CHAPTER contaminated. This study aims to find out about

CHAPTER 1: INTRODUCTION

BACKGROUND

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Mogadishu
is the capital city of Somalia, so it is based on all the institutions of the
Federal Government of Somalia, foreign embassies, UN agencies, NGOs as well as
the main business in Somalia. That has resulted in the city’s crowd of other
residents of the city who have been looking for a better life in Mogadishu. It
has caused the city’s population to grow. The rapid urbanization of the city
leads to increased use of water. It is therefore important that special
consideration is given to the city’s drinking water, so that their quality and
quantity will be improved.

Since the central government collapsed there was a gab
in knowledge of Groundwater quality and as well as characteristics of the
aquifer the bearing layer of groundwater. Therefore, this study will try to
address the existing borehole water qualities in Mogadishu city, also it will
reflect knowledge of hydraulic properties in the area in order to be aware the
magnitude of water that can be relied on the long term in future. This study
should be asset to the Somali people as a whole, especially those in Benadir
region.

The
water used in Mogadishu is borehole water which is similar to all parts of the
country where the boreholes are the most sources of water. The disturbance that
the water users of Mogadishu residents fear is the water quality. This is
because most of the boreholes situated over a local area in the city, and the
city spread across borehole areas. That can lead the contaminants to transport
into the aquifer layers and get in touch with the bearing water layers under the
ground, thus the water contaminated. 
This study aims to find out about the quality of water used in terms of
physical and parameters as well as the properties of aquifer. I thought that my
study becomes one of the first studies on evaluation of water quality and
aquifer characteristics since the collapse of the central government in Somalia
in 1991, especially in the city of Mogadishu and it will add significant
improvement to the knowledge of borehole water qualities and the aquifer
characteristics.

This study will focus on ensuring the quality of
water in the Yaqshid district of Banadir region, Mogadishu. We will also
explore the lower floors of the water using the VES method. Therefore, we will
enable to do numerical analysis of the hydraulic properties of the aquifer.

OBJECTIVES

OVERALL OBJECTIVES

The overall objective of this study
is to evaluate the existing borehole water qualities and Aquifer
characteristics of hydraulic properties using Vertical Electrical Sounding
“VES” Instruments.

SPECIFIC OBJECTIVES

The specific objectives of my
research will be

To establish the aquifer parameters for Mogadishu
area groundwater.
To determine the nature and extent of
contamination of water supply from the boreholes.
Establish seasonal variation of the quality of
water supplying from the boreholes.

PROBLEM
STATEMENT

In 2015 Mogadishu has
experienced the death of at least 50 people due contaminated water supplied by
a borehole in Yaqshid district. Also it affects many families who have been
used this borehole as a supply and many of them had been deployed to the
hospitals in Mogadishu.

Therefore, Mogadishu has a concern
about its water quality and it should be evaluated in order to check the
quality of borehole water. To be clear about this problem, I have a report to
quote it from CNN Channel in December 11, 2014 and the following is the quoted
report:

By
Omar Nor and Greg Botelho, CNN in December 11, 2014.

“At
least 50 people have died in Somalia after drinking contaminated water from a
well in northern Mogadishu, an official in that East African Country said
Thursday.

The
deputy commissioner for Yaqshiid district, told CNN about the deaths among
those who drank from the newly constructed well. More than 150 people who had
water from that well were recently hospitalized.”

Therefore, from here it is clear
that the borehole water contaminations exists in Mogadishu and need to take
action in order propose the level of quality we have and appropriate needs
again to raise water quality in the city.

This study intends to evaluate the
physical and chemical parameters in order to check the quality of borehole
water in Mogadishu, and to propose appropriate solution to solve the identified
problem.

The population growth of the
city and rising water consumption makes it an important step in assessing the
quality and quantity of borehole wells. Therefore, the study will concentrate
on discovering the quality aspects in terms of physical and chemical parameters
and hydraulic properties of the aquifer zone.

 

 

 

 

 

 

 

 

 

CHAPTER 2: LITERATURE REVIEW

GROUNDWATER IMPORTANCE AND DISTRIBUTION OF WATER ON THE EARTH

As we know, most of the earth has
been covered by water. An over 75% of the earth’s surface is covered by water.
The oceans constitute the majority of that which is not fit for human
consumption. The fresh water mostly is protected up in the icecaps and
glaciers.

The freshwater on the earth’s
surface which is fit for the human consumption is less than 1% of the total
water in the world. (1)

The distribution of the world’s
water is presented in Table 1-1:

Salt water in
oceans:                             
97.2%
Ice caps &
glaciers:                                2.14%
Groundwater:                                         
0.61%
Soil
moisture:                                       
0.005%
Atmosphere:                                         
0.001%
Fresh surface
water:                              0.0009%

 

 

 

 

 

 

 

 

Table
1-1. The distribution of the world’s water

 

Groundwater, which is in aquifers
below the surface of the earth, is one of the most important natural resources
of all Somalia’s regions including Mogadishu as domestic water supply,
livestock and small scale irrigations. That means, apart from the areas along
the Juba and Shabelle rivers, all other regions depend on groundwater for their
water uses.

HYDROLOGY

SOMALIA CLIMATE AND WEATHER

Somalia generally has climate which is arid type,
especially at the coasts with annual rainfall of less than 250 mm in the north
up to the 5th parallel, with 400 mm in the south and 700 mm in the
south-west. In Mogadishu the average annual rainfall has been estimated about
520mm. (6)

Somalia has four seasons, two of them are highly
important in the country, and they are; Gu and Dayr. These are when the most
frequent rains fall down in the country. In these seasons are when the rivers
floods, farms are irrigated and livestock grow up. The above main seasons are
separated by two secondary short seasons and they are; Jilaal and Hagaa.

Let’s give short descriptions from each season, and we
get as follows:

Jilaal: from mid December to mid March, with dominant
north-east monsoons

Gu’ : from March to May; this is the spring
transitional season

Hagaa:  from
June to the end of September, with dominant south-east monsoons.

Dayr: from October to December; the autumn
transitional season. (6)

GROUNDWATER OCCURRENCE / HYDROLOGIC CYCLE
AND GROUNDWATER

According to the Freeze and Cherry (1979),
groundwater is defined as the subsurface water that occurs beneath the water
table and flows though geological formations of voids in the soils and
permeable layers that are fully saturated. It is valuable supporter of general
ecosystem and does not exist in isolation but it is part of main factors in the
hydrological cycle as shown in the figure 2.1 below. (2)

Figure 0?1
Hydrologic cycle

The water cycle is the continuous
dynamic cycle of water circulation from the earth’s surface because of
evopotranspiration and to the atmosphere and vice versa. This circulation of
water is known as the hydrologic cycle.

As a definition of hydrologic cycle

The hydrologic cycle is the process
by which the water is circulated from the earth’s surfaces to the atmosphere
through evaporation and transpiration and back again to the surface through
precipitation. (1)

There are many processes that
involve the formation of hydrologic cycle, the most important ones include:
evaporation, transpiration, condensation, precipitation and runoff. Although
the perimeter circulation cycle is consistently stable, the distribution of
different systems is constantly changing.

The sun is playing major role in hydrological cycle
systems. The sun takes water from stored water in different storage systems (in
the oceans, lakes and rivers etc) and transferred it through the atmosphere.
The water back again to the earth’s surfaces such oceans through different
routes. The rainfall component on the earth’s surfaces infiltrates into the
soil with remainder evaporating into the atmosphere or as runoff to rivers.
Soil moisture can both be taking up by plants and transpired or flow quickly as
inter flow to a river channel. Some of that infiltrated water will go down
deeply into the ground through pores and voids in the permeable layer
formations, then it will accumulate on an impermeable beds and make it
saturated and eventually forms what is known as groundwater. The underground
water-bearing formation that is capable of yielding considerable amount of
water is referred to as an aquifer.

 Figure 1-3. A generalized and simplified
diagram of the hydrologic cycle

GROUNDWATER
FLOW

Large appreciable amounts of water
are stored in the subsurface. The moving of groundwater normally is very slow.
As appreciating of water cycle, the water of the ground comes from
precipitations that infiltrates downward from the earth’s surface.(3) The water that goes below the surface of the earth
may be determined to exist in two main zones or environments classified as
Vadosa Water and Phreatic water or Groundwater.

In Vadosa water consists of the
upper layers near the earth’s surface which is unsaturated zone, and it is
exists in three different types of environment; soil water, intermediate vadose
water and capillary water.

¾   
The
soil water forms a thin layer confined to the near the surface depth of the
earth. It may estimate to occur at depth between 1.0 to 9 m and is held up by
the root zone of vegetable cover and it is lost to the atmosphere due to
transpiration and evaporation.

¾   
The
intermediate vadose zone, it occurs emediately after the soil water zone.

¾   
The
capillary water zone, also called as capillary fringe. This is the zone which
in-touch with the water table, therefore in the fine particles the groundwater
is drawn upward by capillary action from the saturated zone lying underneath.

Figure ?0?2 Groundwater occurrences elasterations
diagram

a)    
The
upper layers near the earth’s surface which is unsaturated zone, and water is
available in varying amounts that change over time, but does not saturate the
soil.

b)    
Below
this layer is the saturated zone, where all of the pores and spaces between
rock particles are saturated with water.(3) This area is used to describe term of groundwater.

The groundwater movement/flow
depends on the geological gradient of that particular area. In generally the
water flows to the downward, from higher energy elevation to the lower energy
an elevation. As well as the groundwater flow and rate of movement depends on
the aquifer hydraulic properties and permeability.

According to (Freeze and Cheery
1979) aquifer is defined as an
underground layer of water-bearing permeable geologic formation that can
transmit significant amounts of water to wells and springs, under ordinary
hydraulic gradients. (2)

TYPES
OF AQUIFERS

1.  
Unconfined
aquifer: is an aquifer that is close to the ground surface, with serious layers
of materials of high permeability extending from the earth’s surface to the
base of the aquifer formations. (4)

It recharges from downward seepage
through the unsaturated zones, lateral groundwater flow, or upward seepage from
the beneath geologic formations.

Figure 0?3 Unconfined Aquifer elastration

The equations governing unconfined aquifer, applying
to the Darcy’s formulas are expressed below:

                (1)

Rearranging this
equation, we get

                         (2)

In integration
equation 2, we get the following result:

                   This is the equation of unconfined aquifer.

2.  
Confined
aquifer: An aquifer which located in between two impermeable layers. It is also
known as a pressure aquifer, or artesian aquifer or phreatic aquifer. It is
completely filled by water and it doesn’t have a free water table and aquifer
is under pressure.  

Applying by Darcy’s formula, we can express as
mathematically:

                (1)

Rearranging this equation, we get

                         (2)

In integration equation 2, we get the
following result:

                   This is the
equation for confined aquifer

Figure?0?4 is
shows flow of Confined aquifer

3.  
Perched
aquifer: Perched aquifer is an
aquifer that located above the regional water table in the vadose zone. This
occurs when there is an aquitard layer above the main water table and below the
earth’s surface.

Figure 1?0?5 Perched Aquifer

AQUIFER
PROPERTIES

1.  Porosity

The porosity is the present of
spaces and voids in the formation of geological aquifers to allow water pass
through it and store water within that voids in the materials.  It has pore spaces, where groundwater is
stored and allowed to move within it.

Mathematically porosity we can
express as follows:

Where:

n is the porosity, and its
dimensionless and they denoted mostly in %

Vv is the Volume of void
spaces in a unit volume of earth materials L3

VT is the total volume of
earth materials, including both voids and solids L3

The porosity depends on how the
particles are packed and particle size distribution. Porosity also depends on
other factors such as:


Shape
of particles (angular particles give higher porosity)


Cementation
and compaction


Degree
of fracturing of rock aquifers

 

2.  Transmissivity

Tranmissivity is best to define as the ability to transmit amount
of water horizontally through a unit width of fully saturated thickness of
aquifer under a unit width of hydraulic gradient. In mathematical we can
arrange as follows:

Where

T = Transmissivity L2/T or L2/d,

K = hydraulic conductivity L/T

B = Saturated thickness of the
aquifer L or M

 

 

3.  Hydraulic
conductivity

Hydraulic conductivity is a measure of the material’s ability to allow water
to pass through it. It is defined as the proportionality constant with respect
to the specified discharge of a porous method under the hydraulic gradient of
the unit in Darcy’s law:

Where v is specific discharge L/T,
K is hydraulic conductivity L/T and iis hydraulic gradient dimensionless.

 

GROUNDWATER ABSTRACTION

 

 

SOMALIA GROUNDWATER
QUALITY

WATER QUALITY CONSTRAINTS

To meet the demand of the maximum amount of water
required in a particular area which can be recovered from an aquifer is not
only a problem to be addressed. The groundwater quality must also be taken into
consideration. Therefore, the groundwater abstraction rates must be sustained
without causing a reduction in water quality need to be estimated.

In Muqdisho vicinity there are two potential sources
of groundwater contamination: (5)

1.      Due to saline water at the coast

2.      Due to poor quality from the north of the river shabelle
recharges.

These potential
constraints were the time that the borehole fields were outside the city; in
Afgooye road and Balcad road. But nowadays, after we have missed our central
government and violence spread, there was more boreholes/wells constructed in
the city within the residential houses in Mogadishu, therefore we’re expecting
to be contaminated by the human and environmental activities in the city. These
contaminants can be septic tanks, garbage collection point and other from
industrial wastes.