Assessing Reservoir Sedimentation Using Multidate Landsat Imagery
Ideally, bathymetric reservoir surveys are conducted about once per decade and typically cost between $50,000 to $500,000, require one or two weeks of field data collection, and a few months of staff time to process the data and produce new and detailed surface area and storage capacity tables. In between these detailed bathymetric surveys, a less expensive and coarser method is to use satellite measurements of RSA to assess reduced reservoir surface area and volumes due to sedimentation. Although numerous earth resource satellites provide imagery that could be used for this application, Landsat images were chosen for use in this study because the Landsat archive contains radiometrically-calibrated and orthorectified moderate-resolution imagery (30 m pixel size) going back to 1984, all of which are available free of charge from the U.S. Geological Survey. The consistent nadir-look of the Landsat satellites also limits sun glint from lakes and reservoirs, allowing for more reliable, automated identification of water pixels.
Need and Benefit
In the absence of sediment management, all reservoirs have a finite lifetime, as sedimentation gradually reduces available storage volume over time. These reductions are quantified using hydrographic surveys that measure changes to reservoir bathymetry over time. Bathymetric survey data obtained from singlebeam or multibeam echo sounder data at a given reservoir elevation are combined with terrestrial elevation data generated from either high-resolution image or LiDAR (light detection and ranging) data acquired when the reservoir is at a lower elevation. The result is a continuous bathymetric surface from maximum pool elevation to the bottom of the reservoir, from which reservoir surface areas and volumes can be calculated.
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Bureau of Reclamation Review
The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.
Assessing Reservoir Sedimentation Using Multidate Landsat Imagery (final, PDF, 3.8MB)
By David Eckhardt
Report completed on September 30, 2020