the film forum library tutorial contact

Snowpack Affects Power Supply, Salmon Migration, Irrigation by Bill Roberts The Idaho Statesman, January 20, 2001

Eighty percent of Idaho's water falls from the sky as snow.

So when officials with the Natural Resources Conservation Service measure the snowpack each winter, they are really finding out how much water Idaho will have for irrigation, power generation and moving salmon downstream to the Pacific Ocean.

The conservation service looks at snow as water. But since snow contains lots of air, inches of snow don't equal inches of water. For example, Bogus Basin has about 40 inches of snow. But if you melted that down, it would be about 10 inches of water.

That's about 5 inches below where it should be, said Ron Abramovich, a water-supply specialist with the conservation service.

Up in the Clearwater Basin, the yield is about 13 inches of water. It should be about 35 inches.

The amount of snow that falls is important. But so is where it falls.

Snow that accumulates at lower elevations -- around 6,000 feet -- tends to melt and run off first. Snow in the higher elevations melts more slowly.

This year, the snow accumulation at lower elevations is about normal. But higher up, it is off by 40 percent.

That means the state could see strong flows of water in spring and early summer. But those flows may not be maintained, because the runoff from higher elevations will likely be less.

Many reservoirs' water levels below normal

Idaho's reservoirs are huge storage containers that capture snow melt and hold it for use through the summer. Water levels in many of Idaho's reservoirs are below normal for this time of year.

For example, Anderson Ranch, Arrowrock and Lucky Peak reservoirs are at about 82 percent of where they should be for January.

Little Wood and Mackay, around Blaine County, are at 53 percent of where they should be.

Some reservoirs are just about on target. Cascade Reservoir, for example, is at 99 percent of its expected level. But others, such as Lake Lowell, are at 87 percent.

That may not seem like much, but with the winter season about half over, it will take above-average precipitation for the remainder of the season to make up the 13 percent deficit in the reservoir outside of Nampa.