The investigation of the zooplankton community in the newly formed Ribb Reservoir, Ethiopia: the tropical highland reservoir.

Understanding the composition, diversity, and abundance of the zooplankton community is crucial for better utilization of the Ribb Reservoir, as zooplankton are the second link in the food chain in aquatic systems (they are also excellent bioindicators of aquatic health, given their central food web position) and the reservoir also serves as a source of income for the fishers. Therefore, sampling including some water quality parameters was conducted twice in the four seasons: autumn, summer, spring, and winter, from September 2020 to August 2021, in the first week of September, December, February, March, May, June, and August. Most of the physicochemical parameter values recorded in this study indicated that they were within the range of standards for zooplankton community requirements. Of the 14 species identified, Mesocyclops aequatorialis similis, T hermodiaptomus galebi, and Brachionus angularis had the first, second, and lowest records, respectively. Species abundance showed a decrease from autumn to winter and then to spring and summer. Species richness (14), abundance (6736), Margalef's diversity index (1.48), Menhinick's diversity index (0.17), Simpson index (0.098), dominance index (0.902), Shannon index (2.47), equality index (0.934), and reciprocal Simpson index (10.2) of the species were calculated in the reservoir. Some of the proposed management measures include reservoir buffering, impact assessment of over-abstraction of water for irrigation, time series of water quality data, and the reservoir water level should be above the conduit.

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

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.

Potential impact and mitigation measures of pump irrigation projects on Lake Tana and its environs, Ethiopia.

Environmental Impact of pump irrigation projects from Lake Tana (Megech - Seraba, Tana Asrate, Tana Mekonta, Tana Wenjeta, and Tana Zegie) was studied from July 2018 to February 2019. Interactions between project activities and environmental parameters were also done by a matrix, and quantitative and qualitative analysis. As a result, identified positive impacts are new job creation, the opportunity to promote traditional agriculture and income increase, whereas land, fisheries and wetland degradation, pollution, deforestation and wildlife, inefficient water use, the decline in soil fertility, erosion, sedimentation, small aquatic animal death, and cumulative impacts are negative ones. Mitigation measures for these impacts to reduce their effects to the minimum level and recommendations have been proposed so that the execution of the projects becomes a success without harming or with the least negative effect on the environment.