Monthly Archives: October 2012

Water Towers of the World

Global warming has melted much of Grinnell Glacier since 1911

Glacier National Park is famous for its mountainous landscape and glacially carved terrain. What many people don’t realize is that mountain glaciers provide more than just scenery. Glaciers are an integral part of the ecosystem, providing water to mountain and downstream environments. In today’s warming climate, these giant marvels of snow and ice are rapidly disappearing.

Mountains have been called “water towers of the world. More than 50% of the world’s fresh water supply comes from runoff in mountain environments. While much of the runoff from mountains comes from rain and melting snow, alpine glaciers are an important contributor to mountain streamfl ow. Globally, glacial meltwater provides one-fourth of the water in mountain streams.

By providing a dependable source of cool, fresh water, glaciers are essential to the health of aquatic and riparian ecosystems. They also provide fresh drinking water for downstream populations and dilute pollutants that are generated mostly in lowland areas. As climate warms and glaciers melt, these ecosystems are losing an important source of fresh water.

Glacier National Park has already lost more than 70% of its glaciers in the last century. Today there are 25 of the 150 glaciers that were recorded in 1850, the end of the period called the Little Ice Age. At the present rate of warming, scientists predict that all of the glaciers in Glacier Park will be gone by the year 2020. The demise of glaciers will affect both the amount and timing of mountain streamflow.

Stream Regulators

Snow melt in spring at Logan Pass, Glacier National Park

Mountain streams in Glacier National Park are fed by alpine glaciers and snowpack. In summer, once it becomes warm enough to melt the snowpack, a rush of water comes down the mountains from glaciers to join the streams and rivers. Then, for the rest of the warm season, mountain streams are augmented by a constant flow from melting glaciers. When rain is sparse, as in the late summer and during drought years, mountain glaciers may be the only source of base flow in some mountain streams.

As climate warms, this pattern is changing. With a warming climate, less winter precipitation falls as snow but more of it falls as rain. Also, spring comes earlier. The longer warm season will allow even more snow and ice to melt. Earlier, warmer summers mean spring runoff from mountains happens earlier in the year, and often in a bigger rush of water downstream. In the Pacific Northwest region, spring runoff is now happening up to two weeks earlier than it used to. A concern with global warming is the possibility of more spring floods due to the pulses of rain combined with melting snow and ice.

As mountain glaciers melt and spring runoff happens earlier, there is less water later in the season. For many small mountain streams, melting glaciers provide the only source of base flow in late summer. With no glacial meltwater to augment them, some streams may become ephemeral, drying up late in the season. This will have major consequences for stream ecology.

In addition to regulating stream flow, glacial meltwater affects the temperature of mountain streams and rivers. Many of the invertebrates that live in Glacier National Park’s waters are very temperature sensitive and can only live within a narrow temperature range. Because aquatic invertebrates are at the base of the food chain, putting them at risk threatens the entire stream ecosystem.

Links for further information:
The potential impacts of climate change on native aquatic ecosystems of the northern Rocky Mountains:
http://www.nrmsc.usgs.gov/research/climate_fish

Snow Survey and Water Supply Forecasting:
http://www.nrcs.usda.gov/programs/snowsurvey/

Glacier Research in Glacier National Park:
http://www.nrmsc.usgs.gov/research/glacier_research.htm

Climate Change in Mountain Ecosystems:
http://www.nrmsc.usgs.gov/research/global.htm

United States Global Change Research Program’s
Climate Change Wildlife and Wildlands ?A Toolkit for Formal and Informal Educators:
http://www.globalchange.gov/resources/educators/toolkit

The Story Behind the Landscape

By: Lex Blood

With the return of winter and snow to the mountains and floor of the Flathead Valley, we are reminded of a time beginning about 2 million years ago and concluding about 10,000 years ago when great masses of ice up to 3,000 feet thick periodically covered almost everything we see today.

Initiated by a modest 4-6˚ F decrease in temperatures, snow fall accumulated annually to the north in Canada and in the higher mountain elevations and gradually compacted to form deep slowly moving rivers of ice. Combining, much like the river systems of today, this ice moved south in the Rocky Mountain Trench covering all but the highest peaks and advancing as far as St. Ignatius.

Glacier National Park’s landscape is evidence of the work of glaciers thousands of years in the past.

The ice sculptured the rocks of the mountains and valley floor over which it flowed and carried huge quantities of rock fragments ranging from clay to car-sized boulders to a mixture called glacial till. This till was deposited beneath the great ice sheet and along the valley sides.

Then as the ice retreated numerous large rivers from the melting ice flowed across the valley reworking the till by carrying away the fine fragments and redistributing the larger ones into a broad nearly level sheet of sand and gravel hundreds of feet thick while winds also blowing across the open valley floor formed sand dunes.

Finally, as the ice vanished, the remnant rivers etched their modern channels and continue today to feed the ice-carved basin containing Flathead Lake.

Flathead Lake as seen from the Swan Crest atop Columbia Mountain.

The beautiful landscape and rich wildlife habitat we see today of steep mountain sides, forested valley edges, level, rich agricultured lands, many lakes, abundant river side wetlands and riparian areas, and the jewel of Flathead Lake are the legacy left to us by the unfettered action of the natural processes of wind, water and ice.

As we celebrate and enjoy the abundance and diversity of vegetation and wildlife still present in the valley stop to ponder the fascinating Story Behind the Landscape.

Melt Down: Spring Thaw and Climate Change

By Patti Mason

After the spring equinox on March 20th, the days get longer and allow the earth in the northern hemisphere to absorb heat. The sun shines down on the peaks that rim our valley, defining the boundaries of the Flathead basin watershed. The snow which has accumulated in the watershed during the winter begins to melt and soak in. The ground becomes saturated and water flows off, drawn ever downward into our many creeks and rivers, to collect in Flathead Lake. The past journeys are reflected in the landscape of our valley, shaped through floods and shifting stream channels.

1964 Flooding of Flathead Valley

The weather in the spring has a great influence on this journey. In warm years, the snow melts rapidly and the rivers become full to overflowing. The waters rush across the floodplains, eroding unstable stream banks and carrying the muddy debris downstream. A warm rain falling on the snow can cause rapid melting and result in large scale flooding, such as happened here in 1964. Dramatic changes may be the result.

 

If the river is carrying too much sediment, it may divide into several channels separated by islands of deposited debris. Large islands may become vegetated and provide important wildlife habitat. This braided pattern is typical of the Flathead River in the upper valley.

Evergreen 1995 flooding

It may abandon some channels, only to take them up again a few years later, or create new channels. The river channel may shorten its path by cutting off a big bend and creating a “slough” or oxbow lake. There are many examples of this in the lower Flathead valley. Over time, the river moves back and forth across its valley.

 

Changing climate adds another dimension to the local pattern. Over the last two decades the average March temperature has increased almost 6 degrees F. This means spring thaw happens earlier, causing the runoff to peak earlier in the year. Summer temperatures are increasing too. By August, there is less and less snowpack left in the mountains to sustain rivers during hot dry times. Glaciers and snowfields in the mountains are disappearing year by year. These changes will also be reflected in our ever changing landscape.

References:
Steve Running, December 20, 2007, “Climate change in Montana,” Flathead Basin Commission meeting.

Learn more about the power of water at Flood Awareness Day, May 1, 2008.
Join in collecting important climate change data on the timing of leafing and flowering in your area through Project BudBurst! http://www.windows.ucar.edu/citizen_science/budburst/