SAMPLING TIMES:
Sampling times are indicated in the DateTime column, and were collected in the America/New_York Eastern Time Zone. All date times are reported in local time. Please note there are some observations taken during overnight sampling campaigns. In version 12, we added in times for observations that we could find from historical records. When we could not find the time of an observation it was set to 12:00 and flagged with a 1 in the Flag_DateTime column.
FIELD SAMPLE COLLECTION:
At each sampling site in each reservoir, water temperature, dissolved oxygen (DO), conductivity, pH, and oxidation-reduction potential (ORP) were collected at discrete, approximately 1-m increments from the water surface to the sediments using a YSI ProPlus sensor with Quattro cable (pH, ORP, conductivity) (2014-2017) and YSI ProODO optical dissolved oxygen meter (dissolved oxygen, temperature) (2017-2023). Specific conductance was measured in 2021 - 2023 using the EcoSense EC300A Conductivity Meter (conductivity, salinity, TDS, temperature). Additionally, in 2021 - 2023, we measured pH using an Ohaus Starter 300 pH meter. Dissolved oxygen was calibrated approximately weekly using the water-saturated air technique. The dissolved oxygen probe cap was replaced on June 30th, 2021, at which point a two-point calibration was performed. The pH sensor was calibrated approximately weekly using a series of three standardized pH solutions (pH 4, 7, 10) and the ORP sensor was calibrated approximately weekly using Zobell and Hatch solutions.
Specific conductance was measured only sporadically for a check on the streaming sensors, or in streams at Carvins Cove Reservoir. Therefore, there are not a lot of specific conductance observations compared to the other variables.
Photosynthetically active radiation (PAR) was collected at discrete, approximately 1 m increments from the water surface to the depth of light extinction (~ 0 micromole m-2 s-1) using a LiCor LI-192 underwater quantum sensor. PAR was also measured in air approximately 0.1 m above the water surface; these depths are recorded as -0.1m.
ORP was only collected in 2016 and 2017, while pH was only collected from 2014 - 2017 before these probes were removed from the YSI. Subsequent pH measurements included in this data package in 2021 and 2023 are from the handheld pH meter described above.
Secchi disk depth was measured using a standard 20 cm diameter circular Secchi disk attached to a calibrated rope. Secchi depth measurements were made without the aid of a plexiglass viewer. The Secchi disk was lowered from the shaded side of the boat or dock. To determine the mean Secchi depth, we took the average of two depths: 1) the depth at which the disk first disappeared in the water column on the way down and 2) the depth at which the disk reappeared while being raised.
YSI and PAR profiles and Secchi depths were collected approximately fortnightly in the spring months (Mar. - May), weekly in the summer and early autumn (Jun. - Sept.), and monthly in the late autumn and winter (Oct. - Feb.) in Falling Creek and Beaverdam Reservoirs; data coverage in the other three reservoirs varies among years. Most sampling occurred between the hours of 9:00 and 15:00. Times were included in this data product when recorded on the field sheet. If times were not recorded, the time was set to 12:00 and Flag_DateTime column was set to 1. Some sampling occurred outside of our routine hours, including some overnight sampling; these instances were noted by the actual sampling time within the DateTime column. For more information about nighttime sampling, see Doubek et al. 2018.
DATA PACKAGE SUMMARY:
This data package includes 2 data files (Secchi_depth_2013_2023.csv and YSI_PAR_profiles_2013_2023.csv), QAQC R scripts (Secchi_qaqc_2013_2023.R and YSI_PAR_profiles_qaqc_2013_2023.R), maintenance logs (Secchi_MaintenanceLog_2013_2023.csv and Ysi_MaintenanceLog_2013_2023.csv), visual inspection R scripts (Secchi_inspection_2013_2023.Rmd and YSI_inspection_2013_2023.Rmd), and sampling sites (site_descriptions.csv). The QAQC scripts include functions to process data, remove outliers, and apply the maintenance log to clean the data files included in the package; the visual inspection scripts provide code for plotting and visualizing current and historical data. Please note that there was a major revision of this dataset from version 11, which includes correcting times to observations, including negative ORP values, and adding observations from an outflow at Falling Creek Reservoir, among other changes.
QUALITY ASSURANCE AND QUALITY CONTROL OVERVIEW:
The Secchi_qaqc_2013_2023.R script reads in the maintenance log to automatically assign flags to data that 1) were averaged together because there were more than one observation (flag = 2) or 2) are identified to be suspect (flag = 3). Data flag = 1 indicates that the Secchi depth was not taken on a particular day.
The YSI_PAR_profiles_qaqc_2013_2023.R script reads in the maintenance log to automatically assign flags to data that 1) were not collected or not reliable due to instrument malfunction (flag = 2), 2) are identified to be suspect (flag = 5), or 3) were digitized incorrectly (flag = 6). The remaining flags are defined as follows: flag = 1 if data were not collected for a particular day/variable, flag = 3 if the data are below the detection limits specified in the QAQC script, and flag = 4 if any variable (besides temperature) has a negative value.
SITE DESCRIPTIONS:
Secchi depth was typically measured only at the deep site (50), though was occasionally measured at upstream sites in Falling Creek Reservoir and Beaverdam Reservoir. The YSI and PAR depth profiles were measured at the deepest site of each reservoir adjacent to the dam (Site 50), a gauged weir on the primary inflow tributary at Falling Creek (Site 100), inflows and outflows to Falling Creek (Sites 1.1, 99, 101, 102, 200) and Beaverdam (Sites 40, 100, 200), inflowing streams at Carvins Cove (Sites 100, 101, 200, 300, 301, 400, 500), and other in-reservoir transects in all reservoirs (Sites 10, 20, 30, 40, 45). A littoral site (Site 51) located near site 50 was also sampled at Beaverdam Reservoir in 2021. See site_descriptions.csv for coordinates and site descriptions of all sampling sites.
WHOLE-ECOSYSTEM EXPERIMENTS:
Multiple whole-ecosystem experiments have been conducted at Falling Creek Reservoir, including intermittent operation of hypolimnetic oxygenation (HOx) and pulsed epilimnetic mixing (EM) engineering systems. We encourage you to contact the lead author of the data package for more information.
REFERENCES:
Doubek, J. P., Campbell, K. L., Doubek, K. M., Hamre, K. D., Lofton, M. E., McClure, R. P., Ward, N. K., and Carey, C. C. 2018. The effects of hypolimnetic anoxia on the diel vertical migration of freshwater crustacean zooplankton. Ecosphere, 9(7), e02332.
