Available Technology

A Cost Effective Instrument for Measuring River Height and Snow Depth

The iGage is a low-cost, portable, rapidly deployable sonar instrument for providing river stage and snow depth information.  Developed by NOAA for remote field use in Alaska, the iGage is lightweight, durable, and compact, measuring just 5” x 7” x 3”.  The device is solar-powered so it requires no existing site power and can be boom-mounted to a variety of fixed platforms. 

The iGage’s acoustic sensor measures the distance to the water or snow to determine the level. The commercial-off-the-shelf (COTS) sensor and iridium modem allow for easy maintenance and replacement.  These components are combined with a proprietary circuit board that couples and controls the two components and provides for global telemetry coverage.

The iGage accuracy is approximately one percent of the distance measured, so a sensor mounted on a bridge 20 feet above the river’s surface would be accurate within two and a half inches. While not precise enough to meet USGS standards, the iGage does provide valuable river stage information at locations that lack real time data and at sites with only one daily observation.  For flood monitoring and forecasting there are many locations that can benefit from a lower cost, albeit less accurate device.

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