Brent T. Aulenbach Joshua C. Henley Kristina G. Hopkins 20230404 tabular digital data Reston, VA U.S. Geological Survey https://doi.org/10.5066/P9G8HZTY Brent T. Aulenbach Joshua C. Henley Kristina G. Hopkins 2023 publication USGS Scientific Investigations Report 2023-5035 Reston, Virginia U.S. Geological Survey This dataset contains the estimation data that was used in combination with the regression models to estimate streamwater constituent loads for 12 water-quality constituents for 13 watersheds in Gwinnett County, Georgia for the water years 2003 to 2020. Load were estimated using the U.S. Geological Survey (USGS) LOADEST load estimation software. Variables in the estimation dataset include a storm condition indicator variable, streamflow, streamflow during base-flow conditions, base flow, turbidity, and turbidity during stormflow conditions. Variants of the streamflow variable were used depending on whether the regression models were fit with turbidity explanatory variables. The time-step of the estimation datasets varied by watershed and ranged between four to twelve hours, which represented the typical length of the storm composite samples for the particular watershed. The purpose of this dataset is to make assessable the LOADEST estimation time-step datasets used in estimating streamwater constituent loads in support of the USGS Scientific Investigations Report " Hydrology, water-quality, and watershed characteristics in 15 watersheds in Gwinnett County, Georgia, 2002-20". This study is part of a long-term program to monitor and analyze the hydrologic and water-quality conditions of 15 watersheds in Gwinnett County, Georgia by the USGS in cooperation with Gwinnett County Department of Water Resources. 20021001 20200930 publication date Complete None planned -84.2721 -83.8468 34.1514 33.7676 ISO 19115 Topic Category inlandWaters USGS Thesaurus surface water quality streamflow mathematical modeling USGS Metadata Identifier USGS:6350427ad34e47431c15c5cd Geographic Names Information System Gwinnett County State of Georgia 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. Brent T Aulenbach U.S. Geological Survey, Southeast Region Research Hydrologist mailing address

1770 Corporate Drive Suite 500

Norcross GA 30093 US 678-924-6626 678-924-6710 btaulenb@usgs.gov Funded through a cooperative agreement between Gwinnett County Department of Water Resources and the U.S. Geological Survey MacOS Big Sur, version 11.7.1; Microsoft Excel for Mac, version 16.67, 14_GwinnettCoGa_LOADESTEstimationData.csv 25.6 MB No formal accuracy assessment was conducted. See Sauer and Turnipseed (2010) and Turnipseed and Sauer (2010) for typical accuracies in measuring stream stage and discharge, and in the development of stage-discharge relations. Sauer, V.B., and Turnipseed, D.P., 2010, Stage measurement at gaging stations: U.S. Geological Survey Techniques and Methods, book 3, chap. A7, 45 p., accessed May 24, 2022, at https://doi.org/10.3133/tm3A7. Turnipseed, D.P., and Sauer, V.B., 2010, Discharge measurements at gaging stations: U.S. Geological Survey Techniques and Methods, book 3, chap. A8, 87 p., accessed May 24, 2022, at https://doi.org/10.3133/tm3A8. No formal logical accuracy tests were conducted. Dataset 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. U.S. Geological Survey 20220405 application/service https://doi.org/10.5066/F7P55KJN Digital and/or Hardcopy 20021001 20200930 publication date NWIS Instantaneous (15-minute interval) streamflow and sonde turbidity for 13 watersheds in Gwinnett County, Georgia. This load estimation dataset was used in conjunction with load regression models to predict streamwater constituent loads and yields using the U.S. Geological Survey (USGS) LOAD ESTimation software (LOADEST; Runkel and others, 2004). Dataset variables include a storm condition indicator variable and the natural logarithms of streamflow, streamflow during base-flow conditions, base flow, turbidity, and turbidity during stormflow conditions. The dataset was compiled on a computational time-step basis, which accommodated incorporating storm-composited samples into the concentration-discharge relations used by the regression-based load estimation approach (Landers and others, 2007; Joiner and others, 2014; Aulenbach and others, 2017; Aulenbach and others, 2022). Watershed computational time steps ranged between four to twelve hours and represented the durations of each watershed’s storm-composite water-quality samples (Aulenbach and others 2023). Time-step average streamflows and turbidities were determined from instantaneous streamflows and field-deployed sonde turbidities. These instantaneous 15-minute interval frequency data were downloaded from the U.S. Geological Survey (USGS) National Water Information System (NWIS) AQUARIUS Time-Series application on June 2-3, 2021. Streamflow was monitored using standard USGS protocols, which includes measuring stream stage, making discharge measurements, developing and maintaining a stage-discharge relation (rating curve), and computing discharge (Sauer and Turnipseed, 2010; Turnipseed and Sauer, 2010). Field turbidities were measured using multi-parameter in-situ water-quality meters, which were maintained and their corresponding sensor records checked, using the quality-assurance and quality-control procedures outlined in Wagner and others (2006). Poor quality data were removed from the record. Stream base flows were determined by hydrograph separation of daily average streamflows using the Web-based Hydrograph Analysis Tool (WHAT; https://engineering.purdue.edu/~what/, accessed June 2021; Lim and others, 2005). The simple local minimum method was used, which required no parameters to be fit. Hydrograph separations were performed on June 4, 2021 and June 10, 2021. For watershed-constituent combinations in which turbidity was not an explanatory variable, the “flow-only” model was used in combination with the Flow streamflow explanatory variable. When turbidity was an explanatory variable, loads were estimated twice using the primary “flow-turbidity” model and the fallback “flow-only” model. The “flow-only” model was fit without turbidity terms and was used to estimate loads for periods when turbidity data was unavailable. The “flow-turbidity” model used the Flow_QT streamflow explanatory variable variant while the “flow-only” model used the Flow_Q streamflow variant. In this situation, annual and calibration period load uncertainties from LOADEST for the flow-only and flow-turbidity models were proportioned to the amount of load represented by the time steps in which each model was employed. In order to minimize the effects of time steps not used by each model on LOADEST reported annual and calibration period loads and uncertainties, variant streamflow and turbidity variables were assigned artificially low values during those periods such that estimated loads were small and would not appreciably impact the overall load and uncertainty estimates. For time steps when turbidity was present, the “flow-turbidity” model was used with the Flow_QT streamflow variable, with Flow_QT assigned a value of 0.01 cubic feet per second and the ln_Turb variable assigned a value of -2 for time steps where turbidity was missing. For time steps when turbidity was missing, the “flow-only” model was used with the Flow_Q streamflow variable, which was assigned a value of 0.01 for time-steps when turbidity was present. Estimation datasets were compiled between June 8, 2021 and June 10, 2021. Aulenbach, B.T., Henley, J.C., and Hopkins, K.G., 2023, Hydrology, water-quality, and watershed characteristics in 15 watersheds in Gwinnett County, Georgia, water years 2002-20: U.S. Geological Survey Scientific Investigations Report 2023-5035. Aulenbach, B.T., Joiner, J.K., and Painter, J.A., 2017, Hydrology and water quality in 13 watersheds in Gwinnett County, Georgia, 2001-15: U.S. Geological Survey Scientific Investigations Report 2017-5012, 82 p., accessed July 11, 2020, at https://doi.org/10.3133/sir20175012. Aulenbach, B.T., Kolb, K., Joiner, J.K., and Knaak, A.E., 2022, Hydrology and water quality in 15 watersheds in DeKalb County, Georgia, 2012-16: U.S. Geological Survey Scientific Investigations Report 2021-5126, 105 p., accessed August 8, 2022, at https://doi.org/10.3133/sir20215126. Joiner, J.K., Aulenbach, B.T., and Landers, M.N., 2014, Watershed characteristics and water-quality trends and loads in 12 watersheds in Gwinnett County, Georgia: U.S. Geological Survey Scientific Investigations Report 2014-5141, 79 p., accessed July 11, 2020, at https://doi.org/10.3133/sir20145141. Landers, M.N., Ankcorn, P.D., and McFadden, K.W., 2007, Watershed effects on streamflow quantity and quality in six watersheds of Gwinnett County, Georgia: U.S. Geological Survey Scientific Investigations Report 2007-5132, 62 p., accessed July 11, 2020, at https://doi.org/10.3133/sir20075132. Lim, K.J., Engel, B.A., Tang, Zhenxu, Choi, Joongdae, Kim, K.-S., Muthukrishnan, Suresh, and Tripathy, Dibyajyoti, 2005, Automated web GIS based hydrograph analysis tool, WHAT: Journal of the American Water Resources Association, v. 41, no. 6, p. 1407-1416, accessed July 11, 2020, at https://doi.org/10.1111/j.1752-1688.2005.tb03808.x. Runkel, R.L., Crawford, C.G., and Cohn, T.A., 2004, Load estimator (LOADEST)--A FORTRAN program for estimating constituent loads in streams and rivers: U.S. Geological Survey Techniques and Methods, book 4, chap. A5, 69 p., accessed July 11, 2020, at https://doi.org/10.3133/tm4A5. Sauer, V.B., and Turnipseed, D.P., 2010, Stage measurement at gaging stations: U.S. Geological Survey Techniques and Methods, book 3, chap. A7, 45 p., accessed May 24, 2022, at https://doi.org/10.3133/tm3A7. Turnipseed, D.P., and Sauer, V.B., 2010, Discharge measurements at gaging stations: U.S. Geological Survey Techniques and Methods, book 3, chap. A8, 87 p., accessed May 24, 2022, at https://doi.org/10.3133/tm3A8. Wagner, R.J., Boulger, R.W., Jr., Oblinger, C.J., and Smith, B.A., 2006, Guidelines and standard procedures for continuous water-quality monitors--Station operation, record computation, and data reporting: U.S. Geological Survey Techniques and Methods 1-D3, 51 p., 8 attachments, accessed July 11, 2020 at https://doi.org/10.3133/tm1D3. NWIS 20210610 14_GwinnettCoGa_LOADESTEstimationData.csv Comma Separated Value (CSV) file containing the estimation data used to estimate streamwater constituent loads using the LOADEST regression method Producer Defined Site_nu U.S. Geological Survey site number Producer Defined "02205865" Sweetwater Creek at Club Drive near Lilburn, Ga. Producer defined "02207120" Yellow River at Ga 124, near Lithonia, Ga. Producer defined "02207185" No Business Creek at Lee Road, below Snellville, Ga. Producer defined "02207385" Big Haynes Creek at Lenora Road, near Snellville, Ga. Producer defined "02207400" Brushy Fork Creek at Beaver Road, nr Loganville, Ga. Producer defined "02208150" Alcovy River at New Hope Road, near Grayson, Ga. Producer defined "02217274" Wheeler Creek at Bill Cheek Road, near Auburn, Ga. Producer defined "02218565" Apalachee River at Fence Road, near Dacula, Ga. Producer defined "02334480" Richland Creek at Suwanee Dam Road, near Buford, Ga. Producer defined "02334578" Level Creek at Suwanee Dam Road, near Suwanee, Ga. Producer defined "02334885" Suwanee Creek at Suwanee, Ga. Producer defined "02335350" Crooked Creek near Norcross, Ga. Producer defined "02336030" North Fork Peachtree Creek at Graves Rd, near Doraville, Ga. Producer defined Date_TS Date at beginning of time step - time steps and start dates vary by station and can be 4, 6, 8, or 12 hours in duration and span water years 2003 through 2020 Producer Defined 10/1/2002 0:00 9/30/2020 20:00 m/d/yyyy h:mm Flow Time-step average streamflow - used for estimating loads for watershed-constituent combinations in which turbidity was not a model explanatory variable. (Corresponds to model streamflow explanatory variable Q in equation 1 of associated USGS Scientific Investigations Report Aulenbach and others [2023]) Producer Defined 0.007 15000.0 cubic feet per second 0.001 Flow_Q Time-step average streamflow, flow-only model variant - used for estimating loads for watershed-constituent combinations in which turbidity was a model explanatory variable but turbidity was missing such that loads were estimated using the backup flow-only model. Streamflow was assigned 0.01 cubic feet per second for time steps in which loads were estimated using the flow-turbidity model (when turbidity values were available). (Corresponds to model streamflow explanatory variable Q in equation 1 of associated USGS Scientific Investigations Report Aulenbach and others [2023]) Producer Defined 0.01 15000.0 cubic feet per second 0.001 Flow_QT Time-step average streamflow, flow-turbidity model variant - used for estimating loads for watershed-constituent combinations in which turbidity was a model explanatory variable and turbidity was available such that loads were estimated using the flow-turbidity model. Streamflow was assigned 0.01 cubic feet per second for time steps in which loads were estimated using the flow-only model (when turbidity values were missing). (Corresponds to model streamflow explanatory variable Q in equation 1 of associated USGS Scientific Investigations Report Aulenbach and others [2023]) Producer Defined 0.007 6961.979 cubic feet per second 0.001 biny9J Storm indicator variable - 1 indicates storm conditions, 0 indicates base-flow conditions, and values between 0 and 1 indicates the average of conditions during time step. (Corresponds to model stormflow condition explanatory variable S in equation 1 of associated USGS Scientific Investigations Report Aulenbach and others [2023]) Producer Defined 0.0 1.0 0.001 lnQ.BaseQ Natural logarithm of daily average streamflow during base-flow conditions as indicated by the storm indicator variable, biny9J. Calculated as product of the natural logarithm of the "Flow" variable and the difference of one minus the "Storm" indicator variable. Equal to 0 during stormflow conditions. (Corresponds to model streamflow parameter (1-S)lnQ in equation 1 of associated USGS Scientific Investigations Report Aulenbach and others [2023]) Producer Defined -5.026 7.115 natural logarithm of cubic feet per second 0.001 BaseQ Daily average base flow - determined from hydrograph separation. (Corresponds to model base-flow explanatory variable Qb in equation 1 of associated USGS Scientific Investigations Report Aulenbach and others [2023]) Producer Defined 0.01 1790.0 cubic feet per second 0.01 lnQb Natural logarithm of daily average base flow - determined from hydrograph separation. (Corresponds to model base-flow parameter lnQb in equation 1 of associated USGS Scientific Investigations Report Aulenbach and others [2023]) Producer Defined -4.605 7.49 natural logarithm of cubic feet per second 0.001 Turbidity Time-step average turbidity. (Corresponds to model turbidity explanatory variable T in equation 1 of associated USGS Scientific Investigations Report Aulenbach and others [2023]) Producer Defined . No Data Producer defined 0.0 5011.458 Formazin Nephelometric Units 0.001 lnTurb Natural logarithm of time-step average turbidity. Assigned -2 when turbidity is missing. (Corresponds to model turbidity parameter lnT in equation 1 of associated USGS Scientific Investigations Report Aulenbach and others [2023]) Producer Defined -2.0 8.519 natural logarithm of Formazin Nephelometric Units 0.001 lnTrbStrm Natural logarithm of time-step average turbidity during storm conditions as indicated by the storm indicator variable, biny9J. Calculated as the product of the "ln_Turb" and "Storm" variables. Equal to 0 during base-flow conditions. lnTrbStrm corresponds to the lnTurb.Storm parameter name in the LOADEST output files. (Corresponds to model turbidity parameter SlnT in equation 1 of associated USGS Scientific Investigations Report Aulenbach and others [2023]) Producer Defined -2.0 8.519 natural logarithm of Formazin Nephelometric Units 0.001 This dataset contains the estimation data that was used in combination with the load regression models to estimate streamwater constituent loads for 12 water-quality constituents for 13 watersheds in Gwinnett County, Georgia for water years 2003 to 2020. Load were estimated using the USGS LOAD ESTimation software (LOADEST; Runkel and others, 2004). LOADEST was only used to estimate loads for constituents that had at least a minimal relation with the model explanatory variables, as indicated by their concentration model R-square >0.20. Data is provided on a time-step basis that loads were estimated for, which varied by watershed and ranged between four to twelve hours. Variables in the estimation dataset include a storm condition indicator variable and the natural logarithms of streamflow, streamflow during base-flow conditions, base flow, turbidity, and turbidity during stormflow conditions. For watershed-constituent combinations in which turbidity was not an explanatory variable, the “flow-only” model was used in combination with the Flow streamflow explanatory variable. For situations where turbidity was an explanatory variable, the variant streamflow explanatory variables Flow_Q and Flow_QT were used by the “flow-only” and “flow-turbidity” models, respectively. Daily average base flow was determined by hydrograph separation using the Web-based Hydrograph Analysis Tool (WHAT; Lim and others, 2005) using the simple local minimum method on the daily average streamflows. Further details on LOADEST model estimation procedures are available in Aulenbach and others (2023). Aulenbach, B.T., Henley, J.C., and Hopkins, K.G., 2023, Hydrology, water-quality, and watershed characteristics in 15 watersheds in Gwinnett County, Georgia, water years 2002-20: U.S. Geological Survey Scientific Investigations Report 2023-5035. Lim, K.J., Engel, B.A., Tang, Zhenxu, Choi, Joongdae, Kim, K.-S., Muthukrishnan, Suresh, and Tripathy, Dibyajyoti, 2005, Automated web GIS based hydrograph analysis tool, WHAT: Journal of the American Water Resources Association, v. 41, no. 6, p. 1407-1416, accessed July 11, 2020, at https://doi.org/10.1111/j.1752-1688.2005.tb03808.x. Runkel, R.L., Crawford, C.G., and Cohn, T.A., 2004, Load estimator (LOADEST)--A FORTRAN program for estimating constituent loads in streams and rivers: U.S. Geological Survey Techniques and Methods, book 4, chap. A5, 69 p., accessed July 11, 2020, at https://doi.org/10.3133/tm4A5. U.S. Geological Survey GS ScienceBase 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 on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. Digital Data https://doi.org/10.5066/P9G8HZTY None 20230404 Brent T Aulenbach U.S. Geological Survey, Southeast Region Research Hydrologist mailing address

1770 Corporate Drive Suite 500

Norcross GA 30093 US 678-924-6626 678-924-6710 btaulenb@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998