Michael E. Wieczorek Shannon E. Jackson Gregory E. Schwarz 20230801 tabular digital data Reston, Virginia U.S. Geological Survey https://doi.org/10.5066/F7765D7V This tabular data set represents the mean Julian year day of the year of the last freeze, from 30 years of record (1961-1990) compiled for two spatial components of the NHDPlus version 2 data suite (NHDPlusv2) for the conterminous United States; 1) individual reach catchments and 2) reach catchments accumulated upstream through the river network. This dataset can be linked to the NHDPlus version 2 data suite by the unique identifier COMID. The source data for the mean day of the year of a last freeze, from 30 years of record (1961-1990) was provided by the Environmental Protection Agency and is included with this data set (Ryan Hill, EPA, written commun., 2006). The values represent the Julian year day of the last freeze. For example, value of 300 is the 300th day of the year (Oct 27th). Values > 365 mean that the last freeze occurs after Dec 31. It is done this way so that (first_freeze - last_freeze) should always give a positive number; high numbers for an area with a long frost-free period (e.g. Florida), low numbers for an area with a short frost-free period.Reach catchment information characterizes data at the local scale. Reach catchments accumulated upstream through the river network characterizes cumulative upstream conditions. Network-accumulated values are computed using two methods, 1) divergence-routed and 2) total cumulative drainage area. Both approaches use a modified routing database to navigate the NHDPlus reach network to aggregate (accumulate) the metrics derived from the reach catchment scale. (Schwarz and Wieczorek, 2018). This data set was created by the U.S. Geological Survey's (USGS) National Water-Quality Assessment Project (NAWQA) which is part of the USGS National Water Quality Program (NWQP). This effort was undertaken to estimate the mean day of the year of Last freeze, from 30 years of Record (1961-1990) for NHDPlusV2 flowline catchments and upstream river networks to support statistical analysis, map display, and model parameterization. The data processed here uses a modified routing data base for the NHDPlusV2 flowline network (ENHDPlusV2_us, Schwarz and Wieczorek, 2018). The NHDPlusV2 flowline network serves as the spatial infrastructure for many water-quality modeling efforts included under NAWQA Cycle 3 status and trend assessments including the SPARROW (SPAtially Referenced Regressions On Watershed attributes) model (Rowe and others, 2009). The NHDPlusV2 flowline network is a publically available digital geospatial framework (database) that depicts the network of stream segments and their catchments within the conterminous United States (see Moore and Dewald, 2016 for more detail). The NHDPlusv2 data set includes catchments for each reach covering the conterminous U.S. which includes the catchment boundaries in neighboring Canada and Mexico. These catchments are used as the spatial units for zonal statistics. A statistic (summation, average, minimum or maximum) is calculated for each zone (catchment), based on values from the source ancillary data set (See Process_Description for more details). The output of these values are used as the source input data for an accumulation program which uses a routing database to allocate and accumulate landscape metrics. This database (ENHDPlusV2_us) is based on a topologically reconditionedversion of the NHDPlusV2 hydrography network and is used for routing purposes only. No cartographic changes were made to the original NHDPlusV2 in either the flowline or catchment line work. 1961 1990 observed Complete As needed -127.910792 -65.327751 51.657387 23.243486 CONUS United States None Last day of freeze Julian year day of the year SPARROW Inlandwaters NHDPlus Catchment NAWQA USGS Metadata Identifier USGS:57040a6ce4b0328dcb828378 None Conterminous United States none The source data for the mean Julian day of the year of a last freeze, from 30 years of Record (1961-1990) was originally PRISM-based data, with some layers further enhanced by ClimateSource.com and then provided to the USGS by the Environmental Protection Agency (Ryan Hill, EPA, written commun., 2011). Because of budget restraints, the original historical PRISM data are no longer supported or distributed. It should also be noted that Climatesource.com no longer exists, however the data is free to distribute and download from here. It should be noted that the USGS assumes no liability with its use. One should use caution and read this document before using these data to estimate smaller areas. These data should not be used for site-specific evaluation, surveying, or engineering purposes. They should also not be used beyond the limits of the source data's scale. Use of this data is considered acceptance of the limitations of this data and that the user has read and understood this metadata prior to its use in any form. Michael E. Wieczorek US Geological Survey, Maryland Water Science Center mailing and physical

5522 Research Park Drive

Baltimore MD 21228 USA 443-498-5550 mewieczo@usgs.gov We would like to acknowledge the following USGS employees. The original conception and rationale for creating these data is from Robert Gilliom and Daren Carlisle. We also acknowledge Andrew LaMotte in helping to process and format much of this data as well as the helpful colleague reviews provided by Alison Appling and Daren Carlisle. We also would like to thank Dave Wolock, Curtis Price, Roland Viger, James Falcone, and Drew Ignazio for their invaluable input. Gary L. Rowe Kenneth Belitz Hedeff I. Essaid Robert J. Gilliom Pixie A. Hamilton Anne B. Hoos Dennis D. Lynch Mark D. Munn David W. Wolock 2009 Reston, Virginia U.S. Geological Survey http://pubs.usgs.gov/of/2009/1296/pdf/OF09-1296.pdf Richard B. Moore Thomas G. Dewald 2016 American Water Resources Association (JAWRA) 1-10.DOI: 10.1111/1752-1688.12389 http://dx.doi.org/10.1111/1752-1688.12389 James A. Falcone Daren M. Carlisle David M. Wolock Michael R. Meador 2010 Ecology 91 (2), 621 Data Paper in Ecological Archives E091-045-D1 http://esapubs.org/Archive/ecol/E091/045/metadata.htm Basin metrics were compared to values for the same variables available in the GAGESII data set (Falcone, 2010). The following steps were performed before making the comparisons: 1) GAGESII point file with the most current COMIDs associations was joined to the routing database file which contains accumulated basin areas (Schwarz and Wieczorek, 2018). 2) Only those GAGESII points that have a basin area within 1% or less of the accumulated basin areas were processed and used for comparisons. This resulted in 4,713 locations. 3) Using those COMIDs for GAGESII sites, the associated record in the accumulation files were pulled and used in the comparison of one to one plots. Results demonstrated a Pearson's r-squared of over 99%. Outliers can be attributed to either the difference in the basin delineations of GAGESII basins compared to that of the catchment representations in NHDPlus version 2 or to the fact that this data set only reports data from the downstream end of reaches and their upstream contribution. GAGESII basin outlets can occur anywhere along a reach segment which can result in different results depending on the variability of the source data being compiled and the distance between the GAGES II basin outlet and the downstream endpoint of the reach segment. NHDPlus version 2 reach segments can be as long as 95 kilometers and some source data can be widely variable within an NHDPlus reach catchment. As a result, some data processed from the location of a GAGESII pour point compared to the downstream end of a reach segment can result in differences in accumulated variables. None None No formal positional accuracy tests were conducted No formal positional accuracy tests were conducted Gregory E. Schwarz Michael E. Wieczorek 2018 tabular data Reston, VA U.S. Geological Survey https://www.sciencebase.gov/catalog/item/5718d2f8e4b0ef3b7cabdc17 online 2018 publication date nhdplusus_v2.sas The source data provided routing information for the NHDPlusV2 flow line network. U.S. Environmental Protection U.S. Geological Survey 2012 vector digital data Reston, VA U.S. Geological Survey http://www.horizon-systems.com/NHDPlus/NHDPlusV2_data.php online 2012 publication date NHDPlus The source data is the basic hydrologic framework used to process these data. 1) Received the mean day of the year of last freeze, from 30 years of Record from the Environmental Protection Agency (Ryan Hill, EPA, written commun., 2006). 2) Mean statistics were calculated for each NHDPlus version 2 reach catchment using ESRI's "ZonalStatisticsAsTable" function in python. 3) An aggregation algorithm was performed on the assigned variables. See the metadata for "Database of Modified Routing for NHDPlus Version 2.1 Flowlines: ENHDPlusV2_US" by Schwarz and Wieczorek in Source_Information for more details on the routing databse. See the landing page for "Select Attributes for NHDPlus Version 2.1 Reach Catchments and Modified Network Routed Upstream Watersheds for the Conterminous United States" for a copy of the aggregation script and its details. 4) Exported results into a comma separated text file format. 20151221 Common Identifier Code for each catchment and reach segment (COMID) LSTFZ6190_CONUS.txt comma separated tabular data U.S. Geological Survey COMID Unique ID to relate to each NHDPlus version 2 catchment and flow line. http://nhd.usgs.gov/NHDDataDictionary_model2.0.pdf Unique numbers that are automatically generated. CAT_LSTFZ6190 Mean Julian year day of the year of last freeze, from 30 years of Record (1961-1990) per NHDPlus version 2 catchment. The values represent the Julian year day of the last freeze. For example, value of 300 is the 300th day of the year (Oct 27th). Values > 365 mean that the last freeze occurs after Dec 31. It is done this way so that (first_freeze - last_freeze) should always give a positive number; high numbers for an area with a long frost-free period (e.g. Florida), low numbers for an area with a short frost-free period. U.S. Geological Survey 0 212 day of year NODATA Percent of catchment that the source data does not cover. -9999 denotes 100% NODATA. U.S. Geological Survey 0.0 100.0 percent ACC_LSTFZ6190 Accumulated mean Julian year day of the year of last freeze, from 30 years of Record (1961-1990) based on divergence routing. -9999 denotes flow line reach is disconnected from the network and cannot be accumulated. The values represent the Julian year day of the last freeze. For example, value of 300 is the 300th day of the year (Oct 27th). Values > 365 mean that the last freeze occurs after Dec 31. It is done this way so that (first_freeze - last_freeze) should always give a positive number; high numbers for an area with a long frost-free period (e.g. Florida), low numbers for an area with a short frost-free period. U.S. Geological Survey 0 212 day of year ACC_NODATA Accumulated percent of catchment that the source GRID does not cover based on divergence routing. -9999 denotes flow line reach is disconnected from the network and cannot be accumulated. U.S. Geological Survey 0.0 100.0 Percentage TOT_LSTFZ6190 Accumulated mean Julian year day of the year of last freeze, from 30 years of Record (1961-1990) based on total upstream accumulation. -9999 denotes flow line reach is disconnected from the network and cannot be accumulated. The values represent the Julian year day of the last freeze. For example, value of 300 is the 300th day of the year (Oct 27th). Values > 365 mean that the last freeze occurs after Dec 31. It is done this way so that (first_freeze - last_freeze) should always give a positive number; high numbers for an area with a long frost-free period (e.g. Florida), low numbers for an area with a short frost-free period. U.S. Geological Survey 0 212 Percentage TOT_NODATA Percent of catchment that the source GRID does not cover based on total upstream accumulation. U.S. Geological Survey 0.0 100.0 Percentage Michael E. Wieczorek U.S. Geological Survey - ScienceBase mailing and physical

Denver Federal Center, Building 810, Mail Stop 302

Denver CO 80225 USA 443-498-5550 mewieczo@usgs.gov Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the U.S. Government may be held liable for any damages resulting from its authorized or unauthorized use. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, 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. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and/or contained herein. 20260326 Michael Wieczorek US Geological Survey mailing and physical

5522 Research Park Drive

Baltimore Maryland 21228 USA 443-498-5550 mewieczo@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998