Browsing by Author "Mulugeta, Yonas"

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    Hydrogeological investigation of Chacha Catchment a volcanic aquifer system, central Ethiopia
    (Addis Ababa Universty, 2009-06) Mulugeta, Yonas; Ayenew, Tenalem
    Hydrogeological investigation of Chacha catchment, a volcanic aquifer system is carried out on Chacha river shade which is situated about 105 km north east of Addis Ababa on the way to Debre Berhan and covers an area of about 1194 sq.Km with a considerable elevation difference from 700-3500 m.a.s.l and an average elevation of 2728m.River gorge, gentle slope and highland characterize the physiograph of the catchment The catchment gets 939 mm of annual mean rainfall and 13-15.6 °c average annual temperature. Potential evapotranspiration (PET) is estimated empirically 1141mm/yr. The area has two rainfall regimes (bimodal rainfall characteristics). Recent Quaternery deposits, Tertiary Ignimbrites, Basalts, Tertiary Sediments and Mesozoic Sandstone constitute the stratigraphy of the area from the youngest to the oldest respectively. The aquifer system has been defined based on hydrogeological characteristics of lithological units described by the geological maps and data from the field inventory. The hydrogeological characterization of the area revealed the following aquifer / aquitard system: •.Porous aquifer developed in alluvial and colluvial sediments of the plateau, Tertiary sediments, Pyroclastics and Mesozoic sandstone in deep valleys.(T=10-100 sq.m/d and Q=1-5 l/s) •Fissured aquifer developed in basalts on plateau and deep valleys.(T=10-100 sq.m/d and Q=1-5l/s) •Mixed aquifer developed in fissured Ignimbrite and Basalt and porous Tertiary Sediments intercalating volcanic rocks on plateau. (T=10-100 sq.m/d and Q=1-5l/s) •Aquitards developed in Ignimbrites forming water shed mountains along plateau – rift valley edge. (T = 1 – 0.1sq.m/d and Q = 0.05 - 0.5 l/s) The water type in the Chacha catchment is predominantly calcium bicarbonate. Groundwater of the study area is generally suitable for Drinking water supply and irrigation. Generally, the area has enormous surface water and ground water resources thus intensive sustainable water resources development is recommended by sinking dugwells and shallow wells not more than 60m depth on the plateau and small valleys. Springs can be developed on the flat plain and escarpments of the deep gorges. Drilled wells in the range of 100-150m are recommended for town water supply schemes. In addition to water supply, large scale irrigation and hydroelectric power development in Chacha catchment using available water resource specially ground water is possible.