Where does Salem's drinking water come from?

Detroit Lake Aerial View

 

Here in Salem, our drinking water comes from the North Santiam River. The North Santiam River begins high up in the Cascade Mountain Range and is a 92 mile tributary to the Willamette River.

A watershed is an area of land that is geologically formed in a way that channels the flow of water into a common river, stream, or lake. Our watershed, or our source water area is called the North Santiam Watershed and it holds hundreds of smaller streams and rivers, hosts several endangered species, is home to several town and agencies that carefully manage the watershed, and of course is where we get our drinking water!

Use the virtual tour and the tabs below to learn more about your watershed!

 

    Salem's Watershed

    For more than 80 years, the North Santiam River has served as the primary water supply for the City of Salem. This high-quality source water flows over 90 miles from the high ridges near Mt. Jefferson, through Detroit Reservoir, and down toward the Mid-Willamette Valley. The North Santiam then meets  the South Santiam before converging with the Willamette River. The North Santiam Watershed covers about 760 square miles of private, state, and national forest. The large area of undeveloped forested land surrounding the watershed is one reason the river is able to provide such high quality water for the many canyon communities along its route. The high quality water produced from the watershed is suitable for Salem's more natural filtering method, called Slow Sand Filtration, at the Geren Island Water Treatment Facility located near Stayton. The City of Salem has been using this process since the 1930s and continues to make improvements to the facility and treatment process as needed.

    North Santiam Watershed Callout in State Map

    North Santiam Watershed Map View

    Two maps showing the location and extent of the North Santiam Watershed in Oregon, including its position near Salem in the Willamette Valley and a detailed view of the watershed’s river network and sub-basins.

    What do you see when you look at these two maps?

    You may see that the North Santiam Watershed, as big as it is, only takes up a small percent of the Willamette Valley and an even smaller portion of Oregon! That doesn’t mean that changes in our watershed wouldn’t impact water quality downstream. Oregon is made up of dozens of watersheds that provide surface water and groundwater resources to those that live in and near them.

    What creates the flow of the North Santiam River is the geomorphology of the North Santiam Watershed, which is basically the shape of how the mountains and hills are formed. The black lines on the map above show the high ridges that split the watershed into several sub-basins, showing the direction for water flow before it reaches a river. Geologic composition is made up of dense basalt and volcanic rock, blocking rain and snowmelt from seeping into the ground as much as other watersheds in the state. Instead, years of flowing rivers and heavy winter storms has led to the steep channels and valleys that are characteristic to the upper portions of the North Santiam Watershed.

    Salem has some of the best tasting drinking water, and that is in-part because of our watershed and our source water. Many water providers across the country have drinking water sources that are affected by agriculture and fertilizers, large cities upstream of their intake, and industrial waste issues. Fortunately, the North Santiam Watershed is fairly undeveloped and the communities in the watershed do a good job at protecting the river since they use its water too.

    Frequently Asked Questions