Key Drivers of Water Quality in Dire and Legedadi Reservoirs, Ethiopia
| dc.contributor.advisor | Kifle, Demeke (PhD) | |
| dc.contributor.advisor | Fetahi, Tadesse (PhD) | |
| dc.contributor.author | Tilahun, Helnata | |
| dc.date.accessioned | 2020-11-25T11:46:42Z | |
| dc.date.accessioned | 2023-11-09T04:21:09Z | |
| dc.date.available | 2020-11-25T11:46:42Z | |
| dc.date.available | 2023-11-09T04:21:09Z | |
| dc.date.issued | 2019-06-06 | |
| dc.description.abstract | Dire and Legedadi reservoirs are the most important freshwater bodies used as surface water sources for the city of Addis Ababa. They are however, facing pollution problem owing to their establishment near fast-growing towns, industrial activities, and intensification of agriculture and the associated application of fertilizers within their catchment areas. Information on physicochemical and biological parameters of the reservoirs is required to manage their living resources and determine their suitability for drinking purpose. In this study, the seasonal and spatial dynamics of physicochemical and biological water quality parameters were therefore, investigated at monthly intervals during 5 months and 2 months of 2018 at three study Sites (Sites 1, 2 and 3) in Dire and Legedadi reservoirs, respectively. All physicochemical and biological parameters were determined with standard methods. Both reservoirs were characterized by unusually high turbidity (19.43-657NTU) throughout the study period mainly due to sediment input through runoff and wind-induced re-suspension of sediment particles. Water transparency of both study reservoirs was extremely low and showed seasonal variations with mean values ranging from 7.2 to 7.6cm (Dire Reservoir) and 4 to 6.5cm (Legedadi Reservoir). The values of water temperature recorded in the present study varied between 15.7 and 21oC. The pH in both study reservoirs was nearly alkaline (6.23-9.2) for most of the sampling months. Higher values were recorded for the concentration of most of the inorganic algal nutrients indicating the nutrient enrichment. Although TDS values were within the range that drinking water should have, high values were recorded throughout the study period. The unusually high turbidity (low water transparency) seems to be the major cause for the deterioration of the water quality in the reservoirs. The phytoplankton community was constituted by five taxa (Cyanophyceae, Chlorophyceae, Bacillariophyceae, Euglenophyceae, and Cryptophyceae) comprising 30 spp. with the dominance of Cyanophyceae including Microcystis aeruginosa, which are associated with public health risk. The zooplankton community comprised three major taxa (Rotifers, Copepods, and Cladocerans, consisting of 20 spp.) with copepod dominance. In general, the hypereutrophic condition in both reservoirs, which was suggested by the estimated TSI values, is indicative of the fact they are suffering from water quality deterioration associated primarily with the high turbidity and nutrient enrichment linked to human disturbance. In addition, the estimated WQI values placed Dire (57.6-73.65) and Legedadi (39.14 - 43.78) reservoirs under the categories of medium and bad water quality, respectively. The results of the present study seem to suggest the urgency of the need to develop workable strategies of restoration and protection from further degradation of the water quality of both reservoirs through catchment-based management since they together cover about 80% of the water demand of the capital and minimize the cost of water treatment and from the results of the present study a year round (seasonal) study is recommended in order to have a full information on the limnology of those reservoirs. | en_US |
| dc.identifier.uri | http://etd.aau.edu.et/handle/123456789/23578 | |
| dc.language.iso | en | en_US |
| dc.publisher | Addis Ababa University | en_US |
| dc.subject | Dire Reservoir | en_US |
| dc.subject | Legedadi Reservoir | en_US |
| dc.subject | Phytoplankton | en_US |
| dc.subject | Trophic Status Index | en_US |
| dc.subject | Water Quality Index | en_US |
| dc.subject | Zooplankton | en_US |
| dc.title | Key Drivers of Water Quality in Dire and Legedadi Reservoirs, Ethiopia | en_US |
| dc.type | Thesis | en_US |