Saturday, January 25, 2014

Slushy Swim

The river looked arctic as I approached. I recently saw a picture of the Hofsa River in Iceland and it instantly made my bucket list of places to snorkel. Deer creek reminded me a little of that picture. The water ran clear and gained an Aquamarine hue over the last few days. What I found under the surface was a very different scene. Waves of temperature distortion and flocculent ice suspended throughout the water column significantly reduced visibility. I could still see bottom, but not with the crispness I expected. It felt like I was swimming through a partially melted slushy. A tongue of ice formed in the lee of a large rock out in the rapid. I assumed it was just a sheet and I would be able to peer under it. The water behind this rock provides a refuge from the chaos of the rapid. Sculpin lay their eggs on the downstream face in spring, shad use the lee to climb the rapid in April, caddis flies lay their eggs on it in late summer, and eels hunt around it year round. I looked forward to a beneath ice view of this eddy and rock I have come to know very well over the last 5 years. What I found was a solid accumulation of slush to the bottom 2 feet below. Bands of slush filled in some of the gaps on the bottom out in the main flow, looked like coagulated fat, and made everything blurry. This is a phenomenon called anchor ice which forms during periods of extreme cold. Water dips below the freezing point but ice won’t grow on the surface due to the moving water. Ice platelets form in the water column and gather on the bottom. Sometimes anchor ice forms a thick blanket on the bottom of rivers and can cause them to flood. The clear appearing aquamarine arctic view I enjoyed from the bank was water flowing over anchor ice, not crystal clear water flowing over river bottom. Northern case maker caddis flies clung to green sprigs of rock weed on the face of a boulder as anchor ice piled up on the ridge behind them. I didn’t see any of them get picked off by slush hits, but my mask and exposed forehead got pelted as I faced upstream. A larger ice chunk knocked the camera out of my hand as I tried to film the flow of slush. I really can’t wait for spring, not just for the warmer temperatures, but also because the life that is hunkered down right now will return. At the same time, swimming in slush was a unique experience and it helped me understand the ecology of Deer Creek more fully. It helped me understand exactly what life in this rapid experiences, and it made me appreciate it that much more.

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