This dataset was generated during the precision testing of three water-quality sondes before picking one to use for field deployment of high frequency ground-water quality monitoring. Precision is important because the authors wanted to try and minimize calibration drift corrections between site visits. A laboratory experiment was conducted for the three sondes to simultaneously measure at hourly intervals with a setup of standard solution circulating past the sondes to simulate field conditions. The electrical conductivity experiment lasted 33 hours, the pH experiment lasted 13 hours, and the DO experiment failed (no data).

The authors examined the long-term precision of SC, pH, and DO sensors by analyzing the groundwater-quality time-series data generated at a deep municipal supply well (USGS station 364200119420001) during the period from September 2013 to July 2018. The data set presented is the data collected by the RBRmaestro sonde the during the time period from February 2016 to June 2016 and September 2017 to October 2017.

This Data Release serves as a repository for a set of time-series data used in Scientific Investigations Report 2018-5040. The data represent continuous measurements of specific conductance, water temperature, and/or water level (stage), recorded by a variety of types of data loggers during three multi-day interference tests conducted on the Virgin River at Pah Tempe Springs during November 2013, February 2014, and November 2014. The data presented are the raw data downloaded from the data loggers and are organized according to the date of the test and the type and name of the observation site. The Data Release contains 3 items: 1. An explanatory table, "PahTempe_table1.xlsx", which indicates which parameters were collected and on what instrument at each site during a given test 2. The data, "PahTempe_data.zip"; this zipped file contains the raw data logger files in comma-separated values (CSV) format, organized into folders according to the date of the interference pumping test 3. The metadata document, "PahTempe_metadata.xml" Because these data were collected during multi-day interference pumping tests, they do not represent natural hydrologic conditions in the river, springs, or shallow groundwater system. Users of this data are advised to refer to the larger work citation for proper use and interpretation of the data.

This Data Release serves as a repository for a set of time-series data used in Scientific Investigations Report 2018-5040. The data represent continuous measurements of specific conductance, water temperature, and/or water level (stage), recorded by a variety of types of data loggers during three multi-day interference tests conducted on the Virgin River at Pah Tempe Springs during November 2013, February 2014, and November 2014. The data presented are the raw data downloaded from the data loggers and are organized according to the date of the test and the type and name of the observation site. The Data Release contains 3 items: 1. An explanatory table, "PahTempe_table1.xlsx", which indicates which parameters were collected and on what instrument at each site during a given test 2. The data, "PahTempe_data.zip"; this zipped file contains the raw data logger files in comma-separated values (CSV) format, organized into folders according to the date of the interference pumping test 3. The metadata document, "PahTempe_metadata.xml" Because these data were collected during multi-day interference pumping tests, they do not represent natural hydrologic conditions in the river, springs, or shallow groundwater system. Users of this data are advised to refer to the larger work citation for proper use and interpretation of the data.

When water is pumped slowly from saturated sediment-water inteface sediments, the more highly connected, mobile porosity domain is prefferentially sampled, compared to less-mobile pore spaces. Changes in fluid electrical conductivity (EC) during controlled downward ionic tracer injections into interface sediments can be assumed to represent mobile porosity dynamics, which are therefore distinguished from less-mobile porosity dynamics that is measured using bulk EC geoelectrical methods. Fluid EC samples were drawn at flow rates similar to tracer injection rates to prevent inducing preferential flow. The data were collected using a stainless steel tube with slits cut into the bottom (USGS MINIPOINT style) connected to an EC meter via c-flex or neoprene tubing, and drawn up through the system via a peristaltic pump. The data were compiled into an excel spreadsheet and time corrected to compare to bulk EC data that were collected simultaneously and contained in another section of this data release. Controlled, downward flow experiments were conducted in Dual-domain porosity apparatus (DDPA). Downward flow rates ranged from 1.2 to 1.4 m/d in DDPA1 and at 1 m/d, 3 m/d, 5 m/d, 0.9 m/d as described in the publication: Briggs, M.A., Day-Lewis, F.D., Dehkordy, F.M.P., Hampton, T., Zarnetske, J.P., Singha, K., Harvey, J.W. and Lane, J.W., 2018, Direct observations of hydrologic exchange occurring with less-mobile porosity and the development of anoxic microzones in sandy lakebed sediments, Water Resources Research, DOI:10.1029/2018WR022823.

When water is pumped slowly from saturated sediment-water inteface sediments, the more highly connected, mobile porosity domain is prefferentially sampled, compared to less-mobile pore spaces. Changes in fluid electrical conductivity (EC) during controlled downward ionic tracer injections into interface sediments can be assumed to represent mobile porosity dynamics, which are therefore distinguished from less-mobile porosity dynamics that is measured using bulk EC geoelectrical methods. Fluid EC samples were drawn at flow rates similar to tracer injection rates to prevent inducing preferential flow. The data were collected using a stainless steel tube with slits cut into the bottom (USGS MINIPOINT style) connected to an EC meter via c-flex or neoprene tubing, and drawn up through the system via a peristaltic pump. The data were compiled into an excel spreadsheet and time corrected to compare to bulk EC data that were collected simultaneously and contained in another section of this data release. Controlled, downward flow experiments were conducted in Dual-domain porosity apparatus (DDPA). Downward flow rates ranged from 1.2 to 1.4 m/d in DDPA1 and at 1 m/d, 3 m/d, 5 m/d, 0.9 m/d as described in the publication: Briggs, M.A., Day-Lewis, F.D., Dehkordy, F.M.P., Hampton, T., Zarnetske, J.P., Singha, K., Harvey, J.W. and Lane, J.W., 2018, Direct observations of hydrologic exchange occurring with less-mobile porosity and the development of anoxic microzones in sandy lakebed sediments, Water Resources Research, DOI:10.1029/2018WR022823.

The goal of this study was to develop a suite of inter-related water quality monitoring approaches capable of modeling and estimating the spatial and temporal gradients of particulate and dissolved total mercury (THg) concentration, and particulate and dissolved methyl mercury (MeHg), concentration, in surface waters across the Sacramento / San Joaquin River Delta (SSJRD). This suite of monitoring approaches included: a) data collection at fixed continuous monitoring stations (CMS) outfitted with in-situ sensors, b) spatial mapping using boat-mounted flow-through sensors, and c) satellite-based remote sensing. The focus of this specific child page is to document the temporal high-resolution (15 minute) in-situ sensor data collected at the four primary CMS locations. The four primary CMS locations chosen for this study included: a) a Sacramento R. dominated site in the northern portion of the Delta (Freeport, FPT, USGS Station_no. 11447650); b) a site in western portion of the central Delta, which is associated with the Cache Slough Complex and is seasonally influenced by the Yolo Bypass when it flows (Liberty Island, LIB, USGS Station_no. 11455315); c) a site in the southern reach of the central Delta where the Sacramento and San Joaquin Rivers have strong seasonal influences on water quality (Middle River, MDM, USGS Station_no. 11312676); and d) a site in the eastern central Delta where the Sacramento, Cosumnes, and Mokelumne rivers have strong seasonal influences on water quality (Little Potato Slough, LPS, USGS Station_no. 11336790). These four sites were used for monitoring of optical properties and hydrodynamics at high frequency (15 minute) intervals over the 2-year study period. Specifically, the data collected at each site includes tidal stage; velocity; nitrate measured via absorbance spectrometry (SUNA V2, Seabird Inc); and optical measurements of turbidity, chlorophyll-a fluorescence, and fluorescent dissolved organic matter, all measured via deployable multiparameter sonde (YSI EXO2, Yellow Springs, Inc). The time series data for all four CMS sites was downloaded for the 2-year period of record (July 1, 2019 through July 1, 2021) from the USGS National Water Information System (NWIS) website (https://waterdata.usgs.gov/nwis), and are presented here in a single machine-readable datafile (CMS_TimeSeries_Data.csv), which includes data for all of the parameters described above. In certain situations, specific sensors were not operational at a given site for a particular time period, and thus the associated water-quality data are not provided as part of the time series record in those instances. These high frequency temporal records provide the explanatory variables used to modeled THg and MeHg concentrations over time and at high temporal frequency throughout the SSJRD.

The goal of this study was to develop a suite of inter-related water quality monitoring approaches capable of modeling and estimating the spatial and temporal gradients of particulate and dissolved total mercury (THg) concentration, and particulate and dissolved methyl mercury (MeHg), concentration, in surface waters across the Sacramento / San Joaquin River Delta (SSJRD). This suite of monitoring approaches included: a) data collection at fixed continuous monitoring stations (CMS) outfitted with in-situ sensors, b) spatial mapping using boat-mounted flow-through sensors, and c) satellite-based remote sensing. The focus of this specific child page is to document the temporal high-resolution (15 minute) in-situ sensor data collected at the four primary CMS locations. The four primary CMS locations chosen for this study included: a) a Sacramento R. dominated site in the northern portion of the Delta (Freeport, FPT, USGS Station_no. 11447650); b) a site in western portion of the central Delta, which is associated with the Cache Slough Complex and is seasonally influenced by the Yolo Bypass when it flows (Liberty Island, LIB, USGS Station_no. 11455315); c) a site in the southern reach of the central Delta where the Sacramento and San Joaquin Rivers have strong seasonal influences on water quality (Middle River, MDM, USGS Station_no. 11312676); and d) a site in the eastern central Delta where the Sacramento, Cosumnes, and Mokelumne rivers have strong seasonal influences on water quality (Little Potato Slough, LPS, USGS Station_no. 11336790). These four sites were used for monitoring of optical properties and hydrodynamics at high frequency (15 minute) intervals over the 2-year study period. Specifically, the data collected at each site includes tidal stage; velocity; nitrate measured via absorbance spectrometry (SUNA V2, Seabird Inc); and optical measurements of turbidity, chlorophyll-a fluorescence, and fluorescent dissolved organic matter, all measured via deployable multiparameter sonde (YSI EXO2, Yellow Springs, Inc). The time series data for all four CMS sites was downloaded for the 2-year period of record (July 1, 2019 through July 1, 2021) from the USGS National Water Information System (NWIS) website (https://waterdata.usgs.gov/nwis), and are presented here in a single machine-readable datafile (CMS_TimeSeries_Data.csv), which includes data for all of the parameters described above. In certain situations, specific sensors were not operational at a given site for a particular time period, and thus the associated water-quality data are not provided as part of the time series record in those instances. These high frequency temporal records provide the explanatory variables used to modeled THg and MeHg concentrations over time and at high temporal frequency throughout the SSJRD.

This data release includes time series data collected at the Bremerton Naval Complex, Bremerton WA. Groundwater levels and water quality parameters in two monitoring wells were recorded every 15 minutes during a 7-month deployment. Time series data were collected from June 29, 2018, to February 26, 2019. Field deployment details and quality assurance methods are included in the following paragraphs. Groundwater monitoring well MW-709 was monitored using two data loggers. The first data logger is a non-vented pressure transducer (In-Situ Rugged TROLL 100) that was deployed resting on the well bottom (BOT). The well measurement point (MP) elevation is 16.86 feet above NAVD88 with a total depth from MP of 30.00 feet and the transducer rested at -14.14 feet below NAVD88. Data collected at this location is referenced by National Water Information System (NWIS) site ID 473324122382202. Temperature and depth were recorded every 15-mintes for the entire deployment. Time-series data from this data logger are located in the text file “MW-709_BOT_time-series_data.txt”. Temperature ranged from 12.1 to 18.8 degrees Celsius. Pressure transducers, which measure the pressure above the transducer, were programmed in feet for all loggers used in this data set. The collected depth data was corrected for changes in barometric pressure by subtracting the atmospheric (barometric) pressure (feet of water) from pressure transducer measurements for each 15-minute value, with due consideration of units. Barometric-corrected depth data was converted to water level altitude by adding an -13.41 feet offset to each 15-minute value to reference the North American Vertical Datum of 1988 (NAVD88). Water level altitude ranged from 1.75 to 6.71 feet. The second data logger is a non-vented pressure transducer (Solinst LTC Levelogger) programmed to record temperature, depth, specific conductance and salinity. The data logger was suspended from a buoy with a deployment depth of 1.55 feet below the water surface (TOP). Data collected at this location is referenced by NWIS site ID 473324122382201.The buoy system was intended to maintain a constant deployment depth below the well water surface as tidally-influenced monitoring well water levels change. There was a lag in the buoy system response to well water level changes caused by the 150 mL plastic bottle getting stuck moving up and down inside the well casing resulting in water depth fluctuation ranging from 2.77 to 8.75 feet. Temperature readings during the calibration check procedures were determined less than poor (greater than one degree Celsius lower than a NIST-certified thermistor at five temperatures); therefore, the time-series data did not meet USGS publication criteria. Specific conductance readings during the calibration check procedures were determined less than poor (greater than 15 percent lower than a calibration standard); therefore, the time-series data did not meet USGS publication criteria. Water level altitude time-series data from this data logger are located in text file: “MW-709_TOP_time-series_data.txt”. Groundwater monitoring well MW-412 was monitored using two data loggers. The first was a non-vented pressure transducer (In-Situ Rugged TROLL 100) that was deployed resting on the well bottom (BOT). The well measurement point (MP) elevation is 14.66 feet above NAVD88 with a total depth from MP of 24.00 feet and the transducer rested at -9.34 feet below NAVD88. Data collected at this location is referenced by NWIS site ID 473323122382902. Temperature and depth were recorded every 15-minutes for the entire deployment. Time-series data from this data logger are located in the text file “MW-412_BOT_time-series_data.txt”. Temperature ranged from 11.1 to 14.8 degrees Celsius. Barometric-corrected depth data was converted to water level altitude by adding an -9.40 feet offset to each 15-minute value to reference the North American Vertical Datum of 1988 (NAVD88). Water level altitude ranged from