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 data release contains 15 datasets and associated metadata of watershed characteristics and data related to stream water quality and constituent load estimation for 15 study watersheds in Gwinnett County, Georgia. Dataset periods vary but range within 2000 to 2021. The 15 datasets are organized as individual child items. The data release includes three Geographic Information System shapefiles: (1) 01: Watersheds shapefile for the 15 study watersheds in Gwinnett County, Georgia; (2) 02: Stormwater drainage areas shapefile for the 15 study watersheds in Gwinnett County, Georgia, August 2021; and (3) 03: 200-foot stream buffer shapefiles for 15 watersheds in Gwinnett County, Georgia. The data release includes four comma separated value (csv) format datasets related to watershed characteristics: (1) 04: National Land Cover Database land cover at 15 watersheds in Gwinnett County, Georgia from 2001 to 2019; (2) 05: Impervious areas within 15 watersheds in Gwinnett County, Georgia from 2000 to 2020; (3) 06: Property parcel building construction dates and densities in 15 watersheds in Gwinnett County, Georgia in 2021; and (4) 07: Population density in 15 watersheds in Gwinnett County, Georgia from 2000 to 2020. The data release also includes the following eight csv format datasets related to stream water quality and constituent load estimation: (1) 08: Daily average stream base flow at 14 watersheds in Gwinnett County, Georgia for water years 2002-2020; (2) 09: Streamwater quality assurance sample results for 19 water-quality constituents in 15 watersheds in Gwinnett County, Georgia for years 2000-2020; (3) 10: Laboratory standard reference samples for the Gwinnett County, Georgia study for years 2014-2020; (4) 11: Streamwater sample constituent concentration outliers from 15 watersheds in Gwinnett County, Georgia for water years 2003-2020; (5) 12: Model calibration data for fitting regression models used to estimate streamwater loads for 12 constituents in 13 watersheds in Gwinnett County, Georgia for water years 2003-2020; (6) 13: Models coefficients and statistics for regression models used to estimate streamwater loads for 12 water-quality constituents in 13 watersheds in Gwinnett County, Georgia for water years 2003-2020 (includes 488 portable document format files (pdf) with reports and plots for evaluating model fits); (7) 14: LOADEST estimation dataset used to estimate streamwater loads for 12 constituents in 13 watersheds in Gwinnett County, Georgia for water years 2003-2020; and (8) 15: Streamwater load and yield estimates for 12 constituents in 13 watersheds in Gwinnett County, Georgia for water years 2003-2020. The purpose of this product is to provide and document datasets related to watershed characteristics and streamwater constituent load estimations in support of the USGS Scientific Investigations Report "Hydrology, water-quality, and watershed characteristics in 15 watersheds in Gwinnett County, Georgia, 2002-20". The shapefiles, datasets 01 through 03, define the study watershed drainage areas of the natural watersheds, for diverted stormwater, and within the 200-foot stream buffers. The watershed characteristics datasets (datasets 04 through 07) were used to evaluate differences in stream runoff and water quality of the study watersheds. The daily base flow dataset (dataset 08) was used to calculate watershed base-flow indexes, and as an explanatory variable in load estimation models. The water-quality assurance and laboratory standard reference samples datasets (datasets 09 and 10, respectively) were used in the water quality assessment. Datasets 11 through 15 document the water quality outliers, water-quality and model explanatory variable input files, constituent models, and load results for the streamwater constituent load estimates. Loads were estimated for 13 of the watersheds for water years 2003 to 2020 for 12 constituents: total suspended solids, suspended sediment concentration, total nitrogen, total nitrate plus nitrite, total phosphorus, dissolved phosphorus, total organic carbon, total calcium, total magnesium, total lead, total zinc, and total dissolved solids. Note that the time period of some of the watershed characteristics data brackets the study period encompassed in the associated report (water years 2002-20), or was only available for 2021, just after the end of the report study period. 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 U.S. Geological Survey (USGS) in cooperation with Gwinnett County Department of Water Resources. 2000 2021 publication date Complete None planned -84.2721 -83.8468 34.1514 33.7676 ISO 19115 Topic Category inlandWaters imageryBaseMapsEarthCover structure society environment Other impervious area Gwinnett County Department of Water Resources water quality assurance laboratory quality control USGS Thesaurus surface water quality population (human) datasets streamflow stream-gage measurement mathematical modeling land use and land cover runoff material standards water quality Alexandria Digital Library Feature Type Thesaurus buildings drainage basins Marine Realms Information Bank (MRIB) keywords watershed stream USGS Metadata Identifier USGS:62bdab10d34e82c548cec125 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 See individual metadata files for each dataset See individual metadata files for each dataset See individual metadata files for each dataset See individual metadata files for each dataset Unknown Vector G-polygon 45 NAD 1983 StatePlane Georgia West FIPS 1002 Feet 0.9999 -84.16666666666667 30.0 2296583.333333333 0.0 coordinate pair 0.000000007285694270109391 0.000000007285694270109391 meters D North American 1983 GRS 1980 6378137.0 298.257222101 Not applicable 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