Field Notes

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Gilbert Tract: 2022-03-23 09:45:00 (DOY 82)
Author: Ariane Arias-Ortiz
Others: Joe, Dennis, Carlos

Summary: Channel survey at the ADCP location, delivered fancy tea bags to school, swapped 7500, cleaned 7700, reinstalled north otter-cam

Gilbert Tract
2022-03-23

Dennis, Ariane, Carlos and I arrived at about 10am PDT. It was clear sunny and warm with a nice breeze form the west. Green tules and cattails are coming up but not enough to change the overall color of the wetland. Today’s main goal is to conduct a channel survey to estimate the cross-sectional area at the ADCP location to estimate volumetric discharge. Tide was out going while we were there.

We dropped Ariane and Carlos off on the south side of the channel to inflate the boat and Dennis and I drove around to the north side to set some anchors for a guide rope and a level line across the channel. In about five tries and with some discus throwing wisdom from Dennis we manage to throw a rebar stake attached to a string across the channel. With that string we pulled across the channel a heavy rope to guide the boat against the ebb tide and a mason’s level line to measure from (if there is a next time, it would be easier to do the channel survey during slack water). Dennis and I returned to the south side to help Ariane and Carlos get started with the measurements.

The rope and level line were tied to the solar power post. We used a meter stick to mark 0.5m intervals (south 18m) and 1.0 intervals (north 18m) on the level line double checking occasionally with the long tape measure. Then the distance from the level line to the ground surface was measured. For the deeper parts we used a fiberglass telescoping pole with pieces of an old tape measure cable tied to it. Ariane and Carlos got in the boat and made measurement across the channel. The deepest parts had almost 3m of water and it was very difficult manipulating the long measuring pole in the water against the current.

At about noontime while Ariane and Carlos made the measurements, Dennis and I went to the Knightsen School to drop off the special tea bags needed for the tea bag decomposition experiment.

At about 12:30 PDT I stopped at the tower to swap the 7500 for calibration, sn 0041 came off and sn 75H-2182 went on. I update the pressure coefficients and reset the box.
0041 read: 437.7ppm CO2, 554.0mmol/m3 H2O, 102.0kPa, 21.8C, 99.2SS
2182 read: 440.5ppm CO2, 587.6mmol/m3 H2O, 102.2kPa, 22.3C, 99.2SS

The 7700 had some spider webs and cattail fluff on it and looked dirty especially the upper mirror.
The 7700 read: 2.28ppm CH4, 11.0RSSI – after cleaning 2.06ppm CH4, 80.7RSSI
The wash reservoir was about half empty so I think it has been washing occasionally, but if the signal strength is low next time, the wash cycle should be manually tested.

I also reinstalled the north otter-cam with fresh batteries and on a taller metal stake.

Back at the channel Ariane and Carlos were just finishing the measurements. We measured the location on the ADCP:
70 cm from top ADCP to water
266 cm from soil to reference line
8 meters horizontal distance from enclosure post.

We left a couple of rebar stakes on the north side of the channel so that Scott Jones can get the location with the fancy GPS.

Our measuring stick had a rusty metric tape attached. It had very sharp edges and punctured the inflatable boat, luckily this happened after we finished the survey. If there is a next time, we could either get metric tape stickers or replace the rusty tape with something easier to handle.

We left at about 14:00 PDT

Channel survey data has been uploaded to box:

https://berkeley.box.com/s/i6nzqaewzyl8sbhzm0hneav4xt47jmg0

_fieldnotes