Summary #
Most drinking water comes from surface water or groundwater. Pennsylvania’s drinking water sources are directly connected to watershed health — contamination from AMD and other sources can threaten both. This page covers where drinking water comes from, how it is treated, and why the global supply of fresh water is far more limited than most people realize.
Where Is Drinking Water Found? #
Most drinking water comes from either surface water or groundwater. Surface water is found in rivers, lakes, and reservoirs. Groundwater occupies aquifers — underground rock formations that store and transmit water. Springs are another source of drinking water, though these begin underground before surfacing.
Treatment #
There are many ways to treat water to make it suitable for drinking. Exactly how a water source is treated depends on the supplier. Chemicals such as chlorine or fluoride are commonly added to kill pathogens. Special treatment may also be required to remove toxic chemicals present in the water.
The Limited Supply of Fresh Water #
Less than 1 percent of all water on the earth’s surface is suitable for consumption — the remainder is found in oceans, polar ice caps, and other forms unavailable for drinking. As population increases, so does demand on water supplies.
The table below shows the distribution of Earth’s water resources:
| Water Compartment | % of Total Water on Earth |
|---|---|
| Ocean | 97.600 |
| Ice / Glaciers / Packed Snow | 2.070 |
| Groundwater | 0.280 |
| Lakes and Reservoirs | 0.009 |
| Saline Lakes | 0.007 |
| Soil Moisture | 0.005 |
| Moisture in Living Organisms | 0.005 |
| Swamps and Marshes | 0.003 |
| Atmosphere | 0.001 |
| Rivers and Streams | 0.0001 |
Over 99 percent of water on earth is in undrinkable form. How Pennsylvania manages its waterways affects people far downstream — most of the state’s water drains eventually into the Mississippi River system.
For more information on drinking water see Plain Talk About Drinking Water by Dr. James M. Symons.
Related Pages #
- What is a Watershed?
- Water Cycle
- Ground Water
- Water Quality (Watershed Tools — Water Monitoring)
- Impacts of AMD (AML and AMD Basics)
Source and Last Reviewed #
Source not explicitly cited beyond book reference in original text.
Last reviewed: 2026-03
Tags: monitoring, education, volunteer, practitioner, pa
