A Watershed

"...is that area of land, a bounded hydrologic system, within which all living things are inextricably linked by their common water course and where, as humans settled, simple logic demanded that they become part of a community". John Wesley Powell


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Boulder Creek-St. Vrain Creek Watershed

The St. Vrain Creek watershed includes two major subwatersheds:

  • Boulder Creek
  • St. Vrain Creek

Boulder Creek and its tributaries flow through the southern portion of Boulder County and St. Vrain Creek and its tributaries flow through the northern portion of Boulder County (See Map). The two streams join to form the main stem of St. Vrain Creek, just east of the Boulder-Weld County line, and ultimately flow into the South Platte River near Greeley, Colorado.

Major tributaries to Boulder Creek include

  • Coal Creek (and its tributary, Rock Creek)
  • South Boulder Creek
  • Fourmile Creek

Major tributaries to St. Vrain Creek include

Urbanized areas in the watershed include

  • Boulder
  • Erie
  • Lafayette
  • Longmont
  • Louisville
  • Superior

There are also several smaller non urbanized communities such as Eldora, Nederland, and Lyons within the watershed.

Water quality in the watershed is influenced by natural geology, land use including impervious surfaces, stream channel characteristics, discharges of treated wastewater, urban and agricultural runoff, and other conditions present in land areas draining to the major streams and their tributaries. Because the watershed crosses multiple jurisdictional boundaries, a coordinated watershed planning approach among local governments is an effective strategy to improving water quality and protecting streams and lakes.

Watershed Planning

In 2013, the City of Boulder, working closely with the Keep it Clean Partnership, received a grant from the Colorado Department of Public Health and Environment to develop a watershed management plan for the Boulder Creek watershed and to develop a coordinated monitoring plan for the overall St. Vrain watershed. In 2014, grant funding was increased to allow for the entire St. Vrain watershed to be include in the plan. This planning effort focuses on water quality and particularly on actions that can be taken to decrease non-point source pollution. The watershed plan is a framework-level document that documents key characteristics of the overall watershed, assesses existing water quality, and makes recommendations regarding actions that can be taken to improve water quality in the future.

Water Quality

Water quality in the Boulder Creek watershed is good overall; however, elevated levels of E. coli, which is a fecal indicator bacteria (FIB), are present in portions of both the urban and agricultural areas of the watershed. FIB such as E. coli are used to indicate the potential presence of pathogens (disease-causing organisms) associated with fecal contamination. FIB can originate from human sources, pets, and wildlife, as well as persist in the environment outside of a living host. Identifying sources of FIB is an important first step in selecting control measures. Human sources of fecal waste are the highest priority to identify and control, whereas there may be limited ability to control wildlife and environmental sources. Over 80,000 dogs live in Boulder County, with an even larger population frequenting the Boulder County open space and trail system; therefore, proper disposal of pet waste is also a key opportunity to reduce FIB loading to streams. Wastewater treatment plants in the watershed have permits and discharge permit limits for E. coli, which are much lower than instream recreational use standards.

Although stream standards for total phosphorus and total nitrogen are not yet applicable to streams in the watershed, future compliance with interim values adopted by the Colorado Water Quality Control Commission in 2012 is expected to be a significant challenge. For this reason, watershed planning will also recommend practices to help reduce nutrient loading from non-point sources. It should be noted that the Front Range activities such as coal-fired power plants, automobiles and agricultural activities release contaminants such as nitrate which can cause atmosphere deposition in the upper watershed.

How Can I Help?

  • Pick up after your dog—on-leash, off-leash and in your yard. See Scoop the Poop for more.
  • Properly maintain your septic system. See Septic Smart for more.
  • Secure garbage cans and pet food to reduce food sources for urban wildlife such as raccoons.
  • Properly apply fertilizer—only apply what your lawn really needs. See Lawn & Garden Tips for more.
  • Keep irrigation on the lawn and out of the gutter. See Lawn & Garden Tips for more.