Sometimes we find inspiration where we are not expecting it. Figure 1. shows the staircase to my room in Vienna, Austria where I co-organized the “2018 Vienna Flow Regatta, Q-Competition, and Lunch” on April 13, 2018 with Beat and Maxence of Photrack Ag. As I gazed down into vortex, I thought about the coming day’s competition; I was out of my depth1, competing against international hydrometricians from the UK, France, Switzerland, and QiQuac’s bitter rival, the Christoph Sommer with his impressive TracerQ system from Sommer Messtechnik from right there in Austria. “Vigilance!” I coached myself.
Conversely, Christoph was the perfect host, finding the site, obtaining the permits, monitoring the river flows, welcoming and cordial to his guests. In fact, there would not have been a Flow Regatta without Christoph’s assistance. “I’m being lured into an uneasy comfort. Stay sharp!” I told myself. “This is not the state of mind to take into an international flow measurement competition where national pride was at stake.” I stared into the vortex, trying to see the bottom in the darkness of the eye of the gyre. A kind woman asked if I was alright as she passed by. I packed up my trusty QiQuac in his Duck-Box and headed into the bright Viennese morning.
“You’re not in Lethbridge anymore, Dorothy,” I said aloud as I made my way on the tram to the conference center. An elderly man moved to another seat. We gathered a crowd of about 18 from the conference stream, promising free schnitzel and beer. We then headed to the competition site in our 56 seat bus, courtesy of SEBA Hydrometrie. Tension on the bus ran high, each person sitting alone about 5 seats away from each other as they prepared mentally for the competition.
We arrived at the Liesenbach channel site and each champion gave a short introduction to their method and equipment, full of grandiose claims and swagger trying to psych out the other competitors, shown in Figure 2. Because we didn’t know the “True Flow” as we did at Lethbridge, the organizers choose the attendee we considered most resistant to bribes and other forms of coercion to be the judge: Nick of the UK Environmental Monitoring Services. Nick is a gregarious, intelligent, knowledgeable and funny leader, ethical to a fault, whatever than means…
Ears were perked as Nick covertly asked everyone’s Scientific Wild Ass Guess (SWAG)2 The SWAGs ranged wildly from 10 litres per second (L/s) (no claimed owner) to 600 L/s, proudly claimed by the only female competitor, Michelle. Michelle was attending to learn more about the methods, which is something we hope to have more of in future Flow Regattas. The average SWAG was 280 L/s±55%. There was a surprising number of estimates of 320 L/s, possibly influenced by the test results of the previous day. The organizers had been to site to ensure all was well, and, with full disclosure of their bias, used those measurements to guide their SWAG.
The Measurement Methods
Methods employed to measure the flow covered the spectrum. In addition to tried and true methods like current-metering and tracer methods, there were also the new surface imaging methods. There were three flavours being used: Surface Structure Image Velocimetry (SSIV), Large Scale Particle IV (LSPIV), and Radar.
In SSIV, surface features such as ripples, eddies, and even leaves and other LSPs, are tracked in video using a high resolution camera. Using pre-measured reference markers and bathymetry, the velocity vectors are computed and mapped onto the bathymetry. An estimate of the Alpha value, which is the relationship between the average surface velocity and column velocity, is used to estimate the transect-specific column flow. The column flows are added up and presented as the total Q. Attendees are shown using the app in Figure 3.
SSIV was measured using the app Discharge.ch by PhoTrack AG. This powerful software can be installed on any Android device with sufficient camera and computing ability, and used to estimate the flow in an open channel. While it’s possible to gather a rough estimate of flow from pre-measured bank markers only, the champion Beat emphasized the best results require an accurate bathymetric survey. A full explanation of the tool is on their website. The Discharge Keeper is a continuous monitoring version of the algorithm and available from another conference Sponsor, SEBA Hydrometrie from Germany.
Like SSIV, LSPIV tracks surface particles like leaves or detritus, or even introduced tracers. Fudaa is a free windows program available from the EDF group, here championed by Alex, also from EDF.
Radar measures the doppler effect from a low-power microwave radar looking at the water surface. The Sommer Radar-RQ-30 system is mounted on the bridge over the Liesenbach channel. The radar can also measure the distance to the water. While the radar can operate night and day, and return a depth, it returns only an average surface velocity. This is often adequate for estimating the total using an effective channel area dependent on stage.
While no acoustic or hydromagnetic velocity meters were used, the Russian made Vertuschka propellor flow meter was operated by Nick and Maxence. You can see the joy of using this device experienced by Maxence in Figure 4.
RWT Tracer Method
Rhodamine WT is a common fluorescent tracer, considered harmless to aquatic habitat when used in appropriate quantities. It has the benefit over NaCl as a tracer in that it can be detected in very low doses (ml per m³/s) and is unaffected by most background signals such as high conductivity and low temperature. NaCl and RWT can be used concurrently with no interference of the signals. There is some concern over adsorption onto suspended sediment and channel substrate, and photo-degradation over time, in the literature possibly resulting in overestimates of flow.
Sommer’s TracerQ-F system was used to perform two RWT flow measurement, shown in Figure 5.
Salt Tracer Method
Another common method of tracer measurement is using NaCl. This is a robust method employed by both Sommer’s TracerQ-S and Fathom’s QiQuac systems. NaCl has the benefit over RWT in that it’s readily available at most grocery stores, is easy to work with, and not prone to adsorption. However, for very high background conductivities(like in urban channels) a large dose is required to achieve an adequate signal to noise ratio (low uncertainty).
The k-value of a probe indicates the range of specific Electrical Conductivity (EC.T) that it is most suited for. The k-value of the two Sommer TracerQ-S probes are 0.475 indicating a higher range, with less sensitivity at the lower range (<500 uS/cm) than the QiQuac’s two 0.1 probes. As the organizer and a fierce competitor, I was taken off guard by the very high (>850 uS/cm) EC.T value being measured in the channel. This is outside of the optimal range of 0-500 uS/cm that we are normally faced with in natural streams in British Columbia, Canada. We therefore had to make two modifications to the procedure suggested in the QQ manual.
1. Due to the low K-value and high conductivity, the background EC.T was drifting significantly, much more than the sensitivity of the device (around 5-10 uS/cm of drift with a device sensitivity of 0.01 uS/cm). We found we could eliminate the false drift by periodically shaking the probes in the water to remove any buildup of electroplated ions, however it was not sufficiently stable to use the lower dose of 200g tried on Thursday.
2. We had to add more salt. To overcome the sensor background drift, we increased the dose to 2kg (~7 kg /m³/s). Christoph recommended an even higher dose for the high conductivity, using 7kgs on the first injection ( ~23 kg/m³/s) This flies in the face of our goal in BC to reduce dosage, but when in Rome…
Using the higher dosage did give excellent results however and raised the EC.T by about 200 uS/cm over background.
From the photos, we can also see this is not an ideal channel for tracer methods. However, probes placed on either bank were within 7% of one another on the QQ and within 3% of each other on the TracerQ-S for the first injection of 7kg. This implied complete mixing was achieved.
After all the bluster, chest-beating, and posturing of the SWAG competition, competitors got down to the serious business of measurement. Many times I saw Nick approaching competitors and “chatting” but there was not evidence of bribes changing hands.
The very elegant Discharge App was downloaded onto many attendees android phones and, with the assistance of Beat, were programmed with the site bathymetric surveys and reference markers. Competitors were then able to measure the flow for themselves. Beat posted flows ranging from 258L/s to 377 L/s
with an average of 291 L/s.
The Sommer Tracer-F consistently measured 0.32 m³/s over two measurements. Likewise the TracerQ-S system measured 0.31 m³/s from two probes on the first injection. The QiQuac was in-step with these measurements reporting an average of 0.32 m³/s on the first injection of 7kgs and on the second injection of 2kgs. Christoph withdrew the second TracerQ-S measurement of the lower dose as the two probes were not within 3% of one another.
The Vertouschka measurement was 294 L/s, taken by Nick. Hmm.
In traditional pomp and circumstance befitting high Viennese society, an elaborate ceremony at the nearby pub took place. Overseeing the ceremony was the right-honorable Nick, regaled in his finest Hydrologist’s habit consisting of jeans and a plaid shirt.
Nick “explained” that the truth is what the most people believe. He silenced the murmuring crowd with a raise of his hand, and reported the “True” flow as the average of all measurements, including the SWAGs, which worked out to 294.5 L/s. I was impressed with this level of precision from such seemingly course sources, which I remarked to my colleague, when Nick silenced the crowd with a raised hand, and announced that I was the SWAG winner. I jumped up and yelled “Yes, suck it losers!” at the politely clapping attendees and went to claim my prize. At this point Beat stood up and pointed an accusing finger crying “His SWAG was based on a measurement from the day prior!” Sensing the crowd was turning, I lunged for the prize, a bottle of prosecco that Beat and I had purchased the evening before. But Nick was quick to see a chance to win the crowd’s favour and withdrew the prize from my grasp. A gasp, and a fell silence came over the crowd and Nick said “Mr. Gabe Sentlinger, you are hereby disqualified from the SWAG competition on account of apriori knowledge being used in your estimate.”
“I’ve been robbed!” I yelled, and slunk back to my table.
“Instead, I’ve decided to give the SWAG prize, to the lady of the contest, Michelle for having the highest estimate of SWAG! “ Michelle was already a crowd favourite and they responded accordingly with coos and cheers of “Bravo!” With great humility, Michelle accepted the award with her signature grace and poise. I murmured something bitter to my tablemate who simply frowned and changed seats.
Taking the prize for the most “accurate” measurement was, not surprisingly, Nick for his measurement with the Vertuschka. There were again strained cheers and clapping and Nick presented himself with a bottle of the finest Austrian wine, and proceeded to give a speech, paraphrased here but without the pregnant pauses and rolled R’s:
“My fellow Hydrometricians. While I may have won the day, we, indeed, are ALL winners. The sharing of knowledge, the community of spirit, and the vitality of competition, has elevated us ALL to greater hydrometric heights. And while there is only ONE winner, I can say from this esteemed promontory of achievement, that NONE of us (except those disqualified) are the lesser for the days exploits. NOW, let us drink and be merry, eat your schnitzel, grasp your fellow hydrometricians (except those disqualified) and be thankful that we can come together in this fair land, and share….this…VICTORY!” at which point he held up his bottle of wine. The crowd erupted in celebration and cheering and got down to some serious eating and drinking (except those disqualified).
As I sat alone in the corner (where Nick had banished me) staring into the vortex of my beer, I watched the other revelers as they congratulated Nick. A hand alighted on my shoulder, “Cheer up!” he said, “There’s always next time!”
“Thanks,” I said, “that’s true, until next time,” and shook his hand.
I wondered aloud, “Maybe there really are no winners or losers in sport. Perhaps the prize truly is in the competition. What better way to meet new people, challenge one’s skills, and learn the value of persistence and sportsmanship. Surely it’s a testament to the human spirit when we can battle a competitor, and then help them up with an offered hand. Sometimes the prize we seek is not where we expect it. And sometimes it’s not a prize, but a gift.”
“You alright?” our waitress asked me.
“I’m just fine.” I replied. “Join us next year at the 2019 EGU Flow Regatta, Q-Competition, and Schnitzel!”
[Legal Disclaimer: This story is based on actual events. In certain cases incidents, characters and timelines have been changed for dramatic purposes. Nick did not award himself the prize, but was a perfect Judge and Master of Ceremony. Credit for the accurate Vertuschka measurement goes to Maxence. Nick’s the best]