This data set consists of chemical and stable isotope data obtained through the analysis of discrete water samples collected from 14 fixed sampling locations in the northern Sacramento-San Joaquin Delta at roughly monthly intervals between April 2011 and November 2012.

Water stable isotope data (both hydrogen and oxygen isotopes of H2O) from the Snoqualmie River Basin from 2017-2018. This data was paired with USGS gauge data so includes watershed characteristics at the gaging stations near where water isotopes were collected. Water isotopes were collected throughout the basin to cover the range of elevation and stream sizes. Water isotopes were collected 5 times at all locations, and approximately twice monthly at the main stem of the Snoqualmie and larger tributaries. This dataset is associated with the following publication: McGill, L., J.R. Brooks, and A. Steel. Spatial and temporal dynamics of water sources in a mountain river basin inferred through δ2H and δ18O of water. Hydrological Processes. John Wiley & Sons, Ltd., Indianapolis, IN, USA, 35(3): e14063, (2021).

This data release includes a table of 87Sr/86Sr, 234U/238U, δ2H, and δ18O isotope data used to evaluate groundwater- and surface-water-sources contributing to water in perennial wetlands near the mouth of Potrero Creek within the Upper Santa Cruz Basin near Nogales, AZ. Interpretations of those data are discussed in the pamphlet accompanying the USGS Scientific Investigations Map SIM-XXXXX

This data release includes a table of 87Sr/86Sr, 234U/238U, δ2H, and δ18O isotope data used to evaluate groundwater- and surface-water-sources contributing to water in perennial wetlands near the mouth of Potrero Creek within the Upper Santa Cruz Basin near Nogales, AZ. Interpretations of those data are discussed in the pamphlet accompanying the USGS Scientific Investigations Map SIM-XXXXX

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 California State Water Resources Control Board (State Water Board) initiated the Oil and Gas Regional Monitoring Program (RMP) to assess effects of oil and gas development on groundwater designated for any beneficial use. The U.S. Geological Survey (USGS) is the technical lead in conducting the RMP through the California Oil, Gas, and Groundwater (COGG) Program, working in cooperation with the State Water Board, and in partnership with other State and local agencies. The USGS collected and analyzed groundwater and associated quality control (QC) samples for an RMP study of the Santa Fe Springs (SFSP) Oil Field during April 2021 through April 2024. Groundwater samples collected in 2021-2024 were from twenty-seven monitoring wells, two irrigation wells, three public supply wells and a fire hydrant located within the Santa Fe Springs Oil Field study area. Samples were collected using established groundwater data-collection protocols and procedures. Samples were analyzed for water-quality indicators, major and minor ions, nutrients, trace elements, volatile organic compounds (VOCs), naturally-occurring radioactive material, geochemical and age-dating tracers, dissolved organic carbon (DOC) characteristics, dissolved standard and hydrocarbon gases, and dissolved noble gases and atmospheric gases. In total, 261 constituents, water-quality indicators, or properties were measured. QC samples analyzed for the Santa Fe Springs Oil Field study area include five field blanks, one equipment blank, six VOC source solution blanks, four replicates, and four VOC spikes.

Measurements of Sodium 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.).

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.).

Measurements of Sulfate 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.).