Abstract:
As water regulates fish’s life functions such as feeding, swimming, breeding, digestion, and
excretion; the change in water quality and availability due to existing natural or
anthropogenic activities can adversely affect its production. Physico-chemical water quality
characteristics provide important information about the suitability of water for fish
production. Thus, the objective of this study was to determine the physico-chemical
characteristics of Dembi reservoir water in relation to fish production. The study was
conducted during dry season (February, 2019). Water samples were collected in triplicate
from selected 10 sampling stations of the reservoir water using manually prepared water
sampler made from polyvinyl chloride (PVC) tube. Depth integrated sampling technique was
employed to take water samples for physico-chemical characteristics analysis. From the
selected 14 physico-chemical characteristics, four (temperature, electrical conductivity (EC),
pH and dissolved oxygen (DO)) were tested onsite using a multi-system HQ4d electronic
meter (probe), whereas the rest 10 water quality parameters 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
value of turbidity (26.4±0.44 FTU), temperature (26.7±0.36 °C), conductivity (51.0±1.14 μS
cm-1), pH (7.7±0.07), DO (4.6±0.12 mg L-1), total hardness (22.2±0.51mg L-1), nitrate (NO3-N)
(5.4±0.48 mg L-1), nitrite (NO2-N) (0.3±0.11 mg L-1), ammonia (NH4-N) (2.1±0.06mgL-1), total
Phosphorus (3.0±0.16 mg L-1), soluble respective phosphorus (PO4-P) (1.7±0.27mgL-1), total
alkalinity (52.5±0.91mgL-1), calcium (4.2±0.11 mg L-1), and BOD5 (2.7±0.24 mg L-1) were
recorded at the reservoir water. 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 physico-chemical characteristics, except NO2-N, NH4-N, and PO4
-3–P, were found
within the recommended standard limit for fish production. Nutrient loss and leaching from
agriculture land, coffee processing station, municipal solid waste dumping site and residential
wastes were responsible for the increase in those characteristics. 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.
