Is pollution related to the water cycle?

Answer 1

Pollution is a byproduct of human activity, the introduction of materials in quantities not generally found in nature. Pollution is described in economic terms as a "negative externality."

Pollution is a very broad term to describe a lot of problems with natural system caused by man's activities. Various types and effects of pollution do affect the water cycle. Most pollution -- and natural minerals -- wind up in the earth's occeans, which are also the biggest source of water vapor that is often thought of as the start of the water cycle. The many pollutants present and concentrated in the oceans can effect evaporation rates, which affects this start of the water cycle. Greenhouse gas emissions cause a global temperature rise, which also affects evaporation rates from the ocean, and increases the amount of water available to evaporate through the thawing of ice in permafrost, glaciers and ice caps.

Atmospheric pollution also affects cloud condensation. Water vapor can combine with dust, smoke, and other airborne pollutants, in some cases causing a chemical reaction; this affects the condensation and precipitation phases of the water cycle.

Hydroelectric dams are not typically thought of as polluting, but they definitely do affect the water cycle, creating a still body of water which had (prior to the dam) been a fast-flowing river. Dams also divert water from rivers to farm fields and cities. This increases evaporation and reduces how much water reaches the ocean; in the case of the Colorado River, due to the Hoover dam and other dams, for much of the year, water in the Colorado River no longer actually reaches the ocean.