very person, animal, and plant needs water. The adult human body is about 60 percent water (and kids are even more watery!). Although more than 70 percent of the Earth’s surface is covered with water, only about 3 percent is freshwater that can be used for drinking, farming, and other purposes.
Even though water is necessary for life, people have been polluting this natural resource ever since we first started throwing our garbage in the rivers and oceans thousands of years ago. Today we’re facing the result of those actions. The US Environmental Protection Agency estimates that approximately 40 percent of our lakes and streams are now too polluted to drink from or swim in. Many wild-caught fish have accumulated pollutants in their flesh and are unsafe to eat. Coral reefs, which are home to a quarter of the animals that live in the sea, are dying. And in 1969, Ohio’s Lake Cuyahoga--contaminated by decades of industrial dumping--caught fire.
After that shocking event, the US government passed several laws to limit pollution. The Clean Water Act (1972), the Safe Drinking Water Act (1974), and the Ocean Dumping Ban (1988) have made our water safer, but unless we all work together, someday we may not have the clean water we need. Fortunately, as people have become more aware of how precious and limited clean water is, scientists have also developed many ways to treat contaminated water.
Scientists divide water pollution into three categories: point
, and thermal pollution. Each kind presents different risks to the environment and requires unique strategies to address and treat.
can be traced to a specific source, such as a power plant, a raw sewage pipe, or an oil spill like the 2010 Deepwater Horizon accident. Chemicals, microorganisms (such as bacteria from sewage), and nutrients, including nitrogen and phosphorus that lead to decreased water oxygen levels, are some point-source pollutants. The EPA is in charge of regulating point sources of pollution, and sets limits on the amount and types of waste that commercial and industrial sites can dump.
enters a waterway when rain or snow falls to the ground and picks up contaminants as the runoff
flows over the ground and drains into a stream, wetland, or ocean, or into the groundwater
. Some sources of nonpoint pollution
are pesticides and fertilizers used on residential lawns and farms, agricultural and livestock waste products, and even precipitated
air pollutants from car exhaust and chimneys that become acid rain.
describes an increase or decrease in water temperature that damages the quality of the water and changes its oxygen levels. Unable to quickly adapt, plants and animals living in the affected water often die. Water temperatures can become hotter due to discharge from industrial processes, or because shading vegetation has been removed. Colder-than-normal conditions can be caused by deep-water reservoirs around large dams.
Some of the methods used to limit water pollution include watershed
protection, which controls the amount of pollution at its source; treatment systems that clean contaminated water through physical (such as filtration) or chemical processes; and cooling towers that cool heated water before it reaches a waterway
Ultimately, as the global population continues to increase and become more industrially advanced, the quality of our environment depends on our awareness of the importance of protecting all of our natural resources. Water is in all of us; we drink it, we swim in it, we need it to survive. Let’s work together to keep it clean!
For more information on water go to:
"The Water Cycle":
U.S. Geological Survey,
The Water Pollution Guide,
Windows to the Universe,
Performed by Frank Lumia
Directed by Stephen Blauweiss