Physicochemical Characterization of Dembi Reservoir Water for Suitability of Fish Production, Southwest Ethiopia.

Reservoir water physicochemical characteristics provide important information about water suitability for fish production. Accordingly, the study aimed to characterize the physicochemical characteristics of Dembi reservoir water for sustainable fish production. The study was conducted in Dembi reservoir during the dry season. Water samples were collected in triplicate from selected 10 sampling sites of the reservoir water using manually prepared water sampler made from polyvinyl chloride (PVC) tube. The depth integrated sampling technique was employed to take water samples for all physicochemical characteristics analysis. From the selected 14 physicochemical characteristics, four (temperature, electrical conductivity, pH, and dissolved oxygen) were tested onsite using a multisystem HQ4d electronic meter (probe), whereas the rest 10 water quality characteristics were tested in the laboratory. The result showed that the current average depth of the dam was 5.6 ± 1.61 m. The overall mean values of the water quality characteristics at different sites of the reservoir were as follows: turbidity (26.4 ± 0.44 FTU), total hardness (22.2 ± 0.51 mgL^-1), NO₃ (5.4 ± 0.48 mgL^-1), NO₂ (0.3 ± 0.11 mgL^-1), NH₄ (2.1 ± 0.06 mgL^-1), PO₄ ^-3 (1.7 ± 0.27 mgL^-1), total alkalinity (52.5 ± 0.91 mgL^-1), and BOD₅ (2.7 ± 0.24 mgL^-1). There was a significant difference (p < 0.05) in all physicochemical characteristics among 10 sampling sites of the reservoir water. The recorded values of all physicochemical characteristics, except NO₂, NH₄, and PO₄ ^-3, were found within the recommended standard limit for fish production. The change in reservoir water depth and increase in nutrients shows the presence of sediment siltation and nutrient enrichment. Therefore, proper watershed management practices and waste management should be carried out for sustainable water quality maintenance and fish production.