Increasing Stream Ecosystem Health in the Upper Pecos Watershed
The objectives of this project were to address temperature and turbidity impairments for a stretch of the Pecos River through channel and bank restoration and the creation of a new wetland area, thus also improving general river ecosystem health. The project restored 1400 feet of the Pecos River channel and banks below Lisboa Springs Fish Hatchery, and will have the additional benefits of improving water quality and flow control through the Village of Pecos.
How the Project Addressed Problems:
The project was performed in three phases. Phase I of this project proposes to restore the river to its proper functioning condition, while maintaining the legally required water diversion to the Monastery property. The project plan sheet shows the point of water diversion being moved upstream approximately 800 ft, and being conveyed to the existing ditch in a new buried pipe (the pipe will occupy less space than a ditch extension, and it is much more hydraulically efficient so it can convey the water on a flatter slope). The main channel of the river will be re-aligned to flow down the “west channel”, with a channel slope much closer to the natural slope that existed before the diversion dam was built. This will require the removal of the existing old gabion weir structure. The restored channel will allow for the proper passage of sediment, as the new channel will have shear stress characteristics consistent with the upstream and downstream reaches of the river. The improved condition in the west channel will include a narrowing and deepening of the active channel, helping to lower stream temperatures. The construction of a floodplain bench along the channel sides will help regulate shear stress values, improving on the present entrenched conditions.
In-stream structures built with large boulders will provide grade control in the restored river channel, and will add bedform diversity for improved aquatic habitat. An aggressive program of streambank re-vegetation is planned, with a predominance of woody riparian species (willow, cottonwood, dogwood, etc.) so that long term erosion protection can be accomplished in a natural form, and sediment inputs from this reach of the river can be reduced to natural levels. The streamside vegetation will create shade in places where none exits today, which will contribute to water temperature reductions.
Phase I of this project included the restoration of the river in the “west” channel, and the headworks for the new point of diversion to Monastery Lake. Phase II of the proposed plan includes the creation of an open water wetland in the old river channel (east channel). This is a rare opportunity in the Upper Pecos Watershed, where a narrow valley form and moderately steep slopes reduce natural opportunities for the formation of this wetland type.
In the interim time period between Phase I completion and Phase II implementation, water to Monastery Lake was regulated at the new headgate and will flow in the old river channel to the existing ditch. In the planning process, the UPWA considered restoration of the river into the historic “east” channel.
However the logistical challenges of providing the water diversion works, and the extra-ordinary costs of filling the “west” channel back in were recognized as prohibitive.
The UPWA believes that the wetland feature created in Phase II will provide educational opportunities, and a high aesthetic value.
The denuded roadside area between the pavement and the newly developed wetland which is now used for unregulated parking will be bouldered off and re-vegetated in order to prevent sediment and other pollutants from vehicles from being flushed into the wetland during rain or snow melt.
Phase III consists of continued monitoring and required reporting activities.
The implementation site is 1400 feet of stream in the Upper Pecos Watershed in the Willow Creek to Alamitos Canyon Reach. The project area is located in the Upper Pecos Watershed one mile above the town of Pecos, New Mexico.
It starts at the downstream end of the Lisboa Springs Fish Hatchery and includes specific diversion structures, channels and selected river bank and channel restoration below the hatchery and above Monastery Lake.
The total project area covers about four acres and fourteen hundred feet of river in the Upper Pecos Watershed which is part of the larger Rio Grande basin.