Greater Yellowstone
Coordinating Committee

​Importance to the Ecosystem:

The water flowing through the GYA is a vital national resource. The ecosystem contains the headwaters of seven great rivers—the Gallatin, Madison, Yellowstone, Clarks Fork, Wind/Bighorn, Snake, and Green—which flow from the Continental Divide as significant sources to the much larger Mississippi, Columbia, and Colorado River basins and on to the Pacific Ocean and the gulfs of California and Mexico. Rain and snow in the mountains and plateaus of the Northern Rockies flow through stream and river networks to provide essential moisture to much of the American West. Healthy headwaters are critical to fish, wildlife, and recreation, while downstream communities depend on these waters for domestic, agricultural, and industrial uses.

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Status and Trends in Greater Yellowstone:

​The GYA contains some of the most significant, near-pristine aquatic ecosystems found in the U.S. In 2014, the GYA Watershed Condition Classification rated most watersheds as functioning, a small percentage as functioning at risk, and only six watersheds with impaired function. In 2018, Soda Butte Creek was removed from the impaired waters list (Section 303(d) of the Clean Water Act) after the reclamation of an abandoned mine. Water quality is an important component of the ecosystem and is generally very good to excellent across much of the GYA, but changes are being observed and, in some cases, quantified. Increases in water temperature, nutrients, and harmful algal blooms, and changes in timing and quantity of water flow, are a few of the metrics of concern that are being monitored to better understand the current status and trends across the different ecological, geologic, and elevational gradients. 

 

Water issues are at the core of GYA climate change impacts. Since the mid-20th century, average annual total precipitation has remained near 15.9 inches (40.5 cm), but precipitation has increased in spring and fall by 17–23% in April and May and by 42% in October. It has declined by 17% and 11% in June and July, respectively. Mean annual snowfall has declined by 3.5 inches (8.9 cm) per decade, and much of this decline occurred in spring when warming was greatest. Annual streamflow today is similar, but on average the timing of peak flow has shifted earlier in the year by 8 days (range of 1–15 days across all the HUC6 watersheds), extending the length of the water-limited warm season. In selected free-flowing rivers, annual flows have decreased by 3–11%, spring flows have increased by 30–80%, and summer and fall minimum flows have declined by 10–40%. 

 

Managers and communities will continue to face challenges like drought and shifts in seasonal water cycles in the future. Population increase, drought, and climate change may all increase demand on a finite freshwater supply in the West. As the GYA’s 21 counties distinguish themselves as some of the faster growing areas in the U.S., water resources will realize unprecedented importance and pressure to satisfy human needs.​​​​

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Publications/Products Produced:

Greater Yellowstone Area Watershed Condition Framework 2012 (1.3 MB pdf)—In 2012, the hydrologists and other resource specialists classified the condition of all GYA watersheds with National Forest, National Park and National Wildlife Refuge lands.

 

Greater Yellowstone Potential Dam Site Inventory 2014 (3 MB pdf)

 

Watershed Management Strategy Three Year Action Plan 2013 – 2015 (175 KB pdf)

 

Watershed Management Strategy for the Greater Yellowstone 2020 Update (694 KB)

 

Watershed Management Strategy for the Greater Yellowstone 2011 Update (695 kB pdf)

 

Watershed Management Strategy for the Greater Yellowstone 2006 Update (374 KB pdf)

 

Watershed Management Strategy for the Greater Yellowstone 2001 (292 KB pdf)

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Headwaters of the Nation