In a recent article I quoted river levels, rising and falling trends, temperatures, water clarity, and the relationships between two major and several smaller tributaries in the stretch of the Potomac that I fish, all in concrete numbers and all for exact times of the day and night. A friend read the report and asked me a simple question: “How the hell did you know all that?” For him, of course, I just smiled inscrutably and let the impression flourish that I had some mystical connection with the river gods. More like Rivergods.gov, better known as the United States Geological Survey.
If information is only as valuable and useful as it is easy to obtain, the USGS Real-time Streamflow World Wide Web page is the ultimate source of information for river anglers. With a bit of practice and some background, this resource can revolutionize what you know about river fishing, and, I suppose, squirrels. Oh, and it can save your life.
http://water.usgs.gov/realtime.html
Stream gaging is a major activity for the government. (‘Gage’ is a variation of ‘gauge’.) Next time you hear someone disparage the value of government, remind them of what every citizen should know: there are 7,992 stream-gaging stations maintained by the USGS and subsidiary state and local government agencies. That means that at 7,992 points on American waterways--rivers, creeks, and a few reservoirs--a mechanical device measures the water level and transmits it regularly to the proper authorities, and, through them, to you. (For particular information on the nature of these devices or any other information regarding the stream gaging program, consult my primary source: circular 1123 of the USGS at http://water.usgs.gov/ pubs/circ1123/). What’s really cool about this system is the satellite uplink. Anybody with any sense can go to the river and judge its suitability for fishing or wading, but in these fast modern times to be able to access the river levels--here, there, and everywhere, where they’ve been and where they’re going--is an invaluable resource for an angler.
A bit of history and purpose
The stream gaging program serves many masters. In the west, where water rights can be matters of life and death, minor changes in some stream gages are litigated like the Microsoft breakup. Anywhere there is a large body of data (the majority of stations have over fifty years of record) flood conditions can be predicted with excellent accuracy. And long term river flows are extremely useful to a huge number of research projects on every topic imaginable. In fact, on the USGS list of uses for stream gaging, fishing does not appear. But make no mistake, it’s your tax dollars at work.
In the old days, before the invention of volcanoes, the lava had to be carried down the mountain in buckets and poured on the sleeping villagers by hand. Before the invention of remote stream gaging, people checked the gages, took the data down by hand, and archived it. The present WWW page can access data from some stations that is over 100 years old. The majority of stations came on line in the past fifty years with the invention of remote gages that can be positioned well away from the stream. Later inventions allowed data to be transmitted by telephone from the gaging device to offices or other comfortable locations.
The real revolution came with the cheap development of satellite uplink technology. This allowed great flexibility with gaging stations, and permitted the hydrologists to place gages in locations that suited their needs, not in locations that were convenient. Some gaging stations are in quite remote areas and are very rarely touched by an actual human being. For flood control this makes obvious sense; when there’s a flood, when you need them most, it’s tougher and more dangerous to take accurate measurements. Also, in places where water rights are hotly contested, taking the human being out of the loop makes it easier to secure the data and keep it reliable. Not to mention the main reasons: machines are more reliable than people, and we want it now, not when you get around to putting on your hipboots and starting up that truck.
The internet revolution was the next step. In the eighties and early nineties, river level information was available via a phone connection or on NOAA (National Oceanographic and Atmospheric Administration) weather service broadcasts. In these cases, however, the data was point-time; one gage level, which might be stale by hours, and a prediction: falling, rising, or stable. They had more data, but no easy way to convey it. Still, it was a great asset at that time; the only alternative was to call someone by the river and have them look out the window. With the internet uplink, the range of usable data for anglers has exploded.
There are some caveats, however. The main one concerns the accuracy of the gages. Obstructions, ice, vegetation, and other accidents of nature can affect gage readings. The devices themselves are somewhat unreliable and accuracy declines between calibrations. It is important to remember that these stations provide raw data and are no substitute for caution and good sense. It goes without saying that the USGS and the other organizations that provide this data accept no responsibility for its use or misuse.
Uses, abuses, confuses
For fishing, the basic rule of stream gaging is that experience makes the data most useful. To use the gauges, you have to know how the numbers affect the river.
The simplest use of stream gaging technology is to judge the river level, or “stage,” at that moment, in what the USGS calls “realtime.” One drawback to this simple application is that gages are not on a normed or consistent scale. 5.5 feet at Harrisburg at noon on the tenth of March may not be equivalent to 5.5 feet upriver at Sunbury or downriver at Marietta.
In fact, 5.5 feet at Harrisburg is roughly
equivalent in flow and level to 11 feet at Sunbury and 38 feet at Marietta; those values
do not reveal the terrible course of a wall of water bearing down upon Bob Clouser’s
shop, carrying the drowned fragments of the Riverfront Campground and the Pennsylvania
State Capital in its terrible foaming maw. They represent stable/gradually falling levels
on the Susquehanna. To use a gage you must be familiar with the actual river conditions as
they relate to river level.Another factor is the relationship between river stage and flow. Both are simply different forms of the same data, but the way that data affects fishing is up to you to judge. The term “discharge” is used to describe the total amount of water passing the gaging station per unit of time, usually expressed in CFS or cubic feet per second. To understand discharge, simply imagine that the gaging station is at the end of a large pipe; in reality, the water isn’t really being “discharged” anywhere except down the next bit of river.
The relationship between discharge and level is complex, just as the relationship between distance and miles per hour is complex. This is the logic that every kayaker follows; as level increases, so does the speed of water movement and, if you’re a good kayaker, so does the fun. Therefore each additional foot of stage multiplied by the number of feet across the river at that point doesn’t translate simply to another cubic foot of water per second; the time it takes the third (cubed) foot to pass the station has decreased as the flow rate of water has increased. They learned this hydrological lesson the hard way on the Mississippi--higher water goes faster.
So a key river station for our outfit, Paw Paw on the Potomac, a foot of rise in the midrange of flow levels translates to a discharge increase of about 1200 CFS. For the Harrisburg station on the Susquehanna, a foot of rise in the middle range of flow levels translates to a discharge increase of about 18,000 CFS. A one-foot rise at Harrisburg equals a discharge increase of nearly four times the total flow of the Potomac at Paw Paw. That’s a big river. As I write this the Susquehanna is at 10 feet, about 137,000 cubic feet per second of flow.
At low levels, of course, another effect is present: zero flow. Gages are located and equipped with different purposes in mind. Those on hotly contested streams in the West tend to be more accurate as flows decrease; most Eastern gages are mainly to collect data for flood control and monitoring. Therefore some of our gages--including two that would be useful for my guide service, Harper’s Ferry and Shepherdstown--don’t even function when the river is at low or normal flows. Since we guide mainly in the warmer months, when low levels are typical, the gage is too simple to be useful: if Shepherdstown is registering, we don’t fish.
Unfortunately, when the river flows are low the gage plays a very important role. When the flow is very low small changes in flow can make a large difference in fishing. That leads to a rule: for high water we care about river level; for low water we care about change. An application is obvious. In the Susquehanna, and to a lesser extent in the Potomac, a summertime rise can hurt fishing. If the river is at 4 and the gage rises eight inches, the effect will be much less than if the river is at 2 and the gage rises eight inches: the proportion of rise to flow is much greater in the latter example. Of course, the basic rule still applies: Know your gages.
Better and deeper and faster
The best value of the gage pages is their ability to keep data in a historical perspective--from days to decades. Couple that with an intimate knowledge of your watershed and you have a tremendous forecasting tool.
An example: in 1994 I met a client despite my worries about the river conditions. It had rained hard and long in the Potomac basin well upstream of our float section, and I was worried that the river wouldn’t be fishable. News from the gages was sketchy and inconclusive; I feared that there was a lot of water coming down but I couldn’t track it. Unfortunately, I couldn’t contact the client soon enough to pull the plug on the float so I drove out to the river anyway. Once there I was surprised to find that the level hadn’t changed much and the clarity was still good. We discussed it and decided to go ahead with the trip.
We weren’t long out of the gates when I saw an odd sight upriver: what appeared to be a flock of seagulls riding down toward us. It wasn’t seagulls; it was a flotilla of trash, mainly white plastic bottles and styrofoam, the first stuff to break lose and float down when the river comes up. The white wave was the harbinger of a sharp rise, and within an hour the river conditions had deteriorated sharply. A sharp summertime rise can produce a window of good fishing for big bass along the more obvious shoreline cover; in the first two hours of the flood we boated six smallies over 17 inches. But then it became a boatride worthy of an amusement park. We passed Harpers Ferry at a river level of 8.5; ran Whitehorse Rapids in a brown muddy maelstrom (What’s a class IV rapid with logs and propane tanks in it?) and went flying down the Brunswick lake watching for cottonwood blowdowns that would surface behind us like U-boats. At the ramp I rowed the boat up onto the trailer without moving my truck. (OK, that’s a slight exaggeration.) That day the river came up from 3 to 13 in about eight hours.
With the current WWW pages I’d never be caught by surprise by such a change. The gages are spaced up the river at intervals that allow you to track the approach of a “slug” of water and make an accurate prediction of what might happen on any given day. Needless to say, I was glad to be in a very solid whitewater raft with a good knowledge of how to handle it on that day; a jet-boater or canoeist would have had to break for the shoreline or sprint downriver to escape the flood and its dangerous cargo of trash.
More common is the practice of assessing the effect on your stretch of river of the past several days of weather. If you can index that to previous experience on the river, you can eliminate much doubt about the conditions you will be fishing on any given day, or even time your trips to coincide with optimum conditions. You don’t even have to go fishing. If you drive over your river or take a turn past the boat ramp, then check the river level on the computer--bingo! Information!
Where are you, and what’s coming your way?
Remember the effect of the position in the watershed of the area you want to fish. The more gages upstream of you, the more reliable your data. There are two reasons for this. The obvious one is that more stations equals more data; the less obvious one is that the higher in the watershed you are, the more volatile the stream conditions will be. Last spring I made a trip several hours to fish a small stream in southwest Virginia. The night we arrived, we were dismayed to find that the river was out of its banks and clearly unfishable, even though we’d been closely monitoring the gages for the previous week. The next morning, however, the river had fallen enough to fish, and one day later it was in perfect condition.
On the other hand are the largest rivers, especially the Susquehanna. Things happen very slowly up there. You can see trouble coming for days in advance, and the profusion of tributary streams and main-stem gages gives you plenty of data to assess change--perhaps even too much data.
Another interesting effect of gages occurs in large main-stem rivers. At Duncannon, where the Juniata joins the Susquehanna, the river is nearly 3/4 of a mile across. Often one or the other river will be affected by a rise, but the river is so large that the water mixes slowly and I have often run an entire float trip down one bank or another to avoid very different conditions on the other side. Also, it’s possible to look at the condition of tributary streams; even after downpours muddy the water along the bank you can find a stripe of clear water in the middle of the river, and it may be that boundary line between clear and stained water that is most productive. Catfish anglers, for example, might watch the gage for that first sharp rise and head for the river to meet it.
Remember also that the gage can defy simple observation or logic. At Harpers Ferry, the midpoint of our usual float trip, the Shenandoah joins the Potomac. At the mouth of the river the two flows seem equal, but they’re not; it isn’t always clear where the most water comes from, and it’s easy for us to forget that the Shenandoah is much smaller than the Potomac (see table.) Add to that the fact that the Shenandoah and Potomac watersheds are separate enough to have quite different rainfall and you have a really useful application of real-time gage data as long as you understand the relative discharge of the two rivers and take that proportion into account.
Another key consideration--and another situation where experience is the best teacher--is the effect on river levels and water clarity. Sharp rises in the summer; rainfall after drought; gradual rises; secondary rises--all have a particular effect on water clarity. That perhaps is another article but it is generally true that the higher in the watershed, the clearer a stream will run and the faster it will clear. Also, of course, certain tributaries are notorious for running dirty at the least provocation. The Monocacy near Washington is one of those; if the Monocacy is high, or even a bit above average, it will contribute significant mud to the Potomac. The same is generally true of the Shenandoah, though it’s a different kind of mud--agricultural vs. silt. Therefore a gullywasher in the Doah basin in high summer might lead to an algae bloom, thanks to the continued practice in Virginia of fencing cattle pastures down to the water’s edge to give the cows a way to cool off on those hot summer days. That’s another article, too.
In the Washington area, weather often breaks on an east-west axis, so that rainfall can differ sharply just fifty miles to the west. Add to that the tendency of streams in the area to muddy up fast due to development in the suburbs, and you have another use of the gage for our guide service. A simple observation of the river at the Cabin John Bridge on the Washingon Beltway might be misleading until you check the gages upriver and compare that to the flow of the major local tributaries such as the Monocacy River. It may be that the river you are aiming at--say, the Shepherdstown area of the Potomac--is actually fishable even though the eyeball evidence downstream is bad. Again, it’s the habit of use that makes the information more valuable.
Where, what, when, and how
The first-time visitor to the USGS main webpage for river gages might be intimidated. On the other hand, you should know what you’re getting into. Judge according to your own appetite for technology and computer use. In the paragraphs below I’ll talk you through the entire architecture of the site and also supply you with the simple URL’s to get what you need quickly and get out so you can leave the computer and go fishing.
The USGS site is quite streamlined and clear considering the source; since the USGS is a government agency, it has certain bureaucratic tendencies. When you remember that it’s handling an enormous amount of information updated in 15 minute intervals and kept forever, the clarity of the site is pretty impressive.
At http://www.usgs.gov you will hit the home page of the United States Geological Survey. At this point you can go three ways: use a search utility, surf in an orderly fashion, or wander haphazardly around until you hit something interesting. If you have a particular river, region, or station in mind, you may have to make a more careful approach; it’s a big domain.
The best approach is to find the sites you want and bookmark them, but the site designations are not set up for convenience. Each site is given an 8-digit designation to distinguish it from every other site. This is useful when you remember that there are lots of Black Rivers and Muddy Creeks in the country, but tough when you want to search for a particular gage out of the almost 8000 that are out there.
Furthermore, sites are indexed, organized, and funded by state. The Potomac is a border river for West Virginia, Virginia, and Maryland at various points along the way; yet, due to the pre-revolutionary agreement about the river, Maryland owns it to the high water mark on the other shore. Therefore gages on the east bank may not appear on the same web page as gages on the west bank because the states in question may not be inclined to undertake the expense of maintaining a gage on somebody else’s river. Of course, the floods don’t respect the fine print of a 350-year-old land grant. Anyway, some states spend more energy and money on gaging than others so Potomac gages in West Virginia appear on Maryland pages, which is fine because West Virginia gages are less reliable and less accurate than the Maryland gages. Experience and a little research will reveal how your state and watershed line up.
Recent organizations of this data have grouped sites more by river than by administering authority, but it’s still not easy to find every useful site. One way is to navigate your way to the Real-time Water Data page (http://water.usgs.gov/realtime.html) where a large clickable map is displayed. The key steps: From http://www.usgs.gov hit the “water” button at the top of the page; that takes you to http://water.usgs.gov/ Once there, choose “real time” and go to http://water.usgs.gov/realtime.html Remember to bookmark well; these pages are large and take a long time to load. I keep the realtime page on my bookmark list for when I am curious about locations that I haven’t fished before, and I occasionally check up on sites I fished and loved long ago, much the same way we occasionally look up old girlfriends in the phone book. (What? You don’t do that?)
Before clicking on the map, note below the map that you have choices: ten closest gages, state list, or state map. You can also scroll down to the rack on the left and hit your state. The main problem here is that the map is small and choked with sites, and it’s sometimes tough to hit the right spot in the east where, I am proud to note, there is a whole lot of gagin’ going on.
The return from an area click will be arranged in distance from the point you hit; that can make for some confusion about the actual location of the sites you’ve found. One way to check is to go to the page and read the fine print on the gage location. Some pages include a link to a map of the drainage area and other interesting data, usually found under “Historical daily mean or peakflow data for this station.”
Another approach is to navigate through by state, which is easy if your river isn’t a border. Eventually you’ll wind up with a list of stream gages arranged from upstream to downstream along each branch of the river. Become familiar with the place names of the gages, monitor their changes, and you will be linked up.
State and national maps are interesting in that they give a quick picture of the flow situations. Each station is represented by a dot; the color of the dot signifies flow relative to historical averages (actually means; “mean daily exceedance” is another measure of daily flow relative to the history of that site). At the moment the national map reflects low to very low water from Texas to Michigan and high water to record high water in the mid-Atlantic, especially in the Appalachians and around Philadelphia. If you are a flexible angler, more willing to change locations than fishing days, these maps allow a quick glimpse of the “big picture”. All the maps are clickable for the particular gage situations.
Once you are on individual gage pages, the data becomes more directly applicable to fishing conditions. Remember to bookmark the site, but be careful; some web browsers only record url (web address) and title, and the title probably won’t refer directly to the station--the text of the web address, which the computer copies, isn’t set up for convenience. You’ll need to go into your bookmarks and title each one in your own words. For example, before I edited the title, my bookmark for Susquehanna at Harrisburg read “Hydrograph and station description for 01570500” which wasn’t much use.
Each page has three main representations of data: stage, discharge, and exceedance. Stage and discharge are charted on a weekly interval; that is, the line of the chart is always seven days old, with one day of space ahead of it so you can extrapolate the level. Running across the chart is a blue line to represent the water levels. On the flow chart the mean levels are represented by blue triangles. Remember that these are means for the particular day of the year, which is how much of the data is organized.
Exceedance is also a measure of daily flow over years of record in cfs.
Each page also has a ton of basic information about the gage sites, which can help you to decide if it’s the right place, or even help you to find the gage on your next trip down the river. I once was astonished when I searched the web and found a certain river running at a tiny fraction fo the flow I expected, and it took me a few minutes to realize that I was looking at a different river of the same name in Wyoming.
From these pages you can access great piles of data on that site. To illustrate the disastrous Potomac floods of 1996 (and the very high flows all summer between them) I have downloaded the entire year’s data and charted it to quantify the term we used that summer: crappy fishing.
(4-foot banner versions of this chart are available.)
An Easy Starting Point
A simpler and more elementary source of river condition data is the web page of the Middle Atlantic River Forecast Center, or MARFC. Operated from an office in State College, PA, MARFC organizes a diverse set of data including river levels, precipitation, and water temperatures in a concise website at http://marfchp1.met.psu.edu/Forecasts/WBC/index.html For levels and stages it is useful though less thorough and sophisticated than USGS (from which it gathers its gage data) but this site is excellent for one other bit of information: water temperatures. Especially in the spring and fall, temps are hugely important for us smallmouth anglers. The temps are only measured and reported for a gage site well down the watershed but it’s a simple matter for us to extrapolate with experience and jump on those critical windows of rising temperature.
Whassup?
As I’ve said a bunch of times, the key element to this resource is the user’s built-up fund of experience and understanding of the data represented there. For the most part that data is highly specific to the locations you fish, but there are a few details that might help you to judge what’s up with your river.
One detail concerns upriver obstructions to flow, most specifically dams. Most of the rivers in the nation are affected by dams, and familiarity with the effect of dams can explain much about river conditions in your area.
The most obvious dam effect is the stair-step. This is a very distinct change in flow as it is dictated by the dam release. A flat, stair-stepping line is common data from a gage that is located very near a dam. This is important as it affects fish behavior, habitat quality, and safety. A good example of this effect can be found on the Jackson River in southwest Virginia, which is entirely controlled by the flow from Gathright Dam. The Jackson is an excellent trout tailwater, but it is also the conduit through which water travels to a massive papermill in Covington, VA. (and away from the papermill, carrying far fewer trout and far more other stuff.)
Because the dam and river exist for more than just trout, the dam releases and river levels are not entirely logical to the trout fisherman (though the trout don’t seem to mind as long as the bugs keep coming.) Jackson River levels can take on some oddly uniform shapes.
Even a great distance downriver--all the way into the James, the river that
receives the Jackson’s flow--the effect of these releases can be seen as regular
though by now a bit fuzzy changes in the river level--unless a tributary between the dam
and the gauge delivers a slug of water. 
