July 21, 2006 - Setting up Stream Guages, ISCO and Transects Options

[Maggie_Kane]

Today we went straight to the boats and got to work. It was a very busy and successful day. We loaded up (you all know about THAT by now) and motored our supplies 4 km to the south end of Linnevatnet. This boat ride takes about 15 minutes, or longer if the wind is blowing hard from the south!

Hiking the ISCO Water Samplers


I worked with Christina getting the stream transect set up with a rope across the channel. A transect is a line that cuts across something. We made marks every meter and every ½ meter with tape and cable ties. We wore the orange survival suites because the water was waist deep and very cold. We set the rope up so that we can take measurements along a transect and know exactly where we are in the channel.

Why is this important? Well, if you have ever walked across a rushing stream, I bet you know that it is not the same depth everywhere, and I also bet you know that in some places the water flows fast, and in other spots more slowly. This is something we know but the mathematics of it is actually complex. The speed at which an object moves is called “velocity” and it is a ratio or fraction, like miles per hour (miles/hour). We don’t use that ratio in science because we use the metric system so we measure the stream velocity in meters/second (m/s). We also used a pole with markings on it in centimeters (cm) to measure stream depth. We just placed the pole down to the channel bottom and read the water height. The area where the flow is fastest and deepest is called the “thalweg”.

To measure stream velocity, we use a flow meter. This is a hand held probe with a small propeller on the end. It is placed part way down in the water (about 2/3 the depth) and points up stream. Wires attach to a digital box that reads out the velocity. We carefully write all this down in our field books. We make sure to stand downstream of the meter. Why do you think?

We want to know everything we can about this stream. The amount of sediment carried relates directly to the stream velocity and that connects to our larger study of the entire glacier, river and lake system. Every once in a while the reality of it all washes over me – the sediment we are collecting comes from rocks ground up by the glacier, and the water rushing past me has recently melted from it.

Working the Stream Transect


Another group worked at setting up the ISCO samplers. These are totally cool tools! You have seen pictures of us hauling the big green barrels around, so you might want to know what is so cool about them. Inside is a round tray full of 500 milliliter (mL) bottles. This is about ½ a quart. Each one is numbered 1-24. A tube was set into the stream that runs into the box and fills one of the bottles. Then 2 hours later, the tray moves over one bottle so that the water will go into the next bottle. If we want to know about the sediment being carried by the stream, what do you think we will look for in the water samples? I’ll let you think on that for now!

Bennett and Heidi helped set the level loggers in the lake (remember the little “eyeball” mechanism that measures water level that I talked about yesterday?). They banged the post into the lake bottom and then attached the logger to it below the surface in a “stilling well”. The stilling well is a plastic tube that lets water inside, but keeps the instrument from banging around in the waves. They also attached a floating buoy to the top of the post so we don’t drive our boat over the tip of it! What would happen to our air pontoons if we did that? More importantly, what would happen to US if that happened?! After they finished this at both ends of the lake, they had a little float time!

Floating!



Question of the day: When was the last time you played in a stream? If it was more than a month ago, go find one! It is way too much fun to put off! Then, let me know where you went and what you enjoyed most.