Groundwater Circulation and Hydrochemistry of the Corridor (Upper Gidabo River and Lake Awassa Catchments), Sidama Zone, Snnprs
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Date
2007-07
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Addis Ababa Universty
Abstract
The study corridor is found in Sidama zone, SNNPRS. It is situated in the Central sector
of the MER system. The study area with 1582 km2, comprises parts of the two adjacent
catchments namely Lake Awassa and upper Gidabo River, which is delineated arbitrarily
so as to determine whether there is groundwater circulation between them or not and
quantifying the amounts. Recently, the Awassa lake level is continuously rising since
some times and evacuate so many residences from the lake shore and damage properties.
This rising of the lake level causes a major threat for the Awassa town and surrounding
rural communities.
Integrated methodologies are used to find out the groundwater flow system and
hydrochemistry of the corridor along with employing the appropriate software like
Global Mapper, Surfer, ArcGIS, ArcView, and Aquachem that facilitate for analyses and
interpretations of the data in order to get the output. The secondary date are collected
from the concerning offices and some primary date are obtained during field work.
Accordingly, groundwater flow system is considered as shallow and deep aquifer cases
and the outputs indicate that there is the same flow trend within the two flow systems.
Groundwater flows take place from south east towards north west and to the west; and
there are also flows from central west (Yirba area) to the north (Lake Awassa) in the
study corridor. The total groundwater flowing amount that outflow from upper Gidabo
river catchmetnt is quantified to be 5.81MCM.
On the other hand, hydrochemical data analysis part also reveals: evolution of major
ions, water types, potablity of water for human consumption, spatial distribution of some
major ions including fluoride and direction of groundwater flow. For example, the water
sample from hot spring and Lake Awassa is Na-HCO3 type, which indicates the presence
of evolution. Whereas cold springs mostly from highlands and the eastern rift
escarpment has the water type of Na-Ca-HCO3, shows minor evolution. The increasing
trends of the phisico-chemical analyses indicate that there is groundwater outflow
towards the lake region
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Keywords
Upper Gidabo River