Alan Kasprak Nathaniel Bransky Joel B Sankey 20240405 tabular data Flagstaff, AZ U.S. Geological Survey Additional information about Originators: Kasprak, Alan https://orcid.org/0000-0001-8184-6128; Bransky, Nathaniel, https://orcid.org/0000-0003-3113-7491; Sankey, Joel B, https://orcid.org/0000-0003-3150-4992 https://doi.org/10.5066/P1VDGSXE Charles B Yackulic Lucas S Bair Drew E Eppehimer Gerard L Salter Bridget R Deemer Bradley J Butterfield Alan Kasprak Joshua J Caster Helen C Fairley Paul E Grams Bryce Mihalevich Emily C Palmquist Joel B Sankey 2024 cooperator publication Flagstaff, Arizona U.S. Geological Survey https://www.usbr.gov/uc/progact/amp/pdfs/LTEMP/20240408-ModelingImpactsGlenCanyonDamOperationsColoradoRiverResources-508-UCRO.pdf These data were compiled to evaluate impacts of different reservoir management scenarios on sand exposure for aeolian landscape and cultural site resources. Objective of our study was to predict areas of dry, bare Colorado River sand as a function of different management alternative scenarios. These data represent predictions of dry, bare sand for the reach of the Colorado River between Glen Canyon Dam and Bright Angel Creek in Grand Canyon National Park. These data were created during 2023 by the U.S. Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research Center. These data can be used to understand how the area of sand available for windblown transport might be impacted different reservoir management alternatives and scenarios considered in the Near-term Colorado River Operations Supplemental Environmental Impact Statement (Interim Guidelines sEIS) and the Glen Canyon Dam Long-Term Experimental and Management Plan Supplemental Environmental Impact Statement (LTEMP sEIS). The purpose of these data are to demonstrate how areas of dry, bare Colorado River sand might vary as a function of different management alternative scenarios. Cultural resource preservation potential in Grand Canyon National Park (GCNP) increases with larger values of exposed, dry Colorado River sand that is susceptible to windblown (aeolian) transport. These data were created to predict how the area of sand available for windblown transport might be impacted different reservoir management alternatives and scenarios considered in the Near-term Colorado River Operations Supplemental Environmental Impact Statement (Interim Guidelines sEIS) and the Glen Canyon Dam Long-Term Experimental and Management Plan Supplemental Environmental Impact Statement (LTEMP sEIS). The model used here was developed with, and makes predictions of, dry bare sand for the reach of the CRe between GCD (RM -16) and Bright Angel Creek (RM 87). It was not developed to also predict bare sand extent in areas downstream from Bright Angel Creek. Additionally, the drying time component of the model is based on empirical field data of effects of sand drying on aeolian sediment transport collected during March 2021 at Lees Ferry. Locationally-specific sand drying rates depend on numerous other factors that may vary spatially and seasonally, including temperature, solar insolation intensity, and precipitation, among others. The model does not consider effects of implementing High Flow Experiments (HFEs; controlled floods) on the availability of river sand for aeolian transport. HFEs that rebuild sandbars in turn will increase the supply of windblown sand for archaeological sites that are downwind from river sandbars. At present, this model also does not consider effects of variability in wind. Aeolian sediment transport rates increase with frequency of winds above threshold transport velocities, which are more common from March through July of each year. Longer sand exposure times during the spring and summer seasons combined with HFEs may additionally increase the supply of sand for downwind archaeological sites. 1991 2020 ground condition Complete None planned -114.02 -110.84 37.22 35.74 Upper Colorado River Basin USGS Thesaurus geomorphology modeling freshwater ecosystems river systems sand deposits sedimentation unconsolidated deposits USGS Metadata Identifier USGS:65d8eb72d34ec3e1801e3c0e USGS information products data release ISO 19115 Topic Categories geoscientificInformation inlandWaters None aeolian archaeology cultural dam reservoir subaerial Geographic Names Information System (GNIS) Arizona Coconino County Colorado River Glen Canyon Grand Canyon Lake Powell Getty Thesaurus of Geographic Names Glen Canyon Dam none none Joel B Sankey U.S. Geological Survey Research Geologist mailing and physical

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Flagstaff AZ 86001 United States 928-556-7289 jsankey@usgs.gov This work was supported by the U.S. Bureau of Reclamation. Alan Kasprak Joel B Sankey Bradley J Butterfield 2021 IOPscience (online) Environmental Research Letters https://doi.org/10.1088/1748-9326/abc9e4 Joel B. Sankey Joshua Caster Alan Kasprak Helen C. Fairley 2022 Wiley Online Library Journal of Geophysical Research: Earth Surface https://doi.org/10.1029/2022JF006816 Error associated with the model estimates is described in the documentation of the published methods in Kasprak et al., 2021 and Sankey et al., 2022. Attribute values are within expected ranges. Data set 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. Development of the NoAction.csv and ProposedActionAlternative.csv data tables: A model (Kasprak et al., 2021) was implemented that predicts the area of bare, dry sand for the upper ~103 miles of Grand Canyon between GCD and Phantom Ranch/Bright Angel Creek. The model uses (1) a timeseries of daily maximum discharge from GCD, (2) estimates of total exposed bare sand area for given discharge of Colorado River water released from Glen Canyon Dam. The model additionally modifies the estimates of total exposed sand area to incorporate its subaerial exposure time, as longer exposure times result in progressively drier, and thus more transportable, sand. To produce these data in these tables, the model was run using individual hydrographs that are unique to each year and ensemble streamflow prediction of the management alternative scenario evaluated. 2023 Development of hourly_cfs_CM_FS_RM15_parsed.csv to hourly_cfs_NW_parsed.csv data tables (11): A model (Kasprak et al., 2021) was implemented that predicts the area of bare, dry sand for the upper ~103 miles of Grand Canyon between GCD and Phantom Ranch/Bright Angel Creek. The model uses (1) a timeseries of daily maximum discharge from GCD, (2) estimates of total exposed bare sand area for given discharge of Colorado River water released from Glen Canyon Dam. The model additionally modifies the estimates of total exposed sand area to incorporate its subaerial exposure time, as longer exposure times result in progressively drier, and thus more transportable, sand (Sankey et al., 2022). To produce these data in these tables, the model was run using individual hydrographs that are unique to each trace of the management alternative scenario evaluated. 2023 Data Quality Assessment and Quality Control (QAQC): A formal QA/QC was not performed. Project staff reviewed the predictions data and discussed the modelling methods and results. 2023 Finalize Data for Dissemination: Data sent to the Southwest Biological Science Center Data Steward for dissemination and preservation per USGS Data Management Policies SM 502.6, SM 502.7, SM 502.8 and SM 502.9 (1 October 2016). 2024 NoAction.csv and ProposedActionAlternative.csv These data tables represent predictions of dry, bare sand for the reach of the Colorado River between Glen Canyon Dam and Bright Angel Creek in Grand Canyon National Park as a function of management alternatives and scenarios considered in the Near-term Colorado River Operations Supplemental Environmental Impact Statement (Interim Guidelines sEIS).The purpose of these data tables are to demonstrate how the area of dry, bare sand available for aeolian transport may be impacted by alternatives considered in the Interim Guidelines sEIS. NoAction = no action alternative, ProposedActionAlternative = proposed Action alternative. Producer defined Scenario This attribute in the data table represents the year and ensemble streamflow prediction of the management alternative scenario evaluated. Producer defined 1991_80 to 2020_100 Mean Daily Exposed Sand Area (m2) This attribute in the data table represents the mean daily exposed sand area predicted for the year and ensemble streamflow prediction of the management alternative scenario evaluated. Producer defined 1353474.699 1724174.86 square meters Median Daily Exposed Sand Area (m2) This attribute in the data table represents median daily exposed sand area predicted for the year and ensemble streamflow prediction of the management alternative scenario evaluated. Producer defined 1354259 1730261 square meters Standard Deviation of Daily Exposed Sand Area (m2) This attribute in the data table represents the standard deviation of the daily exposed sand area predicted for the year and ensemble streamflow prediction of the management alternative scenario evaluated. Producer defined 94671.19788 259595.87 square meters hourly_cfs_CM_FS_RM15_parsed.csv to hourly_cfs_NW_parsed.csv (11 data tables) These data tables represent predictions of dry, bare sand for the reach of the Colorado River between Glen Canyon Dam and Bright Angel Creek in Grand Canyon National Park as a function of management alternatives and scenarios considered in the Glen Canyon Dam Long-Term Experimental and Management Plan Supplemental Environmental Impact Statement (LTEMP sEIS). The predictions are based on hourly timestep hydrographs of Colorado River discharge in cubic feet per second (cfs) that were parsed from management alternative and scenario datasets. The purpose of these data tables are to demonstrate how the area of dry, bare sand available for aeolian transport may be impacted by alternatives considered in the LTEMP sEIS. Data files names are structured as: hourly = hourly; cfs = cubic feet per second; parsed = analyzed from management alternative and scenario datasets; CM = cool mix alternative; CS = cold shock alternative; FS = flow spikes alternative; NA = no action alternative; NB = non-bypass alternative; NW = new high flow experiment window only alternative; RM15 = triggered by river mile 15 water temperatures; 61 = triggered by river mile 61 water temperatures. Producer defined Trace This attribute in the data table represents the unique hydrological trace of the management alternative scenario evaluated. There are 30 total hydrological traces. Producer defined 1 30 integer number Mean Daily Exposed Sand Area (m2) This attribute in the data table represents the mean daily exposed sand area predicted for the unique trace of the management alternative scenario mean daily exposed sand area predicted for the management alternative. Producer defined 1374897.318 1622446.576 square meters Median Daily Exposed Sand Area (m2) This attribute in the data table represents median daily exposed sand area predicted for the unique trace of the management alternative scenario. Producer defined 1368566.52 1638280.12 square meters Standard Deviation of Daily Exposed Sand Area (m2) This attribute in the data table represents the standard deviation of the daily exposed sand area predicted for the unique trace of the management alternative scenario. Producer defined 117146.2857 269390.74 square meters GS ScienceBase U.S. Geological Survey mailing and physical

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Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov The author(s) of these data request that data users contact them regarding intended use and to assist with understanding limitations and interpretation. 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 for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. This file contains data available in comma-separated values (csv) format. The user must have software capable of displaying the data table. 20240412 Joel B Sankey U.S. Geological Survey Research Geologist mailing and physical

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Flagstaff AZ 86001 United States 928-556-7289 jsankey@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998