Hydro Geochemical Evolution in the Ambo woliso Area
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Date
2007-08
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Addis Ababa University
Abstract
The objective of this research is identification of soda spring sources and
characterization of hydroelectrically evolution on the basis of water
sample data hemispherical analysis. This is attempted through
understanding of geological settings, archaeological effects, and
tectonic activity including other factors.
Geologically it is composed of sedimentary rock and volcanic products,
the later is recognized to be younger resulted from tertiary and
quaternary volcanic episodes. Its products spread over the large part as
out crop overlying the earlier. Mesozoic sedimentary sequences are
limited to the western edge, which is noticed as Adigrate sandstone.
Some hydrometrological parameters are briefly addressed precipitation
depth from isohytal computation is 1143.1-mm/year while arithmetic is
1137.67mm/year, temperature is found to be 18.1oC and annual mean
actual evapotranspiration using SEBAL modeling is 320.4mm.
Roughly it can be said scoracious and fractured basalts are the major
economical water bearing formations while ignimbrite is the confining
layer; moreover geological structures play key role in controlling water
resources of the area.
Noticing the eleven variables (pH, Ca2+ Mg2+ K+, Na+, HCO3-, CO3-, Cl-,
SO42-,TDS) at least two Ionic evolution can be notable (Seifu Kebede et
al, 2005): fresh low TDS Ca-Mg-HCO3- type envisages most western parts
and northern highland (ambo fault belt). Second type high TDS Na-
HCO3_ is limited to thermal spring emerging zone controlled by regional
deep seating geological structures. Perceptible high CO2 presence from
sediment carbonation and magma degassing is responsible for the
evolution, when transferring takes place from shallow circulating to deep
groundwater system. In the deep groundwater system both the igneous
and Mesozoic sediments most likely contribute for the high ionic species.
Key words: Earth processes; Basalt; Igniter; Eleven variables; Ionic
evolution; Degassing.
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Keywords
Earth processes, Basalt; Ignimbrite, Eleven variables, Ionicevolution; Degassing