Experimental Flow Releases El Vado Reservoir

Introduction

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In New Mexico, the Rio Chama, a major tributary of the Rio Grande, receives about 303,000 acre feet of water annually from the 660 square miles of drainage area above El Vado Reservoir. The upper 24.6 miles of the 34-mile upper stretch of the Rio Chama located between El Vado and Abiquiu Reservoirs is federally designated as a Wild and Scenic River. This designation prohibits federal support for activities, such as dam construction, that harm the river’s free-flowing condition, water quality, or outstanding resource values. The remaining 40-mile stretch of the Rio Chama is substantially managed for human water use and consumption. 

In 1972, the San Juan-Chama Project, a Bureau of Reclamation (Reclamation) trans-basin water transfer project, diverted water from the San Juan River (a tributary of the Colorado River) into Heron Reservoir on Willow Creek (a tributary to the Rio Chama) a few miles upstream of El Vado Reservoir. This water helped fulfill human water needs downstream, although the purpose was not to manage the diversion to support riparian riparian
Definition of riparian habitat or riparian areas.

Learn more about riparian flora and fauna. As a result, present-day flow releases do not follow the natural snowmelt-dominated flow regime of the river and therefore do not provide the cues many flora and fauna require for their life histories. 

In 2009, Reclamation released 6,000 cubic feet/second (cfs) of water from El Vado Reservoir into the Rio Chama because excessive snowmelt resulted in high reservoir levels that compromised the principal spillway. This was the largest flow the river had seen in 25 years, and stakeholders recognized the benefits this release had on the river morphology and local ecology. Scientists suggested that similar flows could further improve the ecological health and functionality of the river. 

In 2011, a collaborative group of scientists, river outfitters, and water managers created the informal Rio Chama Flow Project (the Project) to provide suggestions for how the river could be managed for provision of human water needs while also improving the river’s ecology. Using experimental flow releases, the project team assessed how the timing and magnitude of future flows could improve the riparian system’s condition by altering its geomorphology (how Earth surface processes, such as movement of air, water, and ice, shape landscapes). 

Key Issues Addressed

Building El Vado Reservoir in 1935 permanently altered the Rio Chama’s ecology and natural flow regime. Historically, the Rio Chama experienced periodic flood flows throughout the year, mainly in spring from snowmelt runoff and episodic peaks during the summer monsoon season. Current management of the Rio Chama impounds and moderates these flow peaks in the El Vado Reservoir instead of allowing them to flow down the river channel. Additionally, state water law requires the release of unused water allocations by the end of the calendar year. This leads to a large amount of water released in late fall, a time that is misaligned with the phenology of many native species of flora and fauna such as cottonwoods and native fish like longnose dace (Rhinichthys cataractae), Rio Grande chub (Gila pandora), flathead chub (Platygobio gracilis), and white suckers (Catostomus commersonii).

For more than eighty years, the river system was operated to supply downstream water without direct management to support ecosystems. This management regime has provided less diverse habitats and fewer niches for native species, causing a significant reduction in the river’s biodiversity. Further, many local communities have been unaware of these ecosystem impacts.

Though restoration of the river to pre-dam conditions is not an option, there are many opportunities for the Project team to improve the river’s ecology for the benefit of native flora and fauna. Large pulse flows are required to move coarse sediment and debris like trees and vegetation downstream, and disturbances from these flood flows create complex habitats that support native species attuned to the Rio Chama’s naturally dynamic system. Geomorphologists conducted tests that evaluated how the magnitude and duration of flows affected the downstream movement of sediment, a key building block of the river system, as riparian habitat is a function of a river’s geomorphology. 

Project Goals

• Increase community awareness of the importance of improving the river’s downstream ecosystem
• Establish a team of scientists to conduct experimental flow releases to determine how movement of sediment downstream shapes the Rio Chama riparian ecosystem
• Develop suggestions for the magnitude and timing of future flow releases to improve the ecological conditions of the Rio Chama’s riparian system based on collected geomorphology data 

Project Highlights

Helping Hands: The team increased community engagement through water quality monitoring projects with high schoolers that helped students develop a sense of responsibility for the health of the river.

• Prime Study Site: The Rio Chama presently holds more water than it did historically because of inputs from the San Juan-Chama Project. Additionally, no substantial water is consumed for human use in the canyon-lined, Wild and Scenic stretch of the river between El Vado and Abiquiu Reservoirs. These two factors provide the management flexibility to release water for ecological benefit when it is available. This makes the Rio Chama a good test site for studying the effects of flow releases on downstream channel geomorphology, river-floodplain connection, and ecology.
• All-Inclusive Stakeholder Group: The Rio Chama Flow Project is an ongoing collaboration among scientists, tribal members, water owners, water managers, community members, and high school and graduate students. These stakeholders had never worked together before, but combined their experiences and resources to tackle the flow problems of the Rio Chama. 
• Workshops: Through workshops and meetings, stakeholders met to discuss the hydrology of the river and developed a series of flow hypotheses. Scientists, including fluvial geomorphologists, riparian ecologists, fisheries biologists, and engineers, played an important role in data collection that allowed the Project team to establish scientifically-backed hypotheses about the required timing and magnitude of flow releases to support natural geomorphological processes in the river.
• Experimental Flows: The Project team designed two experimental flow releases in 2014 and 2016 based on the hypotheses developed during stakeholder workshops. In April 2014, 2,500 cfs of water was released to determine if this would inundate the post-dam floodplain. In May 2016, 4,000 cfs of water was released to determine if it would move monsoon-season tributary debris flow material downstream to redistribute coarse sediment throughout the system. The purpose of these flows was to practice what had only been numerically modeled by conducting real-world assessments that confirmed their hypotheses.
• Graduate Student Work: Data collection is not easy to conduct along the Rio Chama because it requires down-river travel and coordination with agencies. However, graduate students at the University of New Mexico (UNM) devoted time and effort over the years to collecting data on the Rio Chama that has been invaluable to the success of the Rio Chama Flow Project.

Lessons Learned

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Since the Project is focused on long-term management of the river, establishing trust is important for the continuation of the Rio Chama Flow Project. Stakeholders have legal and professional responsibilities to their own agencies, influencing their decision making. The Rio Chama Flow Project’s success has depended on personal relationships, which is both a strength and weakness. By building rapport, everyone involved has shared their management goals and priorities which has contributed to forming strong, lasting relationships. However, there is no guarantee that these relationships will be maintained with the passage of time and as agency personnel retire. The current sustainability of the group results from its long-term social capacity-building, ability to find common ground on issues, and dedication of resources to ensure people stay engaged. 

Scientists were able to determine if geomorphic objectives were met, but lacked data to show explicitly that experimental flow releases benefited species. Collecting ecological data along the Rio Chama was more difficult than collecting geomorphic data because it can be more labor intensive and time consuming. Additionally, ecological data must be collected for longer periods of time (i.e., multiple years) for ecological benefits to be realized and detectable.

Members of the Rio Chama Flow Project realized that securing more funding would have been beneficial. With more funding, they could have established more study sites to strengthen the basis of the flow suggestions. However, the team made do with what resources they had to make sound geomorphic conclusions. 

Next Steps

• Develop a plan with the local Bureau of Land Management science coordinator, U.S. Forest Service, Project team, and University of New Mexico to prioritize data collection over the next five years
• Study the effects of current flow releases on the ecology of the Rio Chama, such as the effects of flow releases on macroinvertebrate diversity

Funding Partners

• State of New Mexico River Ecosystem Restoration Initiative Program to Rio Grande Restoration
• Reclamation WaterSMART Program grant to the University of New Mexico

Resources

• Jadrnak, J. (April 2012). “Project Examines Rio Chama Flow.” Albuquerque Journal.
• The Rio Chama Flow Project: Improving River Management for People & Wildlife
• NPS Wild and Scenic Rivers Program
• Hanson, B. (1992a) Fishery Studies in the Rio Chama Wild and Scenic River in Northern NM with Emphasis on Brown Trout, 1983-1992. 83 pp. New Mexico Ecological Services Field Office, U.S. Fish and Wildlife Service. Albuquerque, NM.
• U.S. Bureau of Land Management, Taos Field Office
• U.S. Forest Service, Santa Fe National Forest
• New Mexico Trout Unlimited
• Pueblos of Ohkay Owingeh, Santa Clara, San Ildefonso
• Rio Chama Acequia Association
• Acequias Nortenos
• New Mexico River Outfitters Association
• City and County of Santa Fe

Contacts

• Mike Harvey, Fluvial Geomorphologist: Mike.Harvey@comcast.net
• Steve Harris, Project Manager: steve.harris39@gmail.com
• Todd Caplan, Riparian Ecologist: todd@gsanalysis.com
• Mark Stone, Hydrologic Modeler: stone@unm.edu

CART Lead Author

Audrey Wilfong, CART Student Intern, University of California, Riverside

Suggested Citation

Wilfong, A. (2022). “Experimental Flow Releases from El Vado Reservoir in the Rio Chama.” CART. Retrieved from https://www.fws.gov/project/experimental-flow-releases-el-vado-reservoir.