How to Understand the USGS River Gauges for Fishing

Florida’s rivers offer the outdoorsman/woman a plethora of outstanding recreational opportunities. The plant and animal life they support is astounding! Florida has many famous rivers like the Suwanee, St. Johns, and Crystal River, and many more little-known, but equally interesting, spring creeks, blackwater sloughs, bayous, and streams to explore, over 25,000 miles worth in total. Think about that. Over 25,000 miles of rivers to explore!

Many of these rivers are important ecologically, archeologically, historically, and recreationally, but what we as anglers want to know is, are there fish? Almost always, yes there are! Then how do we catch them?

Rivers (as we’re looking at them here) are dynamic conveyers of fresh water from higher to lower elevations (thank you, gravity!). Their flow, measured in cubic feet per second, or cfs, and their water levels change constantly. Has it rained lately? The water is up, the flow is faster. Having a drought? The flow is low, as is the water level.

How do water level and flow affect the fish in the stream? That’s what this article intends to explore.

Climate and River Flow

Our state averages 54 inches of rainfall a year. In Florida generally, the highest rainfall amounts occur during the summer months. In northern Florida, there is a weak winter secondary maximum while statewide the driest months of the year are during the spring.

You might expect that when the rainfall is greater, the rivers run higher and faster. Data support this view. Let’s use Central Florida’s St. Johns River as an example.

The following graph of average yearly rainfall for Melbourne, Florida, near the St. Johns headwaters, shows that most of the rain Melbourne gets falls during the summer:

A graph of the St. Johns River height as measured by the river gauge in Cocoa (near Melbourne) from June 2023 to April 2024 shows the river is lowest in the winter and highest in the summer, corresponding closely to the Melbourne rainfall graph:

There are multiple gauges on the St. Johns, and on most of the other rivers in the country. See “How to Use the USGS Gauges” on page 49 for more information.

In north Florida, an average rainfall graph forTallahassee shows a little winter rainfall “peak,” but most of the rain still falls during the summer. The river flows there will reflect this.

River Levels and Fish

When I go fishing in any Florida river, I prefer low water. When the river is low, the available places for fish to be are much more limited. I never see any fish in the spots where I need to drag my kayak!

In rivers and streams, falling water levels tend to move fish downstream, out of tributaries and into main channels and of course towards deeper holes. Holes with tree limbs and roots are usually the very best habitats where fish will spend their time during low water.

An extreme example of this occurred on the St. Johns River 15 or 20 years ago, during a prolonged drought. The river was so low that even the airboats were having a hard time navigating. We’d access the river through Tosahatchee WMA, and walk up the river (which was ankle-deep between pools), fly-fishing with streamers in the pools. Bass, bream, channel cats, and tilapia made up our catch. Fishing was stupid good! Then the river came up with the summer rains, and the bonanza was over.

Not content to use my own anecdotal evidence, I contacted FWC biologist Eric Nagid, a research administrator for the commission’s North Central to Panhandle region, based in Gainesville.

On the subject of river fishing, Nagid said his general philosophy is: “Don’t even bother going fishing when the water is on the floodplain. Floods are great for many reasons, but they’re bad if catching fish is your main goal.”

As Nagid explained it, “You can add a foot or two or three of water within a confined river channel, but the overall area of water basically remains unchanged. But once you spill over the bank, adding another foot or two or three can mean an exponential increase in the area of land that’s inundated due to Florida’s flat topography. What that means is more area per fish, which makes them harder to catch.”

Basically, Nagid echoed a common refrain among experienced river fishermen: Fishing during high water or high flow makes everything harder.

“The water is usually ‘dirty’ from sediment in the water column,” said Nagid, “so your visual cues aren’t as good. Keeping your boat positioned can be challenging, whether you’re drifting, anchored, or using a trolling motor. Presenting a bait the way you’d like can be challenging.”

Although high water generally means the boat is staying home, Nagid said he likes to think of floods as being an investment in the ecosystem and fish population that’s going to pay off once water recedes.

“Floods reshape and maintain the channel,” he said. “They move loose sediments downstream, they add new trees/snags and other forms of habitat into the river, and they hydrate the floodplain.

“Water in the floodplain means more area for fish, but it also means more groceries per fish. Small panfish and insectivores gorge on terrestrial invertebrates that they usually don’t have access to, while bigger panfish and small bass have a heathy supply of crayfish and minnows to eat.”

When water recedes back into the channel, Nagid says that’s a great time to go fishing. Fish tend to be aggressive.

As for general patterns in Florida, Nagid says, “In Panhandle streams, high flow and floodplain inundation normally occur in the spring following cold front rains. In peninsular Florida, high flows normally coincide with the late summer and early fall months. In areas in between like the Suwannee River, there are two potential seasons of high flows, spring and fall.”

Planning Your Trip

Five-minute’s drive from my house in Central Florida , there’s a bridge over the Econlockhatchee River. There’s a USGS gauge next to that bridge. I like that gauge to read at 2.0 or below when I plan a trip there. Long history has taught me that when the gauge is higher than that, I may have a great paddle, but I will not catch many fish. Below is a screen shot of a graph of the Econ’s water level for the past year. You can see it was not below 2.0 very often. So most of the time, even though that river is five minutes away, I’m fishing elsewhere.

One time, Tammy Wilson, Mike Conneen, and I launched our kayaks at Hidden River Park on the upper Econ. We may have been the last party to launch there before the Park went out of the kayak launch access business. The gauge at Snow Hill Road read 5.5 feet that day.

We had a great time paddling the river, getting wet and dirty, going under, over, and around many deadfalls and log jams. Tammy even entertained us by falling in! But we did not catch many fish, one small bass and a single redbelly, if memory serves.

If you want to be successful while fishing Florida’s rivers, the best time is when the streams are flowing low and clear. For most of us, that means river fishing during the winter and spring months. Once the summer rains start, the rivers rise, the fish disperse, and the best fishing happens elsewhere.

How to Use the USGS River Gauges

When you want to see how any river is running, use your computer and go here. A pop-up window will open. After reading what they’re offering, click in the

“Do not show me again” box. Once it closes, you’ll see a map of the United States, covered with little colored dots. Every dot represents a river gauge. Rather than be overwhelmed by this, appreciate how many there are (your tax dollars at work!), then go to the search box under the National Water Dashboard heading.

Into the search box, type the name of the river you’re interested in, then hit return. A map will open showing the river’s drainage area and all its gauges, as well as a suggestion box if the river has multiple gauges.

Once you’ve found the gauge you want, click on its colored dot. Another pop-up window will open. In this window, the past week’s flow, in cubic feet per second (cfs) will be displayed graphically. Below this, the next line reads “Gauge Height, Feet.” Click on this and that line opens, revealing another graph that shows the river’s gauge measurements for the past week.

It will take a season, perhaps more, for you to be able to read those graphs and know, while you sit in your living room, what the river is actually doing. It shortens the learning curve if, after you read the information, you then go to the river and see what the water level is. If you’re more smartphone savvy than I, you can figure out how to do this on your phone at the edge of the stream, so there’s no lag time.

The river I fish the most is the Econlockhatchee, in Central Florida. I know from experience that I have the best fishing when the gauge at Snow Hill Road reads at 2.0 or below. I know that at 12.0 (every whole number represents a foot of water) it’s out of its banks. Right after a hurricane a couple years back, the gauge read over 22—the bridge next to the gauge was under water.

Again using the Econlockhatchee as an example, if you wanted to fish there and checked the gauge, and that gauge read 5.3 feet, you could either change the plan and fish elsewhere, or fish all the backwater sections of the river, where the fish could get out of the significant current, and you might have a shot at them. I would go elsewhere, personally, but you may be a more skilled high-water fisherman than I.

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• This article was featured in the February 2025 issue of Florida Sportsman magazine. Click to subscribe.

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