Riparian Streamflows

The Colorado-Big Thompson Project was the first U.S. Bureau of Reclamation project in the Western U.S. to stipulate year-round releases from a federally-owned dam and reservoir.

In 1961, several years before the federal government began legislating environmental policy, Northern Water, Reclamation and Grand County representatives negotiated a water-release agreement from Lake Granby into the Colorado River to help preserve Colorado River fisheries.

When the Windy Gap Project came online in 1985, Northern Water’s Municipal Subdistrict agreed to release additional water from Windy Gap Reservoir into the Colorado River to respect downstream water rights and to protect the Colorado River's aquatic wildlife habitat below the reservoir.

Water released from Lake Granby and Windy Gap Reservoir into the Colorado River helps preserve and protect fish and aquatic wildlife habitat. These efforts by Northern Water and Reclamation work in concert with the State of Colorado’s pioneering instream flow program legislation passed in 1973.

State Instream Flow Program
In 1973, the Colorado legislature recognized the need to “correlate the activities of mankind with some reasonable preservation of the natural environment.” Senate Bill 97 created the state’s instream flow program to preserve or improve the natural environment to a reasonable degree.

One of the first of its kind, the program vested the Colorado Water Conservation Board with exclusive authority to protect streamflows through a reach of stream rather than just at a single point, and to protect levels in natural lakes.

Until this law was passed, Colorado statutes required appropriators to divert water from streams and rivers for beneficial use. SB 97 removed the diversion requirement and allowed the CWCB to appropriate water for “instream” uses.
Northern Water has been working with several agencies since  the early 1960s to help preserve Colorado River fisheries.
Northern Water has been working with several agencies since
the early 1960s to help preserve Colorado River fisheries.



Since 1973, Colorado has appropriated instream flow water rights covering more than 8,500 miles of streams and rivers and 486 natural lakes. This protection represents approximately 30 percent of the perennial stream miles in the state.

Habitat and Water Quality Protection
Northern Water has continued to take the lead on instream flows and habitat protection in the last several years:
  • Platte River Recovery and Implementation Program: Northern Water is working with a group of 60 Colorado water users, two other states and the U.S. Department of the Interior to help restore habitat for endangered species in the Platte River basin. The first 13-year phase of the program began on Jan. 1, 2007.
  • Upper Colorado River Endangered Fish Recovery Program: Northern Water and several other agencies are working to re-establish populations of threatened and endangered species in the Upper Colorado River basin.