Our Watershed

The St. Vrain Creek Watershed is one of the most important natural features in the Colorado Front Range. It is unique in its richness of natural and ecological resources and in its diversity of historic and cultural features. Moreover, it is cherished for the recreational opportunities it provides and for the numerous economic, cultural, and social opportunities afforded by the St. Vrain Creek Corridor.

The Saint Vrain Watershed covers 546 square miles and includes about 54 miles of Creek. It begins at the continental divide and ends at the start of the western edge of the plains. The North St. Vrain Creek and South St. Vrain Creek (including Middle St. Vrain Creek) drainage basins are located on the eastern slope of the Rocky Mountains. The two basins join in the Town of Lyons to form St. Vrain Creek. From there, St. Vrain Creek flows to the east from Lyons and at its confluence with Boulder Creek, the St. Vrain River is formed. The St. Vrain River flows easy to the South Platte River in Northern Colorado.

The map below, taken from the St. Vrain Creek Watershed Master Plan, shows the entirety of the watershed and the creek, which is split into reaches for planning purposes.

St Vrain Reach Map


The streams within the Planning Area (shown above) were divided into several smaller reaches along the length of the watershed, allowing the planning team to focus on the needs and characteristics of specific portions of the creek and to better organize ongoing public engagement activity.  To learn about the projects taking place in each reach, click here.The reaches are as follows:

  • Reach 1: Confluence of St. Vrain Creek with Boulder Creek, upstream to the eastern corporate limits of the City of Longmont.
  • Reach 2: The eastern corporate limits of the City of Longmont, west to Airport Road.
  • Reach 3: Airport Road west to US 36.
  • Reach 4: US 36 upstream through the Town of Lyons along both South and North St. Vrain. Due to the complexity of this reach, it was split into 3 sub-reaches:
    • Reach 4a: Encompasses the Apple Valley area;
    • Reach 4b: Includes the South St. Vrain from Andesite Quarry downstream to Old St. Vrain Road;
    • Reach 4c: Covers the Town of Lyons proper down to US 36.
  • Reach 5: North St. Vrain from Apple Valley and upstream to Button Rock Reservoir.
  • Reach 6: Upstream along the South St. Vrain from the choke in the canyon to the Townsites of Riverside and Raymond.
  • Reach 7: The Townsites of Riverside and Raymond upstream to the limit of the Planning Area.



Photo credit from homepage: Thaddeus Roan
Title: Apple Valley Road Bridge, Lyons, Colorado