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.