The city of Seattle is well known for its cloudy skies and high levels of precipitation. However, the city is also known for its technological advancements, with Amazon, Microsoft, and Boeing headquarters all based in Seattle. Seattle's healthy and drinkable tap water comes as no surprise, considering the technological advancements made within the city. However, when looking beyond the greater Seattle region, many cities in western Washington do not receive the same quality of water as residents living in or near Seattle. Despite encountering the same issues of runoff, which can lead to water contamination, Seattle residents continue to have access to clean, fresh water.

Western Washington, on average, has 156 days of measurable precipitation each year, making it the region with the most measurable days of rainfall in the continental United States. With this said, the frequent rain leads to high levels of runoff, which is the flow of water over land surfaces typically caused by rainfall or snowmelt that does not soak into the ground. Expansion in development and growth in population lead to increases in impervious surfaces like pavement and concrete. These impervious surfaces leave fewer surfaces for rain or snow melt to soak into the ground, along with the presence of fewer trees and other vegetation, which assists in evaporating excess water. Runoff can contain toxic chemicals, bacteria, and other pollutants. Following proper water treatment plans is necessary to ensure that the fresh water provided to residents is healthy and safe to use.

Seattle's high-quality drinking water is also a result of the source from which the city receives its freshwater. Seattle gets its freshwater from the Tolt River Municipal Watershed and the Cedar River Municipal Watershed. Seattle capitalizes on the usage of these large watersheds, which collect water straight from the Cascade mountain range, which intersects Washington State. The water collected from these watersheds is so clean that sometimes it does not need to be treated. This allows the city of Seattle to provide residents with clean, safe drinking water.

However, other cities rely on local aquifers to obtain their freshwater. Though aquifers are a great source for collecting and distributing freshwater, they are more susceptible to contamination. In 2015, the City of Issaquah detected per- and polyfluoroalkyl substances (PFAS) in the groundwater within the Lower Issaquah Valley. PFAS are chemicals that can last in the environment for many years and become toxic if accumulated. These chemicals were historically used as a firefighting foam during training, which spread into the environment and soaked into the soil, leading to groundwater contamination. In 2018, the city of Issaquah began investigating how PFAS travel through groundwater and initiated a formal cleanup. In the Sinclair and Dyes Inlet watershed, fecal coliform, metals, and organics contaminated the Sinclair-Dyes watershed as a result of excess runoff from stormwater. The discovery of the contaminants led to the Puget Sound Naval Shipyard, U.S. Environmental Protection Agency, Washington State Department of Ecology, and several local counties and cities coming together to create a water treatment plan for the watershed. Though water treatment plans were instilled after the discovery of the contaminated water, the contamination within the Lower Issaquah Valley and the Sinclair Dyes Inlet demonstrates how smaller aquifers can be more easily contaminated by pollutants.

Seattle, being a technological hub, has contributed to the city's ability to access water from the Cedar River and Tolt River watersheds, which provide spotless drinking water to Seattle residents. Other cities within western Washington obtain their drinking water from more local and smaller aquifers. These smaller aquifers are more susceptible to becoming contaminated from pollution absorbed into the groundwater or from runoff. Western Washington's climate makes it highly vulnerable to the negative effects of runoff due to its temperate and rainy climate that persists for most months of the year. Cities that use local aquifers should ensure that the water quality is tested regularly. More drains and permeable asphalt should also be implemented so that runoff is reduced. Most importantly, emphasis should be placed on assisting cities throughout western Washington so they can receive the information and funding required to treat water and reduce contamination effectively.