Generating High-Resolution Lake Bathymetry over Lake Mead using the ICESat-2 Airborne Simulator

Precise lake bathymetry (i.e., elevation/contour) mapping is essential for optimal decision making in water resources management. Although the advancement of remote sensing has made it possible to monitor global reservoirs from space, most of the existing studies focus on estimating the elevation, area, and storage of reservoirs—and not on estimating the bathymetry. This limitation is attributed to the low spatial resolution of satellite altimeters. With the significant enhancement of ICESat-2—the Ice, Cloud & Land Elevation Satellite #2, which is scheduled to launch in 2018—producing satellite-based bathymetry becomes feasible. Here we present a pilot study for deriving the bathymetry of Lake Mead by combining Landsat area estimations with airborne elevation data using the prototype of ICESat-2—the Multiple Altimeter Beam Experimental Lidar (MABEL). First, an ISODATA classifier was adopted to extract the lake area from Landsat images during the period from 1982 to 2017. Then the lake area classifications were paired with MABEL elevations to establish an Area-Elevation (AE) relationship, which in turn was applied to the classification contour map to obtain the bathymetry. Finally, the Lake Mead bathymetry image was embedded onto the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM), to replace the existing constant values. Validation against sediment survey data indicates that the bathymetry derived from this study is reliable. This algorithm has the potential for generating global lake bathymetry when ICESat-2 data become available after next year's launch.