Browsing by Author "Alemayehu, Tamiru (PhD)"

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    Hydrogeological Controls in Sandstone of Ambo Area
    (Addis Ababa University, 2001-06) Mekonta, Loemessa; Alemayehu, Tamiru (PhD)
    The study area is a sub catch::lent of Abay drainage biCsin wi th a total surface area and ?erimeter of 838km2 and 171km respectively. Two , :her regional drainage basins border the catchment: the Awash drainage basin to th e east and southeast, and the Ghib"- Omo drainage basin to (, e south. The :nain rock outcrops in L0.e area are the basalt:: lava flow of Tertiary and Quaternary age, trachytic lava [ ow and pyroclastic depose,s of Quaternary age . and the Mesozoic sandstone. Application of different modeling techniques shows that the sandstone is part of the Upper 5aIldstone sequence. On annual basis, the area has 1143.3mm, 809mm 2..c'ld 162.8mm of mean total rainfall, Actual Evapotranspiration (AET), and grounr:water recharge respectively. There exist various water bodies in the area: two crate~ lakes (Lake Dandi and Lake Wanchi with a total surface area of 7.4 and 4km2 re s~ectively), river , streams, and springs (both thermal and cold springs) . Hydrogeological descriptions of the lithological units in the area IS mainly based on qualitative interpretation emplo,ing various approaches such as degree of weathering and fracturing, existence/or absence of springs, vege:ation cover, soil co,'er, etc. Despite the presence of many wells there is only a limiter: well data. However , there are some wells with well data tom which some hydraulic parameters ha,'e been determined. The existing well data as well as the qualiE tive interpretation show that the main aquifer in the area are the fractured andj or weathered basaltic lava flowfoHowed by alluvial sediments along some streams, and sandstone. The first two are aquifers for cold groundwater whereas the sandstone is mainly an aquifer of the thermal/or mineral water. Some hydraulic parameters have been determined for these aquifers; accordingly, the basaltic lava flow has a hydraulic conductivity and transmissivity of 3.7 x lO·sm/s to 3.9 x 10sm/s and 97- 100 m2/day respectively. The alluvial sediments have a transmissivity of 23.9m2/day on average. Where as, the sa:1dstone has a transmissivity of 76.5m2/day. The existence of highly permeable units (intensively fractured trachytic lava flow and u nwelded tuf~ at the elevated lands of Dandi and Wan chi at the southern part of the study area favors them to be a recharge area. If comparison is made with in the limit of the study area, good ground water potential with low Total Dissolved Solids (TDS) is found to the eastern side of Ambo town. Thermal and/or mineral water in the area is structurally controlled; the alignment of the thermal springs along the nearly east- west oriented fault line in Ambo area can justify the situation. Currently, the thermal springs are limited to a given area, mainly in Ambo tov-n; but their past extent can be inferred from the travertine deposit in the area whose thermal origin can be verified from the existence of silica sinter with it.
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    Water Pollution/Quality Assessment in Relation to Wet Coffee Processing Plants in Surface and Shallow Groundwater in Sidama and Gedeo Zones (SNNPR)
    (Addis Ababa University, 2005-06) Gobena, Mesfin; Alemayehu, Tamiru (PhD)
    The study area located in Southern Nation and Nationality People Region (SNNPR) and encompass Sidama & Gedeo Zones that are among all the coffee growing region of Ethiopia, bounded between 37° 54'N to 39°8 N latitude and 5° 52'E to 7° 13'E longitude in which most part of it situated in the rift valley lakes basin and the remaining part in Genale Dawa basin . The study area has different land form characteristics varied from High Mountain up to low lands: its altitude varies from the highest peak (3000m) up to lowlands (1100 m) High water usage, channeling residual water and the pulp together, in efficiency of the traditional waste disposal pits, absence of monitoring and lack of sustainable wet coffee production strategy and policy are some of the factors that aggravate the impact of the processing plants on the poll ution of water bodies were di scussed in problem identification and analysis. Measured values of physical parameters such as turbidity and pH are out of the range of WHO guideline values and standards. From the Physical observation itself during coffee processing periods rivers and streams have objectionable color odor and taste so that the waters have evil or pungent small and test. TDS and EC values of rivers and streams in particular spring and boreholes in general shows that the water is fresh. Based on the measured value of the total hardness in terms of CaC03 the surface and groundwaters of the study area classified as moderately hard. The limited water chemical analysis fi'om previous representative sources indicated that the river and ground waters are Na HC03 type of water, the dominant cation being Na and anion bicarbonate. The highest value BOD and COD in river water is 8750 and 3120mg/1 that have a potential for decreasing greatly the level of dissolved oxygen in the rivers that reduces the diversity of aquatic life. The maximum COD value of the effiuent obtained from this analysis (24,600mg/l) is 98 times higher than the EPA standard fro effiuent discharges to inland waters. The highest BOD value was 39 times higher than the EPA standard. The bad, evil and pungent smell that can be sensed along the river courses during coffee processing periods were explained by the concentration of Ammonia (NH3) that was ranged from 1.48to 90mg/1 and was much higher than the recommended limits. The highest nitrite (N02-) concentration was 60mg/1 in Melkadimtu Rivers. From the total analyzed samples about 50% of them had their values were nearly I mg/I, which are far higher than levels in unpolluted waters (0.03mg/I). Rural communities that use river water as their source of water supply may expose to carcinogenic effect due to this level of nitrite. Coffee pulp, which is one of the bypro ducts of coffee processing, have some economical applications that may become evident as their use is increased. Compost and fertilization, Pulp beverage, animal feed, fuel wood substitutes are some of the suggested measures to be taken to mitigate the effects.