If you live in a large town or city, it's most likely that your water comes from a reservoir which is generally referred to as a surface water source. The reservoirs location does not necessarily have to be in your immediate area, but it could be some distance from the area it is suppling. If your home is located in a more rural area you may have a different water source. Very often it is supplied by an underground reservoir or aquifer.
There are a few factors that will determine whether a water source is safe. As well as the body of water, the land that surrounds it plays a big role. It is important to know what the surrounding land is used for. Is it used for agricultural or industrial purposes, for example? This area of land surrounding the body of water is known at the watershed.
What can you do if you want to find out the source of your home's water? It is best to contact the company that supplies your water and ask them for a copy of their annual report. As a consumer you are entitled to a copy, so don’t hesitate to ask. The report will provide information regarding the source of your water and let you know if any contaminates, etc. have been found in it.