Glacial retreat affects river flows and aquifers

Study tracks underground flows of water from melting ice

Alaska’s Susitna Glacier revealed some of its long, grinding journey when the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite passed overhead on Aug. 27, 2009. Photo via NASA Earth Observatory.

Staff Report

Glaciers are not only important sources of surface water, they also help recharge  aquifers as they melt. That role in replenishing underground water reservoirs has been quantified in a new study published recently in Geophysical Research Letters, a journal of the American Geophysical Union.

The research was done in Alaska, where both scientists and residents are reporting increased river discharges in summer and winter. The changes in flowes have implications on river travel throughout the year and impact sea ice growth and nutrient exports to Arctic Ocean coastal waters.

The research shows that melting glaciers are bolstering river flows in the winter even without any extra rain or snow. The University of Alaska Fairbanks explained the findings in a press release. Previous research may have underestimated the role of glaciers as sources of water to the landscape, according to Anna Liljedahl, the lead author and an associate professor at the University of Alaska Fairbanks’ Water and Environmental Research Center.

The scientists focused on a watershed in the semi-arid eastern Alaska Range, tracing how glacial meltwater flowed through the system and influenced the mountain streams, rivers and groundwater all year long.

“These headwater streams, coming off the mountains and into the lowland, are like the water line to your house peppered with holes, half of the water disappearing into the ground and recharging your neighbor’s house well instead of it all reaching your kitchen faucet,” said Liljedahl.

Liljedahl said the recharge of the aquifers is important because they don’t freeze during the winter and are the only source of water to the rivers during this time.

“The winter discharge of the Tanana River has increased since the record keeping began in the ’70s, but there are no increasing trends in precipitation,” she said. “Glacier coverage has, on the other hand, decreased by 12 percent, and that is more than plenty of additional water to explain the increase in river base flow. In fact, about five times more.”

But it may not be long before this process ends all together, she said. The glaciers are disappearing or shrinking to very high elevations where colder temperatures slow melting. As glacier melt decreases, so may the stream flow if there is not enough water to both feed both the aquifer and the stream.



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