Last updated: May 24, 2022
A Glacial Ecosystem
Mount Rainier’s 29 named alpine glaciers1 are an icon of the Northwest and make up one of the largest concentrations of glacial ice in the continental United States. These glaciers not only provide recreational opportunities and stunning vistas, but also serve as the source for rivers that flow throughout Washington (Figure 1).
Rivers that originate from the icy slopes of Mount Rainier provide critical habitat to numerous aquatic species. In particular, threatened species of fish such as bull trout (Salvelinus confluentus) rely on the cold water stemming from glaciers and snowfields for their reproduction and survival2 (Figure 2). In addition, certain species of aquatic invertebrates are similarly sensitive. The northern forestfly (Lednia borealis), a rare and vulnerable stonefly, is found only in Washington’s cold glacial headwaters.3,4 As climate change continues to affect ecosystems of the Northwest, Mount Rainier staff are monitoring glacial headwaters to increase knowledge of habitat health and protect biodiversity.
Why is cold water so important?
Cold water environments are essential to the life cycles of numerous aquatic species. Bull trout, an especially sensitive species (Figure 3), are among those that depend on colder temperatures. These fish, federally listed as a threatened species under the Endangered Species Act (ESA), require cold stream temperature habitats like those found at Mount Rainier to spawn and to rear newly hatched fish.2 And while many bull trout are migratory, similar to salmon, some resident fish remain in Mount Rainier waters for their entire lives.
As climate change causes warming water temperatures, Rainier streams serve as a refuge for fish and other cold water dependent aquatic species that are threatened by decreasing availability of viable habitat elsewhere. Because of bull trout dependence on Mount Rainier cold water streams, the ESA classified 30 miles of streams within Mount Rainier National Park as critical habitat in 2010 (Figure 4).
Monitoring temperature in glacial stream habitat is critical to identifying and safeguarding cold water zones upon which fish, stoneflies, and entire food webs depend.
Monitoring Rainier Stream Temperatures
Mount Rainier National Park is collaborating with partners to understand temperature zones within glacially-fed streams. Data collected through stream temperature monitoring can help identify “cold water refugia” that will be especially important to vulnerable aquatic species.
Several methods are used to monitor water temperatures within Mount Rainier National Park. Approximately 40 stream temperature loggers have been deployed in different locations throughout the park annually since 2009 (Figure 4). These loggers take continuous measurements of water temperature, allowing scientists to observe seasonal changes as well as more long-term trends in temperature change due to climatic factors.
Mapping Water Temperature
In 2019, airborne thermal infrared (TIR) data collection methods were utilized to map temperature regions within glacial rivers and their tributaries. Sensors attached to a helicopter collected readings that were used to make Longitudinal Temperature Profiles (LTP) for streams.5 The flight data show how various floodplain features, such as warm, shallow side channels or cold hyporheic flow (groundwater) impact temperature in glacial tributaries.5 The influence of floodplain features is evidenced in Figure 5: different temperature signatures of both side channels and hyporheic flow are visible along Fryingpan Creek, a tributary of the White River.
The White River, as well as the Puyallup, Carbon, and Mowich Rivers, shows an overall downstream warming gradient as cold water from snowmelt meets solar loading, less shade, and warmer air temperatures.5 While snowmelt, cold tributaries, and hyporheic flow combine to cool water temperatures in the main flow, warming occurs rapidly as water flows downstream and away from glacial headwaters: in its uppermost 15 miles, the White River warms from 0.6 degrees C to 13 degrees C5 (Figure 6).
Ultimately, the combined data from TIR flights and 2019 temperature loggers show that waters within Mount Rainier National Park are significantly colder than reaches further downstream,5 underscoring the important role glacial headwaters play in providing viable cold water habitat (Figure 7).
The Future of Glacial Streams
Climate change models predict a warmer, drier future for the Northwest.6 These changes have already had a marked impact on glacial systems: in approximately the past 120 years, glaciers on Mount Rainier have decreased in area by 39.1%.1 If glacial retreat accelerates in the future as predicted,6 what impact will this have on water temperature in glacially-fed streams and the biodiversity they support? In the coming years, collected stream temperature data combined with glacial mass balance reports can be used to create models for future temperature profiles of glacial headwaters. Understanding how cold water zones might be affected by rapidly melting glaciers will be an important tool in efforts to conserve biodiverse glacial ecosystems and threatened aquatic species.
- Beason, S.R., 2017. Change in glacial extent at Mount Rainier National Park from 1896-2015: Natural Resource Report NPS/MORA/NRR-2017, National Park Service, 98 p.
- Marks, E. L., Ladley, R.C., Smith, B.E., Berger, A.G., Sebastian T.G., Williamson, K. 2018. 2017-2018 Annual Salmon, Steelhead and Bull Trout Report: Puyallup/White River Watershed – Water Resource Inventory Area 10. Puyallup Tribal Fisheries, Puyallup, WA.
- Giersch, J. J., Hotaling, S., Kovach, R. P., Jones, L. A., Muhlfeld, C.C. 2016. Climate-induced glacier and snow loss imperils alpine stream insects. Global Change Biology, doi: 10.1111/gcb.13565. John Wiley & Sons, Ltd.
- Washington Department of Fish and Wildlife. 2015. Species of Greatest Conservation Need Fact Sheets. Invertebrates. State Wildlife Action Plan Update, Appendix 1-5, pp A5 1-117.
- Quantum Spatial Inc., Williamson, K., Puyallup Tribe of Indians. (2020). Technical Data Report – Puyallup River and White River Thermal Infrared Project. Corvallis, OR.
- Frans, C., Istanbulluoglu, E., Lettenmaier, D.P., Fountain, A.G., and Riedel, J. 2018. Glacier Recession and the Response of Summer Streamflow in the Pacific Northwest United States, 1960-2099. Water Resources Research, Vol. 54, Iss. 9: 6202- 6225. https://doi.org/10.1029/2017WR021764.