Missouri Trout Hunter

Blog for sharing thoughts, beliefs and opinions on issues affecting the world of trout fishing in the Ozarks.

Monday, August 28, 2006

How the Recent Rains Will Affect Your Favorite Trout Stream

People all over the state are saying prayers of thanks for the recent rains, except for those of us who have suffered storm damage, of course. River fishermen are often confused about heavy rains and rising waters and what it means for their fishery. On the one hand, we all know that some of our favorite rivers are not just low, but are dangerously low. Some favorite trout fishing areas of a decade ago are darn near dry, today. So, obviously, we welcome all the rain we can get. However, we all still want to fish, and high water does not necessarily dampen our enthusiasm.

The first thing you should do is check the gauge levels of your favorite creeks on our Water Levels Page. You then need to analyze the data. I'm sorry to say this will require some math skills. It's generally at this point that I search the house for my 3rd grader to come and explain fractions and percentages to me.

After you find the graph you want to review, grab a calcuator. Of course, you can determine how many inches the river is up by simply subtracting the recent low number from the recent high number, but that's not the number we're interested in. We're more interested in the percentage of increase. For example, the Meramec River went from a gauge height of 1.38 feet to 1.90, an actual increase of 6-1/4 inches of so, which doesn't sound so bad. That number is misleading, though. Instead, divide 1.9 by 1.38 to get an answer of about 1.376. Read that as 137.6%. In other words, the new level is almost 138% of the old level, which means the Meramec River is up by almost 38%, or more than 1/3. That's a bigger deal than a mere 6 inches.

Now that you have that number, consider the change in current. It's tempting to assume that a 38% increase in water level will mean a 38% increase in water speed, but this is also misleading. As the river gets deeper (by 6-1/4 inches, in this case), it also gets wider. So, to be safe, you should assume that the percentage of increase in height only represents about 1/5 of the actual increase in water volume. In fact, if you were to take a look at the second Meramec River graph titled "Discharge, cubic feet per second", you'd see that the volume of water increased from about 100 cfs to about 280 cfs. 280/100=2.8 or 280%, meaning the new volume is 280% of the old volume, meaning it's an increase of 180%. 38% x 5 = 190%, so our 1/5 estimate was fairly accurate this time. And bear in mind that water volume measured in cubic feet per second is the same thing as speed. The higher the discharge, the faster the current.

Okay, we're done with the math. Apologies. However, I just want to make clear what we're talking about. With even a modest 6" increase in gauge height, a river can be unfishable and certainly unwadable due to depth and speed. Just how much weight are you prepared to put on the end of your line to get your fly down deep? And just how strong are your legs? So, hold off until the river's current is more managable. That's rule number #1. Rule #2: get ready, cuz the fishing's gonna get good!

Right now, as the river's are swelling, the fishing for the future is changing. We all know the water temperatures have been high recently -- sometimes into the 80's. Trout lose their swimming endurance when the water is that warm. Then, when the current jumps from 100 to 280, they just can't keep up with it. Therefore, the trout are being washed downstream even as I write this. So, think about looking farther downstream when you go fishing next week. Also, with poor physical endurance, the trout will have less energy for pursuit feeding, meaning they'll rely almost entirely on feeding on drifting food: mostly aquatic insects and crustraceans. And lucky for them (and us), the increased flow is going to be rolling the rocks over and getting the bugs really moving. The last perk is that the fish will be hugging the bottom of the river seeking shelter from the faster current, so the food will be floating right in their faces. They're going to be hungry due to the excess energy consumption, they're going to be collected together in the most sheltered spots, and they're going to get hooked on nymphs (sorry for the pun). So we fly fishermen are going to have a great time as soon as the water settles a bit, as we just might find trout competitively attacking sub-surface flies in a feeding frenzy type of atmosphere. Then, as the recharge spring pool continues to cool the river, we'll see perkier trout begin to respond to streamers, spinners, crankbaits, and such.

Be patient, my fellow anglers. Some good times are coming.


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