Morgan C. McDonnell Patrick C.Longley Daniel R. Wise 20250116 tabular digital data https://doi.org/10.5066/P1K8G7JS This data release contains measured stream discharge and total dissolved solids (TDS) data and estimated values for daily stream TDS loads, daily baseflow discharge, and daily baseflow TDS loads for 205 locations in the Upper Colorado River Basin. The estimated values, which represent conditions between 10/1/1985 and 9/30/2020, were obtained using the Weighted Regressions on Time, Discharge, and Season (WRTDS) program and a previously published method for hydrograph separation. The results in this data release can be used in the assessment of surface-water conditions in the Upper Colorado River Basin. The data file “ucol_sparrow_cal_data.csv” has too many records to open in Excel without corrupting the data. The file should be opened with software, such as R, that can successfully read large files. 19851001 20200930 ground condition Complete None planned -112.3860 -105.6430 45.5510 35.5090 ISO 19115 Topic Category inlandWaters environment USGS Thesaurus surface water quality hydrology water chemistry salinity USGS Metadata Identifier USGS:666b28c1d34e9bcc607bf01f Common geographic areas Arizona Colorado New Mexico Utah Wyoming None. Please see 'Distribution Info' for details. None. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. Morgan C. McDonnell U.S. Geological Survey, ROCKY MOUNTAIN REGION Hydrologist mailing and physical

2329 West Orton Circle

West Valley City UT 84119 US 801-908-5000 mcmcdonnell@usgs.gov The data obtained from external data bases were reviewed for potential outlier or erroneous values, but no changes to those data were necessary. The results from the WRTDS modeling for each site were evaluated by reviewing the model fit statistics included in the file “WRTDS_errors_allSites.csv” and plots showing: 1) the observed vs estimated values for concentration and load; 2) the variation in the estimated concentration and load through time; 3) the residuals vs estimated concentration and discharge; and 4) the variation in the residuals. through time. The estimated total TDS loads, baseflow discharge values, and baseflow TDS loads produced in this study were within the expected ranges for those parameters. Data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details. No formal horizontal positional accuracy tests were conducted. No formal vertical positional accuracy tests were conducted. Colorado Division of Water Resources 2023 tabular digital data https://dwr.state.co.us/Rest/GET/Help/SurfaceWaterTSDayGenerator Digital and/or Hardcopy 19851001 20200930 ground condition CODWR Provided mean daily discharge for gages operated by the Colorado Division of Water Resources Robert M. Hirsch Douglas L. Moyer Stacey A. Archfield 20100907 publication JAWRA Journal of the American Water Resources Association vol. 46, issue 5 n/a Wiley ppg. 857-880 https://doi.org/10.1111/j.1752-1688.2010.00482.x Digital and/or Hardcopy 20100907 publication date Hirsch_et_al_2010 Provided method for estimating daily SC values based on discrete specific conductance and daily discharge measurements Matthew P. Miller David D. Susong Christopher L. Shope Victor M. Heilweil Bernard J. Stolp 20140826 publication Water Resources Research vol. 50, issue 8 n/a American Geophysical Union (AGU) ppg. 6986-6999 https://doi.org/10.1002/2013WR014939 Digital and/or Hardcopy 20140826 publication date Miller_et_al_2014 Provided method for estimating daily baseflow SC end-member values and techniques for evaluating the WRTDS model results Northern Water 2023 tabular digital data URL:https://data.northernwater.org/applications/public.html?publicuser=Public#waterdata/stationoverview Digital and/or Hardcopy 19851001 20200930 ground condition NORTH Provided mean daily discharge Northern Water gages United States Geological Survey 1994 dataset https://www.sciencebase.gov U.S. Geological Survey https://doi.org/10.5066/f7p55kjn Digital and/or Hardcopy 19851001 20200930 ground condition NWIS Provided mean daily discharge for gages operated by the USGS Annie L. Putman Hannah E. McIlwain Christine A. Rumsey Thomas M. Marston 202404 publication Journal of Hydrology: Regional Studies vol. 52 n/a Elsevier BV ppg. 101673 https://doi.org/10.1016/j.ejrh.2024.101673 Digital and/or Hardcopy 202404 publication date Putman_et_al_2024 Provided supporting information for approach used to estimate periods of missing stream discharge data Susan G Buto 2017 dataset https://www.sciencebase.gov U.S. Geological Survey https://doi.org/10.5066/f76t0jt4 Digital and/or Hardcopy 2017 publication date SPARROW_network Provided SPARROW modeling stream network for indexing of the calibration sites Bureau of Reclamation 2023 tabular digital data https://www.usbr.gov/uc/water/hydrodata/gage_data/site_map.html Digital and/or Hardcopy 19851001 20200930 ground condition USBR Provided mean daily discharge for gages operated by the Bureau of Reclamation U.S. Department of Energy 2023 tabular digital data https://data.ess-dive.lbl.gov/portals/east-river-watershed Digital and/or Hardcopy 19851001 20200930 ground condition USDOE Provided mean daily discharge gages operated by the U.S. Department of Energy Daniel Wise 2024 dataset https://www.sciencebase.gov U.S. Geological Survey https://doi.org/10.5066/p9b0sjys Digital and/or Hardcopy 19851001 20200930 ground condition Wise_2024 Provided TDS data for WRTDS modeling and conversion factors between SC and TDS concentration Wyoming State Engineer's Office 2023 tabular digital data Digital and/or Hardcopy 19851001 20200930 ground condition WYSEO Provided mean daily discharge gages operated by the Wyoming State Engineer's Office Qian Zhang Robert M. Hirsch 20191125 publication Water Resources Research vol. 55, issue 11 n/a American Geophysical Union (AGU) ppg. 9705-9723 https://doi.org/10.1029/2019WR025338 Digital and/or Hardcopy 20191125 publication date Zhang_Hirsch_2019 Provided method to account for the autocorrelation of model residuals from the WRTDS model 1. Retrieved total dissolved solids (TDS) concentrations from Wise_2024 for water-quality monitoring stations located in the Upper Colorado River Basin for the period between 10/01/1985 and 9/30/2020. Wise_2024 2024 2. Retrieved mean daily stream discharge values for stream gages located in the Upper Colorado River Basin operated by CODWR, NORTH, USBR, WYSEO, USDOE, and USGS (NWIS) for the period between 10/01/1985 and 9/30/2020. CODWR NORTH USBR WYSEO USDOE NWIS 2024 3. Selected 205 water-quality monitoring stations as calibration sites in seasonal SPARROW models developed for the Upper Colorado River Basin to evaluate three parameters: total stream TDS, baseflow TDS, and baseflow discharge. The 205 calibration sites represented water-quality monitoring stations from step (1) that were associated with a stream gage from step (2) and satisfied the following criteria for water years 1986-2020: a. The drainage areas for the water-quality monitoring station and the associated stream gage were within 25 percent of each other. b. The water-quality and associated gage were both located at least 2 kilometers downstream of a Bureau of Reclamation reservoir. c. There were at least 100 TDS results in the water-quality record. d. There were at least 50 uncensored TDS results in the water-quality record. e. There were at least 20 TDS results in the water-quality record during each season. f. The stream discharge record spanned at least 10 years. g. The water-quality and stream discharge records had at least 10 years of overlap. h. There were no gaps in the flow record during the overlap period that were greater than 30 percent of the full overlap period. i. When a diversion was located between the water-quality monitoring station and the associated stream gage, the mean annual amount diverted was no more than 15 percent of the mean annual stream discharge at the stream gage. 2024 4. Each site from step (3) was indexed to a reach in the stream network represented in SPARROW_network. SPARROW_network 2024 5. The Weighted Regressions on Time, Discharge, and Season (WRTDS) R program, as described in Hirsch_et_al_2010, was used to estimate daily TDS loads (GenFlux, in kilograms per day) and TDS concentrations (Gen_Conc, in milligrams per liter) at each site. The TDS concentrations and stream discharge data retrieved in steps (1) and (2) were used as input to WRTDS. The estimation period for each site extended no more than 11 months before the first TDS concentration or 11 months after the last TDS concentration in the water-quality record. This approach was consistent with guidance from Hirsch_et_al_2010. Hirsch_et_al_2010 2024 6. Missing stream discharge values at a site were estimated by randomly selecting a value from all values for the day from the WTRDTS normalization window period for the site, centered on the day with the missing value. Putman_et_al_2024 determined that this approach does not disrupt the probabilistic method for estimating flow normalized values in WRTDS. Putman_et_al_2024 2024 7. The WRTDS-Kalman (WRTDS-K) program, as described in Zhang_Hirsch_2019, was used to modify the WRTDS results from step (6) to account for the autocorrelation of model residuals. Zhang_Hirsch_2019 2024 8. The data from the 205 sites were assessed for their suitability for hydrograph separation by chemical mass balance to estimate baseflow volume and baseflow TDS load following Miller_et_al_2014. Specifically, plots of estimated TDS concentration versus discharge were assessed to verify that they followed an inverse power function relationship and that there was a significant difference between the runoff and baseflow end-member TDS concentrations (see below for end-member definitions). Applying these criteria resulted in a subset of 121 sites for which baseflow discharge and baseflow TDS load was estimated. 2024 9. The baseflow period during each water year at each of the 121 sites from step (8) was estimated by identifying the days representing the lowest 5th percentile of stream discharge for that water year. 2024 10. The annual baseflow TDS concentration during each water year at each site was estimated by calculating the 99th percentile of TDS concentrations during the baseflow period for each water year. 2024 11. The daily baseflow TDS concentrations (bf_conc, in milligrams per liter) during each water year at each site were estimated by interpolating between the annual baseflow TDS concentrations estimated in step (10). Miller_et_al_2014 Wise_2024 2024 12. A general runoff TDS end-member concentration (TDS_ro) of 21 milligrams per liter was established for the system, which was equivalent to the specific conductance end-member value of 33 microsiemens per centimeter used in Miller_et_al_2014 (using a TDS-SC conversion factor of 0.649 from Wise_2024). Miller_et_al_2014 2024 13. The runoff TDS end-member concentration (TDS_ro) from step (12) was used at a site unless the lowest estimated daily baseflow dissolved solids concentration was below 21 milligrams per liter. In those cases, a runoff TDS end-member concentration of 6.5 milligrams per liter was used, which was equivalent to the specific conductance end-member value of 10 microsiemens per centimeter used in Miller_et_al_2014. At three sites (USGS-09238900, WQ_Combined_1319662, and WQ_Combined_1320274), the estimated daily baseflow dissolved concentration was below 6.5 milligrams per liter for some days in the record, which resulted in a negative estimated baseflow volume. For those days in the record, the baseflow volume and all baseflow volume-derived metrics were set to zero. 2024 14. The daily baseflow discharge (bf_volume, in cubic meters per second) at each site was estimated using the following equation: bf_volume= Q x (GenConc – TDS_ro)/(bf_conc– TDS_ro), where Q = mean daily stream discharge in cubic meters per second, GenConc = stream TDS concentration from step (5), TDS_ro = TDS end-member concentration from step (12) or (13), and bf_conc = daily baseflow TDS concentration from step (11). 2024 15. When the calculated bf_volume value from step (14) was greater than Q, bf_ volume was set equal to Q. 2024 16. Monsoon baseflow peaks in the bf_volume estimates from step (14) were replaced with linearly interpolated values using the technique of graphical hydrograph separation. Monsoon baseflow peaks were identified as peaks in baseflow that met the following criteria: a. They did not occur during the snowmelt season (April-July). b. They were greater than 10 percent of the range in baseflow values occurring within any 15-day period. 2024 17. The monsoon baseflow peak adjustments described in step (16) were used to estimate monsoon-corrected daily baseflow discharge (bf_corrected_volume, in cubic meters per second) for each site. 2024 18. The daily baseflow TDS load (bf_load, in kilograms per day) at each site was estimated using the following equation: bf_load = bf_conc x bf_volume x 86.4, where bf_conc = daily baseflow TDS concentration from step (11) bf_volume = daily baseflow discharge from step (14), and 86.4 is used to convert the results to kilograms per day. 2024 19. The daily baseflow TDS load adjusted for monsoon peaks (bf_corrected_load, in kilogram per day) at each site was estimated using the following equation: bf_corrected_load= bf_conc x bf_corrected_volume x 86.4, where bf_conc = daily baseflow TDS concentration from step (11), and bf_corrected_volume = daily baseflow discharge adjusted for monsoon effects from step (17). 2024 20. The bootstrap replicates from WRTDS were used to estimate the upper and lower bounds of the 95th confidence interval for the baseflow parameters (GenConc, bf_conc, GenFlux, bf_load, bf_corrected_load, bf_volume, and bf_corrected_volume). 2024 0.001 0.0001 Decimal degrees ucol_sparrow_cal_station_atts.csv Calibration station attributes Producer Defined station_id Calibration station identifier Q_TDS_input_allSites Compilation of total dissolved solids concentrations and specific conductance measurements in the Upper Colorado River Basin, 1894 – 2020 https://doi.org/10.5066/P9B0SJYS Latitude Latitude for station Wise_2024 36.7171 42.5857 Decimal degrees 0.0001 Longitude Longitude for station Wise_2024 -111.637 -105.745 Decimal degrees 0.001 WATERID SPARROW network reach identifier for station SPARROW_network Upper Colorado River Basin SPARROW model catchments and synthetic stream network - 2017 https://doi.org/10.5066/F76T0JT4 Q_gage Gage that provided stream discharge data for calibration site Wise_2024 Compilation of total dissolved solids concentrations and specific conductance measurements in the Upper Colorado River Basin, 1894 – 2020 https://doi.org/10.5066/P9B0SJYS Min_date Minimum date represented by WRTDS estimates Producer Defined 10/1/1985 5/27/2009 Max_date Maximum date represented by WRTDS estimates Producer Defined 9/30/1996 9/30/2020 Q_TDS_input_allSites_template.csv Streamflow and TDS data used as input for the WRTDS calibration and predictions Producer Defined station_id Calibration station identifier Q_TDS_input_allSites Compilation of total dissolved solids concentrations and specific conductance measurements in the Upper Colorado River Basin, 1894 – 2020 https://doi.org/10.5066/P9B0SJYS Date Date represented by data Producer Defined 10/1/1985 11/30/2021 Q_cfs Mean daily stream discharge NWIS 0 52428 Cubic feet per second 0.01 tds_result_mg_L TDS concentration used in WRTDS calibration Wise_2024 << empty cell >> No Data Producer defined 2 6617 Milligrams per liter tds_remark Remark code for TDS measurement Producer Defined << empty cell >> No Data Producer defined < Less than Producer defined > Greater than Producer defined ucol_sparrow_cal_data.zip Compressed archive containing the discharge, TDS concentrations, and TDS loads estimated by WRTDS for each station Producer Defined station_id Calibration station identifier Wise_2024 Compilation of total dissolved solids concentrations and specific conductance measurements in the Upper Colorado River Basin, 1894 – 2020 https://doi.org/10.5066/P9B0SJYS Date Date represented by data Producer Defined 10/1/1985 9/30/2020 GenConc Daily TDS estimate output from WRTDS (mg/L) Producer Defined 2 51100 Milligrams per liter 0.000000000000001 GenConc_0.025 Lower bounds of 95th confidence interval for GenConc Producer Defined 1.650869107922 51099.9999999999 Milligrams per liter 0.000000000000001 GenConc_0.975 Upper bounds of 95th confidence interval for GenConc Producer Defined 2 59200.4255026923 Milligrams per liter 0.000000000000001 bf_conc Daily TDS estimate for baseflow component, defined as the 99th percentile (highest SC) occurring during the lowest 5 percent of flows in a WY, then linearly interpolated (mg/L) Producer Defined 18.6800926 4594.89020658416 Milligrams per liter 0.000000000000001 bf_conc_0.025 Lower bounds of 95th confidence interval for bf_conc Producer Defined 17.0500636545399 4482.643483027 Milligrams per liter 0.000000000000001 bf_conc_0.975 Upper bounds of 95th confidence interval for bf_conc Producer Defined 30.7585113915161 8613.81981866577 Milligrams per liter 0.000000000000001 GenFlux Daily streamflow TDS load estimate output from WRTDS (kg/day) Producer Defined 1.89461864584797 550431238.493078 Kilograms per day 0.000000000000001 GenFlux_0.025 Lower bounds of 95th confidence interval for GenFlux Producer Defined 1.31545379294981 266769014.903341 Kilograms per day 0.000000000000001 GenFlux_0.975 Upper bounds of 95th confidence interval for GenFlux Producer Defined 2.57060396741129 962082888.269252 Kilograms per day 0.000000000000001 bf_load Baseflow TDS load, derived from bf_volume* bf_conc (kg/day) Producer Defined 0 23667382.070808 Kilograms per day 0.000000000000001 bf_load_0.025 Lower bounds of 95th confidence interval for bf_load Producer Defined 0 23563383.8745778 Kilograms per day 0.000000000000001 bf_load_0.975 Upper bounds of 95th confidence interval for bf_load Producer Defined 0 23698442.2065631 Kilograms per day 0.000000000000001 bf_corrected_load Baseflow TDS load corrected for monsoon flows (bf_corrected_volume * bf_conc) (kg/day) Producer Defined 0 23667382.070808 Kilograms per day 0.000000000000001 bf_corrected_load_0.025 Lower bounds of 95th confidence interval for bf_corrected_load Producer Defined 0 23563383.8745778 Kilograms per day 0.000000000000001 bf_corrected_load_0.975 Upper bounds of 95th confidence interval for bf_corrected_load Producer Defined 0 23698442.2065631 Kilograms per day 0.000000000000001 bf_volume Baseflow discharge (m3/s) derived from chemical hydrograph separation Producer Defined 0 411.77102382738 Cubic meters per second 0.000000000000001 bf_volume_0.025 Lower bounds of 95th confidence interval for bf_volume Producer Defined 0 387.074652060976 Cubic meters per second 0.000000000000001 bf_volume_0.975 Upper bounds of 95th confidence interval for bf_volume Producer Defined 0 428.979800887142 Cubic meters per second 0.000000000000001 bf_corrected_volume Baseflow discharge (m3/s) corrected for monsoon flows Producer Defined 0 411.77102382738 Cubic meters per second 0.000000000000001 bf_corrected_volume_0.025 Lower bounds of 95th confidence interval for bf_corrected_volume Producer Defined 0 387.074652060976 Cubic meters per second 0.000000000000001 bf_corrected_volume_0.975 Upper bounds of 95th confidence interval for bf_corrected_volume Producer Defined 0 428.979800887142 Cubic meters per second 0.000000000000001 WRTDS_errors_allSites.csv Calibration diagnostics from WRTDS load estimation Producer Defined station_id Calibration station identifier Wise_2024 Compilation of total dissolved solids concentrations and specific conductance measurements in the Upper Colorado River Basin, 1894 – 2020 https://doi.org/10.5066/P9B0SJYS R_squared_ln_conc R-squared for natural log of estimated concentration Producer Defined 0.0822 0.976 0.001 R_squared_ln_load R-squared for natural log of estimated load Producer Defined 0.725 0.998 0.001 RMSE_ln_load Root mean squared error for natural log of estimated load Producer Defined 0.0441 0.511 Kilograms per day 0.0001 SE_ln_load Standard error for natural log of estimated load Producer Defined 4.41 54.6 Kilograms per day 0.01 GS ScienceBase U.S. Geological Survey mailing address

Denver Federal Center, Building 810, Mail Stop 302

Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Digital Data https://doi.org/10.5066/P1K8G7JS None 20250116 Daniel R. Wise U.S. Geological Survey, NW-PACIFIC ISLAND REG Hydrologist mailing and physical

601 SW 2nd Ave

Portland OR 97204 US 971-413-0036 dawise@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998