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Title: HYDROCHEMICAL AND ISOTOPIC CHARACTERISTICS OF THE GROUNDWATER SYSTEM OF ALLEYDEGE PLAIN
Authors: Bizuneh, Bekele
Advisors: Seifu Kebede(Dr.)
Engida Zemedagegnehu(Ato.)
Keywords: Hydrochemical
isotop
Copyright: Jun-2011
Date Added: 24-Jul-2012
Publisher: Addis Ababa University
Abstract: On the bases of geomorphology which is controlled by en echelon normal faults, the area is classified into two parts; the Alleydege plain, and Awash River valley. The groundwater dynamics of the area with emphasis given to surface water and groundwater interaction, origin of recharge; groundwater flow direction, groundwater evolutionary trend and direction, causes and origin of salinity and general groundwater quality issues relative to temporal variation are studied in this research using hydrochemical and isotopic data. Ultimately conceptual hydrochemical groundwater model of the area is constructed. XLSTAT _Pro version 7.5.2; for agglomerative cluster analysis, Aquachem 4.0 software package; for graphical plots and representation of hydrochemical data, PHREEQC built in aquachem 4.0 version; for inverse geochemical modeling, ArcGIS _9.3 software version; for Analysis of areal distribution and variation of hydrochemical and isotopic data and for production of different maps and Autocad-2007 version; for production of longitudinal geologic and hydrogeologic profiles, are employed in this study. Hydrochemical and isotopic studies reveal that there is interaction of Awash River with the groundwater of the alluvial aquifer of the Awash River valley and the Alleydege plain that lie within few kilometer distances from the Awash River during rainy season; during dry season such interaction is not observed. Recent meteoric water contribution to the groundwater reserve of the Alleydege plain is very limited. As a result subsurface inflow or percolation along the slope from southern, southeastern, and eastern highlands are found to be the major recharge mechanism for the Alleydege plain. Towards the rift, from the recharge areas of southern, southeastern, and eastern highlands; the ionic concentration, salinity and isotopic enrichment (δ2H and δ18O) increase following the groundwater flow paths. In general the groundwater flow and evolutionary trend direction follows the surface topography flowing from the south, southeastern and eastern elevated areas to the Alleydege plain and finally to the rift floor converging to the Awash River in the northern direction. The recharge area is characterized by Ca-HCO3, Ca-Mg-HCO3 or Ca-Na-HCO3 water type, where as the Alleydege plain and the marginal areas are characterized by a Na-Ca-HCO3-Cl water types. Na-HCO3-Cl and Na-HCO3 are the dominant water types in the Awash River valley and rift floor. K-mica, olivine, pyroxene, plagioclase and illite are the primary minerals of the Alleydege plain groundwater system.
Description: A THESIS SUBMITTED TO THE SCHOOL OF GRADUATE STUDIES IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF MASTER OF SCIENCE IN HYDROGEOLOGY
URI: http://hdl.handle.net/123456789/3467
Appears in:Thesis - Earth Sciences

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