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Scuffling with Towed Gear, Repairing GPS, and House
Having end deploying magnetotelluric stations (MT) on land to picture the distribution of contemporary and saline groundwater alongside two rivers in Bangladesh, we now turned to a complementary towed TEM (transient electromagnetic) system to enhance the imaging. The place the floor and groundwater are contemporary has a big impact on the agriculture. We’re additionally imaging deeper freshwater, under the saline groundwater, which may be tapped for consuming water.
Earlier than we began the TEM, we first needed to choose up the MT stations deployed the day earlier than. Due to the excessive winds, my crew went to the final web site by highway. The nation boat took us to the close by bridge with the primary highway south. There, our information Romeo employed two autorickshaws to drive our crew to the gear. Whereas the primary highway was advantageous, the smaller highway alongside the channel that led to our instrument was fairly bumpy. Ultimately, we bought there, packed every part up and made it again to the Kokilmoni. One other crew picked the opposite two devices utilizing the nation boat.
By the point we returned, Kerry had began assembling the raft that can carry the devices. There’s a rectangular body product of Kevlar with ropes to tighten it. Coils of wire are wrapped for the transmitter and receiver wires and a smaller receiver will probably be towed behind on an inflatable kayak. The whole body is mounted on inflatable boats, tubes and kayaks. Assembling it took the remainder of the morning.
We towed it out to the Kokilmoni utilizing the nation boat and arrange the tow strains. Then the debugging course of began. We sailed up the Andharmanik River and began to get a sense for how briskly we may tow it. The spherical floats tended to flip and needed to be secured higher. We additionally added weight with 5-gallon jugs full of water as ballast. We spent all the day doing this and nonetheless hadn’t began the survey, so we had been falling delayed.
In a single day the crew went ashore and bought lengthy bamboo poles. Once we towed the Rube Goldberg machine again to the place to begin of the survey, we stopped and the crew added them to the body significantly strengthening it. We began heading north, however now the kayak with the smaller receiver stored flipping over. We added one after which two outriggers with plastic jugs. Lastly, a life preserver underneath its bow stored it from diving underneath the water.
Nonetheless, preventing the tide, we couldn’t safely tow the system very quick. We discovered that 5 km/hr was approaching the restrict for the pace we may towing it and had been largely going slower than that. Even utilizing my contingency day, it was unsure whether or not I may get again to Barisal on time. We didn’t get out of the Andharmanik River and into the bigger Tetulia Channel till the late afternoon. It had taken us over a day and a half to construct the towed TEM system and get it working. It was amassing good knowledge, however our progress over the bottom was very sluggish.
Then issues began to vary. The bigger channel was rougher, however we caught the rising tide and all of a sudden we had been going 9 km/hr. With the next sea we began making up time. On the finish of the day, the captain determined to maintain going after darkish to benefit from the tide whereas we may. We headed for a great location to spend the evening.
We had been nearly there when the Kokilmoni ran aground. Components of the river are very shallow and we hit a submerged sand financial institution. We spent a tense ½ hour maintaining the TEM raft secure whereas making an attempt to maneuver the Kokilmoni to get free. Lastly, we did and headed again south to go round this shallow a part of the river. We nearly made it.
A bit wanting the place we had beforehand crossed to the deeper water, the Kokilmoni needed to swerve to keep away from a fishing boat. In consequence, we ran aground once more whereas going fairly quick in the dead of night. This time we had been solidly caught though there’s deeper water just a bit to our aspect. We couldn’t get free. As a substitute, we needed to look forward to the subsequent excessive tide within the morning to get free, or so we thought. The 2 excessive tides of the day are unequal. We had gotten caught in the course of the larger tide. The morning tide didn’t attain a degree to permit us to get free, so we needed to look forward to the night excessive tide. Getting just a few additional hours of journey with the tide now value us a complete day.
We disconnected the TEM raft for getting the boat free, which occurred simply as soon as the water degree was excessive sufficient. The subsequent morning we reconnected every part and restarted our voyage north. As a result of, we had misplaced a lot time, Adrien and I left shortly after breakfast on the speedboat, together with Céline and Masud, who will do gravity stations by land and meet the Kokilmoni in Khulna on the finish of the cruise. To avoid wasting time, we are going to motor on to Patuakhali, which is nearer than Barisal, and meet Sanju and a couple of others there. They arrived in Barisal from Dhaka that morning on the in a single day ferry. It turned out to be extra of an journey than we anticipated.
The speedboat needed to often sluggish for fishing nets, so our pace was slower than anticipated. Then we encountered a sand financial institution the place the water was too shallow. It took some time to get again to deeper water, together with Romeo getting out and pushing the boat. Then we circled to the opposite aspect of the river. As we did the wind picked up and the waters grew to become uneven spraying us with water. Once we bought to the opposite aspect, we sheltered in a small aspect channel.
At that time, after nearly 3 hours of touring by speedboat, we turned out to be solely 5 km forward of the Kokilmoni. She had caught the rising tide and rode it north at a great clip. She picked us up and gave us a experience. Since time was going by, we modified plans. The automotive continued east from the college internet hosting our GPS, whereas we sailed north and throughout the river on the Kokilmoni, then by means of a set of channels and a small river on the speedboat to satisfy the automotive with Sanju.
We then drove again to the GPS station. The issue turned out to be a defective cable. We didn’t have a spare, so with the assistance of Sarah Doelgar at UNAVCO in Colorado, we bought the receiver able that labored whereas Sarah monitored it in the midst of the evening within the US. We then rushed north to Barisal College, the place I gave a chat, delayed by our mishaps.
To finish the fieldwork, Sanju, Adrien and I traveled from Barisal to Dhaka on one of many in a single day ferries, one thing I had lengthy wished to strive. It didn’t disappoint, and we arrived in Dhaka early within the morning. After two profitable GPS repairs and our in depth EM survey (MT and TEM), the primary of their sort in Bangladesh, it was time to return residence. After a Fast COVID check and conferences in Dhaka, we headed to the airport to fly residence.
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