Simplified Version of Using the USGS River Gauges

 In another article here, I wrote a very detailed version of how to get all the information that you can possibly use from the US Geological Survey river gauges.  This will serve as the simplified version for those just starting out to use these gauges.

There are a lot of apps available these days for checking river levels, but they all get their info from the USGS gauges, and none of them that I've found have enough information to be as useful as the "real thing".  The USGS gauge pages are not as user friendly as the apps, and there is a learning curve to using them.  But the site is free, as is all the information in it, and once you get accustomed to using it, you will find it to be reasonably easy to get the info you want.  

First, what CAN you glean from the river gauges?  Most people who use them do so to check water levels and at most to see what the river has been doing for the last few days.  But if you know what to look for, you can find out exactly what the river is flowing and what it should normally be flowing, so you'll know whether it is higher or lower than normal.  You can see whether it has had a rise in the last few days, and if so how high that rise was and how fast it has been dropping.  Then, with remembering a few simple "rules of thumb", you can tell whether the river has enough water to float, whether it has too much water to float, what the river conditions will be, and even make a good guess on how clear or muddy it might be.  So here is how to begin to use the gauges.

The first step is to find the gauges on the internet.  For Missouri, the site is:

waterdata.usgs.gov/state/Missouri

Whatever state you are looking for, you just switch from Missouri to your state.

This should bring you to the opening page for Missouri.  On your smart phone, it will look like this:

From here you can go to other states if you wish, but otherwise just scroll down a bit on this page, and you will find a map of Missouri showing the streams of the state and all the gauges and their location:

This is one of the things which makes the USGS site less user friendly than the apps.  Since the streams aren't labeled, and neither are the counties, you need to know your geography to pick the gauges you want.  There are other ways to find the gauges, but they are even more cumbersome.  There is no search feature that I can find.  When you get to this map, you have to guess at where your gauge is, and click on gauges in that area until it comes up.  Your only other choice at this point is to set up a Favorites page with all the gauges you typically check, which in itself is cumbersome.  And if you're like me, you might be interested in gauges on streams all over the state, so your Favorites ends up being 75 gauges that you have to scroll through to find what you want.  I just wrote, again, to the USGS in their comments section to plead with them to fix this.

But this map does give you SOME instant information.  The colors of the gauges show whether that gauge is below or above normal flow. You can find a legend showing what the colors signify if you scroll down a bit farther below the map.

So you can zoom in with two fingers on the map (on your phone) to get to the area you want to check.  I'm zooming in on the Jacks Fork (fortunately, I've studied Ozark rivers long enough to know where they are on a map):

Here you can see the three gauges on the Jacks Fork (as well as the two on upper Current River above the Jacks Fork).  I'll click on the most upstream gauge on the Jacks Fork:

Now it gives you the name of the gauge, while showing with an orange circle that you've selected it.  It also gives you the present flow in cubic feet per second (82.7) and shows that this flow is in the normal range.  If you're sure that's the gauge you want, and if knowing the present flow in cfs isn't enough information, you click on the "View Monitoring location page".  This will take you to the actual page for the gauge, with all the information you might need:

This is the top of the page.  It does give you a choice of showing the past information on the graph below for 7 days (the default setting), 30 days, or 1 year.  The others can be interesting but all you need is the 7 day graph.  So leave it at 7 days, and scroll down the page to the graph:

This is the graph for what the river has done in the last 7 days, as far as the level in feet.  For the purposes of figuring out exactly what the conditions are now, it has limited use unless the river has recently had a rise.  Here, it shows that there was a rise a few days ago, but you have to look at the increments on the left side of the graph.  Note that they are fractions of a foot, not feet, so this rise happened to only be an inch or so, completely insignificant.  Otherwise the river has been steadily dropping.  If there was a real rise, it would look like this graph for upper Big River during this same time period:

Note that on this graph, the increments on the left are in feet, not fractions of a foot.  So you know that the river rose several feet at least.  Now note that there is a slider bar at the bottom of the graph.  The vertical line on the slider bar is ordinarily at the right end of the graph, showing the present level.  But you can slide it to the peak of the rise, and it will give you the level in feet across the upper part of the graph.  You can see here that the peak of the rise was 11.42 feet on the gauge.  Now I'll slide the bar over to a point before the rise began:

You can see that the river was at around 2.74 feet before the rise.  Do the math and it shows the river rose 8.68 feet.

The number of feet of rise is important.  We will discuss why later in the article.  But this tells us nothing about what river conditions are now except that it is dropping rather quickly after the peak of the rise a day and a half ago.  So after noting the rise in feet, we need to scroll down, because we are looking for a graph for the flow (discharge) in cubic feet per second.   Moving back to my Jacks Fork gauge page, by scrolling down, we come to this screen area:

You can see a "graph it" button to for "Discharge, cubic feet per second".  When you click on it, the screen changes to this:

There is one more important button to click; "Median day of year statistics--indication of normal levels". Clicking it and then scrolling back up to the graph, it will have changed to this:

It's now showing the discharge in cubic feet per second instead of the level in feet, and the series of horizontal gray lines show the median flow for each day.  So you can quickly tell how close the river is to normal for the time period--in this case, it has been above normal for the last 7 days.  

This is the real meat of the gauge, but there is one more thing to click on; "Show today's statistics".  Doing so will give you the exact figures for the date:

Note that it gives you the median, 25th (percentile), 75th (percentile), low, mean, and high.  The median is the flow at which 50% of the time the river has been flowing more water on this date, and 50% of the time less water.  It is the best approximation of normal flow for the date.  The mean is the average of all flows, and is actually useless for our purposes, because it is skewed upwards by the fact that any significant floods that have happened on this date are far higher than normal than the low flows are lower than normal.  At least one of the apps you can get shows the mean, none show the median, which is the MOST useful of these pieces of information.

The high is the highest flow ever recorded for this date, the low is the lowest ever recorded.  The 25th is the percentile at which 25% of the flows for the date were lower, and 75% higher.  The 75th is the percentile at which 75% of the flows were lower, 25% higher.  The USGS uses these two figures as the upper and lower limits of what is considered normal flow for the date.

Now you have all the information you need.  You have the present level in feet, and discharge in cubic feet per second.  You know if there has been a rise, and if so how high it was and how long ago it was, as well as how fast the river seems to be dropping.  You know the median flow for this date and that it is a good approximation of normal, so you know whether the river is low, high or close to normal.  So now you can put everything together as long as you remember the following rules of thumb:

1.  If the river may be low, and you need to know if it is too low to be floatable without a lot of dragging boats and scraping bottom, remember one key number--100 cubic feet per second.  On any stream in the Ozarks that can get too low for easy floating, 100 cfs is the absolute minimum for floating without a lot of dragging and scraping.  In our upper Jacks Fork example, the river is flowing 82.7 cfs and dropping, so you instantly know that if you float it, you're going to have to do some walking and you'll be scraping bottom a lot.  Note that you can also figure that anything under 50 cfs and there will be very few riffles that you can float cleanly and you'll be walking a lot of them.  Anything over 150 cfs and you'll have pretty easy floating unless you are terrible at reading water.  

Also, note that the median is only 45 cfs.  That tells you that the river here is NORMALLY too low to float this time of year.  A median of well over 100 cfs would tell you that it is normally floatable.

2.  If the river has had a rise and you want to know if it is still to high to float safely, a general rule of thumb is that a rise of less than one foot is generally not a problem; the river will be only a little bigger and faster than normal, and will probably still be fairly clear.  A rise of 1-2 feet, and it will be considerably faster and heavier water.  The consequences of mistakes can be more severe, and inexperienced paddlers should avoid it with that kind of rise, or at least float with other experienced paddlers who can guide them through the dangers.  The river will probably be murky and may be muddy.  A rise of 2-3 feet means very heavy current, with the consequences of mistakes possibly life-threatening; ONLY paddlers well equipped and experienced in such water should be on the river in these conditions.  The river will be muddy and may have some debris in it.  Over 3 feet of rise, and it should be off-limits to everyone.

Those simple rules of thumb should serve you well in understanding the gauges and knowing how to interpret the information.  There is a lot of other information to be found on the gauge pages, which I go into in the other river gauge article on this site.  But this will be enough to get you the information you usually need.