Saturday, December 17, 2011
The Hengill region became blanketed in snow much earlier this year than last. The snow has greatly limited our access to our sites. We've tried walking (3 hours one way), skiing (2 hours one way), and earlier we described what happened the last time we used a truck. On Friday, the University of Iceland's Geology department allowed us to rent a couple of snowmobiles and borrow Sveinbjörn, a technician who helped out with the equipment and our reconstruction of our heat exchanger. We were able to get to our sites in 20 minutes on the snow mobiles (pics 1, 2, & 3).
The dam feeding water from stream 7 into the heat exchanger was breached in late November. Before we could return and fix the system the water left in the pipes froze. The heat exchanger was fine.
Friday, we traveled in by snow mobile, rebuilt the dam, and excavated three different sections of iced up pipe. One section of pipe was covered in a meter of snow in places (pic 6). After excavating the pipes we let them thaw in stream 8 (20˚C) and then reattached all the piping (pics 4 & 5). Everything was running smoothly when we left Friday evening.
After we finished up with the heat exchanger we went over to our reference stream to retrieve some dissolved oxygen probes before the holiday break. Normally this is a 45 minute drive in the summer, but it only takes 20 minutes on snow mobiles. I know what I was for Christmas. About 70% of OH2 was covered in a layer of hard packed, wind blown snow (1 to 3 meters worth). Here is Jim trying to pull a probe out of the lower section of OH2. There's really a stream down there. I swear.
Wednesday, December 7, 2011
Hengill has gotten a lot of snow recently. So, for our December sampling we got help accessing our streams from the Hveragerði Rescue Squad. Most Icelandic towns have Rescue Squads. These are all volunteer organizations which help people lost, hurt, or stranded at sea, on land, and on top of glaciers. In their off time, they generously help us get to our field sites. The Hveragerði Rescue Squad has a truck with very wide tires. When the tires are slightly deflated the truck "floats" on the snow like its wearing snowshoes.
Tuesday, December 6, 2011
After a fairly sunny summer, there has been a lot of rain this fall. In November, discharge in many of our streams was approximately 10 times higher than during the summer, although the discharge in some streams has hardly changed. These differences in flow arise because some of our streams drain large watersheds (like stream 14, shown above in Nov and below in July) while others have tiny watersheds and appear to derive almost all of their water from springs (e.g., stream 8). These differences in discharge variability among streams likely translates into large differences in disturbance. Disturbance is known to play an important role in shaping stream food webs and ecosystems.
Below, Wyatt dances while he measures nutrient uptake in stream 14 sometime in July.
Since the summer, we’ve been measuring the magnitude of disturbance in each of our landscape streams. We use super glue to attach tiny pieces of flagging tape to 50 randomly selected rocks in each stream. The photo below shows a transect of flagged rocks in stream 7. The flagged rock at the bottom of the photo has been moved downstream away from the transect.
After three months, we return to each streams and determine whether each rock has moved. In sum, these rock movement measurements give us a metric of the degree of disturbance in each stream.