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Groundwater Investigation for Domestic Purpose Zala Woreda, Gamo Gofa

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Research · November 2017

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ISSN 2321 3361 © 2016 IJESC

Research Article Volume 6 Issue No. 7

Groundwater Investigation for Domestic Purpose Zala Woreda, Gamo

Gofa Zone, Southern Ethiopia
Leu lalem, S.B.1 , Alemayehu A.2 , Elias G.3 , Assefa G.4 , Yegelilaw E.5 , Temesgen L.6
Arba Minch University, Post code: 21, Ethiopia

Abstract
The study area, Zala woreda is one of the water supply problem areas in Gamo Gofa zone. This research work was conducted in
three specific locations, namely Mela village, Galima town and Deboch village. In these areas there is no alternative water
resources rather than groundwater investigation and use groundwater for do mestic supply; because the area where characterized
as arid and semi arid. Th is groundwater investigation was focused on the assurance of presence or absence of water and to
identify thickness of the aquifer. This study was used different methods such as geological, geo morphological and vertical
electrical sounding. When to consider groundwater availability we have to know the geology of the area. Geology of the area i s
characterized as low laid flat land is covered by uncons olidated sediments; mountains, ridges and domes are covered by rhyolite
and basalts. These rocks are contained mostly secondary porosity rather than primary porosity. Most of the VES points located on
unconsolidated sediments except Mela site. Either VES on fractured rock or unconsolidated sediment show a thick aquifer in the
area. The identified aquifers are mostly confined and the confining layers are both clay and hard igneous rocks. The depth of the
groundwater for main aquifer is starting from 38m-50m. The reco mmended depth which will be expected to drill is 80m for
shallow well and 244m for deep borehole.

Keyword: Geology; weathered rock; aquifer; porosity; VES; confine.

1. Introducti on health care and productivity of the peoples. In order to attain

1.1 Background sustainable and equitable solutions to these problems due
As far as water supply for hu man consumption is concerned, it attention has been accorded by the Arba Minch University in
is to be noted that over 85% of Ethiop ians’ livelihood is based partnership with local governments, civil society, and
on farming and livestock agriculture. This has consequently implementation partners.
resulted in subsistence level of economic life and thinly spread A key element of our strategy is helping communities gain
out settlement so that providing reliable and safe water at access to safe water, sanitation and hygiene. In pursuance to
minimu m cost becomes very difficult. the above goal, Zala woreda, Deboch, Galma, and Mela
In Gamo -Go ffa zone Zala Woreda especially the targeted Kebeles Water Supply Project here after proposed to be
areas Deboch, Galima town and Mella village are usually designed by the Arba Minch University to conduct the study,
affected by drought and there is especial water scarcity. As design and preparation of documents for the project.
observed during field visit, rural people in these areas are This research work was used essential methods to investigate
under serious problems because number of population and the groundwater site selection. The basic methods which were
water supply is as such not balanced. used are geophysical resistivity methods, topographical
Hence over 90% of the population living in rural Zala woreda setting, geological structure tracing and existing shallow wells.
has no access to potable water. People have to travel long
distances for many hours and fetch unsafe and unreliable 1.2 Statement of the problem
water fro m rivers and other undeveloped sources. Even in For sizable proportion of the rural population(84% o f the
urban center of the woreda services are apparently better in country total) in Ethiopia, the major sources of drinking water
relative terms, the supply and quality of water is inadequate are surface run offs represented by unprotected springs, ponds,
and unreliable co mpared to the demand. rivers, and hand dug wells whose health risk is significant as
The majority of woreda people engaged in farming and they are exposed to contamination caused by human beings,
pasteurization. They forced to drive the livestock long livestock, wild life and uncontrolled flooding. The main
distances, both in the highland and lowland areas, in search of reasons for this very low level of performance in the supply of
water and pasture. safe drinking water, and the quandary for not efficiently
While herding their cattle from place to place in search of utilizing the water resources potential of the wo reda towards
water they move away fro m centers of social services like realizing sustainable development is attributed to lack of
health care, clean water, education…. etc ground water potential investigation and insufficient
As far as the economic problems are concerned, the long investment for safe drinking water supply. According to
distance movement of the livestock in search of water and Ministry of Water & Energy "adequate water supply to mean
pasture resulting in lo w yields and poor health has a negative 20 liters of water per person per day is accessible within a
impact on the economy. Hence, the water sector will have to range of 0.5 to 1.0 km fro m a dwelling place”. But generally
formulate appropriate imp lementing strategies for the supply in Zala woreda the water consumption is approximately 20
of water for livestock in the areas. liters per household per day. Until now people to get water
These shortcomings will have to be solved sooner than later they travel tens or greater kilo meters. Not only distance but
to achieve rapid socio economic development through better what they using water for domestic purpose is affecting their
healthy due to quality problem. As stated in description of the

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study area, most of the area climatically characterized so bounded between West Demba Gofa woreda and North by
called ‘Ko la’; most of the streams in the area are non- Maze River; East and Northeast by Kamba and Daramalo
perennial; because of this problem people spent their time to woreda respectively. Topographically the area is
search water in dry season. characterized valley between two mountain ridges and it is
mostly flat land. Climat ic conditions of the area are mostly
1.3 Decryption of the study area characterized ‘ko la’ weather condition. Their specific
1.3.1 Location and accessibility locations are at UTM-37 which is bounded between 787393
The study area is located in West of Arba-Minch town, about to 791504.64mN and 464382.02 to 469449.7mE and an
234km. Its accessibility fro m Arba M inch to Sodo asphalt altitude of 1194– 1484 m.a.s.l.
road and Sodo to Zala through graveled road. The study area
covers about three rural and one town kebeles. The area is

Figure: 1.1 location map

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 1.3.2 Topography, climatic conditions and drainage in the area is seasonal, poor distribution and variable fro m
The study area is characterized by undulating topography year to year. Rainfall d istribution over the valley is in
along south main Ethiopian rift system. The area is monthly distribution is bimodal even if there is different in
dominated by flatland and some part of the area is controlled different area. The average lowest monthly rainfall
by ridge forming flood basalt and rhyolite. Th is rugged registered during the month of February at Mela is 36.4 mm.
topography of the area is the sources for rivers and streams whereas the average monthly maximu m rainfall is 166.4 mm
that flows through the vicinity. observed during the month of May. About 16 years rainfall
Climatic conditions of the area are mostly characterized data of the area imply that most of months are dry which are
under ‘kola’ weather condition. The main feature of rainfall getting rainfall below 100 mm.

Mean Monthly Rainfall

180
160
140
120
RF (mm)

100
80
60 RF
40
20
0
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Month

Figure:1.2. Mean monthly rainfall

Temperature fro m November to February hot and dry indicated in figure (1.4) except six months the mean
weather is predominant. Fro m the long-term temperature temperature is greater than 30 o C the area is getting high
data obtained fro m National Metro logical Agency (NMSA), temperature.
the mean maximu m temperature of Mela is 33.5 o C. As

Mean Monthly Maximum Temperature

34.0
33.0
32.0
Max.Temp(oC)

31.0
30.0
29.0 Max.Temp
28.0
27.0
26.0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month

Figure:1.3. Mean monthly maximu m temperature

1. 4 Research questions following interdependent questions should be addressed

This project concept note work to give the solution for the while addressing the rationale of this project.
problem which justified in the introduction part. The

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  Where is groundwater and how much its  It will give awareness on vertical and horizontal
potential? distributions as well as quality of groundwater; and
 What is the nature of the interconnections between  This investigation expected to indicate that at what
the groundwater and surface water systems? depth groundwater presents and its seasonal
fluctuation.
1.5 Objecti ves
1.5.1General objective 1.7 Beneficiaries
The general objective is to investigate groundwater potential The beneficiaries are:
site for shallow and deep well drilling  The scientific co mmunity can use for further
studies;
1.5.2 Specific objectives  Gamo-Go fa water and mine Bureau; Zala woreda
 To map topography of the area on the way water office;
know the flow d irection of groundwater;  A rural person who drill shallo w wells on his home
 To map lithology and geological structures garden for micro irrigation, livestock, drinking
towards indicate the controlling factor of purpose;
groundwater flow direct ion;  Non-governmental Organizat ions which are
 To measure the thickness of aquifer by using planned to accesses water for rural peoples; and
geophysical methods( VES and imag ing)  There is also Minster of water and energy; and
 Identify the spatial and temporal occurrence Regional water Bureau will use this research work
and distribution of the ground water resources to access water for ru ral peoples.
and ensure its utilization for the different
water uses. 1.8 Scopes and limitations
 Implementation of appropriate technologies This research work limited only on water supply for
for the exp loitation of ground water in water domestic purpose on a specific area. The investigation
deficient areas in order to mit igate water included the geological succession, vertical and horizontal
scarcity problems variation and the presence and absence of groundwater.
Beyond this there will be other proceeding activities which
1.6 Expected output will focus on drilling, water quality and supply network
The expected outputs of this research work are designing.
 The detailed hydrogeological map of the study area To interpreter the data collected during field work fro m
will be produced; Deboch area there is no drill borehole nearby study area.
 This investigation also will provide comprehensive Due to this problem through interpretation researchers used
informat ion for the development of groundwater; only standard resistivity as base line. Th is base line standard
 The produced hydrogeological map consists of usually does not working because of the geological
location/pinpoints of hand dug well, shallow well formation within a few d istance varies vertically and
and deep well d rilling; horizontally.

2. Materials and Methodol ogy

2.1 Materials

Figure: 2.1 Different matterials (Instrument)

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2.2. Methods limits the presence or absence of groundwater. Thorough this
method we characterized the co mposition of soil in site and
To achieve the above objectives of the research the by what processes those soils are formed.
following methods and procedures were used.
2.2.3.3 Hydrogeological methods
2.2.1. Office work The ground water potential of an area mainly depends upon
Under office work special documents and randomly related the hydrogeological set up, for which a detailed and
data were collected fro m d ifferent governmental and systematic hydrogeological survey is a prerequisite. Well
nongovernmental offices. The prior assessment extent and inventory study is very important in any ground water
details were identified during this office work. After exploration programme. Especially in hard rock terrain is
identifying the main researchable gaps which will be filled groundwater confines to the weathered mantle and
fro m this study, the different data type have to collect from geological structures. The weathering thickness, joint & fault
were designed. Then the base map of the study area was system of the area was studied in depth. Water level
prepared to put the geological data were sited on map. measurements, water level fluctuation studies are the
Analyzing and interpreting of top map and aerial photos for important factors in the assessment of ground water
the preparation of base map. This research wo rk was used potential. On ly by a systematic hydrogeological study, the
the satellite images and aerial photos to identify the ground water abstracting structures like open well, bore well,
lineaments, topographic setting and accessibility of the study tube well were thoroughly identified during hydrogeological
area. survey. The recharge and discharge areas were identified.
The fluvial hydrological studies like the river, stream flows
2.2.2. Reconnaissance field survey and spring source, whether they are perennial or intermittent
Basically, through reconnaissance survey assuring the were identified to characterize the groundwater potential of
geological condition and topographic setting observed the area.
during office work. Depending on base map which was
prepared through office work to verify d ifferent 2.3 Geophysical Method
topographical setting and geological lineament reviewed in Fro m different geophysical methods this research work used
office works was clarified in the field. Also the current to investigate groundwater is vertical electrical sounding
accessibility of the study area was clearly identified during (VES). Resistivity sounding is the study of resistivity
this stage. Furthermore the major lithologies and geological variation with depth for fixed center i.e. vertical
structures were recognized. The specific area for vert ical investigations of subsurface geological layers. This method
electrical sounding was selected based on the geological gives the information about depth and thickness of various
setting of the area. subsurface layers and their potential for groundwater
exploitation. Since the fraction of total current flows at a
2.2.3. Detail fiel d study depth varies with the current electrodes separations, the field
2.2.3.1 Geological methods procedure is to use a fixed center with an expanding
This method is very important especially developing spread(Okonkwo AC, 2013). The Schlu mberger array is
countries like Ethiopia because geophysical instrument is too particularly suited to this technique, because Schlumberger
costy to use every where everybody. This geological method array has some specific advantages. There are always some
depends mostly on geological background and work naturally developing potential (self-potential, SP) in the
experience. The groundwater occurrence and movement ground, which have to be eliminated and nullified. Thus, in
were main ly controlled by the geology of the area. such electrode configuration, the potential difference for a
Geological studies are very much essential. The type of selected value of AB/2 is measured and in turn, the
terrain, rock format ions, lithological units, geological resistivities are obtained. The resistivities are plotted against
structures like lineament, fo ld, fau lt, jo ints and fracture AB/2 on a double log graph. A log-log plot of the apparent
system have to be studied in depth. Only after the geolog ical resistivity versus current electrode spacing (AB/2) is
investigations, the type of geophysical method to be commonly referred to as the “sounding curve”. Resistivity
conducted was decided. Therefore, to identify geological data is generally interpreted using the “modeling” process. A
setting being on mountain and visualize the orientation of hypothetical model of the earth and its resistivity structure
geological structures which controls groundwater occurrence (geoelectric section) is generated. The theoretical electrical
and movement. Then come to river cuts, road cuts and hill resistivity response over that model is then calculated and
sides to identify the thickness of each geological formation, compared with the observed field response. The differences
orientation of geological structures, and contact between between the observed and the calculated are then adjusted to
different lithologies and weathering condition of the rocks. create a response, which very closely fits the observed data.
When this iterative process is automated, it is referred to as
2.2.3.2 Geomorphological methods “iterative inversion” or “optimization”.
After a thorough study of the satellite imagery and
topographic map, a field check is highly necessary to know
the geomorphological features to assess the ground water 2.4 Data presentation and interpretati on
potential. The geomorphic units like pediments, flood plains,
drainage pattern, soil types, lineaments which primarily The apparent resistivity data obtained from the VES survey
control the occurrence, movement and potential of ground were presented as depth sounding curves by plotting the
water have to be investigated in detail. As we know different apparent resistivities along the ordinate axis and the half
geomorphological features composed of various types of current electrode spacing (AB/2) along the abscissa. This
geological products due to different geological processes plot was made on bi-log paper. The resistivity depth

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sounding curves were classified based on layer resistivity obtained in the study area were HK (VES one, two and three
combinations. in Mela village), KQH (VES two) and HKQH (VES one)
For a three (3) layer case, there are four type curves, the H, fro m Galma town. The curves obtain from third site
K, A, and Q type curves. Any type curve can be derived (Deboch) were HA (VES two), and H (VES one).
fro m any combination of these type curves. The curves

2.5 Fl ow chart of the research work

Research Approach

Literature review and office studies

Review on: Base map preparations from: Selection of

-Published and unpublished materials -Topographic maps necessary
-Map and aerial photographs -Aerial photographs materials and
-Journals, reports and etc. -Satellite images equipment

Preliminary field investigations /reconnaissance survey

-Delineation of the study area
-Mapping of features such as river, drainage and etc.

Detailed field investigation

Hydrogeological investigation
Geological investigation - Delineation of water shade
- Lithological -Measurement of groundwater table by
- Structural using resistivity method and test pits

Sample collection analysis and interpretations

 Field sampling and testing
 Laboratory tests and analysis

Identify groundwater potential site for shallow and deep well drilling; and water quality

Recommend groundwater potential site and its chemistry

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3. Geol ogy and hydrogeology of the area soils are widely observed along streams and near to the foot
3.1 Geology of mountains of Galitsa ridge. These soils are mostly dark
The study area is covered by igneous rocks such as basalt, and some places red in color, loose to stiff and in places
rhyolite, dolerite and gran ite. Dolerite and granites are too stratified. Co lluvial deposits are common along foot of steep
small to map lithologic units in the study area exposed as slopes of Galitsa ridge, Deboch Mountain and Mela rid ge.
dykes and sills. In the most of the above mentioned This deposit ranges from 0.2 to 3m in thickness.
geological format ion overlaid by unconsolidated sediment in The residual soils range in grain-size fro m clay to sand with
the flat land of the area. This recent deposits are like some remnants of angular boulders, mainly b lack in co lor,
colluvial, alluvial and residual soils. To study groundwater are found in areas of gentle slopes and flat areas.
properly any researcher has to know the geologic setting and 3.1.2 Basalts
geological formation of the area. Basalts mainly covered ridges, mountains and some of p late
3.1.1 Unconsolidated Sediment area. They are mostly exposed at hill sides, around road and
These sediments consist of alluvial, colluvial deposits and river cuts. These basalts characterized fractured and
residual soils. In the study area, alluvial soils cover at the flat weathered i.e. there are a good condition to hold
lands on the foot of mountain, banks of rivers and at mouse groundwater. Fractures in this lithology are penetrative and
of gullies and flood plains . Its thickness ranges from 0.5 to persistent. The upper most part of basalt is highly weathered
70m when measured from pervious boreholes and out crop. along joint and miner fau lts. These fracturing and weathering
The alluvial deposit ranges in grain-size fro m fine grain soil is not uniform especially on basaltic rocks because in some
to granular soils such as sand, gravel and boulders. Fine where it is highly weathered and fractured but in somewhere
grain soils (silt and clay) widely observed around the center else it is not. The follo wing photos was taken from quarry
of flat lands that we so called Shambara flat land. Granular exposure especially indicates spring during both seasons.

Figure: 3.1. Basalt

3.1.3 Rhyolite The weathered color of rhyolite is whitish and this
Rhyolite covered eastern and western part of the study area. weathering is not uniform even if in part of rock body some
It is also weathered and fractured at mountain area; and part is massive and within a few distances there is highly
massive at ridge area. Different fractures oriented averagely weathered. Around Deboch area on this rhyolite this is
0
45 NE and they are penetrative to vertical to some extent. spring in road cut and local people uses as developed spring.

Figure: 3.2. Rhyolite

3.1.4 Metamorphic rocks identified dark. The rock is deeply weathered and it is friable
The metamorphic rocks are exposed base of Galista ridge on on the hand. Different fractures filled with sills and veins by
road cut near Galma town. The area coverage of quartzes and calcite minerals. Most of springs seeps from the
metamorphic rock is very small relatively with other rock through the contact between basalt and this metamorphic.
units. The weathered color of these metamorphic rocks is The name this metamorphic rock is mica schist.

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 Figure: 3.3. M ica schist
3.1.5 Geological structures strikes of the joints are generally parallel to the faults of the
The study area is found within western escarpment of area and seldom perpendicular. Most of the joints are
Ethiopia main rift system. The area is do minantly affected vertical and some are horizontal, parallel to lava flow
by rift faults which are north east to south west orientations. bedding planes in volcanic rocks.
A plenty of springs that people have been using are along Two major jo int sets are observed (NNE & W NW trending)
these fault zone. with some minor sets (NE & NW strike, Fig. 3.4).
The faults are interpreted fro m air photographs (verified in There is also unevenly distributed different fractures are
the field), wh ile the other structures are observed and some characterized in the area. These jo ints mainly observed on
measurements were taken in the field. The study revealed N- basalt. Local people use groundwater as spring on surface
S and NNE-SSW with minor E-W striking faults (Fig. 4). through these joints.
Joints are other structures common in the study area. The

Figure: 3.4. Geological & VES location map

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3.2 Hydrogeol ogy of different lithologies streams. It comprises of clay, silt, sand and gravel sized
particles in different proportion as identified in the field. In
As it was observed in the shallow and deep wells, the range the central and eastern parts of the study area, these deposits
of thickness of the weathered and fractured zones of basalt can be considered as potential water bearing format ion due
rocks are about below 12-50 m fro m surface. Secondary to their primary porosity and location of deposition whereas
porosity due to fracturing is significant in this unit. This in due to their location in the northwestern, central and
turn indicates its capacity for water transmission and southern parts of the study area unconsolidated deposits act
provides good site for water supply. Existing borehole was as an aquitard rather than being an aquifer.
that the depth of 130m with good permeability that is 4.5 l/s.
However, in some parts, it has massive rock which reduces
its water bearing capacity and productivity. In general this 4.0 Result and discussion
formation can be considered highly potential aquifer in the
flat land of the study area due to its secondary porosity and The results of geological and geomorphological
permeab ility. investigation overlapped with vertical electrical sounding
But rhyolite, dolerites and granites covered mountains, hill (VES) outco mes show that a good indicator of groundwater
sides and dome shaped topography act as a conduit rather occurrence. Groundwater recharged to Shambara flat land
than an aquifer. Therefore, these mountains, hills and domes fro m eastern part of Galista ridge provide springs, streams
considered as recharge area to the flat lands. Along different and runoff fro m high lands. In the area there were one bore
fractures fro m h ill sides some small spring flow to flat land hole and shallow well with the depth of 130 and 50
this shows the recharge of the area is not only from rain fall. respectively. In nearby and in the compound of study area
Unconsolidated deposits ranges from 6-70m thickness there are also different bore holes and shallows wells wh ich
measured in d ifferent shallow and deep wells. This unit is this research used to interpreted the aquifer thickness and
overlying two majo r stated litho-units in the northeastern, groundwater levels. Based on existing borehole
eastern, southeastern and central parts of the study area hydrogeological logs and logs from different outcrops the
particularly along the marg ins of the major and minor VES data were interpreted.

Table 5.1: Layer resistivity and their corresponding thickness (Mela Village)

VES Curve ƍ1 ƍ2 ƍ3 ƍ4 H1 H2 H3 H4 RMS

type Ώm Ώm Ώm Ώm (m) (m) (m) (m) %
1 HK 19.5 6.51 421 0.613 0.981 28.8 44.5 ∞ 11
2 HK 19.5 6.5 362 1.38 0.983 28.5 50.3 ∞ 11.2
3 HK 8.44 3.44 11.3 42.1 1.04 2.36 46.9 ∞ 4.79

All curve types in this VES points are HK section indicated 0.981m. The second layer of VES 1 is deduced as saturated,
in the table (5.1) above that is the resistivity of middle geo - fractured and fairly weathered basalt rock with the thickness
electric layer is less than the first and third layer is so called of 28.8m. This weathering and fracturing of the basalt
H-type curve and the reverse is K-type. Around these VES decreased on the third layer and the fourth layer is highly
points the upper most layer of soil with the thickness of 2m fractured, considered as main aquifer.
measured fro m hand dug well. The depth of hand dug well is VES 2 and VES 3 follow nearly similar resistivity and
12m and it is well developed with concrete casing and thickness with VES 1 by means of little resistivity and
installed hand pump in the position of 6m depth from the thickness variation. Generally the model table and resistivity
surface. Based on this hand dug well and geological out graph assumed that the aquifer of the area is extensive and
crop, in the above model table VES interpreted as the first thick even if its total thickness is unknown.
geo-electric layer is moist clayey soil with the thickness of

VES 1

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VES 2

VES 3
Table 5.2: Layer resistivity and their corresponding thickness (Shafe/ Galma town)

VES Curve ƍ1 ƍ2 ƍ3 ƍ4 ƍ5 ƍ6 H1 H2 H3 H4 H5 H6 RMS

type Ώm Ώm Ώm Ώm Ώm Ώm (m) (m) (m) (m) m m %
1 HKQH 75.7 9.1 54.8 9.87 1.61 967 1.43 1.96 2.26 109 130 ∞ 7.16
2 KQH 11.3 23.5 10.8 1.16 998 4.45 7.03 78.3 85.7 ∞ 5.21
3 HK 15.3 4.5 73.4 7.02 4.37 2.35 3.74 ∞ 5.87

This VES point found at graben between two horsts. From Fro m VES 2 graph and the model resistivity nu mber this
geological points of view basalt rocks inclined fro m Galitsa investigation presumes that the thickness decreases as of
and Deboch horsts towards the study area beneath the thick VES 1.
unconsolidated sediments. When we select groundwater
potential site at graben, it needs serious flow up of geology
because at center of graben mostly the deposition is silt and
clay. As we know silt and clay is considered as aquitard
rather than aquifer (we cannot get sufficient water fro m clay,
fine sand and silt deposition, “aquitard”). Near to this VES
location there were 50m depth shallow well and 130m deep
boreholes. Based on this shallow and deep borehole, for VES
1 geo-electrical layer one is co mpacted dry clay with the
thickness of 1.43m. The second layer is the resistivity of 9.1
Ώm and thickness of 1.96m wh ich is characterized moist
clay. The expected aquifer is some part of layer four and Figure: 4.1. Horst and graben
total thickness of layer five with the total thickness of 179m.

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 G VES 1

G VES 2

G VES 3
Table 5.3: Layer resistivity and their corresponding thickness (Deboch Village)
VES Curve ƍ1 ƍ2 ƍ3 ƍ4 H1 H2 H3 H4 RMS
type Ώm Ώm Ώm Ώm (m) (m) (m) (m) %
1 H 13.3 0.622 16.2 1.23 1.43 ∞ 37.5
2 HA 18.8 7.17 10.2 22.8 0.75 4.6 32.9 ∞ 3.41

The purpose of this VES investigation is for shallow well were construed. Supported from the geological out crop and
drilling for Deboch village and high school in the area. There unconsolidated sediment observed in the area, VES 1 first
was no previously drilled either shallow or deep well layer ind icated that moist clay with the depth of 1.23m. The
because of this, near to exact interpretation is difficult. Based expected aquifer depth is from VES 2 about 38.3m.
on geology and topography of the area the above VES data

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 D VES 1

D VES 2

5.0 Conclusion and recommendati on The over lapped geophysical investigation assured that the
geological assessment most of the area is effective and on
5.1 Conclusions few of the area is with some doubts. Except Deboch site the
other two areas measured three VESs for one bore whole
The result of geological, geomorphological, geo-botanical point. This because to identify the vertical and horizontal
and geophysical data signifies that some of the area is high variation of geology.
potential for groundwater and some others with some doubts
it good potential. Geology of the area is mostly covered by This geophysical data interpreted by using IPI2win soft ware
igneous rocks. The igneous rocks founded western and along with previously drilled shallow and boreholes. Over
eastern mountainous part of study area. Fro m d ifferent 90% of the investigation was effective which means
igneous rocks rhyolite covered around the peak point of successful.
eastern and western part of the study area. Mostly the area is
covered by basalt which found beneath unconsolidated 5.2 Recommendati ons
sediment of central part, and under rhyolite in different parts
of the study area.  It is recommended that a borehole will be drilled at
Mela Village VES station with specified thickness
By studding geology we hope fully know the presence of of the aquifer, to a depth of about 170 m. The depth
geological structures, type of lithology and the water bearing of fracture rocks in d ifferent traverses and even
formation detail wo rked assured the probability to within t raverses have different depth. If drilling far
occurrence of groundwater. Based on geological away fro m VES po ints it may be difficu lt to get
characterizat ion most of areas are with sufficient water for groundwater, because the geological format ion
irrigation and water supply for domestic purpose. varies within a few meter distances. To minimize

International Journal of Engineering Science and Computing, July 2016 1880 http://ijesc.org/
 this problem concerning bodies have to flow up case study in a coastal area, J. African Earth Sci.,
driller and supervisor. 33: 673-686.
 When drilling of bore well it should be fully  Okonkwo AC, Ujam II (2013). Geoelectrical
penetrated the thickness of aquifer, to get whole studies for the delineation of potential groundwater
groundwater potential. Especially Shafe town the zones at Oduma in Enugu state; southeastern
first/upper water bearing format ion is Nigeria. International Journal of physical
unconsolidated sediment with lo w water y ield science,Vo l 8(35): Pp. 1761-1771
capacity due to soil distributions. Therefore, it
needs to touch/strike the fractured rock
aquifer/lower aquifer.
 The area was identified during field investigation
the upper 3-5m is collapsible soil therefore, it needs
surface casing up to 6m. The diameter of borehole
will be drilled by using 12’’ bit and casing of 9’’
PVC for case of Mela and Shafe.
 At last but not the least, this investigation is the first
phase the remain ing second and third phase will be
immed iately start, because we hope to the fruit of
this research work.

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