Decision-Support System to Balance Flows

Introduction

Image Details

In 1988, the Upper Colorado River Endangered Fish Recovery Program (Recovery Program) was initiated to recover four endangered fish endemic to the Colorado River: humpback chub (Gila cypha), bonytail chub (Gila elegans), Colorado pikeminnow (Ptychocheilus lucius), and razorback sucker (Xyrauchen texanus). The work of the Recovery Program covers the Colorado River and its tributaries throughout Colorado, Utah, and Wyoming in accordance with a cooperative agreement among the three states and other public and private partners.

The 15-Mile Reach of the Colorado River lies immediately above the confluence with the Gunnison River in western Colorado. The 15-Mile Reach contains clean gravel bars that are ideal for spawning Colorado pikeminnow and razorback sucker. As such, this reach is recognized as critical for the recovery and delisting of these endangered fishes. In addition to natural flows, reach flows are supported with reservoir releases, including several reservoirs storing water allocated for endangered fish. Maintaining adequate stream flows in this reach is necessary to maintain habitat conditions favorable for the endangered fish.

The Upper Colorado River Basin is heavily managed for many water users and needs. Since 1998, the Bureau of Reclamation (Reclamation) Eastern Colorado Area Office (ECAO) has been facilitating coordination meetings between stakeholders responsible for managing reservoirs and diversions from the Colorado River headwaters to the confluence with the Gunnison River. These weekly calls during the irrigation season, called the Historic User Pool (HUP) coordination calls, allow stakeholders to propose operational changes affecting river flows and then discuss and determine how these changes will meet stakeholder water needs, including those for Colorado River endangered fish. 

To streamline the evaluation of options in real-time and increase the accuracy of water deliveries, the ECAO in partnership with the National Weather Service’s Colorado Basin River Forecast Center developed the Upper Colorado River Basin Decision Support System (DSS) in October 2019. The DSS simulates expected streamflow from the river’s headwaters to the 15-Mile Reach using real-time hydrologic data, including both forecasts of natural river runoff and projected reservoir operations. Importantly, the DSS incorporates the varying travel times from each reservoir to improve flow forecasts at downstream locations.

Key Issues Addressed

The U.S. Fish and Wildlife Service defined a suite of recommended flows for the 15-Mile Reach decades ago based on the habitat needs for endangered fish under different hydrologic conditions. However, it is often difficult to meet these flow targets while balancing other stakeholder water needs. Water managers state that the 15-Mile Reach is one of the most challenging river reaches in which to maintain satisfactory flows, particularly because of two major water diversions immediately above the 15-Mile Reach that divert water primarily for irrigation at the federal Grand Valley Project and the private Grand Valley Irrigation Company. Meeting these flow needs is especially challenging during summer months when more water is diverted for agricultural use and drought impacts are more acute. 

Irrigation season water management decisions in the Upper Colorado River Basin historically relied heavily on data from various sources that were not integrated into a single interactive evaluation tool available in real-time for HUP calls. Managers lacked the real-time ability to explore various what-if scenarios to inform management decisions and more effectively address stakeholder needs. This strategy limited the confidence in final water delivery decisions. The DSS does not increase the amount of water available for river uses, but it does provide managers increased confidence in how they are managing water throughout a season to make wiser and more efficient water delivery decisions on a near real-time basis. Increased confidence in water delivery decisions helps support resources like endangered fish while also maintaining flows for other priority needs like municipal use and agriculture. 

Project Goals

• Develop an online water management tool that integrates expected streamflow, reservoir operations, and real-time hydrological data for use in practical real-time decision making by Upper Colorado River water users, managers, and scientists
• Meet the water needs of Colorado River users while also supporting native endangered Colorado River fish by facilitating more effective and transparent stakeholder engagement and collaboration in the reservoir operations decision-making process during low-flow summer months

Project Highlights

Real-Time Results: The DSS allows managers to assess what-if water delivery scenarios in seconds with much greater accuracy than previous calculations that relied on internet-accessed data and multiple models.

• One Hydrologic System: The DSS is an accessible, integrated system designed for managers, scientists, and water users alike. The system incorporates data inputs such as the latest Colorado Basin River Forecast Center flow projections, anticipated reservoir operations, and real-time flow measurements at USGS gauges in the mainstem Colorado River network. The framework combines these multiple existing hydrological data sources into one simplified, user-friendly tool. The DSS treats potential reservoir releases as variables on top of a constant natural river flow at a given time, allowing various reservoir water release scenarios to be evaluated as a time series for managers, supporting more accurate real-time decision making. 
• Weekly Stakeholder Calls: During the summer irrigation season, the Reclamation ECAO coordinates weekly HUP calls that allow managers and water users to utilize the DSS together to assess various what-if scenarios based on current and projected flow conditions for the next 5-10 days in the Upper Colorado River. Stakeholders use these data to make water management decisions regarding the quantity and timing of reservoir releases to assure flow needs are met to the best of their ability for endangered fish as well as stakeholders like irrigators and recreational users. Weekly HUP calls bring basin water managers together to make these water delivery decisions in a more efficient and transparent manner.
• Sustaining Flows for Fishes: Flow simulations help biologists better evaluate their options for sustaining favorable flow and temperature conditions for endangered fishes like Colorado pikeminnow and razorback suckers in the 15-Mile Reach. This is especially crucial during low-flow conditions caused by drought or elevated irrigation diversions. Accurate flow forecasts for specified what-if scenarios help managers satisfy the demands of Colorado River water users while also providing sufficient water to maintain endangered fish habitat. 
• Balancing Multiple Stakeholder Interests: In addition to the Recovery Program, irrigators, municipalities, regional utilities, and other river interests such as whitewater rafters, anglers, and fishery managers in the Upper Colorado River Basin have interests in real-time river flows. HUP stakeholders must take these diverse and sometimes conflicting needs into account when determining reservoir release operations.

Lessons Learned

Image Details

DSS demonstrates the utility of a real-time decision-making tool for multiple local and regional water interests in managing river flows. This decision-support tool could be transferable to other heavily managed waterways where environmental flows and short time-steps are key elements of river management.

The DSS does not inherently provide better flows for endangered fishes. Water managers face the difficult challenge of having a limited amount of water available to meet diverse user needs in any given year. Nevertheless, the DSS has given managers a tool to determine with greater confidence how to more wisely and efficiently manage these limited water supplies. 

Water managers must consider various stakeholder needs throughout the summer season. For example, recreational users such as kayakers or whitewater rafters often seek high flow releases during the peak summer recreational season, whereas fly fishing guides may want lower flows to improve river access. Additionally, larger flow releases in certain river reaches can help maintain cooler water temperatures for cold water species. DSS helps equip HUP water managers with the data needed to respond to these interests.

The DSS is an example mechanism for aiding water managers in more effectively managing water for ecological purposes in multiple-use river systems, including in the Upper Colorado River Basin. By partnering and collaborating across agencies and a wide range of water users, Reclamation managers leverage the capacity of stakeholders to make informed water-allocation decisions that help protect native fishes within the 15-Mile Reach.

Next Steps

• Continue modifying DSS in response to stakeholder interests and needs
• Work with state managers to incorporate lessons learned from the DSS to better manage water deliveries to protect native fishes while meeting other water delivery needs

Funding Partners

Two-Year Reclamation Science and Technology Grant

Resources

• Reclamation Upper Colorado River Basin Decision Support System
• Upper Colorado River Endangered Fish Recovery Program

Contacts

• Claudia Leon Salazar, Bureau of Reclamation: cleonsalazar@usbr.gov
• Don Anderson, Hydrologist / Instream Flow Coordinator, Upper Colorado River Endangered Fish Recovery Program: donald_anderson@fws.gov

CART Lead Authors

• Anna Weinberg, CART Research Specialist, University of Arizona: akweinberg@arizona.edu
• Alex Koeberle, CART Research Specialist, University of Arizona: alk239@cornell.edu

Suggested Citation

Weinberg, A., Koeberle, A., Anderson, D., and Leon Salazar, C. (2021). “Decision-Support System to Balance Flows for Water Users and Endangered Fishes in the Upper Colorado River Basin.” CART. Retrieved from https://www.fws.gov/project/decision-support-system-balance-flows.