Stormy

There was a bit of a storm yesterday! It was actually quite welcome, because the temperature dropped like 30˚ to a balmy 70˚F. It came on extremely quickly, and outside went from being unbearably hot and relentlessly cloud-free to looking like it was closer to 10pm than 10am in about 15 minutes.

 

 

Of course, we hung out and watched the storm for a bit, which was cool. Some of the clouds were actually green, which I’ve heard is a sight that is often seen before a tornado. I took a video, actually:

Luckily, the storm mostly missed us. The clouds looks really cool. I might put some more pictures up after I sort through them.

Kool-Aid Stream!

A few weekends ago, we came in to help some visiting researchers who were doing an experiment concerning nitrate levels in the water and something else that I can’t quite recall. The point is that they dumped this fluorescent red dye called Rhodamine in the stream, and it looked AWESOME. Note that photos without rounded corners were taken with Jess’s camera.The dye was pumped to the top of the stream, where it was mixed with water in a trough. Then, the water overflowed and spilled the dye into the stream.

OK, this is pretty cool: Jess took a picture of the exact instant that I took this picture. Here it is:

The first mixing of water and Rhodamine:

 

The dye flows from the funnel to the trough:

 

 

 

 

Here’s a crappy .gif of the initial plume spreading down the stream:

More pictures:

One thing we did have to do was take samples at certain intervals. We used these pumps to get our samples:

One thing that was being done was that the Acoustic Doppler Velocimeter (ADV) had been set up and was taking 3D velocity measurements. Pretty cool (expensive) piece of equipment. Here it is:

More photos!

I took this picture, but I think it was with Jess’s camera:

Lots of pictures because it just looks cool.

 

 

The Corner Office

The day after the cart tipped over, we mostly just did things that needed to get done. We were running the flow up at 285LPS, over our newly installed rock structures. These rock structures are part of an experiment that is running at the OSL for the NCHRP, the National Cooperative Highway Research Program. This experiment is exploring the installation and effects of different in-water structures that are designed to reduce scour–the erosion of banks caused by fast-moving water.

Scour is–apparently–the number one cause of highway bridge failure in the US, with 46 of 86 major bridge failures resulting from scour near piers from 1961 to 1976. Last summer, the OSL tested how installing rock vanes effected scour. This summer, we’re testing out the effectiveness of cross-vanes as anti-scour measures. There are two of these cross-vanes–one upstream and the other downstream. From downstream they look like an uppercase “A” …in 500pt rock-type (heh) font. There are two layers to each cross-vane: the footer rocks at the bottom that are wrapped in black “geotextile” cloth, resting on a bed of gravel, and the header rocks, which are perched (bare) on top of the footer rocks. It took 2 days to get these built correctly.

From what I have gathered, the idea is that the water flows over these structures (they are more inclined as you get closer to the bank, biasing the water to pass over the center of the cross-vane), and is directed away from the banks. These banks normally tend to get scoured away–especially at bends in the stream or river as the water’s momentum causes it to careen into the far bank.

We had hoped that with a calibrated cart we would be able to turn the flow and sediment up and get data about the inevitable formation of a scour-hole just downstream from each cross-vane. Instead, we surveyed every fifteen minutes for the deepest point in each scour hole.

We decided to try turning on the cart and all its instruments on Thursday. However, before this happened, I took advantage of everything being offline and re-grouped all the cables (there are a lot of cables) in an effort to make the place at which I’ll be spending a fair amount of the summer a bit tidier. I also made a mini-desk that allows me to hide the carefully-organized cables underneath, while also giving me a nice flat surface upon which to put the mouse and keyboard. I was kind of proud of this simple desk. I needed to use a chop-saw to cut the wood, which was a little exciting. Here it is:

Also, Peter found this little guy hanging out in the stream:

One time Dick fished out a fallen section of PVC pipe from the head-box and a foot-long crawfish fell out. I did not know they got that big!

We checked the instruments over once more to look for suspiciously unplugged or bent parts, and found none. The plug went in, switches were flipped, and everything turned on! Huzzah! The first hurdle was out of the way. Next, we briefly checked to see whether the instruments were still reading accurately. The Laser and the Massa seemed to be reading a bit off, which was worrying.

After lunch, we realized that in our excitement to turn the cart back on, we’d neglected to level it as you must. So, we leveled it, and set up a level, flat sheet of metal of a known height (relative to the zero-point of the cart) to take readings off of with both the Laser and Massa. To our delight, the error disappeared, and both read the same distance that I had measured down to!

We got the cart to do a sample scan, just to get some (fairly useless) data to play with later. It seemed to work fine, which is extremely lucky. The carriage the instruments are all on moves across the stream in a series of passes–the length of which depends on the numbers we give it. So, we want to be very careful not to run the instruments into the solid, yet delicately placed rock-structures–for both the purpose of protecting the instruments AND of keeping these rock structures in their precise location.

103 Degrees

It was hot today. The Lab’s own thermometer had the temperature at 102.97°F. Some of us came in to work early in order to get everything up and running in enough time. Unfortulately, everything took much longer than planned. In the OSL we have a cart called the DAQ, or Data Acquisition Cart, which has a bunch of different instruments on it, including a Laser, Sonar, and Ultrasonic (“Massa”) sensor. I spent most of the morning fine-tuning the calibration of the Sonar and Massa with one of the tech guys from the lab, and we finally got it working as it should.

Then we ran a scan (or, really, a series of 8 scans) across a section of the stream, with the flow turned up. After this scan, we turned the water back down, because one of the structures we had installed (rocks in the stream) had become dislodged. I jumped into the water just downstream from the structure, wearing my rubber boots, and sank in over my hips! This was an area of the stream that we were able to walk in without getting wet with boots on just an hour prior. My feet got kind of stuck in this quicksand-like mixture at the bottom of the stream, and I had to crawl onto land to escape. Pretty thrilling! I think this may be a picture of it:

We wanted to get more scans done, and each set of scans took ~50 minutes to complete. So, I thought I’d just help get the structure fixed, turn up the flow, and start my scan, after which I’d be able to run off and get lunch.

 

Unfortunately, the damn tent blew away. It was staked in with foot-long metal spikes, yet somehow the wind wrenched it loose. The tent is there to protect the DAQ from the elements, but when the wind flipped the tent up the bottom of the tent frame caught on two poles from the DAQ, and tipped the extremely heavy (we use 4-6 people to move it inches and feet each day) cart until it was at 90 degrees, with instruments flying off.

The instruments on this cart are very expensive, in the thousands of dollars range, so as I saw it perched on its side, I was slightly perturbed to say the least. I ran over and yanked out all the power plugs as soon as I saw it stand on end, because the last thing we needed was someone being electrocuted. We got it back down and surveyed the damage. One metal box had gone for a swim, but thankfully there did not seem to be any expensive equipment in it. We are drying out the equipment in the sun before we try anything out, because we want to try to avoid frying anything that isn’t already fried.

Thankfully, it was 103 degrees out today.

 

No photos from today, I was running around outside all day and didn’t get lunch until 3:30. Here’s a cloud:

Out to Afton

Unrelated to the lab. I went on a bike ride today with Andy. We went out to Afton and back, something like 50 miles or so. Good ride, but pretty tiring and a little warm.

Once there, we met another guy who was going for a bike ride, Brad, and rode back with him. He was a baby-boomer. On the way home, I saw a turtle near Crosby Park.

The End.

Friday Fun, Continued

After we had finished surveying the stream (as detailed in my previous post), we did something that was pretty neat. First, we got out the big bucket of 6-inch, rusty staples. Using these, we stapled back the vegetation from the stream edge. The reason we were doing this was because we were going to get a large bucket of confetti and feed it into the stream (by hand) so that people watching from the top of the wall above us could take long-exposure photographs of the stream that would reveal the ways in which the water flows. Pinning back the vegetation gives the camera an unobstructed view of the water from bank to bank.

It was pretty fun, and kind of an unexpected thing to do. I don’t think I’ve ever actually thrown confetti before.

 

 

 

Fun Friday

As the OSL is perched right next to the  St. Anthony Falls, we occasionally get a fair amount of spray blowing in.

When it is hot out, this is great. But when it’s cold and windy, it can become tiresome . This past Friday fit into the latter category–we spent the whole day trying to figure out if it was finally raining, or if it was just misting in a downwards direction. But that was okay, because we did a few cool things to make up for (or perhaps in spite of) the weather.

Firstly, we did our first survey. They have some awesome, expensive equipment at the lab for doing all sorts of things. We were instructed in the use of a Total Station, which is basically a hyper-accurate level/compass/protractor/distance-measurer. First, you have to take it out of its waterproof, impact-resistant fluorescent orange case and mount it on a tripod. Or, in our case, a large metal column that has been stuck in the ground for precisely this purpose (which is supposed to be easier to use than a tripod, which has more potential to move).

Once you’ve screwed the Total Station in, you need to level it. This is a pain in the ass. There are three different (for lack of a better word, or perhaps indeed just because I like making it confusing for you) “levels” of levelling. First, you have a simple bubble level, with a circle you want the bubble to reside in. This is when you’re still adjusting the legs of the tripod. Next, you move on to another bubble-level, this one being parallel to the ground. You need to go around and check that the bubble sits in the middle while the rotating Total Station is in each of the six vertices of a hexagon. Finally, you begin the most frustrating process of them all. There is an internal level that you must once more check in 6 rotated states of the Total Station. In order to  make adjustments, one twiddles the EXTREMELY sensitive dials that control the elevation of each of the three supports of the Total Station (not on the tripod, but part of the machine itself, made for these such adjustments). Of course, whenever you get one of the six perfect, the other five are completely off. Or, perhaps even worse, all of them are perfectly leveled except for the last stubborn point.

Eventually once you get that more or less sorted out, you get to do the actual surveying. This involves wielding what resembles a magic staff–it even has a crystal attached to the top! Okay, so it’s not a “crystal”, it’s an incredibly expensive prism. But it still feels vaguely… wand-like. Then, you stand in the stream (or wherever you’re surveying) and do your absolute best to hold another small little bubble in the center of a tiny wee circle, all while your friend is manning the Total Station, shooting lasers at you (to bounce off the prism, and thus record a precise measurement of the exact position of the bottom of the wand).

Neat system. Also, the optics have INCREDIBLE magnification. Afterwards we pointed it at the Stonearch Bridge (probably 800m away) and could see kids on a field trip spitting off the bridge. Pretty awesome.

Closer To Normal

This past Monday we began a slightly more typical week. There is a lot that needs to get done before the start of the “season”, and not much time to do it.

The big focus of this week is getting the systems in the OSL dialed in. Allow me to explain the basic outline of how the lab works:

This year, we have a new Sediment-Feeder. It is an auger that brings up sediment from the Sed Tank, which then spills into a funnel, accompanied by a jet of water to flush it down and into the stream

1. We control how much water enters the head-box at the top of the section of stream. Water comes straight from the Mississippi, and we turn a large valve to determine the flow rate.
2. At the same time, we adjust the rate at which sediment is fed into the stream system–which is also done at the head-box.
3. Water+Sediment flows through stream.
4. The sediment is dumped by the water into one of three bays in what is called the ‘tail-box’. The stream water flows down to rejoin the Mississippi.
5. We move the sediment back to the top of the stream, after analyzing how much was deposited en-route.

This year, we have a new Sediment-Feeder. It consists of an auger that brings up sediment from the Sed Tank, which then spills it into a funnel, from whence it is flushed down with a jet of water.

The sediment gets shuttled up that white PVC pipe, and then dumped into the waiting funnel below.

Our sediment is stored in a huge 2,500 gallon tank that sits near the head-box. They are very particular about making sure that none of our sediment gets lost, which I can understand. The rod you can see to the left of the tank on the ground has a tape measure attached to it so that one can measure how much room is left in the tank:

The auger is driven by a motor, and thus the sediment feed-rate is determined by the motor speed. Unfortunately, I’ve been told that the current gear-box is inadequate, as we only end up running the motor at about 3hz, which apparently is bad (too slow) for motors. So, every once in a while the Sed Feeder gets jammed, and the auger stops spinning. In order to get the system going again, we’re supposed to just get this HUGE wrench and give a good rotational yank to the auger-shaft to try and unstick it. At first I was worried about doing this, thinking that perhaps something in it could get broken, but I no longer care. This whole system was designed and built by Dick, who works at SAFL. Pretty ingenious!

A lot of what we were doing early on this week was trying to figure out what we need to set the motor at in order to achieve the golden rate of sediment dispersal of 8L/2min.

First Days

I met two fellow students I’d be working with over the summer, and had a fairly standard safety meeting. Then we got to work shoveling sediment. We (the research assistants) do a lot of sediment-moving.

However, after lunch we did not continue shoveling. Instead, we got a brief (thankfully) safety training on how to use an electric drill, were handed 350 buckets, and were told that each and every one needed 74 holes drilled in it by the end of the next day.  These buckets were to be used as tree-planters, and were specially designed. First, the bottom 3 inches of each bucket had been cut off with a table saw. Then, we were to cut slits up either side of the bucket so that the main top part could be fit into the bottom which had been cut off. Then we drilled holes through the part where they overlapped and zip-tied the bottoms to the tops. Finally, we drilled 8 columns of 8 holes each, for drainage.

These planters are to be placed in a large square basin (outside the OSL) which can be filled with water. In each planter will grow either Cottonwoods or Tamarix, in one of three different formations. The planters are there in order to keep the roots of each planted system distinct from the others, as these various plantings will be transplanted to the OSL after they have grown for a few months in order to study emergent vegetation in a stream setting–or at least this is what I have gathered. The Tamarix is actually a pretty interesting plant: it brings up salt, excretes it, and leaves (heh) it on the soil surface, which tends to kill other plants. It’s an invasive tree.

Eventually we finished the buckets. The cordless drills sucked, so we used ancient corded ones. Well, the batteries probably just weren’t used to being asked to drill ~26,000 holes in the span of 2 days.

 

Later in the week, the researchers arrived. They had shipped cross-country around 2,000 of both Tamarix and Cottonwood seedlings, carefully packaged in their lab. The Tamarix were shipped by UPS, and arrived on time. USPS was a day late with the Cottonwoods.

We put flags in those buckets that had a certain type of planting arrangement, in order to make counting easier.

That was the first week.

Working at SAFL

This summer I have the good fortune to be working as a research assistant at the St. Anthony Falls Laboratory. I will be spending my time with the Outdoor StreamLab (OSL), which is an awesome facility.

The OSL is located on Hennepin Island, in the Mississippi River. Here is a panorama of the OSL that I stitched together using the freeware program Hugin. As you can see, there is a nice view of a cool stretch of Minneapolis riverfront.

View southwest over the OSL (click for zoom-able large size)