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How Land-Use and Geology Affect Mountain Streams, with Dr. Nelson Ham

Description: I've long been fascinated by the way geology affects the character and richness of a trout stream, and I know other anglers are as well. My interview this week is with geology professor Dr. Nelson Ham [40:36], who has been studying the effects of both geology and historical land use practices on the character of our trout rivers. The discussion also goes into the value of ground water on how productive our rivers can be. I learned a lot in this interview and I know you will as well.
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Podcast Transcript:

Tom: Hi, and welcome to "The Orvis Fly-Fishing Podcast." This week, my guest is Dr. Nelson Ham. And I've been looking for the right guest to do this podcast for a while. I've wanted to do a podcast on the effects of geology on trout streams and their character and I got even more than I bargained for. Nelson and I were corresponding on a totally unrelated subject, and I happen to see that he was a professor of geology. And so, I asked him if he'd like to do this podcast and he said, "Yeah, in fact, I'd also like to talk about, you know, land use practices and historic land use practices, and how they affect the character of what we see today in our trout streams, especially in the groundwater resources that we have."
So, I found this to be a fascinating discussion, because I like this geeky stuff and I know a lot of you do as well when I talk to scientists. So, hope you enjoy the interview today. I'd also like to apologize for the background noise today. I'm not sure if you can hear it but I'm home with a 13-week Labrador puppy who is not happy that he's in his kennel today. So, you may hear a little yelling in the background, so I apologize for the background music there. But let's do the podcast, podcast is where I try to answer your questions if I can.
And I don't answer them all. Some of them I've answered so many times that I don't want to answer them again and I don't think it's fair to those of you who listen to every episode and have to hear the answer to the same question again. And also, I typically don't answer questions that someone could solve with a quick search on the internet. So, anyway, other than that, I'm happy to answer almost any kind of question you have or take your comments. And you can send a question to the podcast by emailing me at This email address is being protected from spambots. You need JavaScript enabled to view it.. I read all of them. I'm the only one that reads them and answers them. And you can put your question in your email or you can attach a voice file if you want and maybe I'll read it on the air.
Anyways, the first question is an email from Andy from Colorado. "I live in Denver and fish all around the state. I have six Helios 3 rods, and I'm looking to sell one and wonder which one you'd recommend I'd need the least. With a high school or in college kid, I don't get out as much as I'd like and I tend to go anywhere to avoid the crowd, so my fishing has been limited, rivers, small streams and still water." So, Andy has a Helios 3D 4-weight nine foot, a nine-foot 6-weight, and a 10-foot 7-weight. And then the 3F, he has an 11 foot 3-weight Euro nymphing rod, an eight and a half foot 4-weight, and a 10-foot 6-weight. "Which one do you think is redundant in Colorado considering the other rods I own? I don't want to sell any of them, but I need to sell one and I need your help to push me over the fence. I'm pretty sure that I want to keep the three-weight and the seven-weight."
I'm going to answer this part of Andy's question because Andy has a second question, I'm going to answer this one first. So, Andy, first of all, you're a lucky guy. I think you've got more H3 rods than I do and you've got quite a quiver there that'll cover lots of different things in Colorado. So, you said you want to keep the 10 foot 7-weight, good still water rod, good streamer rod from a boat. And then you want to keep the 11 foot 3-weight, obviously, you want to do a lot of Euro nymphing. That 11-foot 3-weight is also not a bad little dry fly rod for small dry flies, I find it kind of fun the slow action on dry flies. So, that leaves you with, in 3D, a nine-foot 4-weight, a nine-foot 6-weight, and in 3F, an eight-and-a-half-foot 4-weight and a 10-foot 6-weight.
So, I think that...I think if I were to get rid of one, I think I would get rid of that or sell that nine-foot 6-weight. You have a 10 foot 6-weight, so you've got a good...and you've got 10 foot 7-weight, so you've actually got two of those, you know, that serve similar purposes, bass fishing, streamer fishing, carp fishing, things like that. And you probably want that nine-foot 4-weight 3D for bigger rivers or dry fly fishing, and then I'm sure you want that eight-and-a-half 4-weight for small streams. So, I think, you know, I would get rid of one of those 6-weights, either the nine-foot 6-weight or the 10-foot 6-weight. And that probably depends, if you're going to do more still water, I get rid of the nine-footer. If you're going to do more river fishing, I'd get rid of the 10-footer. So, that's my opinion anyways.
And then let's go on to second part of Andy's question. "Finally, do you think that fly fishing popularity will ever cool back down? I know everyone needs to be new to something at some point, but I'm 48 years old and I started fishing when I was 23 long before it was cool. When I get into it after years of spinner fishing with my dad, it was a dorky thing for a young guy to do. Now it's all the rage. I know you need to be careful in how you answer since part of your job is to promote the sport but it's disheartening to see so many people driving around town with rod racks on their SUVs and it just feels like it's the new trendy thing for 30-somethings. It feels like so many of the newbies are doing it because it's suddenly cool. I've felt things died down after the popularity boom in the '90s after "A River Runs Through It" and I'm hoping the same thing happens once the COVID swell goes down. Anyway, I presume you'd be like my wife and tell me not to focus on the negative aspects of gentrification, yadda-yadda. As everyone tells you, I love your show and your perspective and take on so many issues."
So, Andy, I think it's gonna cool down. You know, what we saw after "A River Runs Through It" movie was lots and lots and lots of people getting into fly fishing and doing it because they thought Brad Pitt look cool and they thought fly fishing look interesting. And you know what? A lot of the people I know now who are really serious about fly fishing and are, you know, just really dedicated to it, when you scratch the surface, they'll admit that they were at first stimulated to fly fish because of "A River Runs Through It." And I think the same thing is gonna happen with COVID. You know, the people who are doing it just because it's cool, well, they're going to move on to the next cool thing.
The people who really get turned on by it, they're going to become, you know, the legends and the icons of our sport in a few years. They're gonna get into it, they're gonna get serious about it, they're going to be the ones that are going to fight to protect our rivers. So, yeah, I think it's going to cool down but, you know, it's kind of reached a new plateau now. I mean, we've had so many people entering fly fishing that, you know, we're at another level now above "A River Runs Through It." And yes, that's going to slow down but there's still going to be more people fishing.
I think that...unfortunately, I think that everybody that's gotten into this thinks they have to go trout fishing, and that's where we're seeing all the crowds. And I wish more people would concentrate or at least spend some more time fishing for things like largemouth bass, smallmouth bass, white bass, catfish, panfish, carp, whatever. There's lots of other cool things and fun things to catch with a fly rod. So, hopefully, we can encourage some of these people that think fly fishing is cool that maybe it's cool to do some alternative species as opposed to trout.
Here's an email from Kevin. "Hello, Tom. I was pointed in this direction by a friend of mine who has been on my case about a fly rod I found in the attic of the house I just bought when I was tracking down a roof leak and I do mean on my case. According to him, it's an 1856 Orvis fly rod about eight feet long. My question for Orvis is was this the date manufactured or is it like firearms and that's the year it was first designed? My next question is can it still be fishing? It apparently has no damage or standing on the handle and is in fantastic condition according to the other fly fisherman I know. My last question is should I take him up on his offer of, "Go pick any rod in the fly shop and I'll buy it for you," as a trade although I'll probably just slip it under his Christmas tree for all he has done getting me into this hobby. Anyway, more info on your bamboo rods would be amazing."
Well, Kevin, the 1856 rod was not made in 1856. 1856 was the year that Orvis was founded and, in 1856, there were no split bamboo rods which is what that rod is. That type of rod wasn't invented until the 1870s. All the rods then were solid wood, usually lancewood or ash or greenheart. Some bamboo but it wasn't split bamboo like that is. That rod is probably less than eight years old. In the 150th anniversary of the Orvis company, which by my calculations would have been 2006 if my math is right, we came out with a rod to commemorate the 150th anniversary and that's why it's called The 1856. It's still sold, it's still made and sold, and if might have noticed that this is called "The Orvis Fly-Fishing Podcast."
Orvis has a website and we sell all kinds of cool stuff, and among the cool things we sell is the 1856 fly rod. So, you can go on there and you can find out how much it costs, what it's worth, and all sorts of other interesting things about the 1856 rod. Now, the other thing is that we can actually tell who bought that rod because every bamboo rod we sell is registered. So, if you want to call our customer service department if you curious at 800-548-9548, you can actually give them the serial number on the rod and they'll tell you who bought it and when it was purchased. But yes, it's's a fairly new rod, I'm sure it's in great condition, it sounds like a mint condition, it would be a great fishing rod. For a bamboo rod, it's relatively powerful. I don't use that particular one on small streams, I use it on medium to large rivers because it is quite a powerful rod and, you know, it'd be a good rod for some of your larger trout streams. But if you want to put it on your friend's Christmas tree, then you can do that as well.
Brendan: Hi, Tom, this is Brendan from Pennsylvania. Thanks so much for your podcast, I really appreciate all the helpful information that you put out there. So, I got a question for you. Today, I was fishing a dry dropper in a little creek here in Pennsylvania that holds wild brown trout. And on my nymph, it was a size 18 zebra midge. I was catching fairly small trout, you know, four to five inches, and nothing in this stream is large, you know, a large trout for this stream would be 10 inches. So, I was catching these little trout on the nymph but I could see that there were larger fish in the creek, they just would not move as I was site fishing them. They just had no interest in the nymph but I also had a couple of these bigger fish attempt to take the dry fly.
And so, I know it's not always true that big fly means big fish because I've seen the small fish also take the big dry fly. But I'm wondering on certain days are smaller fish just keen into a different source of food and maybe the larger fish are keen into another source of food? Or is that not really the case? I'm just trying to figure out why. Maybe all the smaller fish were going for the zebra image and the larger fish really seemed uninterested in the zebra midge but did attempt to take the dry a couple of times. Thanks, Tom, for all you do, look forward to your answer. Bye.
Tom: So, Brendan, yeah, that's an interesting situation and it could have been due to a number of things. One of the things that it could have been due to is that smaller fish are less likely to be spooked than large fish. Large fish have learned that people waving their arms close to them are predators, and so they all kind of sulk on the bottom and not feed when they're scared. But often, the smaller fish, a little more naive, will keep on feeding even when they see a predator nearby. They may soon become a meal because they haven't figured it out yet, a meal for you or for an osprey, but that's one scenario could be possible.
The other scenario is that smaller fish feed more frequently generally than large fish. Large fish usually take advantage of really heavy hatches and will feed heavily during periods of food abundance and then they'll kind of chill out during periods when food is not so abundant, whereas smaller fish tend to peck at stuff all day long. So, that's another possible scenario. And yes, they could also be feeding on different things. You know, the bigger fish could be waiting for a hatch or waiting for a larger bug to drift by. So, you know, there's all kinds of scenarios and, of course, I don't know exactly what is the case there but those are some likely explanations for why the larger fish were behaving differently than the smaller fish.
Here's an email from Brandon in Tampa. And Brandon, I hope you survived the hurricane okay. "I have a comment about some of the guys that have been upset about your jokes involving styles of fishing. Your material on the podcast is basically nothing but helpful. People who've listened long enough know that you poke fun at any and every type of fishing and fisher to include yourself. I'd even love to hear a fun podcast maybe with Ben Sittig, who, if you don't know who Ben Sittig is, he's the huge fly fisherman on YouTube on stereotypes of fly fishers." That's a good idea, Brandon, by the way. "Fly Fishing is supposed to be fun and really, if being mad at a joke you make on the podcast is the worst part of someone's day, that person should realize they have it pretty good. On a lighter note, thanks for everything you do and keep the jokes coming."
So, Brandon, yeah, you know, I agree with you in part, but people do rely on me and it's sometimes a little bit scary, but they rely on my opinion for things and when I make fun of something, they may not realize that I'm doing it in fun. And so, I do need to be careful about when I make fun of different styles of fishing because I'm always telling everyone here on the podcast that any way you want to fly fish is fine. If it gives you pleasure and it gives you fun and it challenges you, then you should do it that way. So, thank you for your comment but I'm gonna still try to be a little more careful.
Nick: Hi, Tom, this is Nick from Harpswell, Maine. I just got a question regarding fly fishing for Atlantic mackerel. There's still a few in the area here. A lot of them migrated down but there's still a few in the area and I'm wondering what flies you would recommend using for them. I know I'm thinking about a woolly bugger or just some streamers but I'm wondering is there anything else that you'd recommend flies or gear that I would use to target these schooling fish? Thanks.
Tom: So, Nick, Atlantic mackerel are really cool fish on a fly rod, they're a lot of fun. You can use a standard trout rod, you know, they don't get very big, but they're beautiful fish, they're kind of like...the coloration kind of a brook trout. And, you know, for their size, they fight pretty hard. They're usually really abundant and they're not at all picky. They might take a woolly bugger but I would use something a little slimmer, you know, a trout-style streamer or a very small Clouser or Lefty's Deceiver. By small, I mean like, you know, one and a half to two and a half inches long. They feed on smaller slimmer bait fish, they're not that picky at all.
And, you know, if you just get a flashy streamer of nearly any type in front of a mackerel, it's probably going to eat it. So, small streamers, a little bit on the flashy side, trout rod, maybe, you know, nine-foot 6-weight or even a nine-foot 5-weight, the same thing you'd use for trout, and you'll have a lot of fun with mackerel. And some people like to eat them, I love mackerel, and they're supposedly very healthy for you. And I don't think they're endangered, so you can harvest a few of those without having to worry.
Here's an email from Troy from Connecticut. "I had a question about small streams. I've been doing a lot more small stream fishing for brook trout, and I've had a hard time catching any trout. All I catch are dace, aka Creek Chubs. Wondering if the hot and dry summer we had this year pushed all the trout out? And if so, do you think they will re-inhabit these streams again? Also, have you noticed this up in Vermont? Thanks for all you do for our sport, love the podcast."
Yeah, Troy, you know, we have had a number...with the exception of last summer, the summer of 2021 where we had a pretty good water summer, our summers have been very low water, very warm, very dry. And a lot of these smaller streams have contracted to the point where there isn't much space left for the brook trout and they get a little warm. And what the brook trout will do when that happens is they'll drop downstream into bigger water. Unfortunately, sometimes when they drop downstream into bigger water, they get into water that's too warm and they can't tolerate and they die. And also, in very low water, they're very susceptible to predators because they're so visible and they don't have much depth to protect them and they don't have any place they can swim away from predators.
And you're going to see this...if you do enough small stream fishing, you're going to see the populations fluctuate based on water levels. You know, if you have a couple of good cool wet summers, for the next few years, you're gonna have really good small stream fishing because there's been more habitat available to the fish. These small streams are are not limited by food, they're really limited by the number of places that a fish can live and be protected and feed efficiently. And a biologist friend of mine calls these seats in a restaurant and every stream has prime seats and has seats that aren't so good. And as the stream contracts, you're going to lose a lot of the habitat so you're just not going to have space for as many fish, you won't find as many, and you're going to be...they'll warm up and you're going to be finding Creek Chubs and things.
The good thing is that there always will be a remnant population of a few brook trout maybe way up in the headwaters where it's really cold, or a really brushy tributary to that smaller stream. There's always going to be some trout left. And it doesn't take many spawning pairs of brook trout to repopulate a stream. You know, when you have fewer fish spawning, you have a better survival of the young and the young are able to find more seats in the restaurant because there just weren't as many fish before, they'll repopulate the stream.
And brook trout have, you know, a maximum of three-to-four-year lifecycle. They don't live much longer than four years old. So, those streams can repopulate quite quickly. And yes, I have seen that, I have seen some...over the years I've seen lots and lots of fluctuations of small stream brook trout. Here in Vermont, it goes up and down. And as long as the habitat is protected and the water stays cold, the fish will re-inhabit those streams. So, pray for a good snowpack and a wet spring and a wet summer next year, and a lot of your fish will be back.
Here's an email from Mike. "I do feel a huge piece was missing on your podcast on younger people getting into fly fishing. With Project Healing Waters starting 18 years ago creating opportunities for injured 20-somethings from the wars in Afghanistan or Iraq, I've had many opportunities and know many other vets that have gotten involved thanks to this opportunity and others like Warriors and Quiet Water. I also got to use the GI Bill to attend Sweetwater Guide School in the Bighorn with four other young vets in my class and they said about half of each of their 12 courses here are veterans. Our local TU chapter, Mountain Bridge TU in Greenville, South Carolina has been doing excellent work in our area in conservation with the hard work of Army vet Gary Davis and organizational leadership of Army vet, Tom Theus. Just wanted to put it out there that a major group of young fly fishers was overlooked and the use of the sport as recreational therapy as our world moves faster and faster, young people are seeing the benefit of slowing down."
Well, thank you, Mike, for making that point. That's a very good point. By the way, if any of you are interested in the work that Project Healing Waters has done and similar organizations, I've done two podcasts in the past, one was in 2011, but the most recent was in February of 2020. So, if you do want to learn more about Project Healing Waters, you can go back to the archives and look up those podcasts. Here's an email from Matt in Berkeley. "I'm getting ready to go on a trip to Bolivia targeting Golden Dorado. The drip is in the spring and is long way off, but I've been starting to tie recommended flies which are all big six to eight inches on long shank hooks.
Golden Dorado are known for their aggressive fighting, jumping, and violent head shakes, which is the whole reason I'm going, but these big flies and long shanks will give the Dorado an advantage in shaking the hook. What do you think about tying on a tube fly platform? I use tube flies, mousing in Russia, and those tube flies were so much more effective than the traditional single hook mouse patterns. The fly disconnects from the small hook tucked into the tube once the fight begins and the fish loses that leverage they would have from a traditional long shank hook. And as a bonus, the fly doesn't get torn up during the fight. As a result, my loss and hookup ratio were much better with the tube fly and the fly lasted longer.
I would just go ahead and tie all my flies on a tube platform but I see no evidence based on Google searches that anyone is using tube flies for Dorado. I'm hesitant to go rogue with the tube fly since I would be going all the way to Bolivia with an unproven system for Dorado. What do you think? Do you believe in tube flies? Should I break with tradition or play it safe? Can you talk about the pros and cons of big flies on traditional hooks versus tube flies? I believe a tube fly episode would be a great discussion for your podcast. I searched the Learning Center for tube flies and only got float tubes and YouTubes. I know this would be a new topic for your listeners if you believe or care about tube flies."
So, Matt, I think it's a great idea. I think that tube flies are a vastly underrated and an underused resource. There are a number of advantages to tube flies. The biggest one is what you mentioned, you can tie a big long fly with a wide short shank hook and a wide short shank hook is going to give you a much better catch ratio in any fish. You found that with mousing in Russia, I've found that with steelhead fishing, I use tube flies a lot for my steelhead fishing. In fact, you know, a lot of these intruder flies that you see tied on an articulated shank with a piece of wire or backing that then attaches a intruder hook to it, these would be great on tubes.
I use them in salt water a lot, I use it for striped bass and blue fish, occasionally tarpan. And for any fish that fights hard like that and you need a long fly, I think that tube flies make all the sense in the world. The other advantage is that if your hook rusts, you can just replace the hook and your fly is still good. You know, usually, the reason flies have to get trashed is because the hook gets rusty. And if you don't have...if you can replace the hook, then you don't have to worry about that. And also, you can pack a lot of them in a fly box because you don't have those hooks sticking into all those grabby materials. And I just think the world for tube flies as you can tell, and I think that more people should use them.
Now, that being said, I've never fished for Golden Dorado and as you said, nobody seems to be fishing for them with tube flies. I think that you're on to something but I would hedge my bets. Since you're a fly-tyer and you got a lot of time, I'd tie half the patterns on standard hooks and half on my tube flies or maybe some with a intruder hook tied on a piece of wire or a backing that hangs behind it. So, I would take both with you but I think you're gonna find that the tube flies are going to be a big advantage for Golden Dorado. But I think you should tie both and you should report back to us after your trip. And nothing is...yeah, I should do that either for one of my live tying sessions on Mondays or do a podcast on tube flies, I think that's a great idea. So, yeah, more people should use them. I use it for trout two ways and I use it for trout streamers. So, anyway, yes, I would try it but hedge your bets, just in case.
Here's an email from Alex from New York. "As we travel around from state to state and river to river, regulations change regarding number of flies you're permitted to use and you got to be careful with all the supplemental regulations. But as an example, in New York, to the best of my understanding, general inland regulations permit up to 5 flies and up to 15 hooks in any combination on a single line." Wow. "Frequently, I most often see people using one or two flies and I occasionally hear of a three-fly rig. So, this all said, I started experimenting with three-fly rigs last year were permitted.
Typically, a triple dry since I've had pretty good luck avoiding tangles using all dries versus other configurations. Dare I say I've had better luck fishing three flies than two. My questions, regulations aside, how many flies would you ideally put on a line when trout fishing? How does fishing dries versus dry dropper versus nymphing affect that decision? Have you ever fished four or more flies on a single line for trout? I have to say my confidence is high watching my trio of dries float down the river toward rising trout. But am I getting out over my skis as I consider upgrading my trio to a quartet?"
Well, I think so, Alex. I regularly use three flies and I use a dry dropper, I use a big dry, I use a relatively large nymph hung from that, and then I'll hang a smaller nymph from the bigger hook. And it tangles, as you said, fishing three dry flies, you don't have tangles as often. But I think four is excessive and particularly if you've got any kind of brushy situation or you've got a lot of wind where you might hit your rod or hit yourself with a tangle. I think that you can probably do really well with three and I think, in my opinion, four might be excessive. You know, in the old days when people didn't do as much casting, you know, I'm talking like 1850s, 1860s, and they only fished wet flies, they would fish as many as, I don't know, 10 or 12 different flies on a single leader.
But they weren't doing a lot of casting, they were just, you know, picking it up and putting it back on the water and swinging it, so they didn't have as many problems. But, you know, it's certainly part of the tradition of fly fishing to fish multiple flies. So, I would stick with three. If you want to try four, so ahead and see how it works. I think you're going to start getting into tangled situations and you're gonna...don't forget that you're going to get fouled hook more fish when you fish multiple flies because a lot of times, fish will go for one fly and you'll set the hook and they'll get fouled by second or third or fourth, in your case, flies. So, that is also a consideration. Anyway, I'd stick with three, I think you're good enough.
Alex: Tom, this is Alex from Texas, I just want to thank you for everything that you're doing for the fly fishing community. It's amazing how much information I'm gleaning from you and how much time it's saving me from making mistakes on my own and learning from those mistakes. I had a tip and a couple of questions. The first tip was, I remember from our previous podcasts and we talked about bringing a garbage bag with you so that you can kind of pick up trash on your way down or the way out from fishing. I started doing that but if I'm fishing multiple days, sometimes I'll forget to refill the trash bag, a little grocery bag when I'm going down to the water. So, what I do now is I just pack my snacks for the day inside a fresh bag and that way, I have a bag with me to collect garbage on the way out. On my regular waters, I've already noticed a marked difference in just how much more pleasant things are now just picking up just the odd things and garbage on the way in and the way out.
A couple of questions for you. First of all, so when ting flies, I really don't always like to use head cement or nail polish superglue or UV resin or anything like that because sometimes it interferes with the hackles, sometimes, you know, the goop that comes out, sometimes it clogs up the hook guide. And so, I was wondering what do you think about just doing a double or triple-turn wood finish on there? Just wood finish it twice so in case one breaks, that you still have another wood finish under there. Sometimes I've been putting a little bit of the head cement on the thread as I wood finish it but even then, sometimes a little bit of cement squeezes out and gets in the way and it looks kind of messy. I don't know what you thought about that or if you thought this is recommendable or not.
The second question is one time I was out on the water and my fly line broke. Well, so I haven't had spare flying line with me but I couldn't remember how to do an Albright knot to connect the flight line to the backing and I didn't have a cell signal to look it up. So, all I did was I did an overhand loop on the backing and that way, I can create a loop-to-loop connection. Is that something that I should be worried about? Should I go back and redo the knot, or do you think an overhand loop would work fine? This is for a 5-weight rod. I'm just mainly doing trout fishing with this one, so it's not like I'm really going to put a whole bunch of torque on there.
The last question is regarding throat pumps. So, I've been using them and fascinated by the things I'm pulling out of the fish's gullet and try to figure out what's going on. It's kind of teaching me that I actually learned some things from your podcast and some things I'm just trying to figure out and still learning. So, today, I was on the water, the first couple of fish, I was able to extract the contents from the gut and identify things, and then the next six fish I caught, there was just nothing. And I've gotten pretty proficient, I'm kind of surprised when I don't pull something out. But for the rest of the day, anytime I would try and extract the contents of the gut, nothing but water came out. And so, I was kind of surprised about that. Should there always be things in the gut of a fish? Or is that something that's you find hit or miss, sometimes they just don't have anything that they've been feeding on?
And one request, I went to the Orvis Learning Center, I was hoping to find information or maybe...I see the flashcards for the nymphs and different types of bugs. But is it possible for you to ask the good people over at the Orvis Learning Center if they can put some kind of graphics or diagrams about the different types of bugs that...when they're extracted from a fish. And so, there's real-life photographs and examples of how to identify what's there. Certain things are easy to see and recognize, certain things are know, they're a lot harder, and maybe a great addition for the Learning Center I think, especially as you're starting to talk about throat pumps more and I'm finding it very useful for my time on the water. Anyways, I'm sorry about this long voicemail, but I do appreciate you and I look forward to hearing the answers. Thank you, Tom.
Tom: So, Alex, those are some good questions. I like your tip, you know, taking some kind of bag to pick up trash is always a good idea and everyone appreciates the fact that you do that and more people should do something like that. As far as double whip finish is concerned, yeah, a lot of people do that. I know Tim Flagler does it sometimes. Double whip finish is probably going to be almost as good as using head cement. And, you know, if you don't like using head cement or any kind of adhesive, yeah, go with a double whip finish. I think that's probably going to protect your flies just fine.
Regarding that fly line that broke, I assumed that the fly line broke toward the rear end in the running line. Yeah, a double surgeon's loop in your backing will work fine. What a lot of people do is tie a bimini twist in their backing and then make a loop out of that that's a little bit stronger and has a little bit of flexibility. But, you know, for trout fishing where you're probably almost never going to see your backing, then I think that double surgeon's loop in the backing should be fine. And then your question on throat pump. Yeah, sometimes what happens when you hook a fish and you play it is that they spit out what's in their gullet.
Don't forget, you're not really going into the fish's stomach, you're going into their throat, or I guess the gullet you'd call it. And that stuff is fairly close to the surface and a lot of times when they're fighting, they'll spit it out as they're fighting. So, that may be a reason that they don't have anything in them. Or it could be that you just happened to...they weren't feeding and you just happened to put something attractive in front of them and they ate it. But yeah, I frequently find fish...when I use a throat pump, I frequently find fish with nothing in them and I'm never sure why either but probably one of those two things is the reason.
And your request for graphics on different types of bugs when extracted from a throat pump. Nah, not going to happen. It's a little limited, and I don't have those graphics nor do I want to spend a summer getting them. So, I don't think you're going to see that. I think the best thing you can do is carry a little white bowl or a jar lid or something with you and once you extract those contents, put some water in there and swirl it around with, you know, the tip of your pocketknife or something and just see what you can identify.
And yeah, you're not always going to be able to figure out exactly what the fish is eating, but at least you can tell about the relative size of what they were eating and, you know, learn your entomology a little bit better so you can tell the difference between the head or the tail or the abdomen of a stone fly versus a may fly versus a caddis fly. But I don't think you're gonna see those graphics, so don't hold your breath. All right, that is the Fly Box for this week. Let's go talk to Nelson. And I know that I learned a lot in this podcast, and I find it fascinating and I hope you do as well. Well, my guest today it Dr. Nelson Ham? You've got a doctor?
Dr. Ham: Yeah, officially is doctor but nobody calls me that.
Tom: And I noticed that Nelson had email something to the podcast, I forgot how we originally got started, but I noticed his signature, he was a professor of geology. And I've wanted to do a podcast about the effects on trout streams of geology and the landscape. And luckily, Nelson has also done some other research and has studied the effects of logging and land use practices on trout stream. So, I thought that you'd be the perfect guest for the podcast. Do you want to tell people a little bit about your background?
Dr. Ham: Yeah, I can do that. You know, as an undergraduate student in geology, I had a mentor who was a geomorphologist. Geomorphology is basically studying landforms and landscapes and I fell in love with that kind of geology. I went to graduate school at UW Madison here in Wisconsin, and got really lucky, I had three really great mentors that were all geomorphologists. But I got really interested in glacial geology, Ice Age geology, and worked in Alaska on a modern glacier. And then had a chance to map geology in the Northwoods of Wisconsin in two counties that basically had some of the, you know, original premier trout streams, at least that folks think about in our state. The Wolf River, which I'm sure folks have heard of before, which is a wild and scenic designated river, the Prairie is another one that's really well known in Wisconsin, and a few others.
But I wasn't a fly fisherman then, but I had a couple of buddies in grad school who were and as soon as I got my first job at St. Norbert, this actually is direct he related to you. I was watching a weekend show and there was some sort of fishing show and I can't remember if you were on it or not, but I went out and grabbed "The Orvis Fly-fishing Guide." That was back when it was in black and white, probably that was 1996 or something like that. Read that book, and it totally convinced me that fly fishing was the way that I wanted to get back into fishing. Took a class, I learned to tie, basically reading like Randall Kaufmann's books, I remember him from Kaufmann Streamborn. I think I bought every A.K. Best video when those came out because they were so good.
And was fishing and then one day, I don't know a couple of years later, this guy named Tim Landwehr opened a fly shop about a block from my school. And I know you've had Tim on your show I think maybe last year or a couple of years ago, he's now, of course, really well known for writing, you know, that relatively recent book on modern strategies for fishing for smallmouth. And just has a fantastic shop, you know, one of the best in the Midwest. And I hung around the shop, he started to ask me if I wanted to help out a little bit, and then eventually, it turned into him offering me a guiding opportunity in the summer for smallmouth. And so, I owe a tremendous amount to Tim, he is a phenomenal guy, of course, and everybody knows that.
So, when the guiding started, a lot of the trips were on the Menominee River, which is the border river between Wisconsin and the UP large river system, great for smallmouth fishing. But when I started floating it, things just didn't look quite normal to me. I mean, as a geologist, I was seeing things in the stream channel that I didn't expect in typical natural rivers. And, of course, it turned out that river had run, you know, millions of board feet of logs down in the late 1800s. It had rocks dynamited out of it. And I really got into the history of that river in particular and that really started, you know, me falling head over heels for combining geology and talking about streams, and then also trout streams as well. It was really the Menominee that got that going.
And then it snowballed. I got asked to give talks for local TU chapters, and I said, "Well, you've got plenty of guys around here who can talk about fishing, but what if I talk about, you know, the evolution of these streams that we fish and how they've changed over time and what, you know, Euro-American settlement did to them" And eventually, that's turned into the last 10 years of working with our state DNR, the U.S. Fish and Wildlife...I mean, the U.S. Forest Service, workshops and things like that, because people involved in trout stream restoration and management nowadays just really are soaking up, you know, the information on the geology. They want to know why a river is the way it is, and also what it was like before, you know, we started altering it and what's the so-called legacy effects. So, even 100 years later, you can see things in a river that are left over from how people modified them, you know, when they were first moving into the Midwest or the Northwoods and probably cutting down trees and modifying chance. So, that's kind of the short story.
Tom: Well, let's talk about...first, let's first talk about some of these historical effects of land use practices and what they have done to trout streams and, you know, how they've shaped the rivers.
Dr. Ham: Sure, I think, just as a teacher and a former student, and my guess is a lot of your listeners have heard of a meandering stream, you know, kind of the classic view of a river that kind of sneaks its way down the floodplain. And, of course, we were taught, you know, 20-30 years ago that that was a real common type of river system and it's really common today. And everybody assumed, "Oh, that's got to be the way those rivers were before," and it's just not not the case at all. Rivers are and were in many places really different naturally before we started changing them. And, you know, there are some cool examples from the kind of mi-Atlantic region, thinking about, you know, your area plus to the Northwoods up in the northeast and the Great Lake states.
So, one quick example of that is, of course, the whole eastern United States was covered with forest in the 1600s, and of course, there's very little of that left, you know, Great Lakes in the northeast and few other places. And as your American settlers came in, you know, the thought was, "We want to conquer this forest." In Europe, of course, they were coming from places that had been logged off, you know, for hundreds of years. And the idea of this vast impenetrable forest, no places to grow crops, kind of drove them to start clearing the land so they could grow crops and basically start the agricultural period in the early history of the U.S.
And so, that clearing really caused a lot of problems. So, all the trees were cut down and then they didn't know how to manage the soil very well, so soil erosion was tremendous. And that's in the Eastern U.S. and we have great examples in the Upper Midwest too. There were lots of mill ponds that were built, of course, on the rivers, and a lot of those mill ponds trapped just tremendous volumes of sediment that was being eroded from the landscape. And I think I read in an article that one geologist estimated 6,000 to 7,000 or more mill ponds. So, imagine every single river in places like Pennsylvania having multiple mill ponds along and, you know, if they were of any size.
Tom: Oh, yeah, if you look at old maps of some...even these little tiny Vermont trout streams, if you look at old maps, you can see just dam after dam after dam after dam, and I still find some of the old foundations. Yeah, it's amazing how many dams were on these rivers, mill dams.
Dr. Ham: Yeah, exactly. And there was a really neat paper, kind of a game changer in river science. About 15 years ago, a geologist named Dorothy Merritts from Franklin and Marshall College, I don't know exactly where that is. Her and a partner of hers were out looking at these stream channels in Pennsylvania, and these really thick piles of silt and clay. And they looked at the bottom of those sequences and started to find that there were layers of wetland plants and gravel that were buried by all of this stuff and realize that, "Oh, yeah, this, you know, 8 or 10 feet of silt and clay is really all a product of soil erosion, it's not natural, these rivers weren't doing this naturally before settlement. It's really what was underneath that pile is what probably the rivers were like and the streams were like before."
And the picture of what streams used to be like now has changed. So, instead of a single channel, that kind of, you know, snake-like, you know, goes down the river valley, you have what's called's a $10 word, it's called a nastimose [SP]. But basically, you got to imagine a stream that has two or three or four or five small channels that are connected to each other. They're stable, they're really well connected to their floodplain, and you have a lot of wetland, you know, next to those. So, soil erosion was minimized, there was a really good connection between the groundwater and the water flowing in the streams. But that was such a fundamentally different way of thinking about streams in the past.
And basically, her and another person she worked with wrote a neat paper called, "Are there any wild rivers left at all when you really think about it?" And I think the answer in like the eastern seaboard and the Midwest, we're not thinking about remote areas of Alaska and so on, is probably almost every typical trout stream that we fish in the lower 48 is not what it was before we started to change things. Even though, you know, the forest might be back...Wisconsin's a great example, you know, I walked through trout streams in northern Wisconsin, there's not a soul around, you would think you were there 500 years ago, but those rivers are not what they were, you know, before we settled them. And that's a really interesting and kind of eye-opening part of river science today is that what we think of wild rivers is really not even close to probably what they were in the past.
Tom: And so, you said the classic meander scenario is more a result of logging and erosion and siltation than it is of a natural stream course?
Dr. Ham: Well, you know, in the right situation meandering would expect it. It can occur naturally but there's one kind of really interesting aspect of how people have think about rivers and how that drives a lot of stream restoration work. There's some great examples like in the western U.S., California was one that I can think of, a project of a couple of million dollars to know, "restore" a trout stream. And when they had finished, there was this absolutely beautiful, perfectly symmetrical meandering stream and there were boulders placed at just the right spots, and so on. And less than a year later, it was completely destroyed during a couple of big storm events and it didn't look like a meandering river anymore.
Basically, it was back to a type of river you would expect in terms of the dry West, which is called a braided stream and you see those at glaciers too. And people that kind of studied that failure, one fella, in particular, he had a really interesting idea. He said, "I wonder if a lot of stream restoration and our notion that rivers have to be meandering streams is a product of, you know, what people were making them look like in England, for example? And is it more the aesthetic, meaning they don't understand that maybe that's not a natural stream system for a certain, you know, combination of climate and geology, but we always think that's the best stream, you know, like, that's the ultimate?"
And it's clear now that that's not the case, it really depends on the geology and the climate, you know, in particular, as to what kind of stream is the natural stream for that area. But we've kind of forcing things to look like the classic meandering stream when that's really not necessarily the right thing to do.
Tom: That's fascinating.
Dr. Ham: There's a great river scientist, a woman named Ellen Wohl in Colorado, and she was here in Wisconsin and gave a talk and one of her two talks actually, she had the slide up and the title is, "Messy streams are healthy streams." And she's been trying really hard over the last 10 or 20 years to convince people more and more that the messier a river is...and what I mean by that is a lot of wood and a lot of variability physically and a lot of changes in the types of boulders, whether you go with gravel or sand or big boulders, basically, the messier it looks, ecologically it's probably the best.
And what we've done to a lot of rivers is we've kind of cleaned them out, you know, to the point where there's just not a lot of physical complexity there. And in turn, there's not enough of those ecological niches for, you know, in one place to have spawning gravel and other places for cover, you know, things like that. Places where aquatic insects are really, you know, doing well, that we've got to kind of step back from the old notion that, you know, a pretty snaking river down the valley, easy to get to, easy to fish is really best for the trout and really best in terms of showing us what a stream used to be in the past.
Tom: And so, what other things historically were features on trout streams? I'm thinking, for instance, beaver ponds.
Dr. Ham: Yeah, beaver is a really...that's a great question. Beaver, as you probably know because you get to travel so often, some anglers are okay with beaver and many of them are not.
Tom: I have a lodge in my backyard on my stream.
Dr. Ham: And I wish I did too. Just to give you an example, in Wisconsin, beavers are not particularly popular in terms of letting them come back, you know, and reoccupied streams, but it's different in other places, beaver actually being used as a restoration tool, you know, in the western states.
You know, I kind of think of the fur trade as being the first really widespread systematic change in the stream systems across North America. You know, so Canada and good chunks of the Northern, you know, lower 48 states. So, you would read historical accounts Wisconsin, someone writing in the 1700s that basically, they had to bust through 100 beaver dams over the course of just a few miles on a stream because they were just so dense and what it was like to portage through some of that stuff. But when the beavers were here in abundant numbers, so pre-fur trade, river systems were really different in terms of how they function, so I'm talking about the river, you know, streams, that beaver would typically be on, the kind of small to medium size.
So, imagine you got a big storm, a bunch of rain gets dumped in the landscape, and what happens is those sequences of beaver dams slow the water down. You know, the water moves fast in between any two dams but it really gets slowed down when it enters one of the ponds, the beaver pond. You know, it gets released kind of in a more controlled way through the dam to the next section of the stream. That really, you know, enhanced wetlands, wetland development in the ponds, it reduced the effect of floods in the landscape, there was far less erosion of the channel and mobilization of a lot of sediment.
The fur trade comes along and we just take these, you know, tremendous numbers of beaver out of the landscape, their dams are gone, and, in general, the view was we're not going to let them back, right? So, we don't want to back so, so river systems now are just connections of open channels, that basically water can move through much more quickly. And in the Upper Mississippi Valley, there's a fellow years ago who basically said, "We should really bring beaver back, you know, not just because it might be a good thing ecologically but fundamentally because of flood control." Because the numbers of big floods in some of the river systems in the Upper Mississippi, you know, clearly started to increase, there were more floods and there were bigger floods after the beaver gone versus, you know, when they were here in the past.
And, you know, there are folks who would say, "Well, I don't like beaver because, you know, it killed my favorite fishing hole." And I've had that happen to me, I understand that. But, you know, if you want to think of things a little more broadly and a little more holistically, in many places now, you know, putting beaver back in the landscape has lots of benefits. It raises the water table, you know, encourages the development of wetlands, which have all kinds of positive impacts. And people are forgetting that, you know, brook trout in the eastern half of the United States, they evolved with beaver. They're not exclusive, right? They were all there together. And I think really slowly in some parts of the country and faster in others, people are realizing that letting beaver come back in the right streams in the right situations is a really good thing to do.
Tom: Yeah, I actually did...sorry.
Dr. Ham: Yep, go ahead.
Tom: Well, I was gonna say actually did a podcast on beavers and trout last year, and had an expert on beavers who've written a book called "Eager." And he made the point, which was a total game changer for me, that everybody thinks that beaver ponds warm up the water because the water gets stagnant when actually, that water that floods around the margins goes underground and is cooled before it comes back into the stream. So, they actually keep the water cooler as opposed to warming it up.
Dr. Ham: Yeah, and that's exactly right. And I think, you know, over the years in places like the Upper Midwest, there were very few studies and there was one, in particular, that seemed to kind of drive decades of anti-beaver sentiment in terms of, you know, letting them come back into streams because it was a fairly basic study but it said supposedly that beaver dams warm the water. And a lot of that recent work like with your guest, and even more recent stuff that I've seen, that's just not nearly that simple. Is it going to happen in a few places? Sure. But actually, a lot of the things that we thought beavers did that might be detrimental to trout, it's just not true or it's not the most common situation.
Cool quick example I can think of, we in Wisconsin, like many places around the country, have started to see storms that are more intense. You know, you get a lot more rainfall in a short time and you get a lot of water coming in. Up around Lake Superior, there's a county, Ashman County which has some really great brook trout streams. In a couple of recent storms in the last two years, they had just tremendous rainfall. Culverts were completely washed out, roads were washed out at bridges, tremendous erosion inside these channels now that might, you know, have 8 or 10 feet of sediment exposed.
But in the few places where the beaver are there and there are some places where streams still have beaver along them naturally, you almost couldn't tell that you had a storm of any kind just looking at the stream systems, you know, after those storms had passed. So, a lot of wetlands guys, I think, they're really focused on trying to do a better job educating, you know, that beaver good in the right circumstances. They may not be perfect in every circumstance, there's a lot of things to consider, but, you know, fundamentally we're slowly figuring out maybe by being dragged along by some of the recent science, the good science that's done that beaver are great to have in a watershed.
Tom: Yeah. Well, let's get into geology a little bi and how it shapes a trout stream. How important is the geology of the landscape?
Dr. Ham: You know, you've written, I remember, a great article a few years ago that I first saw in "MidCurrent." And I don't know if you wrote it specifically for that website, but I think it was called, "Rich and poor trout stream."
Tom: Yeah, it was an excerpt from a book I did called "Prospecting for Trout" many years ago. Yeah.
Dr. Ham: And I remember reading that and thinking, "Well, you know, Tom Rosenbauer knows a lot about geology and trout streams," you know, and it was a really cool article to read and it's still up on the web for those that might want to find it. So, you know, I always think of the classic view of most new fly anglers and old fly anglers, that it's the difference between spring creeks and freestone. I mean, those two terms, right, it's either-or...
Tom: Yeah, or tailwater.
Dr. Ham: Or tailwater, but in a more natural system, you're thinking of whether you've got one versus the other, I'm kind of thinking more of natural system. So, you know, fundamentally, one of the interesting things is what those...the reason those streams are different is fundamentally what the geology, what the rocks are that are in the watershed that the groundwater has to move through. And, you know, the role that groundwater has in shaping the chemistry of the water that's in the river is something that most people don't think about, or they at least don't think about how important groundwater is, in general. to trout streams. So, we could talk about chemistry a little bit but if it's okay, I'll mention just a little bit about groundwater and water temperature.
Tom: Yeah, go. Sounds good.
Dr. Ham: So, you know, if you look at different factors that, you know, seem to predict where trout streams are, and again, because of my experience, it's more upper Midwest. And in Wisconsin, you have a map that shows you something about a stream called a baseflow index, which is not complicated. All that is, is that the baseflow index is at a percent. So, 50%, for example, let's say we've got a stream of 50% baseflow index, what that means is 50% of the total flow of water in that stream is coming from groundwater. And what we see in places like Wisconsin and elsewhere if you look at those numbers, is that it's almost a perfect predictor of where trout streams are and where they're not in the state.
So, if you have a baseflow index of 50% in Wisconsin, plus or minus a little bit or more, there are almost always trout streams there. And kind of the big black holes in the state where we just don't have any trout streams and one of those is kind of my area up near Green Bay and heading directly south of us, the baseflow index is a lot, lot lower, 10%, 20%, 30%. So, the difference really is high baseflow index, you basically got streams that have a large groundwater input. So, they're going to be more stable in temperature, they're more stable in flow, which really enhances trout...not habitat, but trout livelihood in terms of, you know, doing well and surviving the winter and getting through warmer periods in the summer, and so on.
And if you have numbers that are much less than that, those are rivers that have really low flows when it hasn't rained for a while, and then they just explode once you get a big storm. So, they're know, most of their flow is basically rainwater fed, water that's coming off the landscape, you know, or running off, as we call it, or runoff from the adjacent hills. The river gets really high super quick, and then once that rainwater passes, it gets really low again. And in those know, in those streams where you've got such low baseflow in general in baseflow index, those are the ones that tend to rapidly warm, they're too warm for trout, there might be other geological reasons why trout won't do well there.
But the know, if I have one message for people thinking about what's the single most important thing we need to pay attention to if we're worried about the future of our trout streams is it's not know, the in-channel work, that's all really important. But it doesn't matter how much you do in the channel, right, in terms of restoration, if that cold water storage is cut off, that stream is dead for trout. It's not going to be a trout stream anymore, even though, you know, we did a great job trying to enhance the habitat.
Tom: Now, where can people find that baseflow index, Nelson? If you go on the USGS site, will you be able to find baseflow index for different...?
Dr. Ham: Yeah, actually, you can. And usually, the know, if you have a state geological survey, those are always a great source of all kinds of geology information. And oftentimes, the people that work there will not just tell you where to find something but if you have something that you need in a certain form, they'll actually get it to you, which is basically what these state surveys are supposed to do. But even just an online search for baseflow index of the U.S. will bring up maps, or baseflow index of the state. You'll easily find, you know, examples of work that people have been doing on mapping baseflow index for streams across the U.S.
So, the cold water connection and groundwater is something, you know, as a teacher over the years, I've realized that just most people don't know because they've never thought about it or heard about it. But the example I like to use is if you've got a thermometer sitting on the side of your house and it gets to 80 during the day and 50 at night, that's going to be recorded in that thermometer. If you stick a thermometer 10, 20, 30 feet below the surface and you could see what temperature it was recording, you wouldn't see that daily variation. In Wisconsin and in Michigan and up where you are in New England, right? And you've written about this before, the temperature the ground feels a few tens of feet down is the same as the mean annual air temperature for the year. And I can't remember what it was, you had a great map of that in, I think, your book on fishing small streams. That was a few years ago.
Tom: Yes. Yep.
Dr. Ham: Yeah, that map showed, you know, "Well, what's the average groundwaters/mean annual air temperature across the United States?" In our latitude, right, Wisconsin, Michigan, we're in the 40s typically. So, I always consider southern Wisconsin is closer to 50, Northern Wisconsin is maybe closer to 40. So, let's just say the average is 45. When it rains, the know, that rainwater infiltrates and it has to move through the ground, it's moving through that zone where the ground has a temperature of like 45 degrees, and that's really the refrigerant that I always think of that cools off, you know, the water that infiltrates in.
And then, you know, that river discharges to a stream, that's really your prime...that's your number one source of cold water for trout streams, it's the water that gets cooled a few tens of feet below the surface when it gets there. Yeah, sure, rainwater and runoff obviously affect the temperature, you know, when storms pass through and so on, but that's why groundwater is just so critical. That is your primary source of cold water.
Tom: Oh, well, the baseflow index is a new term for me and I guarantee I'm going to use it in the future. Thank you.
Dr. Ham: Yeah, you'll find plenty on it. Forty percent to 50% or more is pretty common. And like I said, 50% or more in Wisconsin is almost a dead giveaway for where the trout streams are. But, you know, the whole idea of knowing what baseflow is and baseflow index is just everything to do with whether or not you're going to possibly have the right geological conditions.
Tom: Okay. Now let's talk about chemistry, let's talk about geology and its effect on chemistry a little bit, water chemistry.
Dr. Ham: Yeah, well, one last thing I'll just say about the groundwater thing...nope, that's okay, it's just, you know, trout anglers are for the most part as a group, they're passionate, right? They want to do good things for trout streams, so much of us as a group are involved in TU work and other kinds of stream restoration and volunteer to do it. If you start to see really big changes in your trout streams and that baseflow index is being affected, so the flows keep going down over a number of years, there's only a couple of, you know, real reasons that that might happen and one is, of course, climates changing.
And so, if you have drought, you know, or if you have long spells of dry conditions, the groundwater is going to go down and so is the flow from the groundwater in the adjacent stream. But, you know, in many places, we're not know, I'm thinking of the Midwest into the East, you're not seeing drier conditions but we still see streams where that baseflow is changing and in many places, it's all about groundwater withdrawal from wells. And we, over the years, have not done a good job managing groundwater resources for surface water like trout streams.
But, you know, the really big wells, what we call high-capacity wells that can pump hundreds of thousands of gallons of water a day out of an aquifer...there's so many examples, Wisconsin included. One of our big areas is called the Central Sands where there's some trout streams that ran completely dry over some parts of the summer in the last couple of decades, but it's the biggest concentration of these high-capacity wells. But we're not managing those well, although it's getting better I think.
The same thing with other places around the country. There's a direct connection between the groundwater and what you see in a stream, they're one and the same, they're not different water. A buddy of mine I teach with has always said that, basically, the surface of a pond or a lake or a stream is the water table, it's just sticking out of the ground because it's all part of one system. But yeah, really paying attention to what's happening in terms of groundwater withdrawals is really critical, you know, in places of trout streams, just to maintain that baseflow. That's so critical. Yeah.
Tom: Are these mainly municipal wells you're talking about, these high-capacity wells?
Dr. Ham: In places like the Midwest, you know, municipalities will always have high-capacity wells, they have to, you know, to supply the water. But you know, the biggest number in the agricultural regions are being used to basically supplement water for dry periods. So, instead of having to worry about, you know, when the next rain is coming, you just make it rain on those crops by pumping water out of the ground. And that's our state, there's many more high-capacity wells that serve agricultural uses that's just municipalities.
And it's kind of that explosion in their use without some really careful thought and how are these going to affect surface water supplies like lakes and rivers that have really created some of the real concerns among, you know, a lot of our trout anglers. And this is the same elsewhere on, basically, what are we doing to groundwater and how is it impacting our surface water supply and the trout stream that needs that high baseflow index, needs that cold water that's sustained throughout the year? So, water chemistry.
Tom: Yeah.
Dr. Ham: Yeah. A couple of things I can kind of think of, I remember reading...and I think this will relate directly to trout anglers because we can talk about mayflies a little bit. There was a study years ago, like 40 years ago, a couple of British scientists were studying the ecology of a river in England. And they did this controlled experiment. So, they collected mayfly nymphs from the river and had them in tanks like aquaria in a lab and they had normal river water for one group, and then the other, they use distilled water. So, I mean, just in general, right? Distilled water has no other dissolved ions in it, it's water for the most part, pure H2O. And those mayflies that were in the tank of distilled water basically all died.
And it was a simple but kind of classic example of pointing out that, you know, the chemistry of the water, first, just having any number of dissolved ions in it, but then, you know, what specific ones are there and how many just exerts this really big control on trout streams, from the aquatic vegetation to the aquatic insects, and then, of course, up the food chain to the trout.
You know, we always think of that classic spring creek, like that would be the Driftless Area in Wisconsin, or the spring creeks of Pennsylvania, or some of the spring creeks in Montana, you know, why are they so rich in trout? Why do they get so big? And it's fundamentally because the geology around those is usually limestone, there's another rock called a dolostone that's pretty similar, and those are rocks that have minerals in them that can easily be dissolved. And again, this happens mostly by the groundwater moving through those rocks. So, again, that's why groundwater is so critical. And the water has the most dissolved ions in it, has the biggest load of, you know, cations and anions.
The pH is usually high, so it's basic instead of acidic, which also promotes all kinds of productivity in trout streams. So, ultimately, everything goes back to that. And I guess to start, what I just say is there was a chart one time I found from the USGS and all it did is it compiled what's typical water look like from rainwater, from groundwater in different streams and surface water streams. And you have to remember, what you need to keep in mind is that all that water that, you know, winds up in your trout stream started as rain to begin with. But rainwater is, generally speaking, really low in dissolved ions, sometimes almost to the point of looking like distilled water chemically.
And the reason is because when you evaporate water off over the ocean, over a lake, or a stream, that's a pretty pure process, and what I mean is just the water is going into the atmosphere, right? And then, you know, there's opportunity for change. So, you know, it'll pick up some components from atmospheric dust and things like that that will give it a little bit of chemistry, you know, beyond simply the water. But the other thing that happens is normal rainwater is always acidic. So, yeah, on the pH scale, right, ordinary rainwater is about five and a half on the pH scale, so it's slightly acidic. So, that water comes down as precipitation, you've got a slightly acidic water that doesn't have a whole hell of a lot in it in terms of dissolved ions. So, why is it then when you look at river water like in a spring creek, it's just loaded with dissolved stuff?
And the answer is that slightly acidic water and the right rock types as it moves through as groundwater reacts with those rocks, breaks them down into their constituents, you know, in the case of limestone, it's calcium and an ion called carbonate ion. It gets more of those dissolved minerals in it, and then finally it reaches the creek or the stream, you know, it's a spring creek, and it's fundamentally different water than when it was raining. And the other thing is, the pH is usually high too. So, instead of being five and a half anymore, it's seven or eight, you know, or even higher than that I've seen in some areas.
So, you know, you're always starting with rainwater that doesn't have a whole lot in it and it's slightly acidic, you know, and kind of think of it as, "Okay, that's my starting point." And then, yet, you know, in different terrains, depending on the geology, that river water is going to look fundamentally different, you know, chemically. So, to use that spring creek analogy, you know, you know there's two and you've written about it, spring creeks are really synonymous with limestone and there can be another rock that's similar to that called a dolostone. And the only real differences, there's a little bit of a chemical difference, but they both are really easily to dissolve if you have that acidic water.
So, if you think of Pennsylvania or the Driftless Area, Wisconsin or the Montana spring creeks, it rains, that water a certain percentage starts to move through the groundwater system, it's acidic, it can do a pretty good job of dissolving some of those minerals in those limestones and dolostone because they dissolve fairly easily compared to lots of other minerals. It gets into that stream and it has really high dissolved ions in it, the pH is above seven, which is, you know, really good. And it also has this third component of alkalinity, which, in a simple way, is just the ability of that water to kind of buffer acids in that change. And you've got just the right water to just cause this, you know, tremendous productivity in the stream, like I said, from the aquatic vegetation to the insects up the food chain to the trout.
Tom: Now, when you have rain that falls on granitic rock, insoluble rock like granite or gneiss, or some other harder rocks that don't solve, what happens there? And is there an in-between? Are there certain geologies that, you know, have slight buffering capabilities?
Dr. Ham: Yeah, that's a really good point that it's not really as simple as saying these limestone creeks are spring creeks, and then everything else is going to be a freestone. But, you know, to start, let's just assume that, yeah, you're in a you're in New England, Northern Wisconsin as an example, some places out west where, you know, what we say in geology is that you've got mostly crystalline rock. And crystalline rock basically means you've got your granites, you know, igneous rocks or metamorphic rocks that mostly have minerals in them that, like you said, they're not nearly as soluble as those minerals that are in the limestones and the dolostone.
So, that acidic water hits, right? It's moving through those rocks in the groundwater system. You just don't wind know, once that groundwater enters a stream, you don't wind up with water that has nearly as high dissolved ions in it. The alkalinity goes down, the pH usually doesn't get as high. I mean, it may become a little more basic but it's not, you know, nearly the same as it is for a classic spring creek. You've got less in the water for all the organisms that are in that stream to work with chemically and you wind up with less general productivity in those streams. They're not bad streams, you know, the natural situation is just the way they are because of the nature of how the chemistry changes as the groundwater moves through the rocks.
You know, you've written about that in terms of some of the creeks, I remember your article, you talked about, I think, a stream that was in New England, maybe in Vermont, draining I think granitic rocks, and you compared it to one of the spring creeks out in Montana and talked about that difference. And it kind know, it's one of is what it is based on the geology, it's not good or bad, it's just the difference between those two. So, yeah, the great question you asked as well, "Are there things in between?" We can call them a tweener, I guess.
Tom: Yeah, the rocks that are a little bit soluble maybe.
Dr. Ham: Yeah. You know, one of the things that really I've seen in the Upper Midwest in Wisconsin and it's mainly because I started off as a glacial geologist, that was really the type of geomorphology I was interested in. You know, you've got ice age deposits that are draped across almost all the states from Washington to Maine in the U.S. Glaciers do something really interesting and there's actually like an analogy to, believe it or not, thinking about volcanic soils. So, if you go into the tropics where weathering is super intense, you'll find people farming right up the sides of active volcanoes. And of course, the thought is, "Well, why in the hell would they do that?"
But that's because every time that volcano burps out ash, you're basically replenishing the soil of the ground with fresh rock that hasn't been leeched, you know, hasn't been altered chemically and had a lot of things taken out of it. And I kind of think of glacial deposits a little bit like that, where in, you know, the upper states, Wisconsin, we could use an example from almost any of the northern states all the way to New England and Washington, where basically what glaciers do is they grind up rock, typically the smallest size is going to be silt.
So, you know, grain sizes go from, you know, gravel, sand, silt, and clay. Silt becomes a really common size of material that glaciers produces, they kind of erode and kind of grind across the landscape and they're doing that to fresh rock, you know, if they're eroding downward, you know, a fair amount. So, they're chewing it up, there's a lot of fresh stuff in there, and then it kind of plasters it over the bedrock. In northern Wisconsin, we have things that, you know, I think a trout angler would...if they knew the difference, would say those are all freestone streams, but they're not exactly freestone when you really start to think about them.
So, for example, a lot of the streams that are in these crystalline areas have fairly high pH, and that's not something you would expect. Yeah, what's going on is it turns out that you're getting a lot of that baseflow from the groundwater that's moving through the glacial deposits above the crystalline rock even though you may see a lot of crystalline rock in the river valleys, you know, at the waterfall and stuff like that. And so, there's just really kind really is kind of this tweener situation, I kind of like that word. A Fisheries person, they told me they use that when you got a river that's know, basically, you can catch a smallmouth one time of the year and a trout, you know, some other times. It's between two states, you know, so they called them a tweener.
But you've got these kind of tweener streams chemically where, yeah, they look like...if you had a picture of them, you're thinking, "Ah, that's a classic freestone." But chemically, that water is a little bit different than that and it actually has even some character of spring creek water, where basically, where the water the groundwater is getting its chemical change, its ions and what's controlling its pH is, is moving through this fine, fresh glacial, you know, stuff that's sitting there. So, yeah, you know, like the total dissolved load, all the ions in the water is not as high as our spring creeks and the Driftless Area, but it's not bad in some places.
The pH really stands out as being, you know, fairly high, it's more basic water and you don't necessarily expect that in a real classic freestone stream either. Yeah, the alkalinity is not as high, you know, it's not as good at buffering acids or, you know, acidic rainwater. But you actually...and I was on a field trip with some Fisheries folks about a month ago in northern Wisconsin and one of them took us to the stream that was loaded with freshwater mussels, lots of aquatic insect life, and if you didn't know where you were and you were just looking at that stream, you'd say, "Maybe I'm in some sort, you know, spring creek situation."
But tilt your head up and you're classic Northwoods forest, cedars and white pine and hemlock and things like that. And a lot of the rocks that are in that stream are not limestone, they're the granite rocks that are real common in that area. So, you've got this really weird situation where everything tells you this is like maybe a freestone stream. But yet, it's not quite that far in that direction, it's kind of between chemically, the water is somewhere between a spring creek and a freestone and it's really productive. I mean, it's just loaded with good stuff for trout to eat.
Tom: Well, that brings up an interesting question because I've often wondered this myself and I had some theories and I get this question every once in a while on the podcast. You have a small freestone stream in Montana, Wyoming, Idaho, about the size of one of our little brook trout streams in New England, yet the fish are much larger and it seems like the food supply is greater. Is this because there's more volcanic rock there that's...?
Dr. Ham: So, where were we comparing between one more time?
Tom: Let's say, you know, a small mountain freestone stream in Vermont compared to a small mountain freestone stream in Montana or Idaho. The fish are going to be bigger in the Montana or Idaho or Wyoming stream.
Dr. Ham: You know, I would be speculating a little bit but, you know, at least here...and I'm thinking about from the Midwest to the Northeast, you know, depending on where you were, if you're in some high mountain streams, for example, in the West, a lot of those streams persisted during glaciation. Meaning the ice sheet that came down from Canada or in the far west, it was a separate one called the Cordilleran ice sheet, eastern U.S. is the Laurentide as it's called in the central, a lot of those peaks never were covered by glaciers. And when they when you get in the Midwest and you think about, you know, the height, the elevation of the streams that you're talking about in the east, you know, in general, you're talking about I'm guessing a few thousand feet high in those places?
Tom: Yeah, at the most.
Dr. Ham: Yeah, maybe a couple of thousand. You know, it's a rugged landscape. But you think about some of the Rockies out west, where you're getting, you know, in many cases, 10,000 feet or more high. What tended to happen in those mountains is that just the valley glaciers formed, which are in the heads of the watersheds. They do good work, basically creating that sediment, that glacial sediment that the water can move through and changes its chemistry but it still wasn't kind of plastered with a continuous sheet of glacial sediment like we have in the Upper Midwest. And then you get out to New England, those hills in many places were low enough that they were also completely buried. And so, you know, that distribution of the glacial deposits is different in different places. But without looking at it, you know, real specifically, I just gotta say that I know what I don't know and I wouldn't know the answer to that for sure.
Tom: Okay, so it may remain a mystery. I'm thinking maybe because those peaks weren't...well, they're not heavily forested too and maybe the soluble minerals haven't been leached out of them like they have been in the East because of all the vegetation.
Dr. Ham: Sure. Yeah.
Tom: But no firm answer on that one. Further study is needed on that.
Dr. Ham: Yeah, hopefully, when was like to say a joke with a buddy of mine, "When you get a Ph.D., hopefully, you get better at knowing what you don't know and when to say it."
Tom: I think the more you, I think the more you fish, the more you know what you don't know. That's what I've found.
Dr. Ham: Exactly.
Tom: Well, this has been great. This has been a fascinating discussion, one that I've wanted to do for a long time, and really appreciate you coming on the podcast. Is there anything else that you wanted to talk about before we let you go? Is there anything else that we should add?
Dr. Ham: Yeah, it's just that people have kind know, like you said, they're kind of caught on to this, this baseflow and baseflow index. You know, as always, what can be confusing to folks is if you look know, people start to go on the internet as soon as they listen to this and poke around for those maps. There's a difference between just baseflow and baseflow index. A baseflow of a stream, right, is just the flow that basically takes place between storms. And it's a good...of course, it's a good thing to just have a high baseflow no matter what, meaning you've got a lot of water moving in that river that's coming directly from groundwater. So, that's also...yeah, that's critically important for trout too and good for habitat.
But the baseflow index is just know, in my case, I'm thinking, "Let's assume the stream has pretty good flow in it, what percentage of this water is groundwater? What part of the total flow is coming from rainwater during a storm?" But both of those things are important but you'll find maps that show...they look kind of similar but they're not exactly the same, they're showing a slightly different thing. But, yeah, baseflow, you know, cold water from groundwater, if we don't sustain that, take care of that, it doesn't matter what...all the work that you put into the channel to alter habitat and make the streams more messy and maybe put in more wood and all kinds of things we know work, but as soon as you start to shut off that cold water supply, you know, none of that mattered anymore. And that's why groundwater, I think, should be on everybody's radar, you know, and let's think about what's happening to the local streams.
Tom: That's a good thing to keep in mind, and a good way to find a new stream too, looking at those maps.
Dr. Ham: You bet. Yeah.
Tom: All right, Nelson. Well, I want to thank you so much for coming on today. It's been fascinating for me and I know it's gonna be fascinating to the listeners, so appreciate you sharing your knowledge with us.
Dr. Ham: No, it's a topic I love to think about and talk about and I think knowing these things has become a really critical part of, I don't know, a more modern kind of progressive stream restoration and watershed protection. And it's just great to see people really interested in knowing a bit more about their trout streams and understanding kind of how they're connected to the landscape around them.
Tom: Yep, it'll make you a better angler besides. Not only it'll make you a better steward, but it'll make you a better angler understanding what makes them tick.
Dr. Ham: You're absolutely right, it will.
Tom: Okay, thanks very much.
Dr. Ham: Thanks again for the invite. All right, take care. Bye-bye.
Tom: Bye-bye. Thanks for listening to "The Orvis Fly-Fishing Podcast" with Tom Rosenbauer. You can be a part of the show. Have a question or a comment? Send it to us at This email address is being protected from spambots. You need JavaScript enabled to view it. in the body of an email or as a voice attachment. You can find more free fishing tips on