Streamflow input datasets and model results using the Weighted Regressions on Time, Discharge, and Season (WRTDS) Models to estimate total organic carbon and other constituent concentrations in eight rivers in Connecticut, water years 1973 to 2019

This data release provides data in support of an assessment of changes in slope of the concentration-discharge relation for total organic carbon in eight major rivers at gaging stations in Connecticut from October 1972 to September 2019 (U.S. Geological Survey water years 1973 to 2019). The rivers include the Connecticut at Thompsonville (01184000), Housatonic at Stevenson (01205500), Quinebaug at Jewett City (01127000), Farmington at Tariffville (01189995), Shetucket at Willamantic (01122500), Naugatuck at Beacon Falls (011208500), Quinnipiac at Wallingford (01196500), and Salmon at East Hampton (01193500). The assessment is described in the article "An increase in the slope of the concentration discharge relation for total organic carbon in major rivers in New England, 1973 to 2019" (Huntington and Wieczorek, in review). Two models were used in this assessment; the Weighted Regressions on Time, Discharge and Season (WRTDS) model (Hirsch and others, 2010), and the Hydrograph Separation (HYSEP model) (Sloto and Crouse, 1996). Both models use data from the USGS National Water Information System (NWIS) database (USGS, 2020). The WRTDS model was used to estimate daily concentrations of various water quality constituents and the HYSEP model was used to estimate the fraction of daily discharge that could be classified as stormflow (event flow) as opposed to base flow. In a separate analysis, for the Connecticut, Farmington, and Quinnipiac Rivers, independent regression models for the early and recent periods were used to compare predicted TOC concentrations given a common daily discharge record for one year. A synthetic record was developed from the average daily discharges for these rivers for the period 10/1/1992 to 9/30/1998. To run the appropriate WRTDS model with this discharge record, the dates for this synthetic record were set to 10/1/1983 to 9/30/1984 when run with the early period model and 10/1/2005 to 9/30/2006 when run with the recent period model. Using these synthetic discharge periods centered the synthetic year in the middle of each period thus controlling for any temporal trends in the concentration-discharge (C-Q) relations during the periods. On the few days of the year during those periods when samples were collected for TOC analyses, the observed discharge in the actual record was substituted for the synthetic discharge so the original concentration discharge data pair would be used in the regression model. This data release is structured as a set of comma-separated values (CSV) files, including a site file, 44 data files, and a data dictionary (Data_Dictionary.csv), which provides information describing the content of each of the data files. The data dictionary contains the filename, data type, description, and units. The site-information file contains the USGS 8-digit site ID, site name, latitude, longitude, horizontal datum, land surface elevation, vertical datum, and drainage area. The data files contain input data for one set of model runs and output data for all model runs of the WRTDS model as follows: There are six input files, one for the early period (1973 to 1995) and one for the recent period (1996 to 2019) for three rivers. These input files contain two columns (date and daily discharge). The file naming convention begins with WRTDS_INPUT_DAILY_Discharge_ and is followed by the date range and the USGS site ID for the specific river. For example, "WRTDS_INPUT_DAILY_Discharge_1996-2019_01196500.csv" is for the recent period for the Quinnipiac River at Wallingford There are eight WRTDS model output files (one for each of the eight rivers) for the full period (1973 to 2019) that contain date, daily discharge, and estimated concentrations of total organic carbon, total nitrogen, total phosphorus, and sulfate. The file naming convention begins with WRTDS_Output_Daily_1973-2019_ and is followed by the USGS site ID for the specific river. For example, "WRTDS_Output_Daily_1973-2019_01184000.csv" is for the full period for the Connecticut River at Thompsonville. There are eight WRTDS model output files (one for each of the eight rivers) for the early period (1973 to 1995) that contain date, daily discharge, and estimated concentration of total organic carbon, and estimated flux of total organic carbon. The file naming convention begins with WRTDS_Output_Daily_1973-1995_ and is followed by the USGS site ID for the specific river. For example, "WRTDS_Output_Daily_1973-1995_01193500.csv" is for the early period for the Salmon River at East Hampton. There are eight WRTDS model output files (one for each of the eight rivers) for the recent period (1996 to 2019) that contain date, daily discharge, and estimated concentration of total organic carbon, and estimated flux of total organic carbon. The file naming convention begins with WRTDS_Output_Daily_1996-2019_ and is followed by the USGS site ID for the specific river. For example, "WRTDS_Output_Daily_1996-2019_01205500.csv" is for the early period for the Housatonic River at Stevenson. There are six output files, one for the early period (1973 to 1995) and one for the recent period (1996 to 2019) for three rivers. These output files contain four columns (date, daily discharge, concentration, and flux). The file naming convention begins with WRTDS_Output_Daily_ and is followed by the date range, the word SYNTHETIC, and the USGS site ID for the specific river. For example, "WRTDS_Output_Daily _Discharge_1973-1995_SYNTHETIC_0118400.csv" is for the early period for the Connecticut River at Thompsonville. There are eight HYSEP model output files (one for each of the eight rivers) for the full period (1973 to 2019) that contain date, daily discharge, and baseflow (the amount of the discharge that is baseflow). The file naming convention begins with HYSEP_OUTPUT_Daily_1973-2019_ and is followed by the USGS site ID for the specific river. For example, "WRTDS_Output_Daily_1973-2019_01127000.csv" is for the full period for the Quinebaug River at Jewett City. References: Hirsch, R. M., D. L. Moyer, and S. A. Archfield. 2010. Weighted Regressions on Time, Discharge, and Season (WRTDS), with an Application to Chesapeake Bay River Inputs. Journal of the American Water Resources Association 46:857-880. Huntington, T. G. and M. E. Wieczorek, in review, An increase in the slope of the concentration discharge relation for total organic carbon in major rivers in New England, 1973 to 2019. Science of the Total Environment. Sloto, R. A., and M. Y. Crouse. 1996. HYSEP: A Computer Program for Streamflow Hydrograph Separation and Analysis: U.S. Geological Survey Water-Resources Investigations Report 1996-4040, 46 p., https://pubs.er.usgs.gov/publication/wri964040. U.S. Geological Survey, 2020, USGS water data for the Nation: U.S. Geological Survey National Water Information System database, accessed January 15, 2020, at https://doi.org/10.5066/F7P55KJN.