Jon saw evidence of building at the primary dam when he went down yesterday morning at 5, and Jean called excited by more work. Tonight things are clearly indicating work on the street side of the primary. Jon says more work this morning. All my fingers are all crossed, and yours should be too.
As I was cruising around the internet yesterday I came across this paper by Don J. Neff, and titled, astoundingly, A 70 year history of a Colorado beaver colony. I can’t tell you how excited I was when I settled down to read it. Would we learn how a colony responded to the loss of a mate? To serious flooding? Or what happens after beavers disperse? 70 years is a good long time. I couldn’t wait to read the secrets observers unfurled during that time.
Alas, the paper was entirely about the work of the colony over 70 years, and not about the beavers themselves. It told the story of new canals and lost dams in much the same way that an observer describing a new off ramp on highway 24 would learn about the lives of the people who drive it every day. I was very disappointed.
Above Moraine Pond Warren found a series of ponds, the first two being of good size and each containing a lodge. About 75 feet upstream was found a pond which was formed when a lodgepole pine on the south bank of the channel fell with the crown pointing downstream. The beavers used the mass of earth in the roots of the tree as part of a dam which created a pond some 15feet wide and 4 feet deep. The boundary of Rocky Mountain National Park crosses the stream immediately above the fallen pine and marks the approximate upper end of the Moraine Colony.
However, no beaver effort is wasted. The most interesting part of the paper is the summary of the 27 years it was observed by Enos Mills. The author of the paper uses his colorful and detailed observations, but describes them as dismissively unscientific and fragmented. I of course bought his book immediately, but found a google version this morning and am thrilled to recognize exactly what I was looking for.
The entire text is searchable here, and don’t bother me after earthday because I’ll be reading my copy over and over again. No radio collars, no telemetry, no regression analysis, no dendrite chronology – just a man with eyes and ears and the rare capacity to really watch beavers. Oh and if that’s not exciting enough for you, guess who the young man Enos was inspired by, met by chance on a SF beach in 1889, and ultimately befriended? I’ll give you a hint. He lived in Martinez.
Muir wrote to Mills in 1913: “I shall always feel good when I look your way: for you are making good on a noble career. I glory in your success as a writer and lecturer and in saving God’s parks for the welfare of humanity. Good luck and long life to you.”
So Enos is famously called the ‘John Muir’ of the rockies, and once said “I owe everything to Muir. If it hadn’t been for him I would have been a mere gypsy.” [Literary Digest, July 14, 1917] . John Muir who lived in Martinez. Where our beavers live. Who died a year after Enos “In Beaver World” was published. Do you ever feel overwhelmed by destiny?
Say it with me now. It’s a small beaver world.
Our friends at Beavers: Wetlands & Wildlife selected this day as International Beaver day, and the good news is it’s catching on. I’m told that today is a great day to give a beaver talk, write a letter to an editor about beavers or set up a display. Hmmm. I already do that on the other 364 days of the year, so I thought I’d do something truly special today. I’ll teach you a brand new thing. I learned about the concept from Michael Pollock on our Yosemite trip, and have been waiting for the right moment to share. Of course the unflattering story line is entirely my own responsibility. I figure a time when we’re waiting for beavers to build is a good time to learn.
‘Only it is so VERY lonely here!’ [without the beaver dams] Alice said in a melancholy voice; and at the thought of her loneliness two large tears came rolling down her cheeks.
‘Oh, don’t go on like that!’ cried the poor Queen, wringing her hands in despair. ‘Consider what a great girl you are. Consider what a long way you’ve come to-day. Consider what o’clock it is. Consider anything, only don’t cry!’
Alice could not help laughing at this, even in the midst of her tears. ‘Can YOU keep from crying by considering things?’ she asked. ‘That’s the way it’s done,’ the Queen said with great decision: ‘nobody can do two things at once, you know.
Consider this then:
A long time ago a tired researcher sat on his lawn chair and glared at the beaver dam in his stream and thought, I really need to blow that thing up, but first I’ll justify it. He took out the thermometer his wife had used to check his daughter’s temperature that morning and he measured the top two inches of water in the pond.
“Ah ha!” he said, comparing it to the top two inches of running water on the other side of the dam. “Beaver dams raise the water temperature and this hurts trout and salmon!” “Beavers destroy habitat for fish!” He trotted back into the house and wrote a paper which was published in the journal of wehatebeavers and soon the paper was quoted in ever other scientific paper on beaver dams known to man kind. (Then he blew up the dam which had been his goal all along, and alot of people were encouraged to blow up their dams too.) Soon every biology, hydrology and icthology student was taught that beaver dams raise the water temperature and regional agencies like Fish and Game or Department of Natural Resources wrote it into their policies and it became the great truth of the land. It was even quoted by the letter I responded to from LADWP yesterday. When a lone graduate student scratched his head and said, how do you know? He was nearly laughed off the campus and his thesis adviser had a tense conversation with his mother in the laundry room.
Hyporheic Exchange (Pronunciation: hi-poe-REE-ick)
So it turns out that when you look at a stream there’s the water you CAN see, the ground water you CAN’T see, and this layer of soggy silt & pebbles that acts as a sponge between the creek bed and the water table. This layer is constantly moving water into the ground, and pulling groundwater back into the stream. Water in the ground is naturally cooler because it gets no sunlight at all so every time it seeps into the creek bank it lowers the water temperature a bit, and when water is returned to the creek bed it is cooler.
Michael Pollock, of NOAA northwest fisheries was interested in this dynamic, and particularly what it meant to that old story about beaver dams choking out salmon and trout. He decided to set up some thermometers at different layers in the water, and also below the subsurface of the stream to find out the truth, then he repeated this at different points along a stream. Before I show you what he found, you need to know that the headwaters of any stream is cooler than the mouth. So we expect the temperature to gradually go up as the water moves down stream.
So reading the river from the headwaters on the right, the blue line is the subsurface temperatures and the lowest, which we would expect. The red line is the surface water of un-dammed areas, and the green line is the surface area in beaver pools. As you can see the red line is consistently higher than the green line, meaning that the surface area of beaver ponds is cooler than the surface area of free-flowing stream, the opposite of what our lawn chair researcher observed. Why is this?
I’m told the next graph has not yet been published so I shouldn’t post it on the web. Okay just imagine that the three measurements are combined we see this gradual sawtooth incline with a huge gap showing that the temperature suddenly falls. And guess where? There’s a huge temperature drop as tons of upwelling water seeps into the banks of the creek. It’s a beaver dam, whose deep pools increase the contact area of the water with the hyporheic zone, so there’s greater exchange and cooler temperatures. Say it with me now, “hyporheic exchange.” This is what the fish like. This is what enlivens the water and makes the creek more healthy. And this is why that researcher in his lawn chair all those years ago should be scornfully forgotten along with his entire findings.
Here’s the take home sentence for you to use in your next beaver argument, and you know you’ll have plenty. “Beaver dams cool streams by maximizing hyporheic exchange.”
Happy International Beaver Day! Celebrate by telling someone you know. Or everyone.
