I was looking at the gauges and noticed a 20 CFS jump overnight in a river that is normally very stable with no precipitation or snow melt in the prior week.
The river I am looking at is a narrow river, and a 20CFS jump means a 4" change in depth.
Does sub freezing temperatures effect the gauge even though the river is not frozen (not even ice sheets)?
Something may have gotten into the
gauge housing, and then washed out, causing a sudden change.
I follow a number of gauges, and some of the baseline readings don’t make sense.
Sometimes there will be an indication that the gauge was checked and recalibrated, accompanied by a step change. Sometimes I think they just reset it and forget it.
Are there nearby dams? Towns?
– Last Updated: Dec-28-14 3:38 PM EST –
EZ's idea that the calibration of the gauge was changed seems like a good possibility, and maybe the float could have gotten stuck too (I think that's what he was talking about regarding something being in the housing, since there'd be no way for any river-borne junk to plug it so thoroughly that the water level inside didn't exactly match that of the river). Otherwise, could there be changes in controlled flow through a dam, either upstream or downstream of the gauge? I see that a lot on some of our rivers here. A change in gate settings on a dam will cause a sudden, obvious change in flow quite far from the dam.
Sewage plants can have a cyclic effect on water levels in a small river. We have a little creek here that carries the output of the area's sewage-treatment plant, and for that reason the creek's flow varies on a daily cycle by about 20 CFS. However, that only translates to about 1.5 inches in elevation change on this little creek, which makes me realize that the creek you describe might be smaller, making it even more likely that you would have noticed some of these human-associated level changes before.
the river is about 25’ wide at gauge
and the closest Corps of Engineers dam is 45 miles upriver which leaks at a consistent 44cfs year round, the river is hovering around 60.