After about 10 days at Lake Hoare, we have finally made it to our most frequented camp, F6. F6 is a quaint little setup located at the mouth of Von Guerard Stream in the Fryxell Basin, and comes fully equipped with a kitchen, helicopter landing pad, outhouse, pull-up bar, and Godzilla action figure. This is the home base of the Asgard Rangers because Lake Fryxell has the most stream gauges of any other lake in the Dry Valleys. For example, Lake Fryxell has 9 gauged streams, compared to 1 at Lake Hoare and 2 at Lake Bonney. As a result, a lot of time is spent at F6.
Now that we are here, we have been focusing efforts on readying the stream gauges. So what exactly does that mean? Well, the stream gauges that we operate consist of wooden boxes that are located at the outlet of each stream and contain various instruments (they can also be used as an emergency shelter!). The instruments utilize nitrogen gas to estimate the amount of water in the stream by measuring the amount of pressure it takes to pump a bubble of gas from a line in the streambed. The idea is that it should take more pressure to pump the gas if there is more water above the line, and using these data we can calculate discharge. This information is all stored onto a storage module over the course of the field season.
When we leave the Dry Valleys at the end of January, we leave these gauges “turned on” in case there is more flow that needs to be measured while we are gone. As a result, the nitrogen tanks in the gauges boxes are empty and need to be replaced, and the data inside the storage module needs to be collected. Therefore, we have to take a new tank and storage module to each gauge, as well as download old data and send it back home.
In addition to this, we need to see how much certain parts of the streambed have changed over the winter from last year. The reason for this is that when we calculate discharge, we have to take into account the lowest part of the stream where the water flows out of our gauge, as well as the height of the line that pumps the nitrogen into the stream. If we don’t take these changes into account, the discharge may be incorrectly calculated later. Therefore, we measure these areas every year to see if elevations have changed due to freezing and thawing. The trick will be to get all this done before the streams start to flow!