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Accueil du site → Master → Pays Bas → 2012 → The use of satellite altimetry for water resources management : case study of the Nile Basin.

UNESCO-IHE Institute for Water Education, Delft (2012)

The use of satellite altimetry for water resources management : case study of the Nile Basin.

Muala, E.

Titre : The use of satellite altimetry for water resources management : case study of the Nile Basin.

Auteur : Muala, E.

Université de soutenance : UNESCO-IHE Institute for Water Education, Delft

Grade : Master of Science (MS) 2012

The Nile basin is a transboundary basin shared by eleven riparian countries, with varying needs and demands for the shared water resources. There is competition among different sectors and functions, as well as between downstream and upstream countries. The water demands have impacts beyond the border of each country. To manage the water effectively, it requires the use of hydrological data for transboundary water resources planning and management. However, there are already limited data available and number of gauging stations is declining. Furthermore, access to in-situ data among countries is at times very difficult. This research presents the use of satellite data to determine water levels, and volume variations of Roseires Reservoir (Sudan) and Aswan High Dam /Lake Nasser (Egypt). The satellite data have also been used to determine reservoir release in each case. The outcomes are compared with in-situ measurements to assess their accuracies. The volume is estimated by integrating the area-level relationship of the reservoir. The area is derived from Landsat TM/+ETM images using NDWI (Normalised Difference Water Index). Water levels are obtained from two satellite altimetry databases i.e. Hydroweb and GRLM (Global Reservoir and Lake Monitoring). The altimetry water levels from Hydroweb for Roseires reservoir compare well with in-situ measurements (R2 = 0.96) and RMSE between the two datasets is 90 cm. The estimated volumes are also in good agreement with in-situ volume measurements with a R2of 0.95, and the RMSE is 22% of the mean volume. The estimated reservoir release computed from satellite and altimetry data using a simple water balance equation of the reservoir agrees well with measurements, with R2of 0.98 and RMSE of 17%. The results for Lake Nasser showed RMSE of 60 cm and R2 of 0.88 for altimetry water levels, while for the estimated volumes R2 is 0.88, and RMSE is 39% of the mean measured volume. This large volume difference also affected the further computed reservoir releases (R2 is 0.31 and RMSE of 236.2%). The error could also be attributed to unaccounted water releases or spills to Toshka Lake which occur at exceptionally high flood. Secondly, Lake Nassir is a very shallow reservoir (area is 6000 km²), and small error in water level may reveal high in reservoir releases. Therefore, it can be concluded that, satellite measurements (satellite altimetry water levels and satellite imagery data) can be used for the operation of Roseires Reservoir with a fairly low uncertainty, while the errors are large to allow a sensible operation for Lake Nasser.

Sujets  : satellites reservoirs water levels nile basin case studies


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