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A human can live up to a month without food, but can survive for about a week without water. Average requirement for human consumption of water per day is approximately 2.5 liters (about 2 ½ quarts). About two-thirds of the human body is made up of water.
Water Use in the U.S.
- Average person uses about 100 gallons (about 400 liters) of water per day.
- Average residence uses over 100,000 gallons (about 400,000 liters) during a typical year.
- Most of this household water (50-70%) is used for outdoor purposes such as watering lawns and washing cars.
“. . . the untreated and unfiltered water in rivers, streams, lakes, and aquifers from which water utilities draw water to be treated, filtered, and tested to produce drinking water.”
“. . . water leaving the plant and ready to be used by consumers after being collected, treated, and, usually, filtered by a water utility.”
“. . . includes water from lakes, streams, rivers, and surface springs. It is vulnerable to contamination by a variety of human, animal, and industrial sources and therefore has been subject to some of the most stringent testing and treatment requirements.”
“. . . comes from aquifers deep underground and is less susceptible to contamination than surface water.”
Groundwater Under the Direct Influence of Surface Water
- “. . . water in aquifers that may be affected or contaminated by surface water.”
- “The EPA mandates more stringent testing, treatment, and filtration requirements for groundwater under the direct influence of surface water than for groundwater alone.”
“A layer or section of earth or rock that contains freshwater, known as groundwater (any water that is stored naturally underground or that flows through rock or soil, supplying springs and wells).”
- “Most freshwater lakes are located at high altitudes, with nearly 50% of the world's lakes in Canada alone.”
- “Many lakes, especially those in arid regions, become salty through evaporation, which concentrates the inflowing salts.” Examples of major salt lakes are the Caspian Sea, Dead Sea, and Great Salt Lake.
Glaciers and Icecaps
- “Glaciers and icecaps cover about 10% of the world's landmass.”
- “These are concentrated in Greenland and Antarctica and contain ~70% of the world's freshwater.”
Hydrological (Water) Cycle
“The natural cycle by which water evaporates from oceans and other water bodies, accumulates as water vapor in clouds, and returns to oceans and other water bodies as precipitation.”
“Water in aquifers and other natural reservoirs that . . . [is] not recharged by the hydrological cycle or . . . [is] recharged so slowly that significant withdrawal for human use causes depletion. Fossil aquifers are in this category.”
“Freshwater that is continuously replenished by the hydrological cycle for withdrawal within reasonable time limits, such as water in rivers, lakes, or reservoirs that fill from precipitation or from runoff.”
“Artificial lakes, produced by constructing physical barriers across flowing rivers, which allow the water to pool and be used for various purposes. The volume of water stored in reservoirs worldwide is estimated at 4,286 km3. . .”
“Water originating as precipitation on land that then runs off the land into rivers, streams, and lakes, eventually reaching the oceans, inland seas, or aquifers, unless it evaporates first.”
“Removal of freshwater for human use from any natural source or reservoir, such as a lake, river, or aquifer. If not consumed, the water may return to the environment and can be used again.”
- “. . . a country faces water scarcity when its annual supply of renewable freshwater is less than 1,000 cubic meters per person.”
- “Such countries can expect to experience chronic and widespread shortages of water that hinder their development.”
- “A country faces water stress when its annual supply of renewable freshwater is between 1,000 and 1,700 cubic meters per person.”
- “Such countries can expect to experience temporary or limited water shortages.”
“Wetlands include swamps, bogs, marshes, mires, lagoons and floodplains.”
The Earth’s 10 Largest Wetlands
- West Siberian Lowlands
- Amazon River
- Hudson Bay Lowlands (in Canada)
- Pantanal (in mid-South America)
- Upper Nile River, Chari-Logone River (in Africa)
- Hudson Bay Lowlands in the South Pacific
- Congo River
- Upper Mackenzie River (in northwestern Canada)
- North America prairie potholes (wetlands made up of shallow depressions in the northern Great Plains)
Water Availability Facts
- Although the earth’s surface (about 70%) is covered largely by water, most of this water is unusable ocean water.
- Approximately 3% of all water is freshwater, of which the majority is unavailable for human use (e.g., frozen in icecaps).
- Remaining 1% of readily accessible water comes from surface freshwater; sources include lakes, rivers, and shallow underground aquifers.
Regions That are Facing Water Scarcity and Water Stress
- Two sections of the world that currently have severe water shortages also are experiencing some of the highest population growth rates in the world.
- Africa (sub-Saharan and North)
- Near East
Treatment of Water for Residential Consumption
Water supplied to the public in the U.S. undergoes treatment in order to meet quality standards set by the EPA for safe levels of chemical contaminants and water-borne microorganisms.
Fluoridation of Water
- Some communities in the United States add fluoride to public drinking water in order to prevent tooth decay.
- Field trials conducted in the 1940s demonstrated a 50-70% reduction in the prevalence of dental caries.
The Four Stages of Water Treatment in Most Plants
- Coagulation–removes suspended material
- Sedimentation–causes heavy particles to settle to bottom of tanks for collection
- Filtration–removes smaller particles
- Disinfection–kills bacteria or microorganisms
- Tanks Used for Additional Skimming During Secondary Processing
Treatment of Water from Aquifers
- For high-quality water from aquifers, minimal aeration, filtration, and disinfection are necessary.
- In some cases, water drawn from aquifers is free from microorganisms, but undesirable for human consumption because of impurities and coloration that impair the esthetic qualities of this essential liquid.
Potential Contaminants of Water That Flows across the Ground
- Chemicals and nutrients (e.g., fertilizers and nitrates from agricultural lands)
- Rubber, heavy metals, sodium (from roads)
- Petroleum byproducts and organic chemicals (from dry cleaners, service stations, and leaking underground storage tanks)
More Potential Contaminants
- Chemicals used in the home (solvents, paints, used motor oil, lead, and copper)
- Heavy metals and toxic chemicals (from factories)
- Microbial pathogens (from human and animal wastes)
- Conditions that are “. . . transmitted through the ingestion of contaminated water and water acts as the passive carrier of the infectious agent.”
- Examples are:
- Certain viral infections
Examples of Waterborne Pathogens
- Enteric protozoal parasites
- Bacterial enteropathogens
- Viral pathogens
- Other agents
Some chemicals that have been reported to cause adverse health effects:
- Disinfection by-products
Health Effects of Chemicals in the Water Supply
- Reported health effects have included:
- Various cancers
- Adverse reproductive outcomes
- Cardiovascular disease
- Neurological disease
Another Source of Water Contamination
- Pharmaceutical and personal care products (PPCPs) represent another source of water contamination.
- They are washed off or excreted from the body.
- Examples include: analgesics, oral contraceptive agents, drugs for lowering cholesterol, and anticonvulsants.
Water Disinfection Byproducts (DBPs)
- Chemicals used to disinfect water are associated with by-products of chlorination called DBPs.
- These chemicals include chlorine, chloramines, chlorine dioxide, and ozone.
- Chlorine is associated with trihalomethanes (THMs), which are among the most common and widely measured DBPs.
Potential Adverse Health Effects of DBPs
- Possible adverse pregnancy outcomes
- Neonatal deaths
- Possible increased risk of birth defects
Beach and Coastal Pollution
- The approximately 1 billion people who live near coastal areas cause great stress on coastal ecosystems.
- Coastal areas are threatened by over-development, poor planning, and economic expansion.
- World’s coastal regions are the recipients of billions of gallons of treated and untreated
Effects of Beach and Coastal Pollution
- Excessive amounts of nutrients that enter the oceans may cause harmful blooms of algae, resulting in reduced levels of oxygen in the water (anoxic conditions).
- An anoxic ocean environment can bring about fish kills and damage other forms of ocean life.
- Urban runoff and sewage contamination of the ocean expose swimmers to waterborne diseases.
- Oil spills from tankers and off-shore drilling platforms can have a devastating impact on the shoreline, aquatic life, mammals, and birds.
- Worst spill in U.S. history was caused by the tanker Exxon Valdez in 1989.