Reservoir-Induced Crustal Deformation: Case Study from the Grand Ethiopian Renaissance Dam

Abstract:

The Nile River stretches from south to north in northeast Africa throughout the Nile River Basin (NRB). The main sources of the Nile River are the While and Blue Niles. The NRB is extended over 11 African countries and represents a home for an estimated 300 × 10⁶ people, majority of whom live in rural areas. The transboundary nature of the NRB contributes to political conflicts and disputes on the NRB’s water resources. Ethiopia, where the Blue Nile originates, has launched a major project to construct the Grand Ethiopian Renaissance Dam (GERD) to generate electricity. In this study, we developed a novel approach for predicting land deformation as well as changes in water storage induced by the construction of GERD reservoir. Specifically, we have simulated three land deformation scenarios related to filling of 74 km³ (expected reservoir volume) using 5-, 10-, and 15-year filling strategy. Our preliminary results indicate that: (1) once the impoundment is complete, the surface area of the GERD reservoir will reach 1773 km² with an average water thickness of 42 m, (2) the average downward vertical displacement is estimated at 170, 86.4, and 57.6 mm/year for the 5-, 10-, and 15-year filling strategy, respectively, (3) the east and west parts of the reservoir are estimated to move toward the reservoir’s center by 45, 23, and 16 mm/year, respectively, during the three scenarios, and (4) the north part of the reservoir is moving southward at a rate of 63.6, 32.4, and 21.6 mm/year, while the south part is moving northward at 40.8, 20.4, and 14.4 mm/year, during the three examined scenarios, respectively. Our results provide significant insights on how current (e.g., GRACE-FO) and future (e.g., GRACE-II) gravity missions could detect spatiotemporal variability in terrestrial storage and deformation induced by constructions of water alteration projects across the globe.