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Water: Resources and Pollution

Chapter 23

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Outline:

• Hydrologic Cycle• Water Compartments• Water Availability• Freshwater Shortages

Increasing Water Supplies• Water Management and Conservation• Water Pollution• Water Quality Today• Water Pollution Control• Water Legislation

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WATER RESOURCES

• Hydrologic Cycle• Describes the circulation of water as it:

Evaporates from land, water, and organisms. (Transpires from plants)

- Enters the atmosphere. Condenses and precipitates back to the

earth’s surfaces. Moves underground by infiltration or

overland into rivers, lakes and seas.

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Mean Annual Precipitation

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Water Distribution

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MAJOR WATER COMPARTMENTS

• Groundwater Second largest reservoir of fresh water.

- Infiltration - Process of water percolating through the soil and into fractures and permeable rocks.

Zone of Aeration - Upper soil layers that hold both air and water.

Zone of Saturation - Lower soil layers where all spaces are filled with water.

Water Table - Top of Zone of Sat.

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Groundwater

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Groundwater

• Aquifers - Porous layers of sand, gravel, or rock lying below the water table. Artesian - Pressurized aquifer intersects

the surface. (Water flows without pumping)• Recharge Zone - Area where water infiltrates

into an aquifer. Recharge rate is often very slow.

- Presently, groundwater is being removed faster than it can be replenished in many areas.

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Question 1

1. Define: hydrologic cycle.

• Describes the circulation of water as it: Evaporates from land, water, and organisms.

(Transpires from plants)- Enters the atmosphere.

Condenses and precipitates back to the earth’s surfaces.

Moves underground by infiltration or overland into rivers, lakes and seas.

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Major Water Compartments

• Rivers and Streams Precipitation that does not evaporate or

infiltrate into the ground runs off the surface, back toward the sea.

- Best measure of water volume carried by a river is discharge.

The amount of water that passes a fixed point in a given amount of time.

Usually expressed as cubic feet per second.

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Question 2

2. Compare and contrast: aquifer and artesian.

• Aquifers - Porous layers of sand, gravel, or rock lying below the water table. Artesian - Pressurized aquifer intersects

the surface. (Water flows without pumping)

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Question 3

3. What is the best way to measure the water volume of a river or stream? Does the season matter? Why?

Discharge. ( example: cubic feet per second)

Yes. Stream discharges usually vary over the year.

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Upper Chatahoochee Watershed

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Major Water Compartments

• Wetlands Play a vital role in hydrologic cycle.

- Lush plant growth stabilizes soil and retards surface runoff, allowing more aquifer infiltration.

Disturbance reduces natural water-absorbing capacity, resulting in floods and erosion in wet periods, and less water flow the rest of the year.

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Major Water Compartments

• The Atmosphere Among the smallest water reservoirs.

- Contains 0.001% of total water supply.- Has most rapid turnover rate.- Provides mechanism for distributing

fresh water over landmasses and replenishing terrestrial reservoirs.

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Question 4

4. Off the major water compartments, which has the greatest volume? The least?

Greatest: the oceans

Least: the atmosphere

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WATER AVAILABILITY AND USE

• Renewable Water Supplies Made up of surface runoff and infiltration

into accessible freshwater aquifers.• Water-Rich ad Water-Poor Countries

Water availability usually measured in per capita terms.

- Highest per capita generally found in countries with moist climates and low population densities.

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Water Use

• Withdrawal - Total amount of water taken from a source.

• Consumption - Fraction of withdrawn water made unavailable for other purposes (Not returned to its source). Degradation - Change in water quality due

to contamination making it is unsuitable for desired use.

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Quantities of Water Used

• Water use has been increasing twice as fast as population growth over past century. Worldwide, agriculture claims about 70%

of total water withdrawal.- In many developing countries,

agricultural water use is extremely inefficient and highly consumptive.

Worldwide, industry accounts for about 25% of all water use.

- Cooling water for power plants is single largest industrial use.

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Water Withdrawal

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Question 5

• 5. State the three modes of water use and briefly describe them.

• Withdrawal - Total amount of water taken from a source.

• Consumption - Fraction of withdrawn water made unavailable for other purposes (Not returned to its source). Degradation - Change in water quality due

to contamination making it is unsuitable for desired use.

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FRESHWATER SHORTAGES

• Estimated 1.1 billion people lack access to an adequate supply of drinking water. 2.4 billion lack acceptable sanitation.

• A country where consumption exceeds more than 20% of available, renewable supply is considered vulnerable to water stress. Globally, water supplies are abundant, but,

along with capital resources, are unevenly distributed.

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A Precious Resource

• Currently, 45 countries, most in Africa or Middle East, cannot meet the minimum essential water requirements of their citizens. More than two-thirds of world’s households

retrieve water from outside the home.- Availability does not automatically

equate to affordability. Sanitation levels decline when water is

expensive.

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Depleting Groundwater

• Groundwater is the source of nearly 40% of fresh water in the US. On a local level, withdrawing water faster

than it can be replenished leads to a cone of depression in the water table,

- On a broader scale, heavy pumping can deplete an aquifer.

Ogallala Aquifer Mining non-renewable resource.

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Ogallala Aquifer

• “The Ogallala Aquifer within the boundaries of the North Plains Groundwater Conservation District is declining at an average of 1.74 feet per year (1,082,631 acre ft).”

• The aquifer is cut off from• natural recharge sources.

http://www.npwd.org/Ogallala.htm

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Depleting Groundwater

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Depleting Groundwater

• Withdrawing large amounts of groundwater in a small area causes porous formations to collapse, resulting in subsidence. Sinkholes form when an underground

channel or cavern collapses. Saltwater intrusion can occur along

coastlines where overuse of freshwater reservoirs draws the water table low enough to allow saltwater to intrude.

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Sink Holes and Karst Topography

CaCO3 + H2SO4 CaSO4 + H2O +CO2

http://www.soils.umn.edu/academics/classes/soil2125/doc/1-snkle.htm

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Question 6

• 6. Compare and contrast: water table and cone of depression.

• The water table is the upper surface of the zone of saturation.

• On a local level, withdrawing water faster than it can be replenished leads to a cone of depression in the water table.

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INCREASING WATER SUPPLIES

• Seeding Clouds Condensation Nuclei

• Towing Icebergs Cost

• Desalination Most common methods are distillation and

reverse osmosis.- Three to four times more expensive than

most other sources.

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Flow Diagram of a reverse osmosis system (courtesy of USAID). (Kahn, 1986.)

In RO, feedwater is pumped at high pressure through permeable membranes, separating salts from the water.. The feedwater is pretreated to remove particles that would clog the membranes. The quality of the water produced depends on the pressure, the concentration of salts in the feedwater, and the salt permeation constant of the membranes.”

http://www.coastal.ca.gov/desalrpt/dchap1.html

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New desalination technology taps waste heat from power plants

• “GAINESVILLE, Fla. --- Desalination is often touted as one solution to the world's water woes, but current desalination plants tend to hog energy. Now University of Florida researchers have developed a technology that can tap waste heat from electrical power plants as its main source of energy, an advance that could significantly reduce the cost of desalination in some parts of the world.”

http://www.eurekalert.org/pub_releases/2004-12/uof-ndt121604.php

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Increasing Water Supplies

• Dams, Reservoirs, and Canals - Trap excess water in areas of excess and transfer it to areas of deficit. Environmental Costs

- Upsets natural balance of water systems. Ecosystem Losses

- Loss of wildlife habitat. Reservoir Size Water Quality

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Dams, Reservoirs, and Canals

Displacement of People- Three Gorges Dams in China will force

relocation of over a million people. Evaporation, Leakage, Siltation

- Evaporative losses from Lake Mead and Lake Powell on the Colorado River is about 1km3 per year (264 billion gallons).

- Dams slow water flow, allowing silt (nutrients) to drop out.

Loss of Free-Flowing Rivers

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Question 7

• 7. Why is the energy cost so high for reverse osmotic plants? What may be a solution?

• To over come the osmotic pressure of seawater ( about 30 atm) requires a higher pressure and therefore, a very high energy cost.

• The waste heat from power plants may provide a cheaper alternative energy source.

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Price Mechanisms and Water Policy

• Throughout most of U.S. history, water policies have generally worked against conservation. Eastern - Riparian Use Rights Western - Prior Appropriation Rights

• In most federal reclamation projects, customers have been charged only for the immediate costs of water delivery.

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WATER MANAGEMENT AND CONSERVATION

• Watershed Management Watershed - All the land drained by a

stream or river.- Retaining vegetation and ground cover

helps retard rainwater and lessens downstream flooding.

Additionally, retaining crop residue on fields reduces flooding and minimizing plowing and forest cutting on steep slopes protects watersheds.

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Domestic Conservation

• Estimates suggest many societies could save as much as half of current domestic water usage without great sacrifice or serious change in lifestyle. Largest domestic use is toilet flushing.

- Small volume of waste in large volume of water.

- Significant amounts of water can be reclaimed and recycled.

Purified sewage effluent

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Infectious Agents

• Main source of waterborne pathogens is untreated and improperly treated human waste. Animal wastes from feedlots and fields is

also an important source of pathogens.

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Infectious Agents

• In developed countries, sewage treatment plants and pollution-control devices have greatly reduced pathogens. Coliform bacteria - Intestinal bacteria.

- Escherichia coli (E. coli)

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Question 8

• 8. Define: point source and non-point source (of water pollution). Give examples of each.

Point Sources - Discharge pollution from specific locations.

- Factories, Power plants Non-Point Sources - Scattered or diffuse,

having no specific location of discharge.- Agricultural fields, Feedlots- Atmospheric Deposition

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Oxygen-Demanding Wastes

• Water with an oxygen content > 6 ppm will support desirable aquatic life. Water with < 2 ppm oxygen will support

mainly detritivores and decomposers.• Oxygen is added to water by diffusion from

wind and waves, and by photosynthesis from green plants, algae, and cyanobacteria. Oxygen is removed from water by

respiration and oxygen-consuming processes.

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Oxygen-Demanding Wastes

• Biochemical Oxygen Demand - Amount of dissolved oxygen consumed by aquatic microorganisms. Dissolved Oxygen Content - Measure of

dissolved oxygen in the water.• Effects of oxygen-demanding wastes on

rivers depend on volume, flow, and temperature of river water. Oxygen Sag - Oxygen levels decline

downstream from a pollution source as decomposers metabolize waste materials.

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Oxygen Sag

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Plant Nutrients and Cultural Eutrophication

• Oligotrophic - Bodies of water that have clear water and low biological productivity.

• Eutrophic - Bodies of water that are rich in organisms and organic material. Eutrophication - Process of increasing

nutrient levels and biological productivity.- Cultural Eutrophication - Increase in

biological productivity and ecosystem succession caused by human activities.

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Toxic Tides

• Excessive nutrients support blooms of deadly aquatic microorganisms in polluted waters. Increasingly common where nutrients and

wastes wash down rivers.- Pfiesteria piscicida is a poisonous

dinoflagellate recognized as killer of fish and shellfish.

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Inorganic Pollutants

• Metals Many metals such as mercury, lead,

cadmium, and nickel are highly toxic.- Highly persistent and tend to

bioaccumulate in food chains. Lead pipes are a serious source of

drinking water pollution. Mine drainage and leaching are

serious sources of environmental contamination.

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Inorganic Pollutants

• Nonmetallic Salts Many salts that are non-toxic at low

concentrations can be mobilized by irrigation and concentrated by evaporation, reaching levels toxic to plants and animals.

- Leaching of road salts has had detrimental effect on many ecosystems.

• Acids and Bases Often released as by-products of industrial

processes.

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Organic Chemicals

• Thousands of natural and synthetic organic chemicals are used to make pesticides, plastics, pharmaceuticals, pigments, etc.

• Two most important sources of toxic organic chemicals in water are: Improper disposal of industrial and

household wastes. Runoff of pesticides from high-use areas.

- Fields, roadsides, golf courses

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Sediment

• Human activities have accelerated erosion rates in many areas. Cropland erosion contributes about 25

billion metric tons of suspended solids to world surfaces each year.

• Sediment can either be beneficial (nourish floodplains) or harmful (smother aquatic life).

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Thermal Pollution

• Raising or lowering water temperatures from normal levels can adversely affect water quality and aquatic life. Oxygen solubility in water decreases as

temperatures increase. - Species requiring high oxygen levels are

adversely affected by warming water.

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Leaking Underground Storage Tanks: A Threat to Public Health & the Environment

• “America's groundwater. Gas stations, industries and other entities use USTs to hold toxic material such as gasoline and oil that contain dangerous substances, including benzene, toluene and heavy metals that can cause cancer and harm developing children.”

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Underground Storage Tanks

• “There are 680,000 USTs and a backlog of 130,000 cleanups; 9,000 new leaks are discovered annually. In 2004, UST cleanups declined by 22 percent compared to 2003. “

• “One pin-prick sized hole in an UST can leak 400 gallons of fuel a year. More than 100 million people drink groundwater in states where delayed cleanups threaten groundwater quality.”

http://www.sierraclub.org/toxics/Leaking_USTs/

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GA UST Fun Facts

• 41% of Georgians drink ground water• Cleanup backlog: 2924 sites• State rank in backlog cleanups: 14th

• Average cost per cleanup: $102,121• Georgia’s daily groundwater use: 1.4 billion

gallons (includes agricultural uses)• Source:

http://www.sierraclub.org/toxics/Leaking_USTs/

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Thermal Pollution

• Industrial cooling often use heat-exchangers to extract excess heat, and discharge heated water back into original source. Thermal Plume

- Produce artificial environments which attract many forms of wildlife.

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WATER QUALITY TODAY

• Areas of Progress Clean Water Act (1972) established a

National Pollution Discharge System which requires a permit for any entity dumping wastes in surface waters.

- In 1999, EPA reported 91.4% of all monitored river miles and 87.5% of all accessed lake acres are suitable for their designated uses.

Most progress due to municipal sewage treatment facilities.

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Water Quality Today

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Watershed Approaches

• In 1998, EPA switched regulatory approaches. Rather than issue standards on a site by site approach, the focus is now on watershed-level monitoring and protection. States are required to identify waters not

meeting water quality goals and develop total maximum daily loads (TMDL) for each pollutant and each listed water body.

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Remaining Problems

• Greatest impediments to achieving national goals in water quality are sediment, nutrients, and pathogens, especially from non-point discharges. About three-quarters of water pollution in

the US comes from soil erosion, air pollution fallout, and agricultural and urban runoff.

- Single cow produces 30 kg manure/day. Some feedlots have 100,000 animals.

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Problems and Progress in Other Countries

• Sewage treatment in wealthier countries of Europe generally equal or surpass the US.

• In Russia, only about half of the tap water supply is safe to drink.

• In urban areas of South America, Africa, and Asia, 95% of all sewage is discharged untreated into rivers.

• Two-thirds of India’s surface waters are contaminated sufficiently to be considered dangerous to human health.

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Groundwater Pollution

• About half the US population, and 95% of rural residents, depend on underground aquifers for drinking water. For decades, groundwater was assumed

impervious to pollution and was considered the gold standard for water quality.

- Estimated 1.5 million Americans fall ill from fecal contamination annually.

Cryptosporidium outbreaks

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Groundwater and Drinking Water

• EPA estimates 4.5 trillion liters of contaminated water seep into the ground in the US every day. MTBE - Gasoline additive, and suspected

carcinogen, is present in many urban aquifers.

In agricultural areas, fertilizers and pesticides commonly contaminate aquifers and wells.

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Groundwater Pollution

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Ocean Pollution

• Estimated 6 million metric tons of plastic bottles, packaging material, and other litter tossed from ships into the ocean annually. Few coastlines in the world remain

uncontaminated by oil or oil products.

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Ocean Pollution

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POLLUTION CONTROL

• Source Reduction Cheapest and most effective way to

reduce pollution is avoid producing it or releasing it into the environment.

- Studies show as much as 90% less road salt can be used without significantly affecting winter road safety.

- Soil Conservation- Banning phosphate detergents

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Sewage Treatment

• More than 500 pathogenic bacteria, viruses, and parasites can travel from human or animal excrement through water.

• Natural Processes In many areas, outdoor urination and

defecation is the norm.- When population densities are low,

natural processes can quickly eliminate waste.

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Municipal Sewage Treatment

• Primary Treatment - Physical separation of large solids from the waste stream.

• Secondary Treatment - Biological degradation of dissolved organic compounds. Effluent from primary treatment transferred

into trickling bed, or aeration tank- Effluent from secondary treatment is

usually disinfected (chlorinated) before release into nearby waterway.

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Municipal Sewage Treatment

• Tertiary Treatment - Removal of plant nutrients (nitrates and phosphates) from secondary effluent. Chemicals, or natural wetlands.

• In many US cities, sanitary sewers are connected to storm sewers. Heavy storms can overload the system,

causing by-pass dumping of raw sewage and toxic runoff directly into watercourses.

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Municipal Sewage Treatment

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CSO Tunnels and Treatment Facilities

• “The tunnel is part of a storage and treatment system that involves capturing and storing combined sewer overflows. The overflows are stored in a large underground tunnel in bedrock similar to the rock that comprises Stone Mountain. When a storm is over, the captured CSO volume is conveyed to a separate treatment system for removal of pollutants and reduction of harmful bacteria with sodium hypochlorite disinfection followed by dechlorination with sodium bisulfite before discharge to receiving waters. The City is building two facilities, the West Area CSO storage tunnel and the East Area CSO underground linear storage facility to handle the overflows.”

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Milestone Completion Date for West Tunnel October 2007

These will collect storm water for treatment.http://www.cleanwateratlanta.org/CSOTunnels/

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Low-Cost Waste Treatment

• Artificial Wetlands Natural water purification

- Effluent can be used to irrigate crops or raise fish for human consumption.

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Water Remediation

• Containment methods confine liquid wastes in place, or cap surface with impermeable layer to divert water away from the site.

• Extraction techniques are used to pump out polluted water for treatment. Oxidation, reduction, neutralization, or

precipitation.• Living organisms can also be used effectively

to break down polluted waters.

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WATER LEGISLATION

• Clean Water Act (1972) Goal was to return all U.S. surface waters

to “fishable and swimmable” conditions.- For Point Sources, Discharge Permits

and Best Practicable Control Technology are required.

Set zero discharge for 126 priority toxic pollutants.

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Clean Water Act (1972)

• Areas of Contention Draining or Filling of Wetlands

- Many consider this taking of private land. Un-funded Mandates

- State or local governments must spend monies not repaid by Congress.

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Summary:

• Hydrologic Cycle• Water Compartments• Water Availability• Freshwater Shortages

Increasing Water Supplies• Water Management and Conservation• Water Pollution• Water Quality Today• Water Pollution Control• Water Legislation

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