Thursday, May 26, 2011

Great Salt Lake Seiche and Runoff Rise

One of my graduate students, Trevor Alcott, noticed this morning that there was a remarkable seiche on the Great Salt Lake thanks to the overnight cold-frontal passage. A seiche is a temporary rise (or fall) in lake level that can be caused by strong winds, earthquakes, and other phenomenon.

At the Saline USGS lake-level observing site, which is located on Promontory Point and in the north arm of the lake, the lake-level averaged about 4196.2 feet from 19–24 May.  On the 25th, however, the lake-level decreased gradually, followed by a rapid spike to 4197.7 feet early in the morning on the 26th (today).  

Source: USGS.  Times appear to be MST or MDT.
Why did this happen?  Note the persistent easterly flow during the day at Gunnison Island, which veered slightly to SE with the approach of the front at roughly midnight MDT.  During this period, the lake-level at Saline decreased as the wind transported water to the western side of the Great Salt Lake.

After midnight, the front passed and the winds shifted rapidly to NW–N, with a gust of as high as 45 mph at 1 am MDT.  As a result, water "sloshed" rapidly across the Great Salt Lake and the lake-level spiked rapidly at Saline.

Following the spike, the lake-level oscillates, which is consistent with a sloshing of water back and forth across the lake.  An industrious student could easily calculate the period and speed of this wave as it moves back and forth across the lake.  

Looking at a longer time scale, the elevation of the Great Salt Lake at the Saltair Boat Harbor has increased almost 3 feet since January.  And the runoff is just getting started! 

Source: USGS
We're still in the lower half of the historic range of the GSL, which is about 4192–4212 feet, so let the restoration project continue!  

1 comment:

  1. Events like this happen more often than you may think.
    I have data but have not yet published. Lance