2017 Hydrology Project Report

2017 was, with one exception, a rather dull year regarding hydrology events in Carroll Cave.  Two major floods were recorded along with one minor flood.

The major floods occurred on 29 April and 5 May.  In both cases Thunder River rose to a bit over 20 feet.  This is not the highest level we have seen, but it is not far from it.  A minor flood occurred on 6 August with Thunder River rising to just under 3 feet.  Otherwise the stream level was normal for the whole year.

The data for the logger in Carroll River shows an interesting anomaly.  The data shows a negative water depth for the early part of May, right after the major flood went through.  I happened to be in the cave on May 13 and visited the area.  According to my trip report, the stilling well was completely out of the water.  I had to put it back.  The data makes it obvious that I did not get it back exactly where it was.  There is a slight offset between the nominal stream levels before and after the flood event.

The rain gauge logger continues to give me fits.  It did not collect any data for 2016 at all, probably because of a mistake that I made in launching it suring the service trip in January 2016.  It collected data from the logger service trip on 28 January 2017 through the trip in late October.  During our service trip on 6 January 2018 I was unable to download any data from the logger.

There is no way to get around that.  I installed a new battery which always erases whatever data is on the logger.  We lost anything it might have collected from the end of October to early January.  Fortunately there wre few if any rain events during those two months.  When I got home, I checked the old battery and found it was low.  It was not dead, but it was rather low.  In the past the rain gauge logger battery has lasted a full year with no problem.  I don’t know why it went flat this time.  Perhaps the battery was not completely fresh back in January??

Rick Hines has an interesting hypothesis.  He thinks the cave floods from downstream Thunder to upstream.  We have always assumed that the floods start in upstream Thunder River and flow down to the Lake Room.  As part of the data logger service trip on 6 January 2018 we installed a new data logger a few hundred feet downstream from Thunder Falls.  By examining the time stamps on flood events we can determine if Rick’s hypothesis is correct.

There is some more work to do on the new stilling well.  My long hammer drill bit lost all of its carbide tips, with result that we got only one hole in the bedrock to anchor the stilling well.  Also, the collar for the top anchors was broken when I lowered it into the cave.  I need to use a different method to attach the top anchor wires.  That will be done the next time I go in the cave.

This post has an attached ZIP file which contains all of the data for 2017.  There are three kinds of files in the ZIP.  Files with .hobo extension are the raw downloads from the data loggers.  To examine these file you need a copy of HoboWare.  There is a free version of HoboWare on the vendor’s Web site http://www.onsetcomp.com.

The CSV files were created by opening the raw data files in HoboWare, then exporting to CSV.  I trimmed them to remove data from 2016 and 2018.  The JPG files are the resulting graphs of the data.

For 2018 I plan to replace the battery in the rain gauge logger sometime around the middle of the year.  That should allow us toget a full year f data.

Bill Gee


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