Water Pollution Causes

Pesticides

Pesticides that get applied to farm fields and roadsides—and homeowners’ lawns
—run off into local streams and rivers or drain down into groundwater, contaminating
the fresh water that fish swim in and the water we humans drink. It’s tempting to think
this is mostly a farming problem, but on a square-foot basis, homeowners apply even more chemicals to their lawns than farmers do to their fields! Still, farming is a big contributor to this problem. In the midwestern United States, a region that is highly dependent on groundwater, water utilities spend $400 million each year to treat water for just one chemical—the pesticide Atrazine.




Fertilizers / Nutrient Pollution

Many causes of pollution, including sewage, manure, and chemical fertilizers,
contain “nutrients” such as nitrates and phosphates. Deposition of atmospheric
nitrogen (from nitrogen oxides) also causes nutrient-type water pollution.

In excess levels, nutrients over-stimulate the growth of aquatic plants and algae.
Excessive growth of these types of organisms clogs our waterways and blocks light
to deeper waters while the organisms are alive; when the organisms die, they use up dissolved oxygen as they decompose, causing oxygen-poor waters that support only diminished amounts of marine life. Such areas are commonly called dead zones.

Nutrient pollution is a particular problem in estuaries and deltas, where the runoff
that was aggregated by watersheds is finally dumped at the mouths of major rivers.

Mining

Mining causes water pollution in a number of ways:

The mining process exposes heavy metals and sulfur compounds that were previously
locked away in the earth. Rainwater leaches these compounds out of the exposed
earth, resulting in “acid mine drainage” and heavy metal pollution that can continue
long after the mining operations have ceased.

Similarly, the action of rainwater on piles of mining waste (tailings) transfers pollution
to freshwater supplies.

In the case of gold mining, cyanide is intentionally poured on piles of mined rock
(a leach heap) to chemically extract the gold from the ore. Some of the cyanide
ultimately finds its way into nearby water.

Huge pools of mining waste “slurry” are often stored behind containment dams.
If a dam leaks or bursts, water pollution is guaranteed

Sediment

When forests are “clear cut,” the root systems that previously held soil in
place die and sediment is free to run off into nearby streams, rivers, and lakes.
Thus, not only does clearcutting have serious effects on plant and animal
biodiversity in the forest, the increased amount of sediment running off the
land into nearby bodies of water seriously affects fish and other aquatic life.
Poor farming practices that leave soil exposed to the elements also contribute
to sediment pollution in water

Plastic

Plastics and other plastic-like substances (such as nylon from fishing nets
and lines) can entangle fish, sea turtles, and marine mammals, causing pain,
injury, and even death. Plastic that has broken down into micro-particles
is now being ingested by tiny marine organisms and is moving up the marine
food chain.

Sea creatures that are killed by plastic readily decompose. The plastic does
not—it remains in the ecosystem to kill again and again

Sewage

In developing countries, an estimated 90% of wastewater is discharged directly
into rivers and streams without treatment. Even in modern countries, untreated
sewage, poorly treated sewage, or overflow from under-capacity sewage
treatment facilities can send disease-bearing water into rivers and oceans.
In the US, 850 billion gallons of raw sewage are sent into US rivers, lakes,
and bays every year by leaking sewer systems and inadequate combined
sewer/storm systems that overflow during heavy rains. Leaking septic tanks
and other sources of sewage can cause groundwater and stream contamination.

Wrap-up

There are as many causes of water pollution as man has had ingenious ideas. We’ve
provided info on the main ones above, but lest you think that’s all there is, here are
a few others that we just don’t have time to get into:

  • Poorly designed landfills
  • Road deicing salts
  • Hazardous waste sites
  • Pet feces and wild animal droppings
  • Cruise ships

Source of the article : http://www.grinningplanet.com/2005/09-06/water-pollution-causes-article.htm