Geography Reference
In-Depth Information
integrated approach of RS and GIS techniques to improve the site selection for
borehole drilling in the Volta basin of northern Ghana. The application of GIS
technology allows swift organization, quantification and interpretation of large
quantities of hydrogeological data with more accuracy and minimal risk of
human error (Pinder 2002). For Sisay (2007), Remote sensing technique
provides an advantage of having access to large coverage, even in inaccessible
areas. It is rapid and cost-effective tool in producing valuable data on geology,
geomorphology, lineaments, slope, etc. that helps in deciphering groundwater
potential zone. A systematic integration of these data with follow up of
hydrogeological investigation provides rapid and cost effective delineation of
groundwater potential zones. Despite the extensive research and technological
advancement, the study of groundwater has remained more risky, as there is no
direct method to facilitate observation of water below the surface. Its presence
or absence can only be inferred indirectly by studying the geological and
surface parameters.
The Birimian formations which are the most representative formations are
gold bearing formations like in most part of the West African craton. The
geological formations are mainly made up of basalts, andesite, rhyodacites of
gabbros, peridotites and volcanic-sedimentary rocks intruded by granites
(Bassot, 1966). These formations, which have been repeatedly deformed and
metamorphosed in low amphibolite facies and green schists facies by granite
intrusions are often overlaid by a thick lateritic mantle, and this latter covers
more than 2/3 of the geological strata which outcrops sometimes at the
riverbeds. The weathering profiles show thickness as much as twenty meters
with different horizons. Also the alluvium thickness can reach few meters at
the riverbeds. A new cartography of Birmian formations (Théveniaut & al
2010) identified that two groups and three suites are present in eastern
Senegal, these are:
Volcano-sedimentary Groups of Mako and Dialé-Dalema;
Magmatic suites of Sandikounda-Soukouta, Saraya and Boboti.
The hydrographic network comprises the Gambia River and Falémé River,
both fed by Fouta Djalon in Guinea. The tributaries of these rivers are non-
perennial and dry up during the dry season (Camus & Debuisson, 1964). The
area is characterized by a dry season from October to April-May and a rainy
season which usually starts at the end of April and continues until October
with a maximum rainfall in August. The yearly average rainfall is about 1200
mm per year at the Kédougou station (Mall. 2009). Hydrogeological context of
