Dam operations

A vision for unlimited clean water
Last year we restored 467 miles of rivers and streams.

With your support, we can continue to implement streambank stabilization solutions, erosion control, and riparian plantings. Be a part of the next mile.


Almost every major river in the American West has a dam somewhere along its course. One of the few exceptions is the magnificent Yellowstone River in Montana — at 692 miles long, the Yellowstone is the longest free-flowing river in the contiguous United States. For most other rivers and their fisheries, dams and their operation cause chronic, daunting challenges for trout and salmon. While many dams are not candidates for removal, their impacts on fish sometimes can be reduced by the way they are operated. For this reason Trout Unlimited works across the West both to improve reservoir operations and advance new ways of managing dams and the water they impound, and to re-think the need for and benefits of dam-based water storage. 

More water storage through data, not concrete

Trout Unlimited has been successful in bringing better analysis of existing hydrologic data to bear on reservoir operations, emphasizing reliance on hydrologic relationships rather than outdated rule-curves or fixed calendar dates. This has effectively created more water storage at these reservoirs through better use of data.

In Montana’s Sun River, for example, Trout Unlimited’s detailed analysis of the 100-year period of record on a daily time-step, combined with extensive use of snow telemetry (SNOTEL) data, drove re-operation of the Bureau of Reclamation’s single-purpose Gibson Reservoir to provide higher winter flows to create more fish habitat, and promoted better reservoir management during the irrigation season to meet a higher summer instream flow target.

Trout Unlimited is working to replicate this kind of success with other western reservoirs. The Henry’s Fork and South Fork of the Snake River, the Yakima and Klamath Rivers, and especially the Colorado River Supply Project’s reservoirs in the upper Colorado River basin all have potential for improved operations or better coordination with other reservoirs through revisiting how they utilize hydrologic data and relationships.

Cost-effective new storage in expanding or re-allocating existing storage

Trout Unlimited is not opposed to new storage. New, small-scale storage projects can implement water supply strategies that we support, such as water reuse and flexible water sharing arrangements between agriculture and municipalities. In some cases, new storage projects can be designed and operated to deliver multiple benefits—for irrigation, municipalities, and stream flows. 

However, it can be a lot cheaper, faster, and smarter to re-allocate or expand an existing reservoir than to build a new one. For example, Trout Unlimited, working with other conservation partners, has identified 102,000 acre feet of new, potential water supply in Colorado, through a combination of expansions and re-allocations of existing projects and other strategies such as water re-use, to meet the Front Range’s growing water demand — without developing any new storage projects.

Rio Grande Reservoir

The Rio Grande Reservoir in southern Colorado delivers irrigation water to the farmers and ranchers of the San Luis Valley Irrigation District. The project is over 100 years old, and the State of Colorado has placed it under storage restrictions because the structural integrity of the dam is in question. The District is in the process of rehabilitating the dam, which will allow for increased storage in the existing reservoir. Much of the reservoir’s additional capacity will be dedicated to providing more reliable water deliveries to the farmers and ranchers served by the District. 

However, the project also has the potential to provide multiple benefits, including serving recreational and environmental purposes that are important to Trout Unlimited members and the local community. For this reason Trout Unlimited is in discussions with the District, the Colorado Division of Parks and Wildlife, and other stakeholders about the possibility of allocating some of that new capacity to meet other purposes, namely interstate compact delivery requirements and enhancement of stream flows in the Rio Grande River.

Windy Gap

For a decade, the Northern Colorado Water Conservancy District has proposed to “firm” the yield of its existing Windy Gap Reservoir by increasing the amount of water the project delivers from the Colorado River to the Front Range. Trout Unlimited had opposed the proposal because of serious concerns about its impacts on the already over-stressed Colorado River. 

However, after many years of discussion, Trout Unlimited and the Northern District reached an agreement. Under the agreement, Northern will: curtail diversions as needed to avoid high stream temperatures caused by low flows; release water from storage as needed to create high spring peak flows to flush sediment on a prescribed schedule; invest several million dollars in construction of a by-pass channel around the Windy Gap Reservoir, which currently is a source of whirling disease and dangerously high stream temperatures; and, has offered up several million more dollars to restore Colorado River habitat. 

When these conditions are implemented, the dual benefits of the Windy Gap firming project — an increase of 32,000 acre-feet annual yield of water supply and environmental improvements to the Colorado River — will leave the Colorado healthier than it is today.

Chatfield Reservoir

On Colorado’s South Platte River, Trout Unlimited has supported, in concept, the Army Corps of Engineers’ plan to re-allocate 26,000 acre-feet of storage water in Chatfield Reservoir from flood-control to providing 8,000 acre-feet of annual yield for irrigation and municipalities. Trout Unlimited is working with project proponents and regulators to address concerns that the current project proposal could deplete flows downstream and degrade the health of the urban reach of the river. Although still in process, the Chatfield Reservoir re-allocation is an example of a water supply solution that doesn’t require new concrete, just new thinking. 

Multi-stakeholder, basin-study collaborative planning produces the best proposals for new storage

Trout Unlimited has learned over the years that the best water supply solutions are usually not the easiest ones. Such solutions typically are grounded in a lot of feedback from multiple interests regarding their water requirements. New water storage projects, therefore, are best planned and executed through a multi-stakeholder, basin-study process that considers a variety of alternatives, looks carefully at hydrology and future water supply forecasts, and integrates storage into a multi-pronged approach for addressing water scarcity. The Yakima River basin study and collaborative plan, completed as one of the Bureau of Reclamation’s Basin Studies,
recommends new storage as one solution among a range of other approaches and is a good example of this process in action.

Yakima River Basin Plan

The Yakima River Basin Integrated Water Resource Management Plan has seven distinct elements, all designed to help communities, fish, and farming thrive in an arid region. These elements are: 1) open fish passage at six existing dams; 2) make structural and operational changes to existing dams to add storage capacity, increase water use efficiency, and improve salmon habitat; 3) increase new surface water storage; 4) improve groundwater recharge and storage; 5) invest in irrigation efficiencies and water conservation; 6) promote water transfers through water markets and water banks; and, 7) enhance protection of multiple watershed values through headwaters habitat acquisition, floodplain restoration, and tributary improvements. No single approach can address the complex challenges associated with water scarcity in the Yakima basin. Rather, it is this multiplicity of strategies—from new surface storage to investing in the basin’s “green and blue” infrastructure—that provides resiliency to water scarcity in the basin. 

Climate Change will bring new challenges to the West’s water supply

The only thing we know for sure about how climate change will affect the western U.S. is that the weather is going to get more unpredictable. Less snow, more rain, and more frequent droughts and storms are expected. If you plan on building a bigger bathtub, you will want to have some assurance that you will be able to fill it, given predicted changes in precipitation. This makes the kind of comprehensive, collaborative planning process exemplified by the Yakima basin plan especially important. A multi-stakeholder, basin-study process that considers a wide range of alternatives increases the odds of developing water supply solutions that will be resilient to climate change impacts. The Yakima basin’s plan for proposed investments in floodplain restoration, headwaters habitat preservation, and tributary restoration, for example, mean that the basin will be more resilient to both droughts and storms, able to soak up high storm flows while slowly releasing water during periods of drought.  This type of multi-pronged approach to improving water security improves the chance for success in making our agriculture, fisheries, and communities more resilient to — and better able to respond to — the impacts of climate change.

Hydropower also faces challenges and opportunities from Climate Change

Climate change is expected to alter the timing and magnitude of streamflows across the West. This will have an impact on hydropower operations and in the cost-benefit calculation for new hydropower development. Adding hydropower capacity to existing projects can help provide a revenue stream for re-investment in project upgrades and enhancements to aquatic ecosystem functioning — and help keep hydropower production viable even in a changing climate.  A roadmap for increasing hydropower would prioritize power gains through efficiency improvements — improvement and modernization of existing resources and equipment — and adding or expanding production at existing, well-maintained infrastructure, like federal storage facilities. 

Opportunity also exists to expand hydropower development in irrigation delivery systems, where water is already in motion for another important use. This type of development has the potential to be particularly beneficial for rural agricultural communities as in-conduit energy production can bring dispersed sources of power to irrigation districts and water users whose power needs are often far from the grid. Trout Unlimited worked with Rep. Scott Tipton from Colorado to assist with passing legislation that does exactly that — HR 678, which was enacted in 2013.

A vision for unlimited clean water
Last year we restored 467 miles of rivers and streams.

With your support, we can continue to implement streambank stabilization solutions, erosion control, and riparian plantings. Be a part of the next mile.