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.

This data release contains two sets of estimated values at selected sites within the Colorado River Basin: 1) daily specific conductance at 143 sites in the Upper Basin and 3 sites in the Lower Basin (WY 1980-2022); and 2) daily baseflow discharge at 100 sites in the Upper Basin and 3 sites in the Lower Basin (WY 1980-2022). The estimates of daily baseflow discharge will be used as input to an application of the USGS GSFLOW model, which is a coupled groundwater and surface-water flow model based on the integration of the USGS Precipitation-Runoff Modeling System (PRMS-V) and the USGS Modular Groundwater Flow Model (MODFLOW).

This data release contains two sets of estimated values at selected sites within the Colorado River Basin: 1) daily specific conductance at 143 sites in the Upper Basin and 3 sites in the Lower Basin (WY 1980-2022); and 2) daily baseflow discharge at 100 sites in the Upper Basin and 3 sites in the Lower Basin (WY 1980-2022). The estimates of daily baseflow discharge will be used as input to an application of the USGS GSFLOW model, which is a coupled groundwater and surface-water flow model based on the integration of the USGS Precipitation-Runoff Modeling System (PRMS-V) and the USGS Modular Groundwater Flow Model (MODFLOW).

This data release contains two sets of estimated values at selected sites within the Colorado River Basin: 1) daily specific conductance at 143 sites in the Upper Basin and 3 sites in the Lower Basin (WY 1980-2022); and 2) daily baseflow discharge at 100 sites in the Upper Basin and 3 sites in the Lower Basin (WY 1980-2022). The estimates of daily baseflow discharge will be used as input to an application of the USGS GSFLOW model, which is a coupled groundwater and surface-water flow model based on the integration of the USGS Precipitation-Runoff Modeling System (PRMS-V) and the USGS Modular Groundwater Flow Model (MODFLOW).

Monthly Mean Dissolved-Solids Concentration and Monthly Mean Dissolved-Solids Load Data Flow weighted monthly mean dissolved-solids concentrations (mg/L) data and monthly mean dissolved-solids load data from 1928-2016 were computed by USGS using raw data from the Bureau of Reclamation. These data were computed by USGS for all of the seven sites (listed below). Colorado River above Imperial Dam, AZ-CA, 09429490 (1976-2016) Colorado River at Lees Ferry, AZ, 09380000 (1947-2016) Colorado River at Northern International Boundary, above Morelos Dam, AZ, 09522000 (1961-2016) Colorado River below Hoover Dam, AZ-NV, 09421500 (1948-2016) Colorado River near Cisco, UT, 09180500 (1928-2016) Green River at Green River, UT, 09315000 (1928-2016) San Juan River near Bluff, UT, 09379500 (1929-2016) Monthly mean dissolved-solids concentrations and loads were not calculated for several time periods (listed below) because of insufficient discrete dissolved-solids concentration data: Colorado River below Hoover Dam, AZ-NV, 09421500 (October 1962 - September 1953) Colorado River near Cisco, UT, 09180500 (October 1936 - September 1938 and October 1939 - September 1940) Green River at Green River, UT, 09315000 (October 1936 - September 1938, October 1939 - September 1940, and October 1942 - September 1943) Discrete Dissolved-Solids Concentration Data Discrete dissolved-solids concentrations (mg/L) data and specific conductance (microsiemens/cm) from 1990-2016 were computed using raw data from the Bureau of Reclamation. These data were computed for four sites (listed below). Colorado River above Imperial Dam, AZ-CA, 09429490 (1990-2016), dissolved-solids Colorado River above Imperial Dam, AZ-CA, 09429490 (1993-2016), specific conductance Colorado River below Hoover Dam, AZ-NV, 09421500 (1993-2016), dissolved-solids Colorado River at Northern International Boundary, above Morelos Dam, AZ, 09522000 (2001-2016), dissolved-solids

Monthly Mean Dissolved-Solids Concentration and Monthly Mean Dissolved-Solids Load Data Flow weighted monthly mean dissolved-solids concentrations (mg/L) data and monthly mean dissolved-solids load data from 1928-2016 were computed by USGS using raw data from the Bureau of Reclamation. These data were computed by USGS for all of the seven sites (listed below). Colorado River above Imperial Dam, AZ-CA, 09429490 (1976-2016) Colorado River at Lees Ferry, AZ, 09380000 (1947-2016) Colorado River at Northern International Boundary, above Morelos Dam, AZ, 09522000 (1961-2016) Colorado River below Hoover Dam, AZ-NV, 09421500 (1948-2016) Colorado River near Cisco, UT, 09180500 (1928-2016) Green River at Green River, UT, 09315000 (1928-2016) San Juan River near Bluff, UT, 09379500 (1929-2016) Monthly mean dissolved-solids concentrations and loads were not calculated for several time periods (listed below) because of insufficient discrete dissolved-solids concentration data: Colorado River below Hoover Dam, AZ-NV, 09421500 (October 1962 - September 1953) Colorado River near Cisco, UT, 09180500 (October 1936 - September 1938 and October 1939 - September 1940) Green River at Green River, UT, 09315000 (October 1936 - September 1938, October 1939 - September 1940, and October 1942 - September 1943) Discrete Dissolved-Solids Concentration Data Discrete dissolved-solids concentrations (mg/L) data and specific conductance (microsiemens/cm) from 1990-2016 were computed using raw data from the Bureau of Reclamation. These data were computed for four sites (listed below). Colorado River above Imperial Dam, AZ-CA, 09429490 (1990-2016), dissolved-solids Colorado River above Imperial Dam, AZ-CA, 09429490 (1993-2016), specific conductance Colorado River below Hoover Dam, AZ-NV, 09421500 (1993-2016), dissolved-solids Colorado River at Northern International Boundary, above Morelos Dam, AZ, 09522000 (2001-2016), dissolved-solids

This data release contains total dissolved solids (TDS) concentrations and specific conductance (SC) measurements collected at surface-water monitoring locations and groundwater monitoring wells within the Upper Colorado River Basin (UCRB) between 1894 and 2022. Discrete TDS and SC results were obtained from the Water Quality Portal (WQP). Continuous SC monitoring results were obtained from the USGS National Water Information System (NWIS). The data set includes 127,294 TDS results that were collected at 12,339 sites between 1900 and 2022, and 705,918 SC results that were collected at 19,630 sites between 1894 and 2022. The SC results represented 244,784 discrete measurements at 19,625 sites and 461,134 mean daily values from continuous monitoring at 193 sites. The data retrieved from the WQP were harmonized to create a standardized and readily usable dataset. The harmonization process included the synthesis of parameter names and fractions, the reconciliation of remarks and other data qualifiers, the resolution of duplicate records, and basic checks of the data quality. The harmonized results at 230 sites were selected for additional data processing because those sites were potential calibration targets for TDS watershed modeling for the UCRB using the USGS Spatially Referenced Regression on Watershed attributes (SPARROW) model. The 230 sites met the minimum criteria for the number and seasonal distribution of samples, the length of the sampling period, and the amount of overlap with the streamflow record at a nearby gage. The measured TDS concentrations at those sites were supplemented with estimated TDS concentrations that were determined from relations between measured TDS and SC results within the UCRB. A site-specific regression of TDS on SC was used to estimate TDS from SC at 143 sites, while a regional conversion factor between TDS and SC was used to estimate TDS from SC at 87 sites. The final TDS data for the 230 sites included 50,003 measured values from the WQP, 378,147 values estimated using the equation from a site-specific regression of TDS on SC (with 350,840 based on mean daily SC values), and 30,880 values estimated using a regional median ratio between TDS and SC.

This data release contains total dissolved solids (TDS) concentrations and specific conductance (SC) measurements collected at surface-water monitoring locations and groundwater monitoring wells within the Upper Colorado River Basin (UCRB) between 1894 and 2022. Discrete TDS and SC results were obtained from the Water Quality Portal (WQP). Continuous SC monitoring results were obtained from the USGS National Water Information System (NWIS). The data set includes 127,294 TDS results that were collected at 12,339 sites between 1900 and 2022, and 705,918 SC results that were collected at 19,630 sites between 1894 and 2022. The SC results represented 244,784 discrete measurements at 19,625 sites and 461,134 mean daily values from continuous monitoring at 193 sites. The data retrieved from the WQP were harmonized to create a standardized and readily usable dataset. The harmonization process included the synthesis of parameter names and fractions, the reconciliation of remarks and other data qualifiers, the resolution of duplicate records, and basic checks of the data quality. The harmonized results at 230 sites were selected for additional data processing because those sites were potential calibration targets for TDS watershed modeling for the UCRB using the USGS Spatially Referenced Regression on Watershed attributes (SPARROW) model. The 230 sites met the minimum criteria for the number and seasonal distribution of samples, the length of the sampling period, and the amount of overlap with the streamflow record at a nearby gage. The measured TDS concentrations at those sites were supplemented with estimated TDS concentrations that were determined from relations between measured TDS and SC results within the UCRB. A site-specific regression of TDS on SC was used to estimate TDS from SC at 143 sites, while a regional conversion factor between TDS and SC was used to estimate TDS from SC at 87 sites. The final TDS data for the 230 sites included 50,003 measured values from the WQP, 378,147 values estimated using the equation from a site-specific regression of TDS on SC (with 350,840 based on mean daily SC values), and 30,880 values estimated using a regional median ratio between TDS and SC.

Total dissolved solids (TDS) in surface waters affect water quality and useability and are of particular concern in the Colorado River Basin. Estimates of current and past TDS concentration and flux in rivers support appropriate management and salinity control measures. In this study we estimated the total dissolved solid concentration and flux at 11 sites on tributaries of the Colorado River, starting as early as 1938 until 2021. Of these sites, eight were not affected by dams. For these we estimated daily and water year flow normalized TDS concentration and flux using the Weighted Regressions on Time Discharge and Season (WRTDS) water quality modeling framework. For the three sites situated below dams, we used flow-weighted concentrations to estimate water year mean TDS concentrations. Along with these estimates, we include information about the timing of construction, and capacity of dams in the Lower Colorado River Basin.

Total dissolved solids (TDS) in surface waters affect water quality and useability and are of particular concern in the Colorado River Basin. Estimates of current and past TDS concentration and flux in rivers support appropriate management and salinity control measures. In this study we estimated the total dissolved solid concentration and flux at 11 sites on tributaries of the Colorado River, starting as early as 1938 until 2021. Of these sites, eight were not affected by dams. For these we estimated daily and water year flow normalized TDS concentration and flux using the Weighted Regressions on Time Discharge and Season (WRTDS) water quality modeling framework. For the three sites situated below dams, we used flow-weighted concentrations to estimate water year mean TDS concentrations. Along with these estimates, we include information about the timing of construction, and capacity of dams in the Lower Colorado River Basin.