Field Notes

Hill Slough: 2022-03-31 09:50:00 (DOY 90)
Author: Daphne Szutu
Others: Joe

Summary: Regular data collection/cleaning, tested CTD conductivity--moved probe outside of well, adjusted heights of miniDOT and dissolved CO2 sensors, removed NR-LITE, removed Campbell water level sensor, new datalogger program

2022-03-31
Hill Slough

Joe and I arrived at 9:50 PDT. It was cool with thin high clouds and a cold wind. Many birds flitting around and at least 2 planes flying into Travis AFB. Since the last site visit, weeds have shot up along the road, including wild mustard and wild radish. The water was very low and the channel was apparent. The water level was just below the staff gauge at about 3.95 feet at 9:48 PST. Joe secured the bottom of the staff gauge to the post with an extra screw.

It was low tide but flooding. The miniDOT was out of the water when we arrived but it was just submerged <30 minutes later. I downloaded the miniDOT, swapped its desiccant, and lowered its chain slightly so it was right above the ground surface. The dissolved CO2 sensor was laying sideways in the mud. I hitched up its cable so the sensor is hanging just above the ground—it might need a more permanent solution to fixing the sensor height.

I downloaded met, cam, and USB GHG data. Joe cleaned flux and rad sensors and topped off the wash reservoir. I changed the eddy clock +45seconds to match the laptop time and restarted logging afterwards.

Joe removed the Rnet sensors NR-LITE sn 990350 to use in this summer’s advection experiment. We also removed the Campbell water level sensor sn 20010770 because the HYDROS21 CTD’s water level data seems reasonable and matches well with the Campbell sensor. However, Ari has found that the CTD conductivity data does not match with the data from nearby Rush Ranch. We pulled the CTD sensor out to test it using conductivity standards that Ari had previously prepared and were stored in the fridge. We also used the YSI handheld probe to independently measure conductivity.

- CTD probe readings
On arrival, the sensor was reading ~81,000 uS/cm. This is way too high. Joe removed it from the well and it was covered in mud. He rinsed off the mud and removed the metal screen.
In surface water next to the well: ~6000 uS/cm
In DI water: 0 uS/cm
In ~2,000 uS/cm std: 2145 uS/cm

- YSI probe (temperature compensated reading)
In surface water: 6020 uS/cm
In DI water: 5 uS/cm
In ~2,000 uS/cm std: 1935 uS/cm

The CTD and the YSI probe agreed reasonable well as long as the CTD sensor was not in the well. We decided to install the sensor outside of the well. Joe tied the sensor to the grounding rod underneath the tower with the sensor just above the ground. We removed the metal screen. We’ll have to watch the data to see if it the sensor remains submerged during low tides. If it is, we could dig a small depression in the ground and lower the sensor. In this new position, the CTD read 6,315 uS/cm, which is reasonable. We didn’t measure the height of the sensor but we can use the staff gauge reading as reference.

I uploaded a new met datalogger program that removed the Rnet, Campbell water level, and soil moisture sensors.

LI-7500 readings:
CO2 419ppm
H2O 492ppm
T 13.6C
P 101.4kPa
SS 93--> 100 after cleaning
LI7700 readings:
CH4 2.0ppm
RSSI 44 --> 72 after cleaning

We left at 11:10 PDT.

0 photos found

4 sets found

20 HS_met graphs found