Posted by: mrmannerz on Jan-06-13 7:41 PM (EST)
I rode along with the USGS guys to check the NF Stillaguamish gauge (western Washington). Every 6 weeks they have to verify it by checking the simple meter stick measurement against the fancy stuff. The realtime gauge uses a tank of nitrogen (housed in a 1930's concrete tower built for the gauge) that pushes a bubble once a minute or so through a submerged tube into the river. The gauge measures the back pressure to determine the river level. The data is transmitted wireless.
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