Reservoir Assessment


Remote sensing data can be used to assess the volume of water in lakes and reservoirs using time series of satellite images. GRAS has developed a technique for this based on time series of satellite images.

Data
Landsat (15-30 m resolution) and SPOT (2.5 - 20 m resolution) are the most relevant data sets as they have suitable spatial resolutions and extensive archives are available. Landsat is the most cost-effective solution as the data are cheaper. Furthermore, GRAS already has a large Landsat data archive.

Times series of data to map volume changes
The illustration above shows four different Landsat scenes through the year with different water levels. This information can be used to generate a Digital Elevation Model of the area between maximum and minimum water level and thus the change in water volume over time.

Mapping bathymetry
For hydropower management the essential water volume information is the volume between maximum and minimum water levels and this information can be extracted from optical remote sensing data. However, if the client needs to know the bathymetry under the minimum water level this can be obtained through echo sounding transects in the deeper part of the lake. This information can be integrated into the DEM. Information about elevations in the rest of the catchment can be included from a DEM covering the upland areas.