Scientists and policymakers often refer generally to the “Puget Sound ecosystem.” Hundreds of millions of dollars go toward its protection. Scientists and sociologists study it, and there is an assumption that we know what it is.

In fact, the Puget Sound region has been divided into many different geographic boundaries. There is the Puget Trough, the Salish Sea (including the waters of Canada), the Puget Sound watershed, ranging from “snowcaps to whitecaps.” Some maps don’t include the San Juan Islands or the Straight of Juan de Fuca. Some do. Some just refer to the marine environment. Other boundaries venture as far as the nearshore.

There are good reasons for all of these designations, but it makes it hard to give a straight answer to a simple question: What do you mean by “Puget Sound?”

Our answer might be “follow the water.” By Puget Sound, we typically refer to the areas that drain into and include the Puget Sound basin. These are represented by the USGS as “hydrologic units” and you can view a map and description of these boundaries on PSI’s Encyclopedia of Puget Sound here. This is also the definition used by the Puget Sound Partnership and others, with the simple idea that Puget Sound does not exist in isolation, but is fed by its many water sources, from high elevation snowmelt to wetlands and floodplains.

Follow the water. At least that sounds better than “follow the hydrologic units.”