This data release supports an analysis of changes in dissolved organic carbon (DOC) concentration and in the slope of the concentration-discharge relation in the Sleepers River Research Watershed W9 near North Danville, Vermont 1991 to 2018. The data release includes pre-processed model inputs and model outputs. W9 is a 40.5-hectare forested sub-watershed of the Sleepers River Research Watershed that was originally established by the U.S. Department of Agriculture in 1959 and has been intensively studied by the USGS since 1991. The W9 headwater sub-watershed drains to Pope Brook and is gaged at USGS station ID 01135100. Pope Brook flows into Sleepers River and ultimately into the Connecticut River. Two models were used to analyze concentration-discharge (C-Q) relations: the Weighted Regressions on Time, Discharge and Season (WRTDS) model (Hirsch and others, 2010) and the Hydrograph Separation (HYSEP) model (Sloto and Crouse, 1996). The WRTDS model used discharge data downloaded from Shanley and others (2021) and DOC data downloaded from Matt and others (2021). The HYSEP model used discharge data downloaded from Shanley and others (2021). The WRTDS model was used to estimate daily concentrations and fluxes of DOC 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. The time series data were analyzed for the entire period, water years 1992 (WY1992) to WY2018 where WY1992 is the period from October 1, 1991 to September 30, 1992. In addition to the WRTDS and HYSEP modeling conducted with the full range of data, two further analyses were conducted with subsets of the data. For one evaluation, the data were separated into two periods (with a breakpoint between WY2002 and WY2003) to detect and quantify changes in DOC concentration and slope of the C-Q relation over time. In a separate analysis, WRTDS was used to estimate DOC concentrations for the observed WY2007 daily discharge record when this record was inserted as WY1997 as a synthetic record. In this synthetic record the original water years 1997 through 2002 were incremented by one year. (Note: the input and output data files that contain "syn" in the filenames include this synthetic or modified daily discharge data and therefore would not match the observed records.) This data release is structured as a set of comma-separated values (CSV) files, including a site file (Site_Information.csv), 13 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 filenames of all 15 CSV files and their, headings, data types, descriptions, and units, and basic statistics where applicable. The site-information file contains the USGS 8-digit site identifier, site name, latitude, longitude, horizontal datum, land surface elevation, vertical datum, and drainage area for the Pope Brook Tributary (W9). The W9Info2.csv file is used by WRTDS to assign the appropriate information for the analysis for this watershed.
There are four pairs of input files. There are two input files for each WRTDS run including a daily discharge file and a daily DOC concentration file, for example "W9Daily.csv" and "W9Sample.csv" for the full period 10/1/1991 to 9/30/2018 for discharge and concentration, respectively. The other input file pairs are for the date ranges given in the file names: "W9Daily1992.2002.csv" and "W9Sample1992.2002.2.7.csv"; "W9Daily2003.2018.csv" and "W9Sample2003.2018.2.7.csv"; "W9Daily1992.2003syn.csv and "W9Sample1992.2003syn.2.7.csv". There is one WRTDS output file for each of the four pairs of input files: "DailyOutput_2.7.csv" (full period); "DailyOutput1992.2002.2.7.csv" (early period); "DailyOutput2003.2013.2.7.csv" (recent period); "DailyOutput1992.2003syn.2.7.csv" (early period with identical hydrologic record spliced following WY1996). There is one output file from the HYSEP model: "Baseflow_Daily_01135100.csv". References: Hirsch, R.M., Moyer, D.L., and Archfield, S.A., 2010, Weighted Regressions on Time, Discharge, and Season (WRTDS), with an application to Chesapeake Bay River inputs: Journal of the American Water Resources Association, v. 46, no. 5, p. 857–880, http://dx.doi.org/10.1111/j.1752-1688.2010.00482.x. Matt, S., Shanley, J. B., Chalmers, A. T., Sebestyen, S. D., Merriam, J. L., Bailey, S. W., Campbell, J., Ryan, K. A., Denner, J. C., Clark, Stewart C., and Schuster, P. F., 2021, Aqueous chemistry database, Sleepers River Research Watershed, Danville, Vermont, 1991-2018., https://doi.org/10.5066/P9380HQG Shanley, J.B., Chalmers, A.T., Denner, J.C., and Clark, S.F., 2021, Five-minute discharge; daily precipitation, stream runoff, and maximum and minimum air temperature; and annual precipitation and runoff for W-9 catchment, Sleepers River Research Watershed near Danville, Vermont, 1991-2018: U.S. Geological Survey data release, https://doi.org/10.5066/P929KMVK Sloto, R.A., and Crouse, M.Y., 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.