dc.description.abstract |
This thesis presents the hydrogeological characterization of basement Aquifers in the Assosa
area, Benishangul-Gumuz Regional State, Western Ethiopia. The study area covers 863 Sqkm of
Hoha and Selga rivers and is mostly covered by crystalline basement rocks (hard rocks) which
are regionally known to be called aquicludes. Recent well drilling in the area shows that the well
yield varies significantly (from abandoned to high discharge well). Currently, the water demand
in the area is highly rising. However, limited groundwater investigation in the area causes well
abandonment. To avoid the problem, combined geological, geophysical (electrical resistivity
and magnetic methods), and pumping test methods, were carried out to investigate the
hydrogeological system of the area. The study aims to characterize the expected aquifer zone /
water-bearing units and map surface and buried geologic structures and weak zones.
Twenty-one (21) VES data points and seven (7) 2D ERI survey data points with Schlumberger
and Wenner configuration were conducted along Hoha and Selga river structures identified by
satellite gravity and 364 magnetic data. The magnetic data and gravity data were processed using
Oasis montaji 6.4.2 whereas IPI2win and Surfer were used for preparing pseudo-depth,geoelectric
sections,
and
2D
ERI.
According
to
this
research
work,
the
hydrogeological
set
up
of
the
area
is highly heterogeneous and mainly controlled by geological structures, weathering, and
fracturing intensity.The aquifer is both intergranular and weathered / fractured volcanic and
basement aquifer with secondary porosity. The study area has a localized shallow and deep
confined and unconfined aquifer nature. Accordingly, the aquifer area is highly heterogeneous
and mainly controlled by geological structures, weathering, and fracturing intensity for hard rock
aquifers, however, granular porosity is dominant in the shallow alluvial aquifers. The
transmissivity varies from 3.94 to 76.6m2/d, hydraulic conductivity ranges from 0.17 to 2.24
m/d. Secondary porosity and permeability that develop from secondary processes mainly control
the aquifer productivity of the area. |
en_US |