How do waterways get polluted?

It gets polluted by acid rain, oil spills, litter, insecticide mixing with fertilizers etc.

1. The emission of waste heat from an electric generating station into a lake, causing common change through their stress.

2. the discharge of nutrients containing sewer wastes, in a water body causing eutrophication.

Uncontrolled algae growth

Phosphorus pollution
Sources of pollution are storm water runoffs, combined sewer overflows, sanitary sewer overflows, failed septic tanks, leaking oil storage tanks, and more.
1. Illegal dumping of industrial waste

2. Rainwater or snowmelt that runs over the land, picking up pesticides, and fertilizers; called runoff

3. Used water from people's homes and communities; called wastewater

All of the above.
There are several things that can pollute water, from the sewage of your drains to the major oil spills around the world. Some examples may be wastewater, which is water that contains waste products from washing dishes, clothes, or a factory that uses water to clean its facilities or make products.
Rain washes off the oil that cars drop on the roads. This runs into gutters and then into waterways.
Water pollution may be both natural or man-made. Obviously man-made water pollution is more significant.

Natural Water pollution;

As water flows down a slope (such as a river) it drags with it all kinds of impurities. These impurities can be heavy metals (such as Arsenic, Lead, Cadmium and Mercury) or soluble impurities (such as Magnesium sulfate or calcium sulfate). These substances are naturally found in the soil.

Water can also be polluted because of substance being released from a nearby volcano. An example is the Anchorage volcano of Alaska which releases huge amounts of Sulfur in the water bodies. As a result the water becomes extremely acidic (due to the formation of sulfuric acid) - this is detrimental to aquatic life.

Pollution due to man-made activities;

One form is to aggravate the natural discharge of heavy metals and other impurities. By working with the soil close to water bodies, the harmful discharge is accelerated. Example of "working close to water-bodies" leading to pollution is the extraction of Gold)

Acid rain are caused due to man-made activities. They cause the acidification of water.

Discharge of water mixed with various detergents from industries and homes.

Discharge of dirty water from industries add impurities and heavy metals (especially from dye-industries).

Untreated sewage water (from septic tanks) leeks into water bodies.

Excess fertilizers leech into water bodies. This promotes the excessive growth of algae (known as algae-bloom). The algae uses excessive oxygen causing other aquatic organisms to suffocate and die. Aerobic bacteria act on the dead organism and further depletes the oxygen content of the water body. Finally the algae also suffocates leading to a lifeless and polluted water body.

This is what I learnt,

,

Arshad.