All pools need something to help keep it clean and safe. Chlorine has long been the sanitizer of choice. Saltwater is no different, as the charged cell breaks down Salt in the water into Chlorine.
Man made water pollution has been around as long as people have. Natural water pollution has been around even longer, and it is when salt water flows into fresh water, animals die in water, or volcanic gases mix with water.
5,0000 years
water wheels have been around since the romans!
NOBODY REALLY KNOWS...........
Thunderstorms have likely been around for as long as Earth has been cool enough to support liquid water in its atmosphere, which is more than 4 billion years.
A pool filter is there to remove particles of foreign matter from the pools water. Without a filter to remove this material it would not take long for the pools water to become cloudy and dangerous to the health of the swimmers.
crocodiles have been around becasue they know how to survive they can survive both on land and water becasue they are amphibians.
how long has deforestation been around
As long as guns have been around.
it's been around for 4,700million years,I wouldn't worry
This is a debatable point, depending upon your point of view. From the Biblical point of view, water has been around since the second day of creation, when the waters of the earth were separated from the waters of the sky. The scientific community will hold a different viewpoint.