Basooma Anthony, Schmidt-Kloiber Astrid, Basooma Rose, Nakiyende Herbert, Kowal Johannes, Funk Andrea, Hein Thomas, Borgwardt Florian
BOKU University, Institute of Hydrobiology and Aquatic Ecosystem Management, Vienna, Austria.
BOKU University, Institute for Integrative Nature Conservation Research, Vienna, Austria.
PLoS One. 2025 Apr 29;20(4):e0322338. doi: 10.1371/journal.pone.0322338. eCollection 2025.
Dams offer indispensable services, including hydropower generation, water for irrigation, and flood mitigation. These barriers disrupt natural river flows, affecting river ecosystems structural and functional connectivity. The number of hydropower dams in the Nile River Basin has increased during the last decades. However, little is known regarding the spatiotemporal variation in the river network fragmentation and the individual dam contributions. We used the Reach Connectivity Index (RCI) and network centrality measures to assess temporal and spatial changes in longitudinal connectivity. We selected the Equatorial Nile and Blue Nile basins, the major hotspots for present and future hydropower developments. We collated 101 existing, under construction, and proposed dams in the Equatorial Nile Basin (ENB) from 1954 to 2035 and 19 dams in the Blue Nile Basin (BNB) from 1925 to 2035. The dams in the ENB have significantly increased over time, with a sharp increase recorded between 2010 and 2015. The mean RCI for the BNB, considering impassable dam scenarios, ranged from 62.5% (SD = 12.5%) in 1925 to 21.35% (11.6%) in 2035. Similarly, in the ENB, the mean RCI for impassable dam scenarios ranged from 50.1% (SD = 2%) in 1954 to 18.1 (12.1%) in 2035. River segments in the middle section of both basins were the most affected. The decline in the mean RCI was significantly higher in the ENB compared to BNB. The reduced connectivity is mainly in the ENB, threatening the basin's biodiversity. Existing dams, including the Grand Ethiopian Renaissance Dam on the BNB and Kakono on the ENB, should have effective fish migratory corridors that allow the passage of fish either upstream or downstream. We also recommend establishing a detailed basin-wide database for barriers and assessing their passability to understand the full extent of the river network fragmentation. We also recommend regular monitoring of barrier impacts by integrating safe, cost-effective methods such as remote sensing and environmental DNA (eDNA) to assess both flora (macrophytes, phytoplankton) and fauna (macroinvertebrates, fish, zooplankton).
大坝提供着不可或缺的服务，包括水力发电、灌溉用水以及防洪。这些屏障扰乱了天然河流的水流，影响着河流生态系统的结构和功能连通性。在过去几十年间，尼罗河流域的水电站大坝数量有所增加。然而，对于河网破碎化的时空变化以及各个大坝的影响，我们却知之甚少。我们使用河段连通性指数（RCI）和网络中心性度量来评估纵向连通性的时空变化。我们选取了赤道尼罗河和青尼罗河流域，这两个流域是当前及未来水电开发的主要热点地区。我们整理了1954年至2035年赤道尼罗河流域（ENB）101座已建、在建和规划中的大坝，以及1925年至2035年青尼罗河流域（BNB）19座大坝的相关信息。赤道尼罗河流域的大坝数量随时间显著增加，在2010年至2015年间出现急剧增长。考虑不可通行大坝的情况下，青尼罗河流域的平均RCI从1925年的62.5%（标准差 = 12.5%）降至2035年的21.35%（11.6%）。同样，在赤道尼罗河流域，不可通行大坝情况下的平均RCI从1954年的50.1%（标准差 = 2%）降至2035年的18.1（12.1%）。两个流域中部的河段受影响最为严重。赤道尼罗河流域平均RCI的下降幅度明显高于青尼罗河流域。连通性的降低主要发生在赤道尼罗河流域，威胁着该流域的生物多样性。现有大坝，包括青尼罗河流域的埃塞俄比亚复兴大坝和赤道尼罗河流域的卡科诺大坝，应设有有效的鱼类洄游通道，以允许鱼类上下游通行。我们还建议建立一个全流域范围的详细屏障数据库，并评估其可通行性，以全面了解河网破碎化的程度。我们还建议通过整合安全、经济高效的方法，如遥感和环境DNA（eDNA），定期监测屏障的影响，以评估动植物（大型植物、浮游植物）和动物（大型无脊椎动物、鱼类、浮游动物）的情况。
