Fig 1.
Overview of the investigation area: The Blue Nile Basin (BNB) (A) and Equatorial Nile Basin (ENB) (B) from the Nile River Basin (NRB).
Maps on the left show the location of the Nile River Basin within Africa (upper left) and the location of BNB and ENB in the NRB (lower left). The basin layers were extracted from RiverATLAS and BasinATLAS_v10_lev4 [42]. The points indicate dam locations extracted from [40,44,45]. Reprinted from [https://www.hydrosheds.org/hydroatlas] under a CC BY license, with permission from [HydroSHEDS], original copyright [2022].
Fig 2.
Trends in dam construction during different periods for Blue Nile Basin (BNB) and Equatorial Nile Basin (ENB).
The first dam construction was reported on the BNB in 1925 compared to 1954 on ENB. However, a significant increase in the dams proposed for construction and already under construction was recorded in the ENB, with a noticeable surge after 2010.
Fig 3.
Trends in the reach connectivity index for the Blue Nile Basin (black line) and Equatorial Nile Basin (blue line) under varying dam passability scenarios.
The horizontal black dotted line is the threshold when the connectivity reduces to 50% of the natural connectivity without dams on the network. *: 0.01 **: 0.001, and ns: not significantly different from the threshold.
Fig 4.
Principal component analysis of the network connectivity index and network centrality measures for the Blue Nile and Equatorial Nile Basins.
Fig 5.
The network centrality measures and connectivity scores of the Blue Nile Basin.
A dam passability of 0.5 was used, and river segments of all stream orders (1 to 7) and all dams were considered. Reprinted from [https://www.hydrosheds.org/hydroatlas] under a CC BY license, with permission from [HydroSHEDS], original copyright [2022].
Fig 6.
The network centrality and RCI of the Equatorial Nile Basin.
A dam passability of 0.5 was used, and river segments of all stream orders (1 to 7) and all dams were considered. Reprinted from [https://www.hydrosheds.org/hydroatlas] under a CC BY license, with permission from [HydroSHEDS], original copyright [2022].
Fig 7.
The correlation coefficient among centrality measures and RCI for both basins.
Fig 8.
Log transformed dam contribution to fragmentation of the river network.
(a) The dam contribution uses the leave-on-out principle in the Blue Nile Basin. (b) dam contribution using the leave-one-out principle in the Equatorial Nile Basin (ENB).