The entire Skagit watershed drains 3,093 square miles, and, excluding the Columbia River, is the largest basin in Washington. The Lower Skagit covers 284,302 acres, flowing through cropland, forest, and urban areas in Skagit and Snohomish counties. Many of the lower areas have dikes and drainage systems to prevent flooding.
The Lower Skagit has varying topography, ranging from floodplains and terraces to steep ridges formed by glacial activity. Many wetlands were drained to provide more cropland and pasture, particularly in the western part of the watershed. Rivers feeding the Skagit rely on glacial meltwater and 60 to 90 inches of precipitation annually, which also nourishes a healthy and productive temperate rainforest. Forestry and recreation are the dominant uses at higher elevations, while lower elevations are mainly the site of agriculture and urban development. Some of the concerns for the health of this watershed include invasive weeds, streambank erosion, and water quality.
- Counties: Skagit, Snohomish
- National Estuary Programs: Puget Sound
- Other Watersheds Upstream: Upper Skagit, Puget Sound
- Other Watersheds Downstream: Puget Sound