It's hard to imagine a few degrees of temperature change or shifts in precipitation patterns could pose a threat to Washington's drinking water supplies; but it can, and it will.
Washington's drinking water comes from three sources: groundwater (wells and springs), surface water (lakes and rivers) and snowpack/snowmelt (supply for rivers, lakes and aquifers).
According to the University of Washington Climate Impacts Group, Washington is projected to experience decreases in snowpack, increases in stream temperatures, and widespread changes in streamflow timing, flooding, and summer minimum flows. Annual streamflow volumes are not projected to change substantially.
Climate change is projected to result in more frequent summer water shortages in some basins, while others remain unaffected. Climate Change Impacts and Adaptation in Washington State, section 6: How Will Climate Change Affect Water in Washingon (PDF).
Changes in Snowpack
The snowpack is critical for recharging our rivers and aquifers through the spring and summer. Historically, snowmelt left the mountains in late June; now it occurs as early as the end of May. All of the glaciers that make the western mountains famous are retreating - another sign of shifting temperatures.
Increase in Floods
The frequency of heavier, more intense rainstorms increases the threat of flooding for many of Washington's communities and rural areas.
In addition to the immediate health threats from flooding, flood waters can damage and contaminate wells and water treatment plants, resulting in short-term outages and increased risk of waterborne disease.
Increased Waterborne Disease Risk
Extreme rain or snow melt flow increases the risk of waterborne diseases in drinking water. These risks come from higher levels of pathogens in the runoff from the areas around drinking water wells and surface water intakes and from flooding of the wells themselves.
The threat to health from fresh-water algae that has been expanding its territory among our state's lakes will continue increasing. Some algae blooms are toxic and can cause illnesses to pets and people who swim in them.
Water Shortage and Drought
While our state has more water than many of our neighbors we also have competing demands among fish, forests, farms and people. These conflicts will grow as changes in temperature and weather patterns affect seasonal availability of our water supplies. Anything that interrupts the storage and recharge of water in our rivers, lakes and aquifers threatens the drinking water supply.
Many Washington communities, government agencies, and organizations are preparing for the impacts of climate change on water resources. Most are in the initial stages of assessing impacts and developing response plans; some are implementing adaptive responses.
View projected change in annual precipitation across Washington.
Learn about climate and health topic areas on our Climate and Health page.