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).

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.

Water temperature, conductivity, and dissolved oxygen data collected at 5 locations in the Sacramento River Deep Water Ship Channel. Each of the 5 stations had a string suspended from a buoy, with instruments located at consistent depths below the water surface. Data were collected at 5- or 10-minute intervals from July 2, 2019 to September 18, 2019.

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.

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.

Two dissolved-oxygen experiments were completed using internally logging water-quality monitors. Dissolved-oxygen sensors on the water-quality monitors were calibrated using various settings and at various elevations in Oregon, USA. Data from these experiments can be used 1) to assess how elevation affects dissolved-oxygen values recorded by continuous water-quality monitors, and 2) to inform best practices for calibrating and recording dissolved oxygen at various elevations. Experiment #1 started by calibrating six YSI 6-series optical dissolved-oxygen sensors in Bend, Oregon, at an elevation of approximately 3,700 feet above sea level: 3 sensors were calibrated to 100% saturation, and 3 sensors were calibrated to 100% solubility (in mg/L) based on USGS DO Tables. During the experiment, sensors always remained in a 100% saturated environment. All calibrations and calibration checks were performed in a 100% air-saturated water environment (air-purged bucket of water). Sensors were kept in a water-saturated air environment (referred to as the wet-towel method) when in transport; the wet-towel method allowed the sensors to remain in a 100% saturated environment while the elevation and barometric pressure changed. Monitors were set to log internally at 15-minute intervals, and the monitors were transported over a pass in the Cascade Range and then to Salem, Oregon, which is at approximately 200 feet elevation. In Salem, sensor calibrations were checked, and then dissolved-oxygen sensors were calibrated again using the same settings as previously described. Monitors were transported back to Bend, Oregon, following the same route, where calibrations were checked. Experiment #2 started by calibrating six YSI optical dissolved-oxygen sensors in Bend, Oregon: 2 YSI 6-series sensors were calibrated to 100% saturation, 2 YSI 6-series sensors were calibrated to 100% solubility (in mg/L) based on USGS DO Tables, and 2 YSI EXO sensors were calibrated to 100% local saturation. Similar to experiment #1, sensors always remained in 100% saturated environments; calibration and calibration checks were performed in air-saturated water, and sensors were kept in a water-saturated air environment when in travel status. Monitors were transported over a pass in the Cascade Range and then to downtown Portland, Oregon, which is approximately 20 feet above sea level. Sensor calibrations were not checked or changed in Portland. Monitors were transported back to Bend, Oregon, following the same route, where calibrations were checked.

In cooperation with the San Antonio Water System, continuous and discrete water-quality data were collected from groundwater wells completed in the Edwards aquifer, Texas, 2014-2015. Discrete measurements of nitrate were made by using a nitrate sensor. Precipitation data from two sites in the National Oceanic and Atmospheric Administration Global Historical Climatology Network are included in the dataset. The continuous monitoring data were collected using water quality sensors and include hourly measurements of nitrate, specific conductance, and water level in two wells. Discrete measurements of nitrate, specific conductance, and vertical flow rate were collected from one well site at different depths throughout the well bore.

Measurements of Dissolved Oxygen (DO) collected at California Aqueduct At Check 13. Currently collected twice a year, previously collected quarterly. Access further information for this data set by contacting Bureau of Reclamation, California-Great Basin Region, Environmental Affairs Division (CGB-157). See ResultAttributes for STAFF_GAUGE, SMPL_DEPTH, SMPL_CATEGORY_NAME, METHOD_CODE, RESULT_RL, RESULT_RL-UNIT_STD_NAME, RESULT_MDL, RESULT_MDL-UNIT_STD_NAME, USBR_QA_SUBTYPE_NAME, USBR_QULFR_DESCRIPTION. STAFF_GAUGE is the water height in decimal feet measured by gauge (e.g., 15.2). SMPL_DEPTH is the vertical depth at which sample is collected (e.g., 0 - 15 cm). For water samples: depth below water/air interface. For sediment and soil samples: depth below water/solid or air/solid interface. SMPL_CATEGORY_NAME is the category type of sample (e.g., Composite). METHOD_CODE is the name of method used to obtain result (e.g., EPA 200.8). RESULT_RL is the result reporting limit (accounting for dilution) (e.g., 0.02). RESULT_RL-UNIT_STD_NAME is the unit associated with RESULT_RL (e.g., mg/L). RESULT_MDL is the result method detection limit (e.g., 0.007). RESULT_MDL-UNIT_STD_NAME is the unit associated with RESULT_MDL (e.g., mg/L). USBR_QA_SUBTYPE_NAME is the quality control type of the sample (e.g., USBR_BLANK_SPIKE). USBR_QULFR_DESCRIPTION is the quality assurance description (if any) (e.g., Result may have a high bias.).