Hydrologist David Evetts drove north from his office in Boise, Idaho, to the former prospecting town of Elk City on May 2. Fifty miles down a dead-end mountain road, he stopped at a gray metal box on a bridge over the South Fork Clearwater River. Reaching inside, he turned off the satellite feed that once relayed the river's water-level measurements from stream gauge number 13337500 every 15 minutes.

"You almost want to say a prayer and wish it well," says Evetts, who works for the U.S. Geological Survey. The gauge, which had operated for nearly 42 years, is one of two in Idaho that had to be shut down when the USGS took a 5 percent funding cut as part of the federal sequester.

The USGS operates some 7,000 stream gauges across the country, used by 850 other organizations for everything from watershed research to bridge design to water supply predictions. Each gauge costs around $14,000 to $18,000 to operate annually, and the budget cuts have jeopardized about 375. The most imperiled are marked with red stars on the agency's Threatened and Endangered Stations website. About 40 have already been shut down, their stars turning black as they blink out.

A stable network of gauges is valuable for water-supply forecasting because the data tie computer models to reality. Since stream flow and snowpack are both part of that forecast, "if you take away one part you don't have a complete picture," says Mike Strobel, director of the U.S. Department of Agriculture National Water and Climate Center.

It's not the first time the existence of hundreds of USGS stream gauges has been threatened, since many also depend on fluctuating funding from both state and federal partners. But sequestration is even hitting the USGS National Stream Flow Information Program, which is meant to protect hydrology's most important gauges, like number 13337500.

The Elk City gauge earned its spot in the program because the National Weather Service used its data for flood forecasting in the Clearwater River Basin, which includes the city of Lewiston. The gauge was just beginning to be useful for climate research, where 30 years of data is barely enough to measure trends, and it was high in a watershed without dams or diversions, providing a rare window on natural peaks and flows.

For those reasons, it was one of 520 "sentinel gauges" nationwide, which help answer questions such as whether snow is melting faster each spring. The Nez Perce Tribe also used the gauge moniter fish habitat.

There was much debate over which Idaho gauges to ax, says Evetts. Sacrificing the Elk City gauge saved others that were even older, or that were important for divvying up water, forecasting floods or managing larger fisheries.

Other gauges have narrowly missed death by sequestration. In eastern Montana, an 85-year-old gauge on the Yellowstone River was on budgetary life support until mid-May. Occasionally flood-prone Miles City appreciated the gauge so much that during the mid-'70s, nearly every time USGS technician Mel White checked it, the local news covered the event. The morning it was turned off, state support came through at the last second, and White called the technician while still in the field to ask her to go back and revive the gauge.

Evetts hopes other fallen stream sentinels will somehow get a second chance too. "When that information is available to you, you become reliant on it. When it's taken away, you suddenly have a void and feel less secure."