Remote Sensing Applications for Assessment of Seepage from Artificial Reservoir: Case Studies from the Nile Basin, Africa
Abstract
We used static (Copernicus Digital Elevation Model), and temporal satellite data analysis (GRACE and GRACE-FO, Sentinel-1, 2, MODIS, Radar altimetry) to quantify seepage from the main artificial reservoirs on the Nile River, namely Lake Nasser behind the Aswan High Dam and the Grand Ethiopian Renaissance Dam (GERD) reservoir. The Aswan high Dam (storage capacity:162 km3) was built over Pan African basement complex and its reservoir extends in southern Egypt and northern Sudan (area: 4530 km2). The reservoir is bound by a plateau formed largely of highly-fractured karstic Eocene limestone and the Nubian Sandstone of Cretaceous age. Our previous studies have shown that between 2010 and 2015, the seepage from Lake Nasser ranged from 7.7 to 18 km3/yr. The GERD was built over the Pan African highlands in western Ethiopia and upon completion, its reservoir will cover an area of 1,904 km2 and impound 74 km3. The reservoir will extend over Precambrian metamorphic rock units (metavolcanics, metasediments, biotite gneiss, metadiorite, metagabbro, marbles), syntectonic intrusives (granite, metagranodiorite, metatonalite, granitoids), late and post tectonic grantic intrusives, calcite, dolomite, and Tertiary basalts. The basement rock units are characterized by deep regolith (up to 60 m) and a highly deformed texture, related to NE-SW extension associated with the breakup of Gondwana and NW-SE-directed extension and opening of the Main Ethiopian Rift. The extended and recurrent tectonic activities left behind a highly deformed landscape in western Ethiopia. Findings reveal the following. (1) The target filling for the GERD in years one (2020) and two (2021) far exceeds the Lake storage extracted from Sentinel-1 but is comparable to that from GRACETWS solutions over the GERD reservoir and its immediate surroundings. (2) Sentinel-1 captures the variations in the reservoir storage, whereas GRACE, with its large footprint (102,000 km2 in our case), measures storage variations in the Lake and its surroundings that receive recharge from the GERD reservoir. (3) Continuous monitoring of the GERD and its Reservoir with temporal satellite data provides efficient, cost-effective data sharing, fact finding, and ultimately adequate and fair resolution of water-related conflicts between the source and downstream countries.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.H25R1326S