Hydro Geochemical Evolution in the Ambo woliso Area

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Addis Ababa University


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.



Earth processes, Basalt; Ignimbrite, Eleven variables, Ionicevolution; Degassing