Yuma Ridgway’s rail (Rallus obsoletus yumanensis, hereafter, rail) are an endangered species for which patches of emergent marsh within the Salton Sea watershed comprise a substantial portion of habitat for the species’ disjointed range in the southwestern United States. These areas of emergent marsh include: 1) marshes managed by federal (particularly the U.S. Fish and Wildlife Service’s Sonny Bono Salton Sea National Wildlife Refuge (SBSSNWR), state (California Department of Fish and Wildlife), and local (Imperial Irrigation District) resource agencies that are sustained by direct deliveries of Colorado River water; and 2) unmanaged marshes sustained by agricultural drainage water. Management of rail habitat in this arid environment is complicated by increasingly limited availability of unimpaired freshwater owing by recent water management decisions associated with the Quantification Settlement Agreement, and risks posed by potentially harmful concentrations of selenium (Se) found in agricultural drainage water that can readily bioaccumulate in aquatic food webs. To provide timely science for managers, the selenium concentrations in this data release are the basis for summary statistics reported in Ricca et al. 2022. These data comprise selenium concentrations and associated locations and dates of the following matrices sampled to describe pathways of selenium exposure to rails occupying managed and unmanaged marshes: 1) unfiltered surface water, midge larvae (Chironomidae), water boatmen (Corixidae), mosquitofish (Gambusia spp.) and crayfish (Astacidae). Selenium samples were collected from 15 fixed sampling points each in managed and unmanaged marshes during late February, April, and June of 2016, which corresponded to rail pre-nesting, nesting, and fledgling reproductive life-stages, respectively. Two areas within the two treatment types (managed vs. unmanaged marsh) were of particular interest to help assess risks associated with changing Sea dynamics and different water management strategies: 1) a large unmanaged marsh (Morton Bay) unintentionally created in approximately 2008 when it became separated from the Salton Sea as water inflows began to drop and a berm formed from accumulated sediment; and 2) a restored marsh (HZ-9A) managed by the SBSSNWR, which is currently supplied with Colorado River water, but may be sustained in the future by a blend of clean (that is, low Se) Colorado River and agricultural drainage water with higher Se from the Alamo River.

Due to declining water levels and increasing salinity in the Salton Sea which may increase the hazards to wildlife, the U.S. Geological Survey and U.S. Bureau of Reclamation are re-evaluating selenium concentrations in the region. As part of this work, selenium concentrations in water and sediment samples and selected other inorganic constituents were compiled from published reports, public databases, and unpublished archives into a tabulated spreadsheet. This spreadsheet represents a rapid synthesis of available data on selenium concentrations in water and sediment in the region surrounding the Salton Sea, however it does not include all data ever published in the region. Additionally, the data compilation was done with an emphasis on selenium concentrations measured after 2005, therefore earlier selenium data may be under-represented.

Due to declining water levels and increasing salinity in the Salton Sea which may increase the hazards to wildlife, the U.S. Geological Survey and U.S. Bureau of Reclamation are re-evaluating selenium concentrations in the region. As part of this work, selenium concentrations in water and sediment samples and selected other inorganic constituents were compiled from published reports, public databases, and unpublished archives into a tabulated spreadsheet. This spreadsheet represents a rapid synthesis of available data on selenium concentrations in water and sediment in the region surrounding the Salton Sea, however it does not include all data ever published in the region. Additionally, the data compilation was done with an emphasis on selenium concentrations measured after 2005, therefore earlier selenium data may be under-represented.

In response to the rapidly evolving conditions at the Salton Sea, with the emergence of both newly formed wetland habitat and increasing hazards to wildlife, the U.S. Bureau of Reclamation and U.S. Geological Survey have funded a re-evaluation of data gaps regarding selenium concentrations in biota the region. As part of this work, selenium concentrations in biological tissue samples were compiled from published reports, public databases, and unpublished archives into a tabulated spreadsheet. Since the California Department of Water Resources summarized selenium biological data in 2005, our compilation efforts focused on the 2005 through 2020 range. The resulting dataset encompasses all records available to us from 1984 to 2020, although we did not find any selenium records after 2017.

In response to the rapidly evolving conditions at the Salton Sea, with the emergence of both newly formed wetland habitat and increasing hazards to wildlife, the U.S. Bureau of Reclamation and U.S. Geological Survey have funded a re-evaluation of data gaps regarding selenium concentrations in biota the region. As part of this work, selenium concentrations in biological tissue samples were compiled from published reports, public databases, and unpublished archives into a tabulated spreadsheet. Since the California Department of Water Resources summarized selenium biological data in 2005, our compilation efforts focused on the 2005 through 2020 range. The resulting dataset encompasses all records available to us from 1984 to 2020, although we did not find any selenium records after 2017.

Estuaries provide critical habitat for a vast array of fish and wildlife but are also a nexus for core economic activities that mobilize and concentrate contaminants that can threaten aquatic species. Selenium (Se), an essential element and potent reproductive toxin, is enriched in parts of the San Francisco Estuary (SFE) to levels known to cause toxicity, yet the risk of Se to species that inhabit the SFE is not well understood. We quantified Se concentrations in muscle, liver, and ovary of the demersal cyprinid Sacramento Splittail from six regions in the SFE at three time points (fall 2010-11, spring 2017) to evaluate Se exposure risk. Here we report fish morphological attributes, total selenium concentrations in fish boneless skinless muscle, liver, and ovary, as well as carbon, nitrogen and sulfur stable isotope values and elemental mass concentrations in fish muscle.

Estuaries provide critical habitat for a vast array of fish and wildlife but are also a nexus for core economic activities that mobilize and concentrate contaminants that can threaten aquatic species. Selenium (Se), an essential element and potent reproductive toxin, is enriched in parts of the San Francisco Estuary (SFE) to levels known to cause toxicity, yet the risk of Se to species that inhabit the SFE is not well understood. We quantified Se concentrations in muscle, liver, and ovary of the demersal cyprinid Sacramento Splittail from six regions in the SFE at three time points (fall 2010-11, spring 2017) to evaluate Se exposure risk. Here we report fish morphological attributes, total selenium concentrations in fish boneless skinless muscle, liver, and ovary, as well as carbon, nitrogen and sulfur stable isotope values and elemental mass concentrations in fish muscle.

Pollutant loads have been increasing over time in the Elk River, B.C. due to coal mining operations and runoff from associate spoil piles. The Elk River is a tributary to the Kootenay/Kootenai River and Lake Koocanusa. Extensive water chemistry monitoring has been conducted in Lake Koocanusa to assess the impacts from the Elk River, however, this is not the case for the Kootenai River downstream of Lake Koocanusa, downstream of Libby Dam (http://deq.mt.gov/DEQAdmin/LakeKoocanusa). This study generated data on selenium and nutrient concentrations and loads in the Kootenai River (Libby Dam to Canadian border), which will help to differentiate between local loads and loads transported via Lake Koocanusa. Working in cooperation with the U.S. Environmental Protection Agency (USEPA), the U.S. Geological Survey (USGS) collected and analyzed water-column samples in the Kootenai River watershed downstream of Libby Dam. Field data collection also included discharge measurements. The following are key design components of water quality sample collection in the Kootenai River watershed downstream of Libby Dam: Sampling locations: (1) USGS gages on the mainstem Kootenai River: Kootenai River below Libby Dam, MT (USGS site identification number 12301933), Kootenai River at Leonia, ID (12305000), Kootenai River at Tribal Hatchery near Bonners Ferry, ID (12310100), and Kootenai River at Porthill, ID (12322000); (2) USGS gages on tributaries to the Kootenai River: Fisher River near Libby MT (12302055), Yaak River near Troy MT (12304500); (3) Ungaged tributaries: Moyie River near the mouth (12307750). Water quality analyses: (1) Low-level nutrients, total water (3 sampling events) (2) Total selenium, dissolved water (3 sampling events) (3) Selenium speciation, dissolved water (2 events): selenite, Se(IV); selenate, Se(VI); selenocyanate, SeCN; selenomethionine, SeMet; and methylseleninic acid, MeSe(IV). Total dissolved selenium and selenium speciations analyses were performed by Brooks Applied Labs, Bothell, WA. The nutrient samples were analyzed by the USGS National Water Quality Laboratory (NWQL), Lakewood, CO. Secondary, total dissolved selenium analyses were also conducted by the NWQL for a subset of samples for interlaboratory comparisons. The three sampling events were: (1) September 2018, a period of low and stable flows in both the Kootenai River and tributaries; (2) December 2018, a period of low, stable winter flows in the tributaries but unstable and increasing flows in the Kootenai River due to dam releases in preparation for spring runoff (3) May 2019, a period close to annual peak runoff from snowmelt in tributaries plus high dam releases of snowmelt originating in the Canadian Rockies. Results: Results of the selenium sampling are compiled and summarized in this data release. These data and the nutrient data are separately published through the USGS National Water Information System (https://doi.org/10.5066/F7P55KJN). No samples exceeded USEPA’s national recommended aquatic life criteria for selenium, expressed as a water concentration, of 3.1 µg/L. Selenium concentrations in the four mainstem Kootenai River sites had low variability across sites and sampling events, ranging from 0.628 to 1.17 µg/L for the 12 samples, for an average concentration of 0.91 µg/L (± 0.17 µg/L, standard deviation). In all measured concentrations, selenate was the dominant chemical species, accounting for 87% of the total selenium, on average (range 79-94%). Selenium concentrations were less than the detection limit of 0.037 µg/L in all of the tributary samples, indicating that selenium concentrations in the Kootenai River cannot be attributed to tributary sources. Daily average selenium loads in the Kootenai River were estimated by assuming that the width and depth integrated water samples collected were representative of average conditions for that day and were multiplied by daily average discharge volumes of the Kootenai River at those locations. In

The U.S. Geological Survey (USGS), in cooperation with the Bureau of Reclamation, completed a review of dissolved selenium data collected from the Selenium Management Program network during each water year (WY) in the lower Gunnison River Basin, in western Colorado. The data tables include dissolved-selenium concentrations, selected streamflow data, and computed loads as well as dissolved-selenium regression model calibration and output tables. Concentration and streamflow data are compiled from the USGS National Water Information System database. Tables include monitoring location identification information, data collection time frames, concentration data, as well as calculations of mean, median, select percentiles, and percentage reduction in loads. Tables are organized by each year, with a zipped folder for WY 2018 (October 1, 2017 through September 30, 2018), WY 2019 (October 1, 2018 through September 30, 2019), WY 2020 (October 1, 2019 through September 30, 2020), WY 2021 (October 1, 2020 through September 30, 2021), and WY 2022 (October 1, 2021 through September 30, 2022). Within each zipped folder is a metadata .xml file describing each comma-separated value (.csv) data file contained therein. The methods used to complete this review are available in Henneberg (2018) and Mayo and Leib (2012). Version 3.0 contains additional zipped folders for WY 2021 and 2022, which were not included in the original data release. While previous versions are available from the author, all records in previous versions can be found in version 3.0. First posted - April 23, 2021 (available from author) Revised - June, 2022 (version 2.0) Revised - July, 2023 (version 3.0)

The U.S. Geological Survey (USGS), in cooperation with the Bureau of Reclamation, completed a review of dissolved selenium data collected from the Selenium Management Program network during each water year (WY) in the lower Gunnison River Basin, in western Colorado. The data tables include dissolved-selenium concentrations, selected streamflow data, and computed loads as well as dissolved-selenium regression model calibration and output tables. Concentration and streamflow data are compiled from the USGS National Water Information System database. Tables include monitoring location identification information, data collection time frames, concentration data, as well as calculations of mean, median, select percentiles, and percentage reduction in loads. Tables are organized by each year, with a zipped folder for WY 2018 (October 1, 2017 through September 30, 2018), WY 2019 (October 1, 2018 through September 30, 2019), WY 2020 (October 1, 2019 through September 30, 2020), WY 2021 (October 1, 2020 through September 30, 2021), and WY 2022 (October 1, 2021 through September 30, 2022). Within each zipped folder is a metadata .xml file describing each comma-separated value (.csv) data file contained therein. The methods used to complete this review are available in Henneberg (2018) and Mayo and Leib (2012). Version 3.0 contains additional zipped folders for WY 2021 and 2022, which were not included in the original data release. While previous versions are available from the author, all records in previous versions can be found in version 3.0. First posted - April 23, 2021 (available from author) Revised - June, 2022 (version 2.0) Revised - July, 2023 (version 3.0)