River’s High Runoff Keeps Scientists Awash In Data Cramble To Get Measurements Plays Role In River’s Restoration

Surf’s up on the Coeur d’Alene River.

Limbs, leaves and the odd plastic bottle swirl past. Trees hide their roots in chocolate water. Winter rains have made the river rise so fast that, upstream of here on the North Fork, some river dwellers slept elsewhere Wednesday night.

The same surge that brings fear of flooding also carries scientific opportunity. High runoff is a good time to gather information that can guide restoration of a polluted river basin.

From the deck of the Rose Lake bridge, Kevin Kirlin cranks with both hands on the handle of a small wheeled crane. It pulls up a cable that dangles into the rushing water. At the end of the cable is a gadget that looks like a tiny torpedo with a silver propeller.

Kirlin works for U.S. Geological Survey. He and Mike Childress were on the bridge Thursday, fishing for answers.

How much water is flowing past? How fast is it moving?

The answers, in cubic feet per second, come from that clicking, whirling meter that’s lowered into the river at 30 places, each 10 feet across.

The measurements must be taken every six to eight weeks because the river’s dimensions change constantly. The information is used to fine-tune the automatic streamflow gauges that are housed in round shacks at such places as Rose Lake, Cataldo and Enaville.

The Geological Survey crew scrambles to come out during high runoff because they have another, non-routine assignment: Take samples to find out how much sediment the water is carrying.

Those fine particles of dirt often carry toxic wastes from a century of mining.

Ninety percent of the pollution carried into Lake Coeur d’Alene each year could be swept downstream in two or three high-runoff episodes, said Mike Beckwith of the Geological Survey.

“If you do sampling on a monthly basis, you could miss those entirely.”

One episode that nobody wanted to miss occurred two months ago. It was what hydrologists call a “rain-on-snow event,” which results from rain hitting mountain snow that’s already saturated. The water has no place to go but into the streams. It goes there quickly, carrying dirt and rocks it picks up along the way.

The effect can be especially dramatic in the Coeur d’Alene watershed, where clearcut logging has left unprotected slopes and a maze of dirt roads.

The natural drama is enough to make scientists grab their instruments and head out at dawn to document what’s happening.

Rain-on-snow events are “very ephemeral, difficult to catch,” said Geoff Harvey of the Idaho Division of Environmental Quality. “Invariably, they peak in the middle of night in the upper watershed.”

They’re also unusual.

“This last one was the first substantive one we had since November of 1990,” said Harvey. “It came up and was gone in a day.”On Nov. 30, 1994, the water was moving at 900 cubic feet per second past Cataldo at 3 p.m. At noon the next day, it peaked at 11 times that amount: 10,500 cfs.In comparison, last week’s nine-fold increase took three days. The flow rose from 1,400 to 13,400 cfs.

Like the Geological Survey crew, state scientists were eager to take water samples during the rain-on-snow event. They’re monitoring pollution for two years.

“We’re looking for metals concentration, which is directly related to how much water is in the stream,” Harvey said.

The federal and state studies will help document not only the extent of pollution, but where it’s entering the river, where it’s deposited along the riverbanks, and when it enters the lake. That may guide some multimillion dollar decisions about where and whether to stabilize banks and dredge up sediment.