Understanding and Using River Gauges, Part 2

So let's say you are planning to paddle, and perhaps fish, a particular Ozark river, and you want to know what the water conditions are before you leave the house.  Back in the old days before the internet, your only real choice was to call one of the float outfitters or campgrounds along the river close to where you wanted to float and ask them.  But now we have this great resource in the U.S. Geological Survey's real time river gauges, where water flows and levels are updated (usually) every 15 minutes. 

However, it seems that most people don't really know how to use the gauges to their best advantage.  There is a wealth of information on them that is seldom utilized, even by avid anglers and paddlers.  Most people look at the level in feet, and then wonder what it really means, because unless you have floated the river many times under many different water conditions and made notes of what the level was after every time you floated it, you have no idea whether 2.2 feet on the gauge is high, low, or normal.  For the average person, that figure means nothing.  So let's run through how to really use the gauges.

I'm going to say for the purposes of this article that you are wanting to paddle or fish a river in the Ozarks of Missouri or Arkansas, but you can get to other states just by inserting the state abbreviation in the appropriate place on the web address.  For Missouri, the address is:  waterdata.usgs.gov/mo/nwis/rt.  For Arkansas: waterdata.usgs.gov/ar/nwis/rt.  This will bring you to the main state page:

From there, click on the Statewide Streamflow Table.  This will bring you to a listing of all real time gauges in the state, grouped by river system:

If you know which river system your river is in, you can scroll down until you reach that river system.  Most Missouri Ozark rivers are in the Osage (Niangua River being the most popular), Gasconade (Gasconade and Big Piney notably), Meramec (Meramec, Huzzah, Courtois, Big, Bourbeuse), St. Francis (St. Francis and Big Creek), Arkansas River (Elk and Big Sugar), and White (almost every other Ozark river, including Black, Current, and Eleven Point).

Then you find the gauge or gauges on the river you're interested in.  More about that in a bit...

I bookmark this page on my phone and computers, because in itself it gives you some of the most important information.  You'll note that on the right side of the table, there is a column for "Discharge, ft3/s" and one for "Long-term median flow (date)".  The discharge figure is what that stream is flowing right now, and the long-term median flow is a good approximation of what the normal flow for this time of year is for the stream at that gauge.  If those two figures aren't far apart, then the stream is near normal.  So if that's the case, this may be all the farther you need to delve into it; if the stream is near normal it's almost certainly good to paddle and fish.  But it is still best to click on the individual gauge, not only a gauge that appears to be close to the stretch you want to float, but also other gauges if there are any for that stream.  

So let's say you are interested in floating the Jacks Fork.  There are three Jacks Fork gauges, "near Mountain View", "at Alley Spring", and "at Eminence".  The order in which they appear on the table is the order of their locations on the stream, with the first one being the farthest upstream.  Here is what the top portion of the "near Mountain View" gauge page looks like:

Most people probably skip over this part of the page, but there are several useful features.  First of all, if you are not sure where the gauge is located--is it above where you plan to float, for instance--you click on the drop down menu at the top for "Available data for this site".  One option on the menu is "Location map", which will bring up a map showing the exact location of the gauge.  Second, under "Available Parameters" on the bottom left, you will see all the available pieces of information for this gauge.  Only the discharge and gage height are checked, which means only those two things are showing on down the page, but you can click on the other parameters, which show the water temperature and precipitation for this location.  Note that these two parameters are not available for all gauges, however.

The third feature that I often find useful is the begin date and end date on the lower right, which you can change to any dates.  By default it is set at the last seven days, but let's say you remember floating the river last year on a given weekend.  You remember what the river was like back then, and you want to know what the gauge height and flow was that weekend so you can compare those figures to the current ones.  You just change the dates in the boxes to a range that covers that weekend last year, click on GO, and it will change the graphs below to what the river was doing back then.

I was planning a float on the John Day River in Oregon earlier this summer.  The last time I'd floated the John Day was 20 years ago.  Back then I'd floated with my friend Corey Cottrell.  I couldn't remember exactly when we'd floated the river, but I thought he might so I called him.  Sure enough, he remembered because we'd been on the river over his birthday.  So I typed in a week back in 1999 that covered his birthdate, and found out that the river had been flowing around 400 cfs then, which turned out to be very useful in planning my recent trip.

If you scroll down the page, you will come to this portion--the meat of the gauge:

The graph for "Discharge, cubic feet per second" is what you want to be looking at first.  On it, the blue line shows what the stream has been doing the last seven days.  In this case you can see that it has been doing a lot of jumping up and down, because the area has gotten thunderstorms with a lot of rain almost every day.  Right now it's close to 200 cfs (the figures to the left edge of the graph).  You will also see small yellow triangles on the graph.  These triangles denote the median flow for each date.  Remember that the median is a good approximation of the normal flow.  So you can easily see that the stream is significantly higher than normal.  But how high is it, really?  Let's zoom in on the table below that graph:

You will see that the median--the normal flow for this date--is 35 cfs, and it's now flowing 194 cfs (Most Recent Instantaneous Value).  That's definitely a lot higher.  Now look at a couple other figures.  The 75th percentile figure is the flow which is higher than the stream has been 75% of the time on this date.  It's only 56 cfs.  So the stream is considerably higher than that.  Indeed, it's higher than the maximum for this date up to this point, which was set in 2011 at 69.5 cfs.  But you need to also look now at one other thing; "based on 17 water years of record".  That means that this gauge has only been recording data for 17 years.  The more years of record, the more accurate the figures on this table will be.  I like a gauge to have at least 10-15 years of record to have much confidence in the numbers like the 25th and 75th percentiles.  So I'm not sure whether a flow of 194 cfs is so high that it makes the stream too dangerous to float yet.  So I scroll down a little farther to see the gauge height, feet.  And I compare it to the Discharge graph:

Note that back on August 20 and 21, the Jacks Fork was pretty near normal, as you can see by how close it was to the little yellow triangles on those dates on the Discharge graph.  So look at the gauge height it was then--about 1.3 feet.  Now look at its present gage height--about 2.3 feet.  This tells me that it is a foot higher than normal.  A foot isn't really too significant a rise on an Ozark stream.

So to summarize, I now know the Jacks Fork near Mountain View, which is considered the upper Jacks Fork (the gauge is at the Highway 17 bridge and the Buck Hollow Access) is about a foot above normal, with normal for this time of year being about 35 cfs.