Freshwater Resources and Water Pollution...•Groundwater pollution –Half of the U.S. obtains drinking water from groundwater sources –Quality is a concern •Pesticides, fertilizers,

Visualizing Environmental Science

Chapter 10

Freshwater Resources and

Water Pollution

Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

The Importance of Water

• Life on Earth would be impossible without water– All living organisms contain water– Humans are approximately 70% water– Uses include drinking, cooking, washing,

agriculture, transportation, manufacturing, mining, energy production, waste disposal

© 2014 John Wiley & Sons, Inc. All rights reserved.

– 97% is salty– Less than 3% of Earth’s water

is fresh

– Uneven distribution -serious regional supply issues across the globe

– By 2025, more than 1/3 of humans will live in areas with inadequate supply of fresh water for drinking and irrigation

The Importance of Water


• The chemical structure of water gives it unique physical properties

– Each individual molecule of water (H2O) contains one oxygen and two hydrogen atoms held together by strong (covalent) bonds

– Water molecules are considered polar molecules• The O end of the molecule has a negative charge

• The H end of the molecule has a positive charge

Properties of Water


• Hydrogen bonds – Each end of every water molecule is

attracted to opposite charges on adjacent water molecules

– This attraction forms weak chemical bonds (hydrogen bonds) between the molecules of H2O

– Responsible for many physical properties of water• High freezing/melting point

• High boiling point

• High heat capacity

• Ability to act as a solvent

Properties of Water


• Surface water– Precipitation that remains on the surface of the land

and does not seep down through the soil

– Runoff

– Drainage basin/watershed

Water Resources


Water Policy

• Florida – unique system, water belongs to everyone in the state equally

– Water is allocated based on a permit system administered by the water management districts

– System aims to prevent waste, provide certainty to existing users, provide equal rights irrespective of economic power, and protect natural resources

Central Ridge Area

• Groundwater– The supply of fresh water that is stored in

underground aquifers (underground reservoirs)

– Considered a non-renewable resource; takes 100s–1000s of years to form

– Rain-fed aquifers begin at recharge zones

Water Resources


Freshwater Resources


Water Resource Problems

• Three categories– Too much water

– Too little water

– Poor-quality water


• Too much water– Flooding

• Occurs when a river’s discharge cannot be contained within its normal channel

• Humans are drawn to flood plains

• Construction replaces flood-protecting plant cover with paved areas that do not absorb water



Land Development Changes the Natural Flow of Water


• Too little water– Arid lands

• Desert• Plant growth is limited by lack of precipitation

– Semiarid lands• Receive more precipitation than deserts, but have long

periods of drought

– Farmers use irrigation to increase agricultural productivity of arid and semi-arid lands• Amount of irrigated land has tripled• 71% of world’s total water is used for irrigation



• The Ogallala Aquifer– Largest groundwater

deposit in the world– Farmers are drawing

water 40 times faster than it can be replaced by nature

– Water table has been lowered 30m (100ft)

– Water conservation esp. through water-saving irrigation will postpone aquifer depletion



• Overdrawing of surface waters– Saltwater intrusion

– Wetlands dry up

– Water shortages have great economic and ecological ramifications



• Salinization of irrigated soil– Gradual accumulation of salt in soil, often as a

result of improper irrigation methods

– Normally, precipitation runoff would carry salts away, but in arid and semiarid areas there is little precipitation, so the salts remain in the soil

– Salt accumulation becomes poisonous for plants, and over time this salinization may render soil unfit for crop production



Water Wars

• Cooperation between countries that share common watersheds is essential to ensure clean water availability for all• The river Nile… the source of wealth and prosperity for

Egypt

• Other countries are considering dam projects

• Egypt is fighting this

• This represents just the first of many such international and even interstate disagreements over “shared” water sources.

Water Management• Sustainable water use

– The wise use of water resources, without harming the essential functioning of the hydrologic cycle or the ecosystems on which present and future humans depend

– Conservation• Includes reusing and recycling water,

improving water use efficiency

• Important part of sustainable use

– Economic policies• If water is cheap, it tends to be

wasted


• Dams and reservoirs– Dams generate electricity and ensure

year-round supply of water

– Costs vs. benefits• Columbia River - 4th largest in North

America

• More than 100 dams generate electricity and provide water

• Negative impact on fish populations

• Three Gorges Dam (China) – largest in the world

Water Management


Water Management

• Water conservation– Reducing agricultural water waste

– Reducing water waste in industry

– Reducing municipal water waste


Reducing Water Use


Water Pollution• A physical or chemical change in water that

adversely affects the health of humans and other organisms– Sewage– Disease-causing agents– Sediment pollution– Inorganic plant and algal nutrients– Organic compounds– Inorganic chemicals– Radioactive substances– Thermal pollution


– Large amounts of organic material (sewage) deposited in water enables the growth of large numbers of microorganisms

– These microorganisms deplete dissolved oxygen, causing fish and the microbes themselves to then die

– Anaerobic microorganisms then flourish, producing toxins and other chemicals that further reduce water quality

• BOD is a critical factor in the health of a waterway

Water Pollution


• Oligotrophic– Unenriched, clear water, supports small populations of

aquatic organisms

Eutrophication of Lakes, Rivers and Streams: An Enrichment Problem


• Eutrophic – Cloudy water due to large numbers of algae and cyanobacteria

– Water is enriched with inorganic nutrients such as nitrogen and phosphorous

– This can be a natural, long-term process, or…

• Artificial eutrophication– Overnourishment of an aquatic ecosystem by nutrients from agricultural runoff and sewage

treatment plants

Eutrophication of Lakes, Rivers and Streams


• Sources of water pollution– Point sources

• Pollutants can be traced to specific sources, such as pipes, sewers, ditches from specific sites

– Nonpoint sources• Pollutants enter a body of water over large areas rather

than a specific, single point of entry, i.e. precipitation washes pollutants out of soil and into the water: polluted runoff

Water Pollution


• Groundwater pollution– Half of the U.S. obtains drinking water from

groundwater sources

– Quality is a concern• Pesticides, fertilizers, organic compounds seep into

groundwater from landfills, storage tanks, backyards, golf courses, etc.

– Cleanup is not always technically feasible• Very costly

Water Pollution


Sources of Groundwater Contamination


Improving Water Quality• Removing contaminants from water supply

before and after use

• Purification of drinking water– Municipal water supplies are treated before water

is used• Turbid water treated with chemical coagulant to clump

and settle out particles

• Filtration through sand to remove microorganisms

• Disinfection (chlorine, ozone, UV) to kill any remaining disease-causing organisms


Is Bottled Water Safer?• Bottled water standards are lower than that for

municipal water.

• About one-quarter of all bottled water in the United States is simply reprocessed municipal water, and much of the rest is drawn from groundwater aquifers, which may or may not be safe.

• A recent survey of bottled water in China found that two-thirds of the samples tested had dangerous

levels of pathogens and toxins.

• Trailer: Tapped

http://youtu.be/72MCumz5lq4

– Artificial wetlands to treat reclaimed water

– Orlando Wetland Park• 16 million gal per day, on 1220 acres

– Wetlands absorb and assimilate contaminants

– Provides wildlife habitat

Improving Water Quality


• Controlling water pollution– Legislation is effective on point sources

– Two very successful laws, but much work is still needed

– Safe Drinking Water Act - 1974• Uniform federal standards for drinking water

• Guarantees safe drinking water supply

• EPA must determine maximum contaminant levels allowed

• 1996 amendment requires municipalities to inform which contaminants are present and in what amount

– Clean Water Act - 1977• Quality of rivers, lakes, aquifers, estuaries, and coastal waters

• Attain water quality levels that are safe for fishing and swimming



Preventing Water Pollution at Home• Individuals produce very little, but collective effect is large


• 1.4 billion people in the world do not have access to safe drinking water

• 2.9 billion don’t have access to sanitation systems

• 250 million cases of water-related illness each year

• 5 million or more result in death

Water Pollution in Developing Countries


• Sewage from densely populated cities is dumped directly into rivers and coastal harbors

• Ganges River-India’s holy river– Used for bathing and washing clothes– Very polluted by untreated sewage and industrial

waste, and ashes of 35,000 humans/year



Documents

Freshwater Resources and Water Pollution...•Groundwater pollution –Half of the U.S. obtains drinking water from groundwater sources –Quality is a concern •Pesticides, fertilizers,