Hydrogeology of Debre Zeit Area
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Date
1992-06
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Addis Ababa Universty
Abstract
The investigated area is located east of Addis Ababa on the
western border of the main Ethiopian rift valley * Being
part of the Ethiopian rift system , it is characterized by
Plio-Quaternary volcanism which gave rise to trachytic- domes,
rhyolitic flows , and rhyolitic ignimbrites in the highly
elevated part of the area while olivine basaltic flows and
surge deposits in the lower elevated plain area . The
maximum point in the area is represented by Mt . Yerer with an
elevation of 3100 m above sea level. The plain area has
an average elevation of 1900 m above sea level .
The yearly minimum possible rainfall average in the area is
859.9 mm , the actual and potential evapotranspiration is
606 , 2 and 857.1 mm respectivly and the runoff that
leaves the basinis 25 . 568 x 10d m3
«of water. From these
determinations, the amount of infiltrated water in the area is
<5 3 calculated and the value is 54.39 x 10 m .
The hydraulic parameters , transmissivity and hydraulic
conductivity are determined based on the pumping test
information obtained for few wells , The transmissivity
and permeability of the rocks found in the central part
“3 2 \ _3 of the area is 0 ,9x10 m /s and 4.0-5x 10 cm/s respectively .8 ,8 x 10 m and the latter is 1.5 x 10 cm/s. But the
storage coefficient is not calculated because of the absence
of observation wells in which the effect of further drowdown
is observed ,
Because of the lack of bore wells in the northern part, of
the area , a thorough study of the actual variation of
groundwater level was not possilble. But based on the
available static level data , for the central part of the
area , appropriate groundwater level contour lines are constructed
The chemical analyses result- showed that most waters are
calcium -magnesium-bicarbonate type .
Description
Keywords
Debre Zeit Area