Water Quality

The U.S. Geological Survey (USGS) offers you the most comprehensive information about the natural water cycle anywhere, and, our information is available in many languages. Here you can download our water cycle diagrams as well as other educational products to assist you in the classroom or on your own learning adventure!

pH is a measure of how acidic/basic water is. The range goes from 0 to 14, with 7 being neutral. pHs of less than 7 indicate acidity, whereas a pH of greater than 7 indicates a base. The pH of water is a very important measurement concerning water quality.

What is in that water that you just drank? Is it just hydrogen and oxygen atoms? Is it safe for drinking? All water is of a certain "quality" (and you can't tell by just looking), but what does "water quality" really mean? It can be thought of as a measure of the suitability of water for a particular use based on selected physical, chemical, and biological characteristics. Here at the Water...

Humans cannot drink saline water but saline water can be made into freshwater, for which there are many uses. The process is called "desalination", and it is being used more and more around the world to provide people with needed freshwater.

Depending on where you live, maybe you've heard of acid rain. Now, acid rain is not pure acid falling from the sky, but rather it is rainfall or atmospheric moisture that has been mixed with elements and gases that have caused the moisture to become more acidic than normal. Pure water has a pH of 7, and, generally, rainfall is somewhat on the acidic side (a bit less than 6). But, acid rain can...

The U.S. Geological Survey's Water Science School Where anyone of any age can learn all about water.

Learn about water using pictures

Learn about different sewage and wastewater treatment methods.

Learn about different methods to keep swimming pool water clean and safe.

Learn about the causes of bad-smelling water and what you can do about it.

Find out more about the causes of fish kills, including dissolved oxygen and toxins.

Learn about groundwater quality and potential contaminants .