Drinking Water

The Drinking Water Vital Sign addresses the quality of water as it enters drinking water systems, including large and small public and private drinking water systems. Access to safe drinking water is a critical determinant of human wellbeing. This Vital Sign focuses on the sources of water provided by the environment, rather than on the ability of the infrastructure to provide water safe to drink. In urban areas, cities provide treated drinking water to Puget Sound residents. In more rural areas, small public water systems and wells are harder to track, but can be threatened by ground and surface water infiltration; the use of pesticides, herbicides and fertilizers; and issues with water storage and distribution systems.


Key Vital Sign Messages

Water Intake Station on Nooksack River. Photo by Eagle-Eye Aerial Solutions, LLC
  • Clean drinking water starts upstream with healthy forests and watershed management and protection. Source water protection has many benefits, including reduced risk to public health, improved habitat for fish and wildlife, reduced economic costs associated with contamination, and increased public confidence in a safe and reliable source of high-quality water.
  • The vast majority of Puget Sound residents get their drinking water from public water supply systems. Nearly 98% of residents are served by large systems known as Group A water systems, which have more than 14 connections or serve 25 or more people, 60 or more days per year.
  • Public water supply systems obtain water from two sources: surface water and groundwater. Large, well-populated metropolitan areas tend to rely on surface water: Seattle’s water supplies primarily consist of surface water from the Cedar and South Fork Tolt rivers, while the Green River serves Tacoma residents. Smaller, rural areas tend to rely on groundwater, which is obtained by drilling wells.
  • Potential causes of source water contamination include industrial and commercial activities, agriculture and animal feeding operations, improper forest practices, failing septic systems, and stormwater runoff.
  • Humans can become ill from drinking or contact with water contaminated with pathogenic bacteria, viruses, and parasites, or toxics such as chemicals, heavy metals, plastics.
  • Nitrate is an acute contaminant that can pollute groundwater. Most groundwater supplying large public water systems in Puget Sound is not contaminated by nitrates. However, Whatcom, Island and Clallam counties had a higher proportion of source groundwater samples with elevated nitrate levels compared to other Puget Sound counties.
  • Elevated concentrations of nitrate may indicate conditions (well depth and surficial geology for example) that make groundwater more vulnerable to contamination from activities at the land surface. The Index of Vulnerability for Elevated Nitrates will identify which areas in Puget Sound are susceptible to groundwater pollution, including tribal and rural areas where monitoring data is limited (modeling work for this indicator is still in progress).

Strategies, Actions, and Effectiveness

Other Resources

Contributing Partners

Nathalie Hamel
Last Updated