “flood and furrow” irrigation, in which fields are liberally flooded with water that may evaporate from shallow standing pools, accounts for 90% of irrigation worldwide.
-Over-irrigation leads to water logging and salinization, which affects 1/5 of farmland today and reduces world farming income by $11 billion.
-Unfortunately, huge amounts of groundwater are being used up for little gain; because of the dry climate and inefficient irrigation methods.
Eutrophication
Most nutrients in water come from organic matter (leaves, waste, etc.)
Nutrients are an essential part of any aquatic ecosystem, but when slow-moving waters contain too much, they are eutrophic.
Eutrophication= build-up of organic matter in water causing algal blooms
Outcomes:
•Decreased sunlight
•Decaying matter uses oxygen
•Suffocation/Fish Kills
Artificial Eutrophication
-Humans act as a catalyst by adding excess nutrients to the soil
-Main culprits= phosphates from fertilizers and cleaning agents
-Human activity can also cause thermal pollution
Pollution of Groundwater
It can take hundreds to thousand of years for contaminated groundwater to cleanse itself of degradable wastes.
Non-degradable wastes (toxic lead, arsenic, fluoride) are there permanently.
Slowly degradable wastes (such as DDT) are there for decades.
Groundwater has low flow rates, few bacteria, & cold temps - all slow down recovery time
Avg. recycling time for groundwater = 1400 years
Surface water vs. Groundwater
Which is generally more polluted?
~ Surface Water
Which is harder to clean up?
~ Groundwater
Groundwater pollution sticks around...
Very cold, no bacterial breakdown, Very slow water movement: recharge can take 100’s or 1000’s of years, Pollutants can stick to rocks in aquifer and pollute new water
Which is generally more polluted?
~ Surface Water
Which is harder to clean up?
~ Groundwater
Groundwater pollution sticks around...
Very cold, no bacterial breakdown, Very slow water movement: recharge can take 100’s or 1000’s of years, Pollutants can stick to rocks in aquifer and pollute new water
Laws
Clean Water Act – surface water
1972 – make water swimmable and fishable by regulating point sources
1977 and 1987 – storm water runoff
Section 404 – requires permit for draining, dredging, filling wetlands
Mitigation banking
Safe Drinking Water Act (1974) – monitors levels of contaminants in groundwater
Sources of Groundwater pollution...
landfills
leaky underground storage tanks
mines
septic tanks
hazardous waste - deep well injection
any pollutant in runoff that percolate
Clean Water Act – surface water
1972 – make water swimmable and fishable by regulating point sources
1977 and 1987 – storm water runoff
Section 404 – requires permit for draining, dredging, filling wetlands
Mitigation banking
Safe Drinking Water Act (1974) – monitors levels of contaminants in groundwater
Sources of Groundwater pollution...
landfills
leaky underground storage tanks
mines
septic tanks
hazardous waste - deep well injection
any pollutant in runoff that percolate
Sewage Treatment
Order of Treatment
-Waste water collects in pipes/sewers
-Moves to local water treatment plants
-PRIMARY TREATMENT
-Removal of Solids- Chunks of debris, sticks, sand, etc… get caught on the bar screens as the sewage enters the plant.
-Grit Chamber-sand, grit and heavy solids settle to the bottom
-Primary Sedimentation Tank- Smaller particles settle scrapers collect the solid matter plus scum or grease floating on top of the tank
-Waste water collects in pipes/sewers
-Moves to local water treatment plants
-PRIMARY TREATMENT
-Removal of Solids- Chunks of debris, sticks, sand, etc… get caught on the bar screens as the sewage enters the plant.
-Grit Chamber-sand, grit and heavy solids settle to the bottom
-Primary Sedimentation Tank- Smaller particles settle scrapers collect the solid matter plus scum or grease floating on top of the tank
![Picture](/uploads/5/9/3/7/59376597/3928221_orig.png)
SECONDARY TREATMENT
85-90% of pollutants are removed
STEPS
-The 1st step is AERATION- Microorganisms and oxygen are mixed with the wastewater. Air speeds the growth of the bacteria which eat the waste matter.
-Followed by SECONDARY SEDIMENTATION- Solids clump together (activated sludge) and settle out for reuse in the aeration tanks.
CHLORINE- Added as a disinfectant before the wastewater leaves the plant to kill disease-causing organisms
What do you do with all of the SLUDGE?
Burn it in specially designed plants to prevent air pollution
A source of methane for powering small power plants or we bury it in approved landfills
Digesters
The purpose of sludge treatment is to destroy the pathogens
Huge tanks in which the sludge is stored to allow it to continue to decompose (15-30 days)
Aerobic digestion (treatment) consists of continuously pumping compressed air into a tank
Anaerobic bacteria present in the waste convert much of the waste materials to carbon dioxide and methane (natural) gas
What if you are not connected to a sewer line?
then you have a SEPTIC SYSTEM
85-90% of pollutants are removed
STEPS
-The 1st step is AERATION- Microorganisms and oxygen are mixed with the wastewater. Air speeds the growth of the bacteria which eat the waste matter.
-Followed by SECONDARY SEDIMENTATION- Solids clump together (activated sludge) and settle out for reuse in the aeration tanks.
CHLORINE- Added as a disinfectant before the wastewater leaves the plant to kill disease-causing organisms
What do you do with all of the SLUDGE?
Burn it in specially designed plants to prevent air pollution
A source of methane for powering small power plants or we bury it in approved landfills
Digesters
The purpose of sludge treatment is to destroy the pathogens
Huge tanks in which the sludge is stored to allow it to continue to decompose (15-30 days)
Aerobic digestion (treatment) consists of continuously pumping compressed air into a tank
Anaerobic bacteria present in the waste convert much of the waste materials to carbon dioxide and methane (natural) gas
What if you are not connected to a sewer line?
then you have a SEPTIC SYSTEM
Septic Tank
The septic tank is a settling tank where sewage from the house is stored temporarily so that solid materials settle to the bottom of the tank to form sludge, while grease floats to the top to form a scum layer.
The scum and sludge must be periodically removed from the septic tank by simply pumping them out.
Drainfield
The absorption field is frequently a network of drain lines (pipes with holes in them) that carry wastewater from the septic tank and apply it to the soil.
The size of the absorption field varies from site to site, but most are small enough to fit in a backyard and cover and area between
400 and 800 ft2.
Suitable Soils
Although effluent can be applied to the surface of any soil, not all soils are able to absorb and purify wastewater.
Soils that can be used for waste disposal are permeable, deep, well drained (not waterlogged) and are not on a steep slope.
In N. C., state law requires that all soils pass an inspection before a septic system is installed on any property.
The septic tank is a settling tank where sewage from the house is stored temporarily so that solid materials settle to the bottom of the tank to form sludge, while grease floats to the top to form a scum layer.
The scum and sludge must be periodically removed from the septic tank by simply pumping them out.
Drainfield
The absorption field is frequently a network of drain lines (pipes with holes in them) that carry wastewater from the septic tank and apply it to the soil.
The size of the absorption field varies from site to site, but most are small enough to fit in a backyard and cover and area between
400 and 800 ft2.
Suitable Soils
Although effluent can be applied to the surface of any soil, not all soils are able to absorb and purify wastewater.
Soils that can be used for waste disposal are permeable, deep, well drained (not waterlogged) and are not on a steep slope.
In N. C., state law requires that all soils pass an inspection before a septic system is installed on any property.
dams
![Picture](/uploads/5/9/3/7/59376597/5513128_orig.jpg)
Hydro power
Pros
1. Dams are relatively inexpensive to operate.
–Yet, they are very expensive to build.
2. Dams generate clean power
–Hydro power is renewable and doesn’t emit greenhouse gases or other air pollutants*
3. Dams improve quality of life
–prevent flooding*, create jobs, and provide cheap electricity, irrigation, and drinking water
Cons
1. Dams alter river habitats in many ways
upstream: flooding
downstream: not enough water
2. Natural cycles are disrupted
- floodplains don’t receive nutrients from sediments because they get trapped behind dams
3. Temperature of the water is changed
- aquatic populations go extinct
4. Dams prevent anadromous fish from laying eggs.
Modern Trends
In the US, the era of large dam construction is probably over.
–Not so in developing countries (Brazil, China, India).
Micro-hydro power :electricity produced in a small stream without having to build a big dam
Micro-hydro power
Much cheaper to build.
Can be used in remote areas
What are the pros and cons of hydro power?
Water Diversion
What are the effects of Water Diversion?
Water diversion projects bring water to areas that need it
We divert – and deplete – surface water
People have long diverted water to farm fields, homes, and cities
The Colorado River is heavily diverted
–What water is left after all the diversions comprises just a trickle into the Gulf of California
On some days, water does not reach the gulf
–Diversion has drastically altered the river’s ecology
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
Pros
1. Dams are relatively inexpensive to operate.
–Yet, they are very expensive to build.
2. Dams generate clean power
–Hydro power is renewable and doesn’t emit greenhouse gases or other air pollutants*
3. Dams improve quality of life
–prevent flooding*, create jobs, and provide cheap electricity, irrigation, and drinking water
Cons
1. Dams alter river habitats in many ways
upstream: flooding
downstream: not enough water
2. Natural cycles are disrupted
- floodplains don’t receive nutrients from sediments because they get trapped behind dams
3. Temperature of the water is changed
- aquatic populations go extinct
4. Dams prevent anadromous fish from laying eggs.
Modern Trends
In the US, the era of large dam construction is probably over.
–Not so in developing countries (Brazil, China, India).
Micro-hydro power :electricity produced in a small stream without having to build a big dam
Micro-hydro power
Much cheaper to build.
Can be used in remote areas
What are the pros and cons of hydro power?
Water Diversion
What are the effects of Water Diversion?
Water diversion projects bring water to areas that need it
We divert – and deplete – surface water
People have long diverted water to farm fields, homes, and cities
The Colorado River is heavily diverted
–What water is left after all the diversions comprises just a trickle into the Gulf of California
On some days, water does not reach the gulf
–Diversion has drastically altered the river’s ecology
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
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