Wednesday, November 11, 2015

What exactly am I doing down here?

I realized that for those of you who did not read my blog last year, you may be curious as to why I am down here.  As I try to figure that one out myself, I will do my best to explain the purpose of my trip.

A view of hut point, and part of McMurdo or "town" to give you an idea of what it looks like.
This year I am a member of what is known as the McMurdo LTER (Long Term Ecological Research) project.  This is a interdisciplinary group who's goal is to study the aquatic and terrestrial ecosystems of the Dry Valleys over a "long" time period (began monitoring in 1993).  Within this group there are sub-groups who focus on different aspects of each ecosystem.  There are groups that focus on glaciers, lakes, soils, ect., and our group focuses on the glacial runoff streams of the Dry Valleys. Which explains our extra cheesy name the "stream team".  It may come as a surprise to you that there is flowing water in this extremely cold and dry environment.  However, the solar radiation is great enough during the austral summer to melt the glaciers and produce glacial runoff streams which eventually flow into closed basin lakes.  These streams are pretty unique because instead of precipitation being the main control of flow rate (like streams back home) it is the sun that has the most influence on stream flow.  This unique control causes highly variable stream flows from day to day, and even season to season.  Therefore it is important for the scientists studying these ecosystems to have a record and characterization of the flow of these streams.  That is where the stream team comes in.  We measure the flow of the streams, as well as collect water samples to test the nutrients, alkalinity, cations, anions, and dissolved organic carbon.

We gauge the flow on 16 different streams in the Dry Valleys.  Most of the streams are in Taylor Valley (where I will be living and spending most of my time).  The other streams are located in Wright Valley, and Meirs Valley.  To get to the streams we either hike, use ATVs on the lake ice, or fly via helicopter.

The gauging process is the same process used by the USGS which I am sure all of you are very familiar with...  In case you need a refresher on that I will explain it in gory detail (you may want to skip the next two paragraphs). We have gauge boxes at each stream which have instrumentation that measure the depth of the water at a specific location in the stream.  These measurements are taken every minute and recorded on a memory device on site.  This gives us nearly constant measurements of the depth of the stream over time.  To convert this depth to a flow rate (volume of water over time) we need to take manual flow and depth measurements at the stream.  This allows us to create a relationship between the flow and depth of the stream.  With enough flow measurements you can develop what is known as a discharge rating curve (shown below).  The points would be the manual flow and depth measurements and the line is the interpolated discharge rating curve.  As you can see from the image, with an accurate discharge rating curve you can translate any depth measurement to a flow measurement.  We make this translation with all of our stream depth data, which ultimately gives us flow measurements every minute for the duration of the season.

Our manual flow measurements are taken using a Flowtracker which is a device that measures the velocity of the stream at a certain point.  We take about 20 velocity measurements across the stream channel and with a knowledge of the stream cross sectional area we can convert these measurements to a flow rate.  If you made it this far into this painful explanation congratulations.  This will be the most dense part of the blog, I just thought I would explain the nuances of what I do for the nerds out there.

So our main goal over the coarse of the season will be to take flow measurements and water quality samples at as many streams as we can.  Currently we have been stuck in Crary Lab in McMurdo (shown below) washing bottles for the collection and processing of our samples.  The goal is to fly out to our field camp next Monday.

Thanks for reading and let me know if you have any questions or if I need to explain anything further.
Our Lab in Crary where we have washed thousands of bottles this week.
Nice view walking into the lab this morning (Crary on the left). Mount Discovery is the peak you can see across the sound

1 comment:

  1. Thanks for telling us what you are doing down there Zach!