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HomeNL-2009-09 USGS Water Gauges

USGS Water Gauges
by John Rich

This article will describe how to use the USGS online web site to view information from water gauges, which record data about stream conditions for a wide variety of lakes, rivers and creeks, all over America.

First of all, I guess we should start by defining what "USGS" stands for. "USGS" is the United States Geological Survey. The word "geological" usually refers to the science that deals with the history of the earth and its life, especially as recorded in rocks. But this government agency deals with far more than just rocks. Here's how they describe themselves:

"An unbiased, multi-disciplinary science organization that focuses on biology, geography, geology, geospatial information, and water, we are dedicated to the timely, relevant, and impartial study of the landscape, our natural resources, and the natural hazards that threaten us."
 
As paddlers, we are mostly interested in the water data from that web site. You can begin to access that wealth of information from their home page, starting here: waterdata.usgs.gov This particular web page focuses on the "water" part of their mission, and contains the information useful to canoeists.

(You can click on the following thumbnail images to display a full-screen version in a separate window.)
 
 
  USGS National
Water Data
From this "water" home page, click on "Water Data, Real-Time Data" in the upper left, for current stream conditions across America. You'll be presented with a map of the U.S., covered in little dots. The color of the dots represents the water level status, from high to low. These can be interesting. For example: since a red dot represents a low water level, when you see a cluster of red dots, that tells you that this geographic area has had less than normal rainfall. From here, click on a particular state to zoom in on the daily streamflow conditions for all the USGS water gauges in that state. 
 
 
  USGS Texas
Water Data
With the state map, you can now click on a dot to see data from a specific stream gauge. But odds are, the dots are too close together to differentiate the one you want. And the only identifying information displayed when you move your cursor over a dot, is the gauge number, which doesn't tell you which stream it represents. So instead of hunting and pecking through a bunch of colored dots trying to find the one you want, click on "Statewide Streamflow Table" in the upper right of the screen, to produce a tabular list of every USGS gauge in Texas - all 486 of them.
 
In the future, if you want to skip all those steps you've taken to get to this point, you can just click this web site: Statewide Streamflow Table, and bookmark it in your web browser as a "favorite" so that you can come back directly to this page as a starting point, any time you wish.

 
  USGS River Basins
Notice in the dark blue boxes at the top that the standard sorted order of this display is by "Major River Basin". This order is difficult to work with when searching for data on a specific stream, because a "river basin" can include many different streams, all mixed in together in the list. It will include a major river, along with all the smaller tributaries which feed into it.

So, to better isolate the data you want, on the bar at the top, you can change the way the list is ordered, by:

• Major river basin (the default)
• County
• Hydrologic Unit (i.e. stream)

To get around the difficulty of grouping by river basin, change the "Group table by"
box to "County", and click "Go".

 
 
USGS Texas Counties

Here's a sample of the stream list when done by county. The sequence you get here is alphabetic by county, then by numeric station number. Generally, the station numbers are designed to cluster those on the same stream together. So, for example, the stations on Buffalo Bayou are all together, and not scattered amongst other streams. But that's not always true. You can use the search button on your web browser (Ctrl-F) to do a keyword search on this table. This is a great way to see what's happening all over in your county of interest.

The drawback to this is that a stream can span multiple counties, therefore the data for that stream is fragmented in many places. So if your interest is in a particular multi-county stream, you don't get the whole picture in one place. For example, Houston's Buffalo Bayou has four gauges in Harris County, and two in Fort Bend County. The Neches River has six gauges in five counties. And the Brazos River has 20 gauges in 16 counties.

But there is a solution to this fragmentation! Go back to the box at the top and select a group list by "no grouping", and then under "Select sites by number or name", type in the name of the stream you're looking for. In the previous example we had the Brazos River spread across 16 counties. But by selecting "no grouping" and "Brazos River", we get all 20 Brazos River gauges in one short list. And, best of all, the order is by the numeric "station number", which is designed to arrange them in order from upstream to downstream. Now we've got something really useful for canoeing!

 
  List of Buffalo
Bayou gauges
Here is a close-to-home example of this: Buffalo Bayou has six gauges, listed in order from where it starts in the Katy prairie, all the way to downtown Houston. If you're starting at Highway 6 at the Addicks dam, you can see the water conditions there, and at every point downstream through which you will pass. You can then click on individual station numbers to see graphs of the current conditions, as well as the recent trend, for up to the last 60 days. This is good planning information.

The standard two graphs that are available for viewing at every water gauge station, are "Discharge" and "Gauge Height".

 
 
CFS discharge chart
 
"Discharge" is the flow rate of the water, measured in cubic feet per second, or CFS.  This is sometimes designated mathematically as "ft3/s" - feet cubed per second. CFS is a common way to indicate the volume of water moving past the station point. Of course, since streams vary in width, a particular number doesn't mean much to you unless you have a frame of reference. 1,000 CFS on a wide river like the Brazos might be fairly tame, because the flow is spread over a large area. But the same 1,000 CFS on the narrow Buffalo Bayou would be terrifying, because it's concentrated in a narrow channel. So the CFS number alone doesn't mean much. You have to know how that relates to actual river conditions. And you get that from watching and observing over time, or from reports from others. Then you can match up the current CFS reading with your knowledge of past readings and conditions, to determine if that's a river condition that you want to enter.

 
 
Gauge height chart

"Gauge Height", is the water depth, measured in feet. Things are a little confusing here for me. Sometimes the height seems to be a number that represents height above sea level. In other cases it seems to represent actual water depth at that point. If you look at that last Buffalo Bayou example, the height starts in Katy at 22 feet, then goes to Fulshear at 90 feet, and finally works it's way downhill to downtown Houston at 1.9 feet. Now I'm quite certain that the Buffalo Bayou doesn't flow uphill 68 feet between Katy and Fulshear, that it's not 90-feet deep at one point, and that downtown Houston is more than 1.9 feet above sea level, and also more than 1.9 feet deep.

Here is what the USGS has to say about this mystery:
 
"Gage height (also known as stage) is the height of the water in the stream above a reference point. Gage height refers to the elevation of the water surface in the specific pool at the streamgaging station, not along the entire stream. Gage height also does not refer to the depth of the stream."
 
That's clear as mud now, eh? So this gauge height number may not mean much in absolute terms. Use these as reference points for past observed conditions, in order to understand the current conditions in which you are considering paddling.
 
For example, I know from experience that if the Lake Charlotte gauge says 8 feet, the water level is going to be too low to paddle through the mangrove trees. If it says 11 feet, I'll make it okay. That's a bit of fact that I have in my brain from personally paddling on Lake Charlotte in different conditions. Whether or not the water was actually that many feet deep at the gauge, doesn't really matter. What matters is that it tells me what to expect on the lake, and how navigable the surrounding water is.
 
Some gauges will also have additional information, like water temperature, precipitation, and specific conductance in microsiemens per centimeter. That last one must be mighty important to someone!
 
Now that you know how to look at the online water data generated from these magic gauges, let's see what an actual physical water gauge station looks like.
 
 
 
Joe & Ken observe the
Lake Charlotte gauge
 
This gauge is mounted on pillars at the south end of Lake Charlotte, which is about an hour east of Houston near the Trinity River. Most of the gauges contain certain common elements:
  • A large metal box, about 5-feet square and 8-feet high, containing instruments and batteries. These are mounted above the flood stage level, to protect the instruments. Pipes running down to the water to take the readings.
  • A solar panel on top to keep the batteries charged.
  • A dome receiving antennae, to pick-up control commands from a home office.
  • A transmitting antennae, to transmit data to a collection station.
The real-time data is typically recorded at 15-60 minute intervals, stored on site, and then transmitted to USGS offices every 1 to 4 hours, depending on the data relay technique used. Data from the real-time sites are relayed to USGS offices via satellite, telephone, and/or radio and are available for viewing online via the internet within minutes of arrival. Recording and transmission times may be more frequent during critical events, such as hurricanes which may produce flooding.
 
 
 
The Bear Creek
gauge in Addicks
 
The location descriptions are sometimes not very exact. This example, just a block from my home, says simply "near Addicks". But Addicks is a large place, and contains a number of creeks, like Langham, Bear and Southmayde Creeks. This may cause you some confusion. I never realized exactly where this gauge was, until one day when I was hiking along Bear Creek, and came up on the USGS box at Clay Road, just west of Barker-Cypress Road. It had all the tell-tale features, and a sign on the door identifying it as a "stream flow measuring station". The antennae and such are mounted on the poles projecting upward from the roof, and are out of frame in this photo. I had driven past this station a thousand times before and never paid it any notice. 
 
 
 
Skip paddles by the
Johnson Ranch gauge
on the Rio Grande River

Some gauges are more scenic than others. This one is on the top of a cliff over the Rio Grande River, in Big Bend National Park. Located next to the gauge is a steel cage that can be used to ride across the river on a cable. Note that these are fully autonomous units, requiring no power lines. You often find them in the middle of nowhere, far from any kind of infrastructure.
 
You might have noticed on that first USA map that the USGS doesn't seem to have any gauges in west Texas. They don't cover some rivers, like the Rio Grande, Pecos or Devil's. The Rio Grande River which comprises the border with Mexico, and other Texas rivers which flow into the Rio Grande, are monitored by the International Boundary and Water Commission, or IBWC. This organization, with participation from both countries, administers international treaties between the U.S. and Mexico on water usage, water quality and flood control for the Rio Grande River, to ensure that there is enough for everyone on both sides of the border. The gauge readings for the IBWC gauges can be found at: http://www.ibwc.state.gov/wad/flowdata.htm. Their flow rate numbers are in cubic meters (CMS) rather than cubic feet per second. A handy conversion calculator can be found here: www.convertunits.com. For quick rule-of-thumb conversions, just remember that it takes 35 CFS to make 1 CMS.
 
I will save details of that IBWC system for another story on another day, as this one is already too long...
 
 
 
Natalie models the
Terlingua Creek gauge
in Big Bend National Park

With these magic boxes sprinkled all over America, we canoeists can sit in the comfort of our homes, on the internet, and monitor water conditions nearly anywhere in America. This is a great planning tool for anticipated trips, and for learning about the behavior of the streams and lakes upon which you paddle.
 
There are warnings and complications about how to use and interpret this data, for sure. You need reference points to understand the stream conditions. Beware of delays. For example, thunderstorms far upstream may take several days to flow down to where you are - watch the gauges at several points upstream to detect what might be coming your way. Sometimes gauges get clogged up with sediment and don't read true conditions, or the stream will change course by meandering away from the gauge thereby giving readings that don't really reflect actual conditions.
 
On the good side, you can see spikes from rainstorms, and how long it takes those high water levels to subside. You can find out whether the water level is rising or falling, so as to expect things to be growing better or worse. Pay attention to the water level and CFS reports from others, so that you can equate what they've described in their conditions, to what you expect to encounter on your trip. This can allow you to predict if there is too little water for the trip, if the water will be moving nicely for a fun, easy trip, or if the water will be too violent and it's best to stay out of it at your skill level.
 
There's a lot of useful data here. But back it up with personal observation or eyewitness accounts, such as from people who have paddled the stream in the past, and residents or outfitters in the area. Use the data - you've paid for it with your tax dollars, and it's there to help you have a safe and enjoyable canoe experience.



The author, John Rich