Surface Water
Water from rivers, lakes, and reservoirs, the drinking water source for the majority of large cities. Surface water requires more intensive treatment than groundwater because it is more exposed to contamination.
How It Works
Surface water sources serve about 68% of the U.S. population. They are more vulnerable to contamination from agricultural runoff, industrial discharge, stormwater, and algal blooms. The Surface Water Treatment Rule requires all surface water systems to filter and disinfect their water. Surface water quality varies with weather (heavy rains increase turbidity and contaminant loads), season (algal blooms in summer increase treatment challenges), and watershed management (protected watersheds produce cleaner source water). New York City is one of the few large cities with an unfiltered surface water supply, made possible by exceptional watershed protection in the Catskill Mountains.
Related Terms
- Groundwater, Water found underground in aquifers, the drinking water source for about half of all Americans and nearly all rural residents, generally cleaner than surface water but vulnerable to contamination from agriculture and industry.
- Chlorination, The most common method of disinfecting drinking water, adding chlorine or chloramine to kill bacteria, viruses, and parasites before water reaches your tap.
- Disinfection Byproducts (DBPs), Chemical compounds formed when disinfectants (chlorine, chloramine) react with natural organic matter in water, including trihalomethanes (THMs) and haloacetic acids (HAAs), linked to cancer and reproductive issues.
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About This Definition
This definition is part of the IsWaterSafe Drinking Water Safety Glossary, 22 terms explaining water contaminants, treatment methods, and safety standards. Written for homeowners, renters, journalists, and public health professionals.