Water is life's most important chemical: it makes up 2/3 human body weight and 71% earth's surface is covered with water. The earth has about 370 billion billion gallons of water; if the crust was smooth, an ocean 3 km deep would cover the planet. Of this vast amount of water, only 3% is fit to drink or use in agriculture and industry; the rest is too salty. Of the amount of fresh water, only 0.003% is readily available since most of the earth's freshwater is located in glaciers, ice caps, soil, or the atmosphere. In other words, if earth's water was represented by 100 liters, only 1/2 teaspoon would be available for use.
Just as there was a carbon cycle which renewed carbon resources, there is a hydrological cycle. Water vapor evaporates from open water and transpires from plants. This water forms clouds whose rain then replenishes the water of the lakes, rivers, and oceans and provides additional resources for plants and animals.
There are a number of issues which affect the quality of water. In 2003 the U.N estimated that 1/5 the world's population had no clean water and 40% lacked modern sanitation (Speth, 2004).

WATER POLLUTION

Knowing that the chemicals that are released into the environment often end up in water supplies, enter into aquatic food chains, and can accumulate in the bodies of fish, how comfortable would you feel eating a fish caught near your home (especially a bottom feeding fish like a catfish)?

Knowing that toxic chemicals are dumped into our waterways, how would you feel if your community depended on the Hudson River or the Mississippi River for their water supply? How safe is your water supply?

As of 2004, an estimated 45% of American waterways do not meet the "drinkable, swimable, and fishable" standard established by the Clean Water Act 30 years ago. In 2003, 270,000 mile of America's rivers were too polluted for fishing and swimming. In 1998, forty percent of America's rivers, lakes, and estuaries were too polluted for fishing and swimming. More than fifty million pounds of toxin are dumped into the Mississippi River each year. The 150 mile section of the Mississippi which ends in New Orleans is often referred to as the "cancer corridor" due to the higher rates of cancer in those areas which depend on the Mississippi for drinking water. The amount of annual water pollution throughout the U.S. increased 26% during the period of 1995-9 (Blatt, 2005). Two percent of Americans (about 5.6 million) drink water which is not in compliance with the Clean Water Act standards. Bottled water is the fastest growing beverage in America and Americans on average drink twice as much bottled water as soda and three times as much bottled water as coffee or milk (Blatt, 2005).

1) SEWAGE & AGRICULTURAL WASTE
A) DISSOLVED OXYGEN, DO

Has human sewage reduced the amount of oxygen available for fish in waterways near you?

Oxygen gas is a nonpolar molecule while water is a polar molecule. As a result, little oxygen dissolves in water, such as the River Tapiracuai (in Paraguay) below. At 20oC, 9mg O is dissolved in 1 million mg water (1 liter) and thus exists as 9 ppm. The amount of oxygen dissolved in water is often a limiting factor for fish communities. As the amount of dissolved oxygen drops, fewer and fewer fish can inhabit the water.

Eutrophication (literally meaning "well nourished") is the addition of nutrients to water which were in short supply. This occurs when human sewage, fertilizers (containing nitrates and phosphates) from agricultural runoff, detergents (which contain phosphates), and animal manure enter bodies of water (a cow produces 14 lb manure/day). These added nutrients allow algae, bacteria, and water plants undergo "blooms" or population bursts.

The following picture is of women who have brought their clothes to the River Tapiracuai to wash (you can see the clothes drying behind them). Although this will release detergents into the water, obviously they have nowhere near the impact that the runoff from more industrialized areas can have.

This eutrophication can lead to fish kills because aerobic bacteria (which depend on atmospheric oxygen) which decompose the sewage or the dead plant matter use a good deal of oxygen. As less oxygen is available for fish, species begin to disappear (most commercially desirable species disappear first). When the oxygen is gone, anaerobic bacteria produce foul-smelling and toxic compounds as they decompose the sewage.
Rivers can recover quickly (even in a matter of weeks). For example, the Thames River was completely anaerobic in the 1950s (so many worms that present in drinking water) and today produces fish commercially. Lakes take longer, up to a hundred years. In 1970s algal blooms choked of oxygen to bottom 2/3 of Lakes Erie and Ontario (by 1958, only 8 of 516 swimming beaches remained closed). Although Lake Erie recovered from the pollution of the 1970s, the current situation is worsening. It is estimated that every year billions of gallons of raw sewage enter the Great Lakes from sewer overflows. This has created a 6,300 square mile dead zone in the lake in the past several years which covers about 2/3 of the lake. The Great Lakes contain 95% of America's freshwater and is the source of drinking water for 37 million people. The Chesapeake Bay has a dead zone which covers hundreds of square miles (with record-breaking reductions in oxygen levels in 2003). The eutrophication resulting from agricultural runoff from the Midwest into the Gulf of Mexico has caused the formation of an anoxic "dead zone" about the size of the state of New Jersey (Raven, 2001).
More than 10ppm of nitrates is unsafe to drink because it encourages bacterial growth in the digestive tract. Infants are even more at risk because they make less stomach acid. In 1989 the Iowa National Guard had to distribute water due to nitrate pollution during a drought. About forty million Americans get their water out of wells. In 1995, 9% tested were contaminated beyond federal limits with nitrates.

B) DISEASE

Two billion people lack adequate sanitation throughout the world (Stokstad, 2008). A number of diseases can be transmitted through water such as cholera, typhoid fever, giardia, hepatitis, and polio. Five hundred types of pathogenic microbes can be present in feces. According to the UN, dirty water and water-born diseases cause 25,000 deaths daily in the Third World. About two million children will die this year from diarrhea, which represents the 3 rd largest cause of child mortality In 2000, the World Health Organization estimated that 4 billion cases of diarrhea occurred due to contaminated water. (Gleick, 2005; Stokstad, 2008). Tragically, most could be saved for pennies a day. The use of "night soil" as fertilizer is still common in Asia (the practice of defecating in your cropland, particularly in rice paddies). More than 2 billion people lack an adequate supply of safe drinking water. In India, 114 cities and towns dump their human waste directly into the Ganges. Some areas have coliform counts of 24 million cells/ 100 ml water (for comparison, U.S. prohibits swimming in water with more than 200 cells/ 100 ml). In 1995 the EPA estimated that 1.6 million Americans have a water supply whose substandard disinfection (i.e. chlorination) has resulted in the presence of microorganisms.
Cryptosporidium is a parasite found in rivers & lakes, especially those contaminated with sewage or animal waste. It causes severe outbreaks of gastrointestinal illness, including diarrhea, nausea and stomach cramps. Since Cryptosporidium can tolerate some chlorine in water, areas whose water is insufficiently chlorinated are at risk. In 1993, a massive Cryptosporidium outbreak in Milwaukee killed over 100 and affected 400,000 others. Usually the infections are not lethal to most people but can especially dangerous to those whose immune systems are suppressed, such as AIDS patients or cancer/transplant patients taking immunosuppressant drugs.
Fecal coliform bacteria exceed federal limits in 1,200 water supplies affecting 12 million Americans. Smaller municipal water systems (with their smaller budgets) are the main problem and 1.5 million become sick/year. Heliobacter pylori is also found in many water systems and is a factor in causing ulcers.
The following picture depicts the backyard of the house where I lived in Paraguay, complete with bathing area, latrine, and well. While I was in Paraguay, cholera broke out in Peru and began to spread to other South American countries. That was a concern. Although you can't see this in the picture, my house was a bout half way down a hill and friends of mine had a house at the bottom of the hill. The water level in my well was certainly no where near what would be acceptable here and the water level in my friends' well was just about at ground level after heavy rains. The water entering these two wells was not being adequately filtered. If any one at the top of the hill contracted cholera, there was a very real danger that this microbe from the latrines at the top of the hill would contaminate the wells of every one downhill from them.

2) OIL

It is estimated that 3-6 million metric tons of oil discharged into oceans/year, often from illegal but routine tank cleaning. Oil spills kill marine life. The 1989 Exxon Valdez spill dumped 42 million liters and killed more than 34,000 birds and 1,000 otters. Oil and grease can accumulate in rivers and streams. In the 1960s, the Cuyahoga River in Ohio contained so much oil that it caught fire as did a Russian river in 1989 (which burned for 5 hours). In 1994, an old Russian pipeline ruptured in about a dozen places, gushing millions of gallons (an estimated 100,000 tons) of hot crude oil into the creeks that feed the Pechora River. Since the 1970s, there have been more than 35,000 oil spills in the Gulf of Mexico, one of which released 140 million gallons of oil. In recent years, the Bush administration has been a strong advocate for increased oil drilling in coastal regions and protected habitats.

3) SALT

Irrigation was first used in Egypt more than 5000 years ago and has increased 500% in this century. Most of the world uses open ditch drainage (such as in the following picture) which lets 70-80% water evaporate or seep into ground while allowing the salts left behind to accumulate.
Farmland can actually glisten white with salt crystals as in the southwestern U.S. and the Aral region of Russia. Salty soil reduces crop yield. In India 7 million hectares have already been abandoned for this reason while 20 million are in danger. Many other parts of the world are losing cropland because of salt accumulation such as China (7 million hectares), Pakistan (3.2 million), Afghanistan, Iraq, and Turkey. Egypt estimates that 50% of its cropland has diminished yield and salt levels in San Joaquin, California have doubled since 1930.

4) CHLORINE
Chlorine is added to drinking water to eliminate threat the threat of many water-borne diseases such as typhoid fever, hepatitis, and polio. About three quarters of Americans drink chlorinated water. Unfortunately, chlorine is a very reactive molecule. It can react with hydrocarbons (such as those of oil) to produce compounds such as chloroform and carbon tetrachloride, both of which are carcinogens. Chlorine can also react with organic material in water (decaying leaves, animal waste, sewage) to produce carcinogenic trihalomethanes. While the amounts of these toxic compounds are extremely small, they do have a cumulative effect. Those who drink chlorinated water have an increased 93% chance of rectal cancer and 53% chance of bladder cancer. While the risk is certainly outweighed by the benefits of preventing disease, chlorine is potentially dangerous. Some Americans are exposed to unsafe levels of chlorine. After the terrorist bombings of 9/11, the government saw the need to increase security at water treatment plants. Should chlorine tanks which supply a major city ever be destroyed, a cloud of poisonous chlorine gas would spread for miles.

5) WETLANDS

Wetlands are incredibly important as habitats for wildlife and are popular recreation spots. They also help buffer the surrounding areas from flooding. As wetlands are developed, areas are much more susceptible to flooding (flooded areas are pictured below).

Without wetlands, water moves more quickly into rivers and streams causing the water levels to rise and fall much more quickly than would otherwise have occurred. Those who view such lands as "unproductive" and thus not economically important rarely factor in the increased costs of flood damage to communities once these wetlands are developed. Although wetlands are protected in this country, the laws can change which lands fit the definition of "wetland" and which wetlands may be exempt from protection, as occurred during the administrations of George H. Bush and George W. Bush.

Mangrove swamps once covered more than 200,000 square kilometers of coastline. This area is being lost at a rate of 1-2% per year and mangroves are approaching extinction in 26 of the 120 countries where they are found (Duke, 2007).

6) MERCURY

Human activity, primarily the burning of coal, produces about 20,000 tons of mercury emissions per year. This rate is increasing at an estimated 5% per year (Zahir, 2005). Here some of it is converted to the poison methylmercury which accumulates in the tissues of living things, such as those of fish. There are fish advisories in 45 states due to unsafe levels of mercury in fish.

It is estimated that mercury accumulation has made it unsafe to eat the fish in more than 766,000 miles of American rivers and 13 million acres of America's lakes. Four of the five great Lakes are under fish advisories due to high levels of mercury. This percentage has increased in the past two years (a 60% increase for rivers and an 8% increase for lakes). In 2004, the EPA estimated that one sixth of pregnant women in the U.S. had mercury levels high enough to threaten fetal nervous system development. At about the same time (early 2004) that the EPA and Food and Drug Administration were warning pregnant women to avoid eating certain fish because of mercury contamination, the Bush administration proposed allowing coal burning plants to release three times more mercury pollution and to delay the enforcement of clean air laws on these plants.
Most of this mercury originated in the burning of coal to produce electricity. Forty-one states have fish advisories to limit fish consumption because of mercury levels. For example, the National Park Service posted the following sign in the Everglades "Do not eat more than one bass per week per adult due to high mercury content. Children and pregnant women should not eat bass." (Blatt, 2005). The fish which are the greatest risk group for mercury contamination are mackerel, shark, swordfish, and tile fish and others fish also represent a high risk for mercury contamination include tuna, lobster, orange roughy, marlin, and grouper (Zahir, 2005).
In 2001 the CDC declared that 375,000 infants (one tenth of those born in the U.S.) are at risk of neurological damage because of the mercury levels in their mother's bloodstream during pregnancy (Blatt, 2005). Methylmercury in a mothers diet can pass to the fetus through the placenta and to the infant through breast milk. The effects of high mercury levels in children include language deficits, attention deficits, motor deficits, and autism. In adults, mercury levels are linked to Alzheimer-like memory loss, muscle deficits, autoimmune diseases, decrease fertility, and birth defects (Zahir, 2005).
Mercury emissions can travel intercontinentally and be deposited far from the original source. For example, a quarter of the mercury deposition in North America originates in Asia and 14% originates in Europe. A third of the mercury deposited in the arctic originates in Asia, 22% from Europe, and 10% from North America (Travnikov, 2005; Lahoutifard, 2005).

7) THE AMOUNT OF FRESH WATER

The global average water supply decreased by one third over the period of 1970 to 1990 (Speth, 2004). Twenty percent of the world's river flow is diverted for human use. The amount of water withdrawn from rivers increased 6 fold in the 20th century which is a rate double the population growth rate (Speth, 2004).
The average American uses 300 liters of water per day for personal use. The amount of water used in a 5 minute shower is enough to eat to cook with for a month. If you add to this amount of water the amount of water used to produce, process, and transport food, the average American uses 7200 liters of water/day. Worldwide, agriculture claims 69% water use and cooling water for power plants is the largest industrial use of water. One pound of paper uses 100 gallons of water to produce, one ton of steel uses 50,000 gallons, and one ton of aluminum uses 1 million gallons (Blatt, 2005). In 1992, a law limited the volume of a toilet flush to 1.9 gallons; it had averaged 5 gallons previously (Blatt, 2005).

Not all areas have the same water availability. Climate patterns provide unequal rainfall; while one area of Chile hasn't had rain in recorded history, one area of India received 72 feet in a year. It is thought that the world may have to pay $600 million in next 10 years to supplement water supplies. When there is not enough water for all needs, there are often difficult decisions which must be made. In the 1991 drought, California had to decide who had rights to water: upstream farmers or downstream cities. About half a billion people live in areas of the earth which experience chronic drought.
As water is removed from underground supplies, the earth can descend forming sinkholes. The California Sacramento river delta sinks 3 inches/yr. Agriculture in the Midwest depends on the water stored in the Ogallala Aquifer which stretches from South Dakota to Texas. This area produces much of the food exported from the U.S. including 25% of its grain and 40% of its wheat. The water levels have dropped 30-60 feet throughout much of Texas and more than 100 feet in other areas (Blatt, 2005). The main aquifer under Mexico City sinking 11 ft/year and water is now being pumped 1,000 meters high to reach Mexico City. The Bejing water table sinking 6.5 ft./yr and in Sheyang, China it is necessary to bring water from 51 km away. The Aral Sea was 4th largest inland sea 10 years ago; its new shoreline has receded 40 km. In the Middle East, water rights has created conflict between between Turkey & Iraq, Israel & Jordan, Israel & Palestinians; the same is true of India & Bangladesh. The Yellow River is seriously polluted along 70% of its length and water demands by the human population lower the river so that it does not reach the ocean during a period of about 4 months (Watts, 2005).

The Aral Sea was once the fourth largest freshwater lake. Because of the diversion of its affluents for irrigation, it has decreased its volume by 80% and its area by 50%. All of its native fish species are extinct from the lake and there is a sharp increase in the human health problems observed in the vicinity (Raven, 2001).

Water is not only important for drinking and irrigation but also for recreation. Pollution limits the amount of fresh water which is fit for human activity. Below is a picture of a popular river in Paraguay.

8) OCEAN DUMPING AND FISHERIES

Marine phytoplankton only represent 1% of the planet’s biomass but they produce almost 45% of earth’s photosynthesis (Simon, 2009). The ocean is an important food source: 80 million tons seafood a year provide 16% world's protein. In Asia, nearly 1 billion people rely on seafood as the primary protein source and 1/2 the world's population live 100 km from a coast (as in the picture of Rio de Janeiro above). Unfortunately, this resource is being threatened.
A) OCEAN DUMPING
Every year, 8 million tons of toxic wastes are dumped in the ocean and 6 million metric tons of litter arrive in the oceans/year. Obviously, this can have an effect on marine life. The Chesapeake Bay oyster catch decreased from 20,000 tons in 1950s to less than 3,000 in 80s. Louisiana 35% oyster beds closed due to sewage contamination. The world has lost 5-10% coral reefs and 60% are in danger. From 1986 to 1992, fish haul in Black Sea decreased 90%. Every year it receives 60,000 tons of phosphorus, 340,000 tons of inorganic nitrogen, 60 tons of mercury, 4500 tons of lead, and 50,000 tons of oil. Mackerel fishing ended in 1968, bonito fishing in 1971, and bluefish fishing in 1973.
To allow for boat navigation, millions of cubic meters must be dredged from the New York/New Jersey harbor per year. While the regulations put in place by the Clean Water Act and Clean Air Act are responsible for a significant reduction in the amount of pollutant (such as mercury) in the sediment, improved testing procedures indicate that the sediments are not fit for ocean dumping. While the harbor must continue to be dredged, the disposal of the sediment is problematic (Wakeman, 2001).

B) FISHERIES

At what point will the world's oceans and rivers be overfished?

After 1989's peak fish catch (82 million tons), 1991's catch was down 6%. it is estimated that all 17 of the world's major fishing areas have reached or have exceeded their natural limits and 9 are in serious decline. Four have been fished out. Overfishing decimated the populations of fish in the great fisheries off the coast of Newfoundland. For example, in the year 1968 120,000 metric tons of fish were caught by Canadians and 700,000 metric tons were caught by boats from other nations. Despite warnings of overfishing, the fish continued to be harvested at levels which simply could not sustain the populations. The numbers of cod fish in the fisheries off the coast of Newfoundland have never recovered from their collapse in the 1990s. More than a decade has passed since a moratorium was placed on fishing but the cod populations have not recovered. The unemployment rate in Newfoundland is twice the national average and the regional population has declined by ten percent (Schrank, 2005). By the early 1990s, the populations of important fish species in the Gulf of Thailand fishery were only a tenth of their 1960s levels. Since the 1980s, the populations of many North Sea fish are at or below minimum acceptable levels (Murawski, 2000).
Every year since 1988, the global fish catch has decreased (Speth, 2004).

--after Kemp, 2004

If a “collapsed” fishery is defined as one whose annual catch has been reduced to less than 10% its historical maximum, then 27% of global fisheries had collapsed by 2003 and it is estimated that all will collapse by 2048 (Costello, 2008). Overfishing giant sharks has resulted in increased numbers of smaller sharks, rays, and skates. This in turn has decreased the numbers of the prey these smaller fish feed on and has resulted in the closure of a scallop fishery which had been in operation for a century (Myers, 2007).

9) CORAL REEFS

Coral reefs not only provide the habitat for a third of all fish species, humans exploit this habitat to harvest 6 million tons of fish per year.  Five hundred million people live within 60 miles of reefs and these reefs provide protection from severe weather (Crabbe, 2008a). Increased temperatures due to global warming and increased ultraviolet light due to the depletion of ozone are stressing corals and causing incidents of mass coral-bleaching. These stressed corals are more susceptible to disease. The extreme weather events which are made worse by deforestation, wetland loss, and costal development are also sources of damage to coral reefs. Nutrients produced by human wastes, agricultural runoff, and nitrous oxides in air pollution also upset coral physiology. As corals decline, other organisms such as blue-green algae become more abundant (Hallock, 2005). As carbon dioxide levels rise, bicarbonate levels rise making it harder for corals to sequester carbonate ions whose concentration drops. In experimental conditions where carbon dioxide levels were raised to 560 ppm (which is a possible scenario for the end of the 21 st century), coral growth was decreased by levels up to 40% (Hoegh-Gulberg, 2007). Climate change and other human influences have put one third of reef building corals in danger of extinction. The corals of the Caribbean are in the greatest risk (Carpenter, 2008).
Stressed corals can become bleached as they lose the algal cells which live within them or as the algal symbionts reduce the pigments they make. Even when corals survive this bleaching, they are more susceptible to diseases in the aftermath. The first mass-bleaching event was recorded in 1982 and by the 1990s, coral bleaching was recorded somewhere in the world every year. A serious mass-bleaching event was recorded in 1997-1998 (Hallock, 2005). By 1987, about 40% of the coral in the Caribbean had been bleached although it did not die as was formerly predicted (Porter, 1989).
It was the activity of cyanobacteria which increased the levels of oxygen in the atmosphere to allow the evolution of eukaryotes. Human activities ranging from sewage production to global warming and ozone depletion are negatively affecting corals but positively effecting cyanobacteria in marine ecosystems (Hallock, 2005). Sixty percent of the world's coral reefs are classified as at medium to high risk (Speth, 2004). Increasing hurricane frequency and strength poses a threat to the survival and propagation of coral reefs (Crabbe, 2008b).