Spring Snowmelt Replenishes Alaska Aquifers

While taking the dogs on a run through the hills above Fairbanks recently, a severe thirst attacked me and I wasn't carrying any water. Although water puddled everywhere along the trail (and in my sneakers), I was afraid to drink any for fear of gulping down any organisms, such as Giardia. Giardia lambia is a microscopic organism that lives in the intestines of mammals and causes diarrhea and lethargy, sometimes for weeks or years.

Drinking untreated water is asking for trouble, even in the wildest areas of Alaska. If all our lakes, rivers and puddles are unsafe because of the parasites they may carry, where do we get all the gallons of fresh water we use every day to shower, wash our clothes, and quench our thirsts?

For an answer I biked to the University of Alaska Fairbanks' lower campus to see Larry Hinzman, an associate professor of water resources with the Institute of Northern Engineering.

Our safe drinking water comes from aquifers, which are underground layers of porous soil saturated with water, Hinzman said. Like wet blankets, aquifers follow the contour of the land. They may lie so close to the surface that shovel holes fill up with water; they may rest hundreds of yards below our feet.

Spring is an apt time to think about drinking water because that's when aquifers are replenished, Hinzman said. Interior Alaska is unique in that almost all of our groundwater recharge comes from melted snow. One might think that summer rains boost the water level within aquifers, but Hinzman said most of the rain evaporates or is used by plants.

Much of our drinking water originates on hill- and mountain-tops. Powered by gravity, snow that falls in high areas either runs off to rivers via creeks or migrates through the soil on a slower path to a river, the low point on a watershed.

Wells sunk near rivers show the impressive filtering ability of soil. Although Hinzman said he won't drink straight from the Chena River, he will drink water from a well near the Chena River. Silt, bacteria and other things not pleasant to ingest are strained out by soil as the water percolates from river to well.

Permafrost in Alaska soils is an "aquitard," Hinzman said. An aquitard, such as clay, doesn't allow groundwater to seep through. When a well is dug through large chunks of permafrost, water sometimes rushes up and shoots out the well hole like a fountain. This phenomenon, called an artesian well, happens in low areas as a result of the pressure from groundwater in the surrounding hills. With its impermeable bulk, permafrost can hold water under the level gravity wants to push it.

Artesian wells, named after a region in France called Artois where many such wells exist, can be a real problem. Unless controlled, the wells can flood lowlands until the pool they create matches the groundwater level in nearby hillsides. But artesian wells under less pressure also can be quite useful; the force of gravity sometimes provides a natural water pump to the surface, eliminating the need for a motorized pump.

Hinzman said he won't drink any water from Alaska's lakes, rivers or streams without either filtering it or boiling it to get rid of microscopic organisms that can make us sick. He drinks from a well, but even the earth isn't a fail-safe water filter, Hinzman said. Chlorine is often added to city well water to kill viruses, which are so small the soil can't filter them out. Although I'd love to drink from a stream like Daniel Boone, I'll stick to the inconvenience of a water bottle.