Impact of irrigation practices on Gilgel Abay, Ribb and Gumara fisheries, Tana Sub-Basin, Ethiopia

Abstract

In Ethiopia, particularly in Tana Sub-Basin, irrigation development practice is increasing. However, this development ignored the fisheries; no, enough information about its effects. The sub-basin is rich in fisheries, including the 17 Labeobarbus species (the only remaining cyprinid species in the world). The fishery is also supporting over 6000 fishers. Hence, this study investigated the impact of irrigation practices on the Gilgel Abay, Ribb, and Gumara fisheries. Methods include fish sampling below and above the weirs, expert interviews, key informant interviews, secondary data, and impact significance matrix methods. The data collection time was from July 2019 to June 2020. The analysis of the data was qualitative and quantitative. The existing irrigation system affects fisheries by blocking upstream spawning migration routes (Gilgel Abay Weir and Ribb Dam, for sure catch below the Gilgel Abay Weir, significantly higher than above the weir, Shannon Index (H’), P < 0.001). Besides, according to local sources, after 2007, Gumara and Ribb Rivers became seasonal because of excessive water abstraction for irrigation, resulting in mass fish-killing and the failure of juvenile recruitment to the lake. In one instance, we recorded the deaths of over 930 adults and juveniles on the Gumara and the Ribb Rivers. Succeeding low water volume, even non-fishers collect fish from the pools; and during spawning time, fishers target spawning migratory species at the weirs where the catch is prime is also the other problem. Other threatening elements can also aggravate the impact. Hence, these impacts need to be ameliorated by practicing efficacious water use, catchment treatment, fishery management, fish ladder development, and factor alleviation can be solutions.

The newly built Ribb Reservoir fisheries, Tana Sub‐basin, Ethiopia: New fishery establishment, diversity, production, challenges and management

“…Although the dam has caused problems with spawning migration, the newly formed Ribb Reservoir has established a new fishery production; as a result, the reservoir is a means of income for over 104 fishers. Similar to the ideas of many studies (Nilsson et al., 2005; Poff et al., 2007; Dudgeon, 2010; Fitzhugh and Vogel, 2011; Grill et al., 2019; Arantes et al., 2019; Mequanent et al., 2021), and the information gained from the discussion, the Ribb River impoundment also results in fairly predictable changes in the downstream, reservoir and upstream of the river system (Figure 4). Thus, the effects are expected to be not limited to the reservoir and often extend to reach far upstream and downstream of the dam.…”

“…However, after the Ribb Dam, the two (parents and their juveniles) could not enter the lake, and new upstream spawning migrations collapsed because of the absence of fish passages (Mequanent et al., 2021). Hence, there was a cutoff to Lake Tana's spawning migratory Labeobarbus species.…”

“…The Labeobarbus species in Lake Tana affected by irrigation practices are the best examples because their migration route has been blocked by the Ribb Dam and weir in Gilgel Abay (Mequanent et al. 2021) and the Shini and Gelda Rivers (Gebremedihin et al., 2017). However, irrigation has also created livelihood opportunities for fishers and changed the economic environment and institutional arrangements (Lorenzen et al., 2007).…”

“…However, irrigation has also created livelihood opportunities for fishers and changed the economic environment and institutional arrangements (Lorenzen et al., 2007). For example, the recent Ribb Reservoir supplies a source of income for over 76 fishers, but due to their heavy involvement in this reservoir, it has resulted in a conflict over resource use (Mequanent et al., 2021).…”

Floristic Diversity, Population Structure, Regeneration Status and Socio-Economic Importance of Fach Forest, South Gondar, Northwestern Ethiopia

“…Fach forest forms part of the Lake Tana Sub-Basin, which is the northeastern part of the Blue Nile Basin (Mequanent et al 2021). It also forms part of the Eastern Afromontane Biodiversity Hotspot (Mittermeier et al 2004).…”