by Jay W. Skinner
The Rio Blanco is a tributary of the San Juan River southeast of the town of Pagosa Springs that has suffered the impacts of hydrologic modification. In the late 1960s, the Bureau of Reclamation built the San Juan-Chama Project, which diverts water from several tributaries of the San Juan River into the Chama River basin for beneficial uses in New Mexico. The Rio Blanco is a flashy and highly erosive watershed that originates high in the South San Juan Wilderness and terminates in the San Juan River just before it flows into Navajo Reservoir.
Past land use practices have not been friendly to the river. Grazing, channelization, and the sluicing of accumulated sediments from behind the Bureau’s diversion dam have left the river in an unstable condition for much of its length. With the help of many of the landowners in the basin, the San Juan Water Conservancy District, hydrologist extraordinaire Dave Rosgen, and the Colorado 319 Task Force, the Rio Blanco is starting to make a comeback.
The Rio Blanco’s Rebound
In the late 1980s, a private landowner upstream of the diversion hired Dave Rosgen, a Pagosa Springs hydrologist, to restore the Rio Blanco from an unstable braided channel to its former stable meandering channel type. The riverbanks were reconstructed and protected using boulders and log revetment structures. Willows were planted to provide long-term stability and overhead cover for fish. In addition, the channel was sized and shaped to match the hydrologic and sediment regime of the river. A functioning floodplain was also re-established. The landowners downstream of the diversion wanted to see the same results for their reach of the river, but lacked the resources to achieve their goal. What they lacked in financial resources, they made up for in perseverance. The Rio Blanco Property Owners teamed up with the Forest Service, the Bureau of Reclamation, the Division of Wildlife, the Colorado Water Conservation Board, and the Division of Water Resources to restore the Rio Blanco to its former state as a productive trout fishery. The Bureau has long since stopped its former practice of sluicing accumulated sediment from behind the diversion dam and has started dredging the sediment from the stream. They continue to operate the diversion by requiring a bypass of sufficient water to preserve the downstream environment. The sufficiency of the bypass requirement is still a matter of concern to several of the entities involved in this project, and state and federal agencies continue to work on this issue.
The bottom line is that the flows that pass the diversion are now and will continue to be much smaller than the flows that formed the channel. Therefore, the channel is oversized for the hydrologic regime. Water in this oversized channel is spread out to a point that water temperatures and dissolved oxygen levels are not appropriate to support trout populations. The Rio Blanco Habitat Restoration Project funded in 1996 by the Nonpoint Source Task Force is designed to demonstrate that there are techniques to mitigate the nonpoint source pollution associated with this hydrologic modification.
Demonstration Project:
After many years of unsuccessful attempts to attain funding to assist in restoring the Rio Blanco, the project team got a boost when the Colorado 319 Task Force came through with grants. The San Juan Water Conservancy District took the lead in preparing a proposal for a demonstration project; the property owners, the Southwest Colorado Water Conservation District, and agencies of the Colorado Department of Natural Resources provided either hard cash or in-kind services to solidify the project proposal. The federal partners, the Forest Service and the Bureau of Reclamation, could not directly participate in the 319 project, but have committed to providing some of the materials (boulders, logs, and vegetation) and transporting them to the site.
The demonstration project will use a restoration design by Dave Rosgen to narrow and deepen the existing channel to provide better habitat for fish and also lower temperatures and raise dissolved oxygen levels. The project will also stabilize approximately two miles of eroding streambank and provide vegetation on the restored banks for cover, shading of the stream, and long-term stability. The project will reestablish the meanders of the Rio Blanco and the associated floodplain. A contractor has been selected and materials are currently being stockpiled along the stream for an anticipated 1998 construction schedule.
The Rio Blanco Habitat Restoration Project is an excellent example of state and local governments working together with concerned landowners and local offices of federal agencies to attack a common problem. This project is the first funded by the Colorado 319 Task Force for hydrologic modification and is one of only a few such projects in the entire nation. One very important feature of the project is that it does not affect existing uses of water or water rights on the stream.
Note: This article is reprinted with permission from the Colorado Conservator, Volume 13, No. 4, October 1997. Progress reports on construction and post-construction monitoring of the Rio Blanco’s recovery will be reported in future issues of the Conservator.