CE 414 Lab 6 - Lake Depth Explorer - Lake Powell data package
Prepared October 1, 2026, Dr. Dan Ames, BYU Civil and Construction Engineering

FILES
  powell_tbdem_30m.tif       Whole-lake elevation surface. 30 m cells, 4,340 x 4,331, float32.
                             Values in METERS above NAVD88 (955.69 to 1,440.73). NoData = -9999.
                             Coordinate system: NAD83(2011) / UTM zone 12N (EPSG:6341).
  powell_wahweap_10m.tif     South-end close-up (Glen Canyon Dam to Antelope Point and Lone Rock).
                             10 m cells, 1,701 x 1,878, METERS NAVD88 (954.77 to 1,318.34),
                             EPSG:6341. Use it to sample ramp toes and to compare
                             cell sizes.
  main_pool_seed.shp         One point in the old Colorado River channel about 2.1 km upstream of
                             Glen Canyon Dam (lake bed about 3,191 ft NGVD29). It is under water at
                             every elevation above dead pool. EPSG:6341.
  powell_elevation_usbr.csv  Daily Lake Powell water-surface elevation, Dec 28 1963 to Sep 30 2026,
                             FEET above NGVD29. Columns: date, elevation_ft_ngvd29.

SOURCE AND PROCESSING
  Elevation surface: Poppenga, S.K., Danielson, J.J., and Tyler, D.J., 2020, One Meter
  Topobathymetric Digital Elevation Model for Lake Powell, Arizona-Utah, 1947-2018: U.S.
  Geological Survey data release, https://doi.org/10.5066/P9XX0J1Y.
  The lake bed is 2017 multibeam sonar; the land around it is 2018 lidar and older topography,
  some of it mapped before the dam closed in 1963. The original is a 1 m raster (3.1 GB).
  What was done to it for this lab:
    - 30 m surface: each 30 m cell is the AVERAGE of the 1 m cells inside it.
    - 10 m surface: each 10 m cell is the AVERAGE of the 1 m cells inside it, for a window
      around the south end of the lake.
    - Values rounded to 0.01 m. NoData rewritten as -9999. Units and datum NOT changed.
  Lake levels: U.S. Bureau of Reclamation, Upper Colorado Region hydrodata, Lake Powell
  (site 919), pool elevation (datatype 49), downloaded October 1, 2026. Recent values are
  provisional.

UNITS AND DATUM - READ THIS
  The surface is in meters above NAVD88. Reclamation's record and every Lake Powell operating
  level (full pool 3,700 ft, minimum power pool 3,490 ft, dead pool 3,370 ft) are in feet above
  NGVD29. At Lake Powell:
      elevation_ft_NGVD29 = (elevation_m_NAVD88 / 0.3048) - 2.91
  The 2.91 ft offset is from the USGS area-capacity report for the 2017-18 survey
  (Scientific Investigations Report 2022-5017, https://doi.org/10.3133/sir20225017).

LICENSE
  USGS and Reclamation data are U.S. Government works in the public domain.

CREDIT LINE FOR YOUR MAPS
  Elevation: USGS 1 m Topobathymetric DEM of Lake Powell 1947-2018 (Poppenga et al. 2020,
  doi:10.5066/P9XX0J1Y), resampled to 30 m. Lake levels: U.S. Bureau of Reclamation.
