Hydrogeological Investigation of the East Nile Area { Khartoum State – Sudan }

Prepared By

KHALID ABDALLA MOHAMMED KHALID

B.Sc. (Hons.). Hydrogeology

Supervisor

Dr. MOHAMED ALI HASSAN DAHAB

A Dissertation Submitted in partial fulfilment of the requirements of the Graduate College For the Master Degree in Geology (Hydrogeology)

Department of Hydrogeology Faculty of Petroleum and Minerals Al NeelainUniversity – Sudan

May 2017

األيت

بسم اهلل الرحمن الرحيم

قال تعالي:

)أوَلم يَروا أنًا نَسى ق ألماءَ إلى األر ض ا لجر ز فنخرج به زَرعًا تأ كل منه أنعامهم وأنفسهم أَفال

يبصرون)) سىرة السجدة / آيه٧٢ )

(Do they not see that we do drive rain to parched soil bare of herbage, and produce there with crops, providing food for their Cattle and themselves? Have they not the vision?)

English translation of meaning and commentary of the Holy-Quran, Bechtel Translation.URL.www.turath.com

Dedications

To my Mother

To my Father

To my brothers sisters and fiancé And Best

Friends

ACKNOWLEDGEMENTS

I would like to express my thanks and gratitude to Al Neelain University for support and help.

I would like to express deep gratitude and appreciation to Dr. Mohamed Ali Hassan Dahab for his close supervision and guidance throughout this work, special thanks and appreciation to

Dr. El Nzeer Gusmelseed Adam.

I wish here to thank Mr. Moataz Amer and Mr. Mohammed Adlan for their assistance during this study. Finally, I thank everyone to help me in the completion of this work.

Khalid Abdalla

III

ABSTRACT

The study area is located east of the Nile in the east of Khartoum state, which is located in central Sudan, it lies between latitudes 15 ° 24' 00″ N and 16 ° 00' 00″ N and longitudes 32º 24′ 00″ E and 32º 54′ 00″ E. The main objective of the study is to evaluate the ground water in term of quantitatively and qualitatively throughout geology, hydro geological, hydro chemical. Aim to study; Understanding, Knowledge and situation the hydrogeology in the area. The study results showed that main the water bearing strata are sand stone and conglomerate in the Nubian Sand stone formation with thickness range from few meters in the northern part to 300-400m in the southern and south eastern part. It forms two aquifers zone, upper one compose of super facial deposit and lower one basically Nubian Sand stone formation which is main aquifers in the study area. The static water level is shallow near the River Nile and Blue Nile and increase gradually to the East and south east, the maximum static water level depth is 66 m in SALAMET ELSHETAT The hydraulic properties of the aquifer system were estimated from the pumping test data analysis using aquitest software which showed the transmissitivity has low value near the River Nile and Blue Nile and increase toward the east and the south east of the study area, this variation related to the lithology of the aquifer. The transmissitivity range in the study area between0.00198 and 0.28 m²/min and the recharge in the study area is approximately (5.2×108) m³/day while the discharge (Annual ground water consumption) is only (720×106) m³/day Ground water in the study area is generally suitable for domestic and other purposes, because it contain small amount of soluble salt. However there are saline zone extend from the south east part to the north east where ground water is not fit for human consumption. The recharge source result was confirmed by hydro chemical analysis, which showed that the

water (Na-HCO3) to (Na-Cl) water type near the River Nile and (Na-HCO3) and (Na-Cl) water type at the centre and the south eastern part of the area.

الخالصت

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List of Contents

Content Page I.…………..………………………….…………………………………………………… األيت Dedication……………………………………...…………..…………...…….…………..…..II Acknowledgement…………………….……………..……...………………………………..III Abstract…………...………………...………………..………………………………….…...IV V....….………………………………..……………...…………..…...……….…………الخالصت List of Contents…………….……...……………..………...…………………………..……..VI List of Figures…………………...………………..………………………………………..…IX List of Table…………………..…………………………….……………………………....…X List of abbreviation……...…….………………………………..………………………….... XI

CHAPTER ONE: INTRODUCTION….….….….….………...…...………………….….....1 1.1 General………………...……………….………….…...………………..…….………1 1.2 Location of study area……………………...…………………….………..….……….1 1.3 Climatic conditions…………………………..……………………………...…..…….3 1.4 Physiographic features……………………….……………………………...….……..3 1.4.1 Topography and Soil …………………………………………………….………….3 1.4.2 Drainage Patterns…………….…………………………………………..…...……..4 1.4.3 Vegetation cover…………………...…………………………………..…...…...…..6 1.5 Population Socio-Economic activities…………..…………………….…….……..….6 1.6 Previous work…………………………………………………………...... 6 1.7 Statement of the Problems…………………………………………….………………7 1.8 The research objectives……………………………………………….…………….…7

CHAPTER TWO: METHODOLOGY…...……………………………….……………...…8 2.1 Material and Methods of Investigation…………………………….……….…….…...8 2.2.1 Collection of data……………………………………………….……………..…….8

2.2.2 Field Investigations…………………………….……………….………………..….8 2.2.2.1 Hydrogeological Investigations………………….………….………………….…8 2.2.2.2 Geophysical Investigations……………….……………….………………….…...8 2.2.3 Laboratory Analysis…………………………………….…………………...... 9 2.2.4 Softwares………………………………………………..………………………..…9

CHAPTER THREE: GEOLOGY AND TECTONIC SETTING………………..…....…11 3.1 Geological Setting……...………………………………...…….…..….……..……....11 3.1.1 Basement complex…………………...………………………….………….……...13 3.1.2 The Nubian Sandstone Formation…………………,,…….…….…………..…..….13 3.1.3 Tertiary Volcanic Rocks…...…………………………..………………..…...... 18 3.1.4 The Gezira Formation……………..…………………………....…...……....……..19 3.1.5 Superficial Deposits……………………………………………….……..…...... …20 3.2 Tectonic Setting……………………………………………..…….………..……...... 21

CHAPTER FOUR: HYDROGEOLOGICAL INVESTIGATION……….……….....…..24 4.1 Introduction……………………………………………….……….…...... 24 4.2 Groundwater Resources in study area……………….………...………….……….....25 4.3 Aquifer………………………………………………...…………….....………....….25 4.4 Water Table measurements………….…………………………………...... …26 4.5 Aquifers Characteristics (Hydraulic Properties)…...………………..…….....…....…28 4.5.1 Hydraulic conductivity (K)……………………...………………..……....…...…...29 4.5.2 Transmissivity (T)……………………………….…….….……….…....…….....…30 4.5.3 Storativity (S)………………………………...……………………..…..…...……..30 4.6 Specific Yield………………………………………..……...……………….…….…31 4.7 Regional Recharge………………………………………..……...……….....…….…31 4.8 Geophysics Investigation…………………..…………………………...…....…...….33 4.8.1 Interpretation of resistivity data…………..……………………………....…..……33 4.8.2 Pseudo Sections….……………………...…………………………....…...….……34

VII

CHAPTER FIVE: HYDROCHEMICAL INVESTIGATION………....……...……...….38 5.1 Introduction………………………………………………………...... ……....38 5.2 Physical characteristics of water……………………………..…...…………...…...... 38 5.2.1 Temperature…………………………………………………………..………....…38 5.2.2 Colour ……………………………………………………………………………...38 5.2.3 Density………………………………………..…………………………...... 39 5.2.4 Taste and Odour………………...……………………..……….……………..…....39 5.2.5 Turbidity ……………………………………………………………………...……39 5.3 Suitability of Groundwater for drinking and domestic uses …………….……...…....40 5.3.1 Hydrogen-ion concentration (PH)………………...………………………..…....…40 5.3.2 Total Hardness (TH)…………………………...……………..…………….…....…41 5.3.3 Total Dissolved Solid (TDS)……………………..………...…………………..…..42 5.3.4 Electrical Conductivity (EC)………………………....……………..……………...44 5.3.5 Sodium (Na+)………………………………………..…………………………..….46 5.3.6 Potassium (K+) ………………………………………...……………..…….…..….47 5.3.7 Calcium (Ca+2) & Magnesium (Mg+2)…………………...….……...... 48 5.3.8 Chloride (Cl-) …………………………………….……………....……...…………51 5.3.9 Bicarbonate (HCO3-)………………………..…………….……....……….………52

- 5.3.9 Nitrates (NO3 )……………………………………………………...……….…..…53 5.4 Suitability of Groundwater for irrigation uses (SAR) ……………….……...……….54 5.5 Groundwater Type……………………………………………………..…………….55

CHAPTER SIX: CONCLUSIONS AND RECOMMENDATIONS ...……...... ….…....56 6.1 Conclusions.....………………………….…………..……………………...…...……56 6.2 Recommendation………………………………..………..……….……………...... 57 REFERENCES ……………………………………..………………………...…………...... 58 APPENDICES……………………………………..……………………………………...... 61

VIII

List of Figures Page

Fig (1.1): Location map of the study area…………...………….………………….…….…….2 Fig (1.2): Drainage pattern of the study area……………………………………….……….…5 Fig (2.1): Flow chart showing the methodology of the study area………………….………..10 Fig (3.1): Geological map of study area………………………………...………….……...…12 Fig (3.2): Sketch block diagram for part of the Khartoum basin. Shows the geological and stratagraphical units in study area.………………………....…………...………………...….17 Fig (3.3): Structural map showing the interior rift basin of the Sudan……….…….………...23 Fig (4.1): Two profiles of subsurface geology and showing the aquifers at some villages in the study area……………………………………………….……………..………..………....26 Fig (4.2): Groundwater flow directions in the study area (Contour value in m, a.m.s.l)…..…27 Fig (4.3): The well location in the study area…………………….………………..…..…...... 29 Fig (4.4): Location of VESes (Northern part of study area)…….………………….………...35 Fig (4.5): Values on contour lines showing the resistivity variations from west to east with Depth………………………………………………………………………………………….36 Fig (4.6): Values on contour lines showing the resistivity variations from west to east with Depth…………………………………………………………………………..…………...…36 Fig (4.7): Location of VESes (Southern part of study area)……….…………………...…....37 Fig (4.8): Values on contour lines showing the resistivity variations from south to north with Depth…………………………………………………..…………….…………….………….37 Fig (5.1): The spatial distribution of the Total Hardness (TH) (mg/l) in the study area…...... 42 Fig (5.2): Concentration of TDS (mg/l) in the study area………………………….…...... 43 Fig (5.3): The spatial distribution of the Electrical Conductivity (mg/l) in the study area...... 45 Fig (5.4): The spatial distribution of the Na+(mg/l) in the study area………………...... 46 Fig (5.5): The spatial distribution of the K+(mg/l) in the study area……………...……….....47 Fig (5.6): The spatial distribution of the Ca+2 (mg/l) in the study area…………..…...…...... 49 Fig (5.7): The spatial distribution of the Mg+2 (mg/l) in the study area……...….…...……....50 Fig (5.8): The spatial distribution of the Cl- (mg/l) in the study area………………...... 51 - Fig (5.9): The spatial distribution of the HCO3 (mg/l) in the study area …………...... 52 - Fig (5.10): The spatial distribution of the NO3 (mg/l) in the study area…….………...... 53 Fig (5.11): Suitability of groundwater for irrigation………………………....………….…...54

Fig (5.12): Piper’s trilinear diagram showing groundwater facies in the study area….…...... 55

List of Tables

Page

Table (3.1): The stratigraphic column of the study area……..…..………..…….....….……..20 Table (4.1): Average Value of Transmissivity (T), Storage Coefficient (S) and Hydraulic Conductivity (k)………………………………………………………………………...... …30 Table (4.2): The average specific yield values for different materials carried out …….….....31 Table (4.3): Resistivity values of rock unit in the East Nile…………………………….…....34 Table (4.4): Range of resistivity values in East Nile area…………………………………....34 Table (5.1): The ground water classification based on Hydrogen-ion concentration…...... 40 Table (5.2): The ground water classification based on hardness……………………….….....41 Table (5.3): The ground water classification based on TDS …………………………….…..43 Table (5.4): EC in the study area…………………………………………….………….……44 Table (5.5): Water classification based on SAR in the study area……….….…………….…54 Table (5.5): Type of water according to piper………………………...……...…………....…55

Abbreviations

Fig Figure SWL Static water level a.m.s.l Above mean sea level m3/y Meter cubic per year m Meter min Minute Ωm Ohm.m B Aquifer thickness T Transmissivity K Hydraulic Conductivity S Storativity (Storage coefficient) PH Hydrogen Concentration TDS Total Dissolved solid EC Electronic Conductivity TH Total Hardness Mg/l milligram per litter SAR Sodium Adsorption Ratio WHO World Health Organization

CHAPTER ONE

INTRODUCTION

1.1 General

Water is essential for life, health and human dignity. In extreme situations, there may not be sufficient water available to meet basic needs, and in these cases supplying a survival level of safe drinking water is of critical importance. In most cases, the main health problems are caused by poor hygiene due to insufficient water and by the consumption of contaminated water. The groundwater is considered an important source of water supply for both human consumption and irrigation. The use of groundwater depends on the quantity, quality of groundwater and the depth from which it is pumped. Other factors which should be considered in planning priorities of water demand (type, distribution, and recharge) are the availability of alternative resources, the existing development plans, and the socio-economic conditions and political priorities. However, both the busy life and agricultural and industrial activities of this area have thrown their direct impact on its environment. Nevertheless, this is also reflected on the potable water management systems and consumption. From this point of view, the study of the ground water, its quality, chemical characteristics and the evaluation of its resources become of prime importance for a better quality of life.

1.2 Location of study area

Fig (1.1): Location map of the study area.

1.3 Climatic C0onditions

The study area is situated at the northern part of savanna belt which characterized by hot summer climate, with only the months of July and August experiencing significant precipitation with an average of 100 to 200 millimetres of precipitation per year. Based on annual mean temperatures, Khartoum is one of the hottest major cities in the world. Temperatures may exceed 53°C (127°F) in mid-summer.the temperatures range between 25°C – 40°C in summer from April to June and from 20°C to 30°C from July to October and decreasing in winter Season from November to march between 15°C to 25°C. 1.4 Physiographic Features

1.4.1 Topography and Soil

The area is topographically characterized by flat peneplain that dominates the entire area. These plains rise gradually from ground 340 meters above sea level to 600 meters towards the east (Salman, 2001). Throughout the plains some isolated hill rise up above the surface to make prominent land marks.The dominant geological formation is the Nubian Sandstone and the Basement Complex; soil type is dark cracking clay plains bisected by depressions and seasonal water courses, covered with pale yellowish-white coarse sand and small gravels. The undulations of the area resulted in three main land forms. The first form has relatively high elevation compared to the neighbouring land forms and is of varying areas and extensions in all directions; known locally as (Daharas) with poor vegetation cover and covered by sand dunes and with large block igneous rocks and small gravels. The second land form is flat plains with soil types ranging from reddish fine sandy soil comprising few centimetres upper layer followed by muddy clay soil up to many meters beneath the upper layer. This characterizes most of the Eastern part of this area which is a part of Butana region whose soil was classified as Verticals which is dark cracking clays referred to as black cotton soil. It is mostly alluvial in origin from material transported by the river, but some might have been formed in situ from basaltic rocks. The third land form of the Eastern Nile is valleys, locally known as (Wadies) which are of low elevations, are characterized by fertile soils. Generally the study area is lie on the Nubian sandstone formation. There exist gravelly ridges and windblown sand sheets.

The soil is formed of reddish- brown, coarse textured materials; Soils along the west bank are of poor quality for agricultural uses except for the narrow strip of the river bank. Soil urban demands are always in increase as these are important in foundations and roads, as the majority of houses are constructed of mud bricks, as well as their use for growing plants. The soil suffers from rapid erosion in the rainy seasons and loses natural quality when dug away or covered with building’s remains and human wastes.

1.4.2 Drainage Patterns

Qualitative and quantitative drainage characteristics of a basin provide an indirect clue to the hydrogeological characteristics of the area and therefore are useful in the assessment of groundwater resources. The important characteristics are drainage pattern and drainage density. These are related with the lithology, structure and permeability of the bedrock. The River Nile and Blue Nile represent the major drainage system in the study area. There are many khors running to Blue Nile and the Nile, Moreover the Khors and Wadies (wadi soba) receive flash floods during the rainy seasons.

Fig (1.2): Drainage pattern of the study area.

1.4.3 Vegetation Cover

The area is covered by savanna type vegetation such as: Acacias, Shrubs (Kitir, Sidir, Tundub, Hegleg, Samar and Arak) and grasses, which grow in valleys and low land with exception of some areas in the extreme northern part of the study area which is dominated by semi desert vegetation.

1.5 Population Socio-Economic Activities

About 80% of the inhabitants in the study area are living along the Nile, the density of the population drops rapidly away from the Nile. The major tribes are Batahine, Shukria, Mesellemia, Hassaniya, Elseilat and Mogarba. The activities of the people in these regions are pasturing sheep and goats, some people depend on agriculture growing crops during rainy season. Groundwater development in the area is mainly to supply domestic needs and partially for irrigation.

1.6 Previous Work

There are many studies and research works carried out in the east of the Nile area by a number of scientists in the field of geology and groundwater to assess the ground water in that region. Delany (1955) complied a geological map of scale 1:250,000 that show the lithological units of the area. Khairallah (1960); worked on the geology and hydrogeology of the Nubian sand stone formation in Khartoum, shandi region.Almond (1976); and dawoud (1970); both described in detail the geology and the structure of pre_Nubian basement complex of Sabaloka area ,White man (1971); who did researches discovered the geology of the Nubian sandstone formation. Sudanese Germany Exploration Report (1979); it aimed to carry out field investigation to evaluate the groundwater resources in Khartoum province within its three towns, they used a steady state 3 dimensional digital stimulation model. Abdel Salam.A.M, and Kheiralla (1987); presented a study of the aspects of recharging the Nubian aquifer system near the confluence of blue and white Nile, they used isotopes and water chemistry technique.

1.7 Statement of the Problems

In the study area some villages in the area suffers from content of the saline waters in ground water wells, many wells are not well designed and are not sealed, that make them susceptible to contamination from surface waste of animals, as well as the falling of some small animals inside.

1.8 The Research Objectives

The main objectives determining the following:

i. To cry out the aquifers characteristics in the area.

ii. To study the subsurface features, detecting the alluvial thickness and the depth to

the bed rocks using the geophysical method (Electrical Resistivity Method).

iii. The boundary between different types of rocks which affect the water quality. iv.

To evaluate the hydrogeological situation in the area.

v. Groundwater quality and assess its suitable for drinking and any another purposes.

CHAPTER TWO

METHODOLOGY

Material and Methods of Investigation The methods of the study are planet achievement the objective of study, it includes some steps:-

Collection of Data The previous data involve: previous studies done in study area such as Geological data, and Geophysical data….etc. A hydrogeological information and borehole report has been collected at the beginning of this study, they had been provided from the database of the water corporation.

Field Investigations Field work consists: Hydrogeological investigation and Geophysical investigation.

Hydrogeological Investigations These include groundwater level measurements, estimation of hydraulic properties of the aquifers, Elevation and location of boreholes were measured with Global Position System (GPS). The hydrogeological investigation carried out in the area aimed to determine both the hydraulic and hydrochemical properties of the aquifers. The hydraulic properties were determined through data collection from field measurements and computers modification included the determination of hydraulic conductivity (K), transmissivity (T), with help of controlled pumping tests.

Geophysical Investigations Electric resistivity methods are frequently used as investigation tool and considered to be two of the most famous geoelectrical techniques that used in groundwater exploration to obtain, quickly and economically, details about the location, depth and apparent resistivity of the sub surface layers.

Laboratory Analysis

Hydrochemical characteristics considered in this study are the measuring : Total dissolved solid (T.D.S), electrical conductivity (E.C) , hydrogen iron concentration (PH) , bicarbonate - - -2 - + +2 (HCO3 ), chloride (Cl ), sulphate (SO4 ), Nitrates (NO3 ) sodium (Na ), calcium (Ca ), magnesium (Mg+2 ) and potassium (K+) in groundwater water. For aggregating and stored the samples of water using plastic bottle.The water level is measured by water level indicator, the next step taking sample by clean jar and measuring Temperature by Thermometer expressed by C° and using PH meter to determine the PH expressed by (PH unit). Electrical conductivity (EC) also measured in field by EC meter expressed by (μs /cm), for 19 water samples. The analysis completed in the Central Chemical lab.

Softwares Several computer software's have been utilized in this study, they include: i. Microsoft office Word 2013 for text processing.

ii. Aquitest version 4.4 used for pumping test data and aquifer parameter

calculations.

iii. Aquachem used for representing and comparing water quality

analysis.

iv. ArcGIS version 9.3, Surfer version 10 and Corel Draw

version 11 were used for maps preparation.

v. ENVI version 4.8 package was used for digital image

processing.

vi. IPI2win used for geophysical data analysis.

Fig (2.1): Flow chart showing the methodology of the study area.

CHAPTER THREE

GEOLOGY AND TECTONIC SETTING

3.1 Geological Setting

The geology of the central Sudan has been extensively studied by many authors, e .g. Andrew (1948), Khieralla (1966), Whiteman (1970, 1971), Almond (1980),Kroner et al(1987),Vail(1988), Dawoud and Sadig (1988) and Awad (1994). The oldest rocks exposed in the region are mainly undifferentiated Proterzoic gneisses and schists. The oldest reported sedimentary unit overlying the basement in central Sudan is of late Jurassic age (Awad, 1994). The Cretaceous non-marine sedimentary rocks, in the study area are Albian – Santonian in age (Awad, 1993). These are fluvio-lacustrine, siltstone and conglomerates strata in the study area were also encountered between Blue Nile and the White Nile. Tertiary basalts are also encountered in the Khartoum basin either cropping at the surface as the case in Jebel Eltouriya, or from wells, as penetrated by an exploration well in the Khartoum Basin south of the studied area. However, their aerial extent is not well known.

Cenozoic strata were encountered in the area between the Blue Nile and the White Nile. They are unconsolidated gravels, sands, silts and clays of the Gezira Formation overlain by recent superficial deposits of the two Niles. However, a generalized geological map of the study area and vicinity is shown in Fig. (3.1). Based on these studies the following general geological succession has been identified:

Fig (3.1): Geological map of study area (Modified After GRAS, 2004).

3.1.1 Basement Complex

The basement in the study area is Pre- Cambrian to early Palaeozoic age (Whiteman 1971) used to embrace all formation older than the Nubian sandstone [Andrew1948]. Mainly composed of high grade grey gneiss of Precambrian age, were found to outcrop on the far southern part of the area. They usually form massive, boulder outcrops or are eroded to flat, sand–covered plains, these gneisses are poorly to moderately foliated, generally grey in colour, medium–grained, and consist of quartz, orthoclase, muscovite and magnetite. They are metamorphosed to the level of the upper amphibolites facies with transition to the granulite facies. Pegmatites of quartz and feldspars, with occasional micas and other minerals cut through the gneisses.

3.1.2 The Nubian Sandstone Formation

Nubian sandstone formation considered to be most important aquifer in the country.it covered together with basement complex about 78% of the Sudan. It was used to describe the late cretaceous sandstone in the Nubian Desert in the northern African. [Whiteman 1971] the first one proposed the Nubian Sandstone Formation in Sudan. They are un metamorphosed bedded and usually flat-lying sedimentary rock which are made up of conglomerates, grits, sandstone sandy-mudstone and mudstone, which are considered to be of post Paleozoic and pre Tertiary age. Geologists give different interpretation the Nubian sandstone as different angle. Kheiralla (1966) used the term Nubian sandstone formation for the sedimentary strata of variegated colours around the Khartoum state and divided the Nubian sandstone into five lithological units from Khartoum to Shendi area. Merkhiyat Sandstone located northern of Omdurman area which is a part of Nubian sandstone formations, which started as made up of clastic sedimentary rock largely sandy and conglomerate poorly cemented and another place with high silicified bed. The beds are generally horizontal or gently dipping. The following lithological unit were established by Kheiralla (1966): i- Pebble conglomerate ii- Intra – formational conglomerate iii- Merkhiyat sandstone iv- Quarzone sandstone v- Mudstone

Hussein (1976) and Omer (1983) they are describe as sandstone environment, first one suggested that it is a tropical fluviatile with the second one proposed a semi dry to tropical paleoclimate and upper cretaceous age. Wycisk et al (1990) adopted the term of Omdurman formation depending to palynological study from subsurface strata. They suggested that in Khartoum area the predominantly sandy Omdurman formation is of Albian to Cenomanian age.. Bireir (1993) Based described based on lithology, grain size, heavy minerals content, geochemistry, clay minerals content, paleogeography and depositional environments, subdivided Omdurman formation into two formation:- i- Upper Omdurman formation (outcropping sediments)

Upper Omdurman formation is clastic sedimentary sequence of Khartoum State. It is comprises a flat-lying or gently dipping sedimentary rocks lying unconformable on an originally uneven basement surface and characterized by an irregular outcrop pattern. This formation exposed at of Abu Weledat and Ummarahik hills. [Barazi, 1989] located at northwest of Omdurman and Aulia hills in southern of Omdurman is many contain sandstone with various grain size (coarse, medium or fine) cemented by siliceous, kaolinitic and ferruginous materials.

ii- Lower Omdurman formation (subsurface strata)

Lower Omdurman formation is represented as the surface and sub-surface strata [Barazi 1989] are proposed that the depositional environment of the exposed strata is fluviatile while sub-surface units display a lacustrine environment. Lower Omdurman formation is composed of fine and less coarse grained, poorly to moderately sorted, silisiclastic sediments [Bireir, 1993].the sediments of this formation were almost transported as subsided particles which rolling to a considerable amount and deposited under fluvio-lacustrine conditions.

This processing are gives 72% course-grained sandy where the sandstone is the dominant rock type it is almost friable, except the mudstone horizons which are frequently compacted and hard. This formation shows fining upwards, and stacked- channel sequences, ranging in thickness from 25 to 35m, rapid lateral and vertical changes of facies [Birier, 1993; Farah et al 1994].

(Awad 1994) distinguished two discrete lithological units of Omdurman formation and consequently subdivided it into:

1. Merkhiyat member (represented by the outcrop sequences). 2. Umm Badda member (from the subsurface).

1. Merkhiyat Member (Turonian-Early Senomanian) This member is represented here by surface sedimentary sequences in the state of Khartoum and vicinity. The type section of this member is located at Jebel Merkhiyat (Awad, 1994). These sediments comprise flat lying or gently dipping siliciclastic sedimentary rocks consisting mainly of conglomerates, pebbly sandstones, and medium- to course– grained sandstones, siltstone, and shale. The conglomerates are mostly grain-supported of oligomictic nature, pebbles size range between 2 and 5 cm although some gravely portions have been observed. The colour of these conglomerates is mainly grayish and brownish. They are commonly massive; rarely do they show planar cross stratification.

The pebbly sandstones are most common observed sedimentary rocks in the study area. Their colour varies from brown to grey rarely dark grey. The most common observed sedimentary structures in these beds are trough and tabular cross stratification. These structures indicate northwest ward and less common northward paleo current direction. Conglomeratic beds which are often ferruginous and less silicified, were found capping most of the investigated, outcrops. The pebbles of these sandstones are rounded to sub rounded, and vary between 2-5 cm in size. They are cemented by ferruginous, kaolintic or siliceous material. The medium- to course–grained sandstone beds are the next most common rock type in the study area. These beds are light to dark brown or grey and rarely violet. They are moderately to highly consolidate owing to the nature of cementation, which is mostly siliceous, ferruginous and less frequently kaolintic. Trough cross bedding is the most observed sedimentary feature in these beds from which a northward to northwest ward paleo current pattern was deduced. In addition, slumping pattern was deduced as well as slumping structure (as load structure) were observed.

Associated with these beds, are some isolated and stacked channel lag deposits. Silicified wood fragments, seldom tree trunks, were found within these units. Siltstones and shale are not widespread. The sedimentary units in the study area reveal more fining than coursing upward sequences. In common, both types end abruptly, rarely they end with shale or iron crust. In the present study the following macro flora fossils have been reported from the Merkhiyat member:

2. Umm Bada member (late Albian – early Turonian) This unit is mainly known form the subsurface. Only small parts of it are exposed at limited localities in the study area, along khor Shambat, in the northern of Omdurman city and in scattered excavation inside the town. The unit is also exposed near Jebel Dura and at the base of Jabal Magroon, Fig. (3.2) and several other places. Lithologically, this member consists mainly of tabular cross stratified, fine–grained sandstone of different colors (brownish, grayish or light grayish), and cementing material but mainly kaolintic. Siltstones, clay stones and shale are subordinate, individual units and are of brownish, grayish or light grayish colour. The cementing material is mainly kaolintic. Siltstones, claystons and shale are subordinate. They are disposed as individual unit show horizons, with low–angle bedded sandstone alternating with finely laminated siltstone and rarely massive claystone. They are hard to moderately consolidated, sometimes show mud cracks and load casts structures. A detailed pollenologic study was carried out and the late Albian to late Cenomanian age given by Awad (1994) to this member is slightly corrected to late Albian – early Turonian.

Fig (3.2): Sketch block diagram for part of the Khartoum basin. Shows the geological and stratagraphical units in study area (after Farah et al 1997).

3.1.3 Tertiary Volcanic Rocks

Volcanic rocks have been reported in many locations e.g. Jebel Marra at (Whiteman 1971) and Bayuda desert in western and northern of Sudan respectively. (Anrdew 1948) correlated that with tertiary volcanic of east African and Ethiopia The area between Khartoum and Shendi regions are observed that, basic volcanic igneous rocks are intrbedded in the Nubian Sandstone Formation (Kheiralla, 1966) which are contain mainly basalt and dolerite dykes. The Basalt is occurring at Jebel Toriya (Jebel mean hills) which forms a low hill about 11 km west south of Khartoum. Extensive geophysical and geological investigations have been carried out the petrology of the basalt has been studied in detail (Almond, 1967). On the evidence of centripetally dipping flow banding inclined at moderate to steep angles, suggested that the basalt is an intrusion rather than a flow. Dolerite dyke and basalt reported in north eastern of Khartoum city, as known Sabaloka Igneous complex (Dawoud, 1970). The dolerite dyke of N- S trends was observed in the western parts of the study area. This is found by drill holes in Nubian Sandstone formation. Which were penetrated at variation of depth between Jebel Aulia and Khartoum (Farah et al 1994).

Basic igneous rocks mainly basalt cut the Omdurman formation at many localities, and are considered to be tertiary in age. (Delany, 1953) described and mentioned several small outcrops of basalt cutting the Omdurman formation in vicinity many locations where volcanic are penetrated in borehole are found near J. Aulia. Two small outcrops of olivine basalt occur south and west of Omdurman. The former makes up the Jebel Toriya and is now quarried-out for road construction purposes. The other one is a small outcrop of hexagonally jointed fine–grained dark green basalt. In addition to, a few scattered occurrence of volcanic rocks at valleys.

.1.4 The Gezira Formation

The term Gezira formation was first introduced by Anderw (1948) to describe the unconsolidated clays, gravels, silt and sand that rest uncomfortably on either the Nubian sandstone or directly on basement complex and is overlain by windblown sand and other superficial deposits (Delany 1966, Whiteman 1971; Vail, 1988; Bireir, 1993). This formation is restricted to the area between the White Nile and the Blue Nile and the east bank of the Blue Nile and the river Nile. Abdel Salam (1966) and Farah et al (1997) classified the Gezira formation in two major formation upper and lower Gezira supra formation. The upper Gezira formation is composed of unconsolidated sands, clays and silts. It is characterized by high percentage of smectite, low percentage of kaolinite and unstable heavy minerals (Birier,1993). The upper most layer as known the black cotton soil which is dark cracking clay. This cracking is representing by the weathering condition. The lower Gezira formation consists of interbedded sands and clays. The sands consist predominately of loose, medium and fine grained. The depth of this formation is identified in the borehole data section at depth of 205 to 240m (Birier 1993).

At Khartoum basin the depth that formation is approximately 180 m to 500m (Sun Oil Company 1989, unpublished report) (Abdesalam, 1966) Suggested that the main source for the Gezira formation is the Ethiopian volcanic plateau and proposed a fluvio-lacustrine depositional environment. Depending to palynological studies is identified the age of the Gezira formation for Oligocene - Miocene.

.1.5 Superficial Deposits

The recent deposits encountered in the study area include windblown sands the White Nile alluvium and Wadi deposits (streamer channel) (Whiteman 1971). It is occurring at many places with different characterized. The eolian sands cover most parts of the compresses between White Nile and Kordofan State (Whiteman 1971). Sites are observed

along the bank of the White Nile and between the dunes and Wadi deposit, consisting of unconsolidated sand, silt sand and gravel and loosely compacted silt, sandy silt and clay. The Superficial deposit include the vast clayey plain in addition to valley fills and deltaic deposit in the Butanna which are seasonally transported by the ephemeral streams during rainy season. The clay plain is dark and heavy montmorillinitic. The thickness of this clay varies from three meter at the slope of hill chains forming the water divide to more than 20 meters in most of area. The stratigraphic column of the study area is shown in Table (3.1).

Table (3.1): The stratigraphic column of the study area.

Geological Unite Age Reference Superficial deposits Recent Vail (1982) Gezira Formation Oligocene – Miocene Awad (1992)

Tertiary volcanic Rocks Early – Tertiary Vail (1982) Omdurman Upper/Merkhiyat Senonian Schrank& Awad (1990), Formation Member Awad(1994) Lower/Ummbada Albian - cenom/early Member Turonian*

Basement Complex Precambrian Sun oil company (1989, unpublished rep.)

2.2 Tectonic Setting

The tectonic evolution of the Sudanese interior rift basins is considered primarily in terms of the effects of Mesozoic-Tertiary movements reactivating the Pre–existing Precambrian weak zoon line Fig. (3.2), Apart from Khartoum basin, these basins are characterized by thick none marine clastic sequences which include thick lacustrine shales and claystones, floodplain claystones, fluvial and alluvial sandstones and conglomerates, Two stages of rift development and fracturing have been identified: From Neocomian to Early Aptian roughly E-W and NW trending troughs opened in response to a sub – meridian extensional regime in central Africa. From Middle Aptian to Late Albian large NW trending troughs opened in response to a northeast extensional regime while the Central African Shear Zone (CASZ) exhibited strike– slip movements generating pull a part basins. These two stages of crustal extension have been correlated to the dichronous evolution of the south and equatorial Atlantic domains during the early Cretaceous (Fairhead, 1988). On the other hand, the regional evolution of rift basin formation in Sudan could be effectively correlated with plate boundary generated lithospheric stresses. However, the rifting episode and its association with alkaline magmatism point to the contribution of asthenospheric dynamics probably related to mantle pluming. The extensional tectonism that forms these basins began in the late Jurassic – Early Cretaceous. Deformation and movement, along major fault trends,continued intermittently into the Miocene and resulted in a complex structural history that led to the formation of half–grabens and, to a less extent, full-grabens. Such wide variety of structures, lead to the formation of important hydrocarbon reservoirs. Three rift cycles were recognized in Muglad Basin, the first rift cycle commenced during the Late Jurassic, or, at the transition from Late Jurassic to Early Cretaceous.The second and the third rift cycles took place in the Cenomanian- Early Paleocene and the Paleocene – Oligocene times respectively. Regional studies (e.g Fairhead, 1988 and Bosworth, 1992) relate the initial rift basin development in Sudan to the early breakup phase of the South Atlantic.

Stratigraphical information obtained through subsurface analysis from the Khartoum basin, indicate a regional NNW to NW striking rift basins in Sudan terminated to the north by a northeast striking wrench fault system along which motion occurred during the breakup of Gondwana land. This major continental scale fault zone is termed the central African

Shear Zone (CASZ), or otherwise the Central African Fault Zone (CAFZ), (Schandelmeier and pudlo, 1990).Potential field data suggested the presence of at least ten sedimentary basins in central Sudan, northwestward of the CASZ.

In the east central Sudan further rift complexes are recognized. These are the White Nile rift complex that comprises the Bara and Kosti basins, and the Blue Nile rift complex with two major basins the Khartoum and the Blue Nile basins Fig. (3.3).

Fig (3.3): Structural map showing the interior rift basin of the Sudan. Modified after Fairhead (1988).

CHAPTER FOUR

HYDROGEOLOGICAL INVESTIGATION

4.1 Introduction

The purpose of most hydrogeological investigations is to locate potential areas for development of adequate quantity of reasonably good quality groundwater for a particular use; domestic, irrigation or industrial etc. Unconsolidated sands, gravels, sandstones, limestone, and dolomites, basalt flows and fractured plutonic and weathered rocks are examples of rock units known to be aquifers. Otherwise, geologic units having little or no permeability. The geological units are subdivided into aquitards, aquicludes and aquifuges. An aquitard is low permeability and transmit it slowly from one aquifer to another such as clays, loams and shale. An aquiclude is low permeable unit and does not transmit water such as unfractured igneous and metamorphic rocks. An aquifuge is an impermeable unit that will not transmit any water. The water bearing formations that act as containers for groundwater are termed aquifers, which is defined as any geological unit or structure that can store and transmits water in sufficient quantity to supply pumping wells or natural springs. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Generally, there are two types of aquifers; confined and unconfined (with semi- confined being in between).Confined aquifers are layers that are bounded from the top and the bottom with impermeable layer. Unconfined aquifers are layers that are not bounded by impermeable layer from the top, this part represents the level of the free surface of the water and can often be a superficial sediments. Unconfined aquifers are sometimes also called water table or phreatic aquifers, because their upper boundary is the water table or phreatic surface. Several hydrogeological studies were carried out at Khartoum area by many geologists khairalla (1966) and EL Bushi (1972).These studies made it possible to understand the changing nature of the hydrogeology of the region. They found that there are two formations hosting groundwater in the area; an upper aquifer and a lower aquifer.

This study aims to identify major water bearing formations, lateral and vertical extents, recharge and discharge areas, as well as the determination of the aquifer parameters such as the transmissivity, hydraulic conductivity and specific yield, etc. Fresh water resources in arid and semi-arid lands have three components: rainfall, surface water and groundwater. The Nubian sandstone is considered to be the major and best aquifer in the Sudan.

4.2 Groundwater Resources in study area

Groundwater is an integral part of the hydrological cycle, it's one of the most important natural resources. Hydrogeologically the Nubian formation constitute the main aquifer in the area. Also the alluvium deposits of the flood plain provide shallow groundwater sources of limited yields and prone to contamination. Due to the existence of the mudstone intercalation, more than one aquifer is found in the Nubian Sandstone in the studied area. So Nubian sandstone will all its geological and hydrogeological characters is considered to be the principal aquifer in the study area.

4.3 Aquifer

Geologically the groundwater in the study area occurrence is defined by two horizons forming the main aquifers in the study area, The boundaries of the aquifer have been determined according to the results of the geophysical survey and from the boreholes lithology data. The Nubian Sandstone Formation Covers about 90% of the study area, this Formation is composed of the Sandstone, Mudstones, Intra formational conglomerates, and conglomerates. The two aquifers are such that: i. The shallow aquifer (Upper aquifer): fine sand stone, extends from few meters to 38 m below ground surface. ii. The Lower aquifer: medium to coarse sandstone (the main aquifer), starts from below 40 m depth.

The two aquifers are separated by a thick mudstone layer or seepage from upper to lower aquifer in some areas, Fig (4.1).

Fig (4.1): Two profiles of subsurface geology and showing the aquifers at some villages in the study area

4.4 Water Level Measurements The records of the water levels within the study area varies from few meters as 3 m near the Blue Nile and river Nile to 66 m further east in study area, it drops by nearly 5m in the shallow wells during the dry months, the Water elevation reaches the maximum level in September depending upon the distance from the Nile and reaches the minimum level in May. In the study area the ground water within the Nubian sandstone aquifers show diverse direction of flows. Most natural fluctuations of the water level reflect recharge to or discharge from the ground-water reservoir. If discharge from a ground-

water reservoir exceeds recharge, the water level will decline; if recharge exceeds discharge, the water level will rise. In Fig. (4.2), the contour level of groundwater surface in reference to sea level indicates that, the regional flow direction is generally towards the South eastern part of the study area

Fig (4.2): Groundwater flow directions in the study area (Contour value in m, a.m.s.l).

4.5 Aquifers Characteristics (Hydraulic Properties)

Pumping test is a controlled field experiment for determining aquifer Hydraulic parameter T, K and S under certain specification. Such test involves the removal from or addition of water to well and subsequent observation of the reaction of the aquifer water. Generally, the pumping test may serve two main objectives, firstly to determine the hydraulic characteristic of the aquifers or draw down of water bearing layers. Secondly, it provides information about the yield and draw down of the well. The data can be used for determining the specific capacity or discharge draw down. The systematic observation and analysis of water level changes yield values of aquifer characteristic. The determination of the transmissivity (T) and storativity (S) from the pumping test involves a direct solution of the partial differential equation that describes two- dimensional flow in radial coordinate Freeze and Cherry,1979, Krueman and Ridder,1979, Fetter et al,1990. This Properties can be calculate following methods (in Confined aquifer Case) Theis method and Copper-Jacob method.

Fig (4.3): The well location in the study area.

4.5.1 Hydraulic conductivity (K)

Hydraulic conductivity is ratio of flow velocity to the driving Force of water under saturated conditions in porous medium Table (4.1). Also it is defined as the quantity of water flowing in one unit time through a surface of unit area, under a driving force of one unit of hydraulic head change per unit length. It’s expressed by meter/min. Due to presence of thick clay beds the hydraulic conductivity is low ranging about 0.000165 m/min especially in Haj Yousef, Hydraulic conductivity in the study area range between 0.000165 to 0.00527 m/min.

3.5.2 Transmissivity (T)

Transmissivity (T) is the rate of flow of water through a vertical strip of aquifer one unit wide and extending the fall saturated thickness of the aquifer Table (4.2). T = Kb ……………. (4.1) Transmissivity in the study area range between 0.00198 and 0.28 m²/min.

3.5.3 Storativity (S)

Storativity (s) is the volume of water that an aquifer releases or in takes into storage per unit surface area of the aquifer under unit change in hydraulic head normal to that surface. Vw = DH ∗ A ∗ S …… (4.2) The Storativity range between 0.00119 to 3.37

Table (4.1): Average Value of Transmissivity (T), Storage Coefficient (S) and Hydraulic Conductivity (k).

Theis Method Cooper and Jacob Method

Well Name

T (m²/min) S K (m/min) T ((m²/min) S K (m/min)

HAJ YOUSIF 0.00207 2.81 0.000173 0.00198 3.37 0.000165 A.9 YAFA 0.121 0.0668 0.00607 0.0694 12.3 0.00347 DARDOOG 0.452 1.22 0.00593 0.446 1.42 0.00585 HAJ YOUSIF 0.00603 0.00985 0.000201 0.00687 0.00187 0.000229 (BARAKA) IDD BABIKER 0.106 0.0766 0.00591 0.107 0.0738 0.00594 EL AISAB 0.000436 0.0712 1.34E-05 0.000483 0.0871 1.49E-05 ELKARAYAB 0.206 0.113 0.00386 0.28 0.00119 0.00527

4.6 Specific Yield

Specific Yield is the ratio of the volume of water that drains from a saturated rock owing of the attraction of gravity to the total volume of the rock, it is the physical properties that characterized the capacity of an aquifer to release ground water from in response to a decline in hydraulic head. Table (4.2): The average specific yield values for different materials carried out by (Johnson, 1967)

Table (4.2): The average specific yield values for different materials carried out by (Johnson, 1967)

Material Maximum Minimum Average Clay 5 0 2 Sandy clay 12 3 7 Silt 19 3 18 Fine sand 28 10 21 Medium sand 32 15 26 Coarse sand 35 20 27 Gravelly sand 35 20 25 Fine gravel 35 21 25 Medium gravel 26 13 23 Coarse gravel 26 12 22

In the Nubian sand stone aquifer the main lithology type that contain the water is sand stone, so the specific yield in the study area is 10%.

4.7 Regional Recharge

The regional ground water flow follows the direction of the surface water bodies. The hydraulic regime described as the Nile role ground water, which flows initially eastwards from the rivers Turns in the big role first to vertical and then to horizontal westward direction passing below the Nile in the highly permeable lower aquifer zone.

Generally, in the Nubian aquifer system, the ground water movement is from the Nile towards the east and principal direction of ground water in the pleuritic Nubian aquifer is from Nile to the east or north east (Abdel Salam.A.M ,and Kheiralla,1988).

In general, the Nubian aquifer system is the area of the Nile has two main aspect of recharge: i. The recent or current recharge, which occurs by infiltration of water from the river Nile and its tributaries. The amount of annual recharge to the ground water under steady state conditions can be complied by application of the Darcy formula:

Q = T × I × L × 365 ……….. (4.3)

Q = the annual recharge (Q) in m³/year.

T = transmissivity in m²/year, which is the mean value obtain by cooper-Jacob and Thies

(713m2/day)

L = the effective length of the river Nile (source of recharge)

I = the hydraulic gradient,which is about 4000m

The recharge value estimated in the study is about 5.2×108 m³/year which almost the same to that estimated by (BGR, 1979), which is 177× 106 m³/year.

ii. Ancient recharge that is evident from the stable environment isotopes. Tritium C14 clearly demonstrates that the Nubian aquifer had pluvial periods of the Pleistocene (Abdel Salam.A.M ,and Kheiralla, 1988).

4.8 Geophysics Investigations

Geoelectrical methods are applied to map the resistivity structure of the underground such as Fig (4.5). Rock resistivity is of special interest for hydrogeological purposes: it allows, e.g., to discriminate between fresh water and salt water, between soft rock sandy aquifers and clayey material, between hard rock porous/fractured aquifers and low permeable clay stones and marlstones, and between water-bearing fractured rock and its solid host rock.

The Resistivity values are affected by many parameters like; quantity, quality of water (fresh, brackish and saline water) and the thickness of aquifers. Also The variation of lithological units, clay and shale have low Resistivity values, dry sand and gravels have higher Resistivity than saturated ones.

The Electrical Resistivity methods were applied in this study as ones of the common geophysical methods used in groundwater investigations. The methods are based on the transmission of the electrical current to measure the apparent resistivity for different lithological units using the Winner configuration for profiling techniques and Schlumberger arrangement for the Vertical Electrical Sounding (VES). The Vertical Electrical Sounding (VES) is a very appropriate method to explore layered underground.

4.8.1 Interpretation of resistivity data A total number of fifteens vertical electrical sounding (VES) have been conducted. The geophysical surveys were applied to cover the lack of well data in some area. The vertical electrical sounding data of the study area represent a wide range of resistivity value, which generally reflects the variation of resistivity within the sedimentary and the basement rocks. Table (4.3): resistivity values of rock unit in the East Nile Based on El Dawi, 1997)

Table (4.3): resistivity values of rock unit in the East Nile Based on El Dawi, 1997)

Rock unit Range of resistivity in Ωm Clays 2 – 15 Sand Clays 15 – 25 Sands 17 – 60 Fine-grained sand stone 65 – 90 Sand stone (saturated) 125 – 206 Sand stone (dry) 190 – 560 Saturated mud stone 5 – 25 Weathered basement 2 – 80 Fresh basement 90 – 2000

Table (4.4): Range of resistivity values in East Nile area, Based on (SGEP 1979)

Lithology Resistivity ranges (Fresh Resistivity ranges (Saline water area) in Ωm water area) in Ωm Sandy Formation 100 - 150 50 -100 Clayey Formation 10 -15 4 – 8

4.8.2 Pseudo Sections

The pseudo sections have been done in the study area to recognize that the general vertical and horizontal (lateral) variations in the apparent resistivity of the sub-surface layers. These sections are constructed by plotting the apparent resistivity values, as registered on the sounding curve at a given electrode spacing (common to all sounding) as observed, along vertical lines located beneath the sounding stations on the chosen profile.

Fig (4.4): Location of VESes (Northern part of study area)

- Section along profile [I]

This section cover an area around El Faki Hashim Fig.(4.5) showing Veses (1,2,3) , it reveal the occurrence of sallow weathered Basement Complex (around 45 m) associated with resistivities values generally exceeding 130 Ωm the relatively steep gradient of the Basement Complex to the east . The thickness of overlaying sediments increased to the west direction which is dominated by fined sandstone grained 30 Ωm which represent saline aquifer.

Also there is a course grained sand stone lens with thickness more than 40 m but contain fresh water according to its resistivity 126 Ωm. The distance of cross section about 4.371 Km.

Fig (4.5): Values on contour lines showing the resistivity variations from west to east with depth.

- Section along profile [II]

This section showing Veses (4,5,6), The shallow weathered basement zone is restricted to the eastern and of the section (20m), one fault zone is suggested on the basis of the relatively steep contact of the basement boundary and the sedimentary units. Most of the upper horizons of this section are shown as fine sand stone (blue in colour) with few intercalation of more mud stone layers , however the deeper part of sand stone (yellow in colour) are most probably saline water. The distance of cross section about 3.432 Km.

Fig (4.6): Values on contour lines showing the resistivity variations from west to east with depth.

Fig (4.7): Location of VESes (Southern part of study area).

- Section along profile [III]

Most of the upper horizons of this section are shown as thin layer from superficial deposits (4m), sand stone layer (10 - 100) Ωm classified sandy formation (Blue in colour) with intercalation of mud stone lens (Red in colour) in the centre of the section, dry sandstone (100-1000) Ωm and basement rock (yellow in colour) from depth 100m .The distance of cross section about 5.809 Km. Fig. (4.8) showing Veses (10, 11, 12)

Fig (4.8): Values on contour lines showing the resistivity variations from south to north with depth.

CHAPTER FIVE HYDROCHEMICAL INVESTIGATION

5.1 Introduction

Generally, the main aquifers of the Sudan have good water quality and the water is fit for all purpose because it contains low chemical constituent and toxic contain are virtually absent Saline ground water pockets are detected in the study area (Abdel Salam.A.M,and Kheiralla,1988). The aims of this study to evaluate the quality of groundwater in the study area and to determine vertical and lateral distribution of the chemical and physical properties and the water types. To achieve the above mentioned objectives water samples are obtained from (19) wells in the study area, the depth of the wells is varied from well to well depend on the saturated zone at different locations.

5.2 Physical characteristics of water

Temperature, colour, taste, odour, etc. are determined by senses of touch, sight, smell and taste. For example temperature by touch, colour, floating debris, turbidity and suspended solids by sight, and taste and odour by smell. Physical properties of water are often fixed in most cases and can be measured easily and these properties may be original or acquired:

5.2.1 Temperature

The temperature of water affects some of important physical properties and characteristics of water such as: thermal capacity, density, specific weight, viscosity, surface tension. Chemical and biological reaction rates increase with increasing temperature. Reaction rates usually assumed to double for an increase in temperature of 10°c.

5.2.2 Colour

Colour in water is primarily a concern of water quality for esthetic reason. Coloured water give the appearance of being unfit to drink, even through the water may be perfectly safe for public use.

On the other hand, colour can indicate the presence of organic substances,such as algae or humus compound. More recently, colour has been used as aquantitive assessment of the presence of potentially hazardous or toxic organic materials in water. In the study area, we find the water with a natural yellow colour.

5.2.3 Density

The density of natural water varies with their content or dissolved substances. It changes with temperature and pressure. The density of pure water at 150 C and at atmospheric pressure is 0.999 gm/cm³.Sea water with a salinity of 35 gm/liter has an average density of 1.0281 gm/cm³. A variation in salinity of 1g/liter causes the density to change by 0.0008 gm/cm³.

5.2.4 Taste and odour

Taste and odour are human perception of water quality. Human perception of taste includes sour (hydrochloric acid), salty (sodium chloride), sweet (sucrose) and bitter tastes are produced by more complex organic compounds. Human detect many more tips of odour than testes. Organic materials discharged directly to water, such as falling leaves, runoff, etc. are sources of tastes and odour-producing compounds released during biodegradation. The taste of water in the study area is natural with the exception of some areas such as (Nabta) farm that found its waters smell of H2S.

5.2.5 Turbidity

Turbidity is a measure of the light-transmitting properties of suspended and colloidal material. It important for health and aesthetic reason. Turbidity in the study area almost rare.

5.3 Suitability of Groundwater for drinking and domestic uses

5.3.1 Hydrogen-ion concentration (PH) The PH is a measure of acidity in the ground water and is expressed as PH= -log [H] where: H is the hydrogen-ion concentration. The hydrogen-ion concentration in the study area varies with in the range of most natural water (6.5 – 8.5).According to classification of ground water based on Hydrogen-ion concentration, most of ground water in the study area in Neutral to Alkaline water. Table (5.1): The groundwater classification based on Hydrogen- ion concentration.

Table (5.1): The groundwater classification based on Hydrogen-ion concentration.

PH Water classification Number of Samples 7 Neutral Water 4 > 7 Alkaline 10 < 7 Acidic 5

5.3.2 Total Hardness (TH) The hardness is property of water, which causes difficulty of lathering with soap and conventionally as calcium carbonate.

According to the classification groundwater classification based on the hardness, the ground water in study area is categorized soft to hard in most parts of area except in (Hattab(2), Hattab(3),East-Hattab(police-camp),Assumra and Droshab) are very hard,in the study area Total Hardness is ranging (56 – 900 )mg/L. Table (5.2),Fig,(5.1)

Table (5.2): The ground water classification based on hardness According to (Fetter, 1990).

Hardness ppm as CaCo3 Water Classification Well Number 0 – 75 Soft 4,5.8,9,19 75 – 100 Moderately hard 7,13,15,16 100 – 300 Hard 2,3,10,11 >300 Very hard 1,6,12,14,17,18

Fig (5.1): The spatial distribution of the Total Hardness (TH) (mg/l) in the study area.

5.3.3 Total Dissolved Solid (TDS)

It measure of the combined content of all inorganic and organic substances contained in a liquid in: molecular, ionized or micro-granular (colloidal sol) suspended from .The TDS were determined by evaporating the water samples to dryness (at 180º C) or by computing them from the electrical conductivity values, using the conversion factor 0.65 (according to robinove et .al, 1958) based on the TDS values. Table (5.3), Fig. (5.2).

Most of ground water in the study is fresh water except in some location in the study area give brackish water such as [Umm Algura, Horabb, Haj Yousif, El Aolyab, Assumra,Kadro and Droshab].

Table (5.3): The ground water classification based on TDS (Carroll, 1962).

Water Class TDS (mg/l) Well Number Fresh Water 0.01 – 1000 1,2,3,4,5,6,7,8,9,10,11 Brackish Water 1000 – 10000 12,13,14,15,16,17,18,19 Saline Water 10000 – 100000 - Brine Water > 100000 -

Fig (5.2): Concentration of TDS (mg/l) in the study area.

5.3.4 Electrical Conductivity (EC) According to Langengger(1990), the importance of the electrical conductivity is a measured of salinity, which greatly affects the tests and thus has a significant impact on the users acceptance of portable water.

According to (Mallevialle and Suffer, 1987) the single most important class of consumer complaint with regard to water supplies.Generally the (EC) in the study area increased in the direction of the ground water flow towards the north-west (El Aolyab, Droshab) and decreased with pumping and toward the Nile (Geraif East).Table (5.4)& Fig.(5.3).

Table (5.4): EC in the study area based on USSL (1954). Class μS/cm Water quality Number of Samples

C1 100-250 Excellent 6 C2 250-750 Good 9 C3 750-2250 Doubtful 2 C4 & C5 > 2250 Unsuitable 2

Fig (5.3): The spatial distribution of the Electrical Conductivity (mg/l) in the study area.

5.3.5 Sodium (Na+)

Sodium is a highly soluble chemical element with the symbol (Na).Sodium is often naturally found in ground water, in the study area sodium is ranging (0 – 2400) mg/L .Fig (5.4) shows the sodium concentration increase in the centre of the study area.

Fig (5.4): The spatial distribution of the Na+ (mg/l) in the study area.

5.3.6 Potassium (K+)

K+ is alkali metals, and was enrichment occurs as result of leaching weathered feldspar and clay minerals. In the study area potassium ranges between (0-60) mg/l, especiallyHattab area is very high.

Fig (5.5): The spatial distribution of the K+ (mg/l) in the study area.

5.3.7 Calcium (Ca+2) & Magnesium (Mg+2)

Calcium and Magnesium are very common elements, Calcium is the fifth most abundant natural element and Magnesium the eighth. Bost elements are present in all natural water. The most common source of Calcium and Magnesium in the ground water is throughthe erosion of rocks. Such as limestone and dolomite and minerals such as calcite and magnesite.

The concentration of the Calcium in the study area is range between (10-130) mg/l, while the magnesium ranges between (0-150) mg/l Fig. (5.6) there are high (Ca+2) concentration in the North West part near to the Nile. The high concentration of Ca near the Nile may be due to the dissolution of Kanker deposit +2 (CaCo3 Nodules) and dissolution of anhydrite, Fig. (5.7) Mg .

Fig (5.6): The spatial distribution of the Ca+2 (mg/l) in the study area.

Fig (5.7): The spatial distribution of the Mg+2 (mg/l) in the study area.

5.3.8 Chloride (Cl-) Chloride in water is originated from natural sources, it may be originated from industrial and domestic wastes. Higher concentration of chloride in water indicates pollution. It give the water a salty taste, when combines with Na+ .The chloride concentration varies generally between (0-3000) mg/l.

Fig (5.8): The spatial distribution of the Cl- (mg/l) in the study area.

- 5.3.9 Bicarbonate (HCO3 )

The main source of HCO3 is the atmosphere and the soil, the concentration of Bicarbonate in the study area ranged between 44 - 460mg/L.

- Fig (5.9): The spatial distribution of the HCO3 (mg/l) in the study area.

- 5.3.10 Nitrates (NO3 )

Nitrates sources are Atmosphere, Organic matter, the Concentration of nitrate in the study area varies from 0.66 to 6.6 mg/L , lowest is that of well (Sourc-For-Sheikh

Amin),highest is that of well (Zakiabb-S-Saria-complex), Fig. (5.10) shows NO3 Zones in the study area.

- Fig (5.10): The spatial distribution of the NO3 (mg/l) in the study area.

5.4 Suitability of Groundwater for irrigation uses The ground water quality lies in the Nubian aquifers is fit for human and agricultural purpose except at few locations, which contain high certain ionic species, as well as high electrical conductivity . The suitability of water for irrigation can be determined with the Sodium Absorption Ratio (SAR) Table (5.6) and Fig (5.11), defined by Todd, (1980) as:

Where: Concentrations are expressed in epm. All well at the study rea are fit for irrigation propose except two wells which are poor in classification.

Table (5.5): water classification based on SAR in the study area. SAR Range Samples Water Class S1 0 – 10 15 Excellent S2 10 – 18 2 Good S3 18 – 26 1 Fair S4 > 26 2 Poor

Fig (5.11): Suitability of groundwater for irrigation, based on USSL (1954).

5.5 Groundwater Type

Hydrochemical facies are distinct zones that have cation and anion concentrations describable within defined composition categories (Appelo and Postma 2005).According to Piper (1949), the hydrofacies of groundwater in the study area are revealed from the trilinear diagram also called (piper diagram), it was used in Fig. (5.12) to classify the groundwater of the study area.

Fig (5.12): Piper’s trilinear diagram showing groundwater facies in the study area.

Fig (5.12) shows that, all the samples taken April 2016 (57.9%) belong to Na-Cl groundwater type, (10.5%) is Ca-SO4 groundwater type, (5.3%) belong to Ca-HCO3 groundwater type, and (26.3%) is Na-HCO3 groundwater type. Table (5.5): Groundwater type according to piper diagram. Well Number Type of water 1, 2 , 3, 5 , 8 , 9 , 11 , 12 , 13 , 15 Na-Cl (saline water) 16 4 , 7 Ca-SO4 6 Ca-HCO3 10 , 14 , 17 ,18 ,19 Na-HCO3

CHAPTER SIX

CONCLUSION AND RECOMMENDATIONS

6.1 Conclusions

The study area lies in Khartoum state, it lies between latitudes 15 ° 24' 00″ N and 16 ° 00' 00″ N and longitudes 32º 24′ 00″ E and 32º 54′ 00″ E, is mainly characterized by flat and peneplained surface, which predominates the entire area. This area is up rise in the east, at UMM GIRA (2) (416.37 m a.m.s.l) and gradually merges into the Nile valley, the topography of the area is structurally controlled. The River Nile and Blue Nile dominate the drainage of the area and there are numerous seasonal water courses drained the area from the east to the west. The geological units in the study area are the Precambrian, basement complex, Nubian Sand stone formation and superficial deposits. The main water bearing strata are sand stone and conglomerate in the Nubian sand stone formation with thickness (20-80)m that over leined by alluvial deposit. It forms two types of aquifers zone shallow and deep. The Nubian sandstone represents the resaris aquifer in the study area. The depth to water level Varies from a few meters to more than 66 meter and direction of flow is south east. The aquifer properties are such that Hydraulic conductivity in the study area the range between 0.000165 to 0.00527 m/min and Transmissivity range between 0.00198 and 0.28 m²/min while the Storativity range between 0.00119 to 3.37. The hydrochemical composition of the Nubian sand stone aquifers at the area east of the river Nile shows that the bicarbonate, Sulphate and sodium ions attain the highest concentration. The TDS in the water is 141 to 4780 mg/l, the water proved to be suitable for domestic and irrigation.

Hydrochemistry investigation in the study area indicate that water from the aquifer ranges generally acceptable to good for domestic uses .however, as at certain locality from the aquifer is comparatively poor for both drinking and household purposes.

Reference are the findings of the study area and the general statues of groundwater conditions this foiling racer could be provided:

i. More drilling in the area would able to resolve most of the uncertainties. ii. Regional monitoring network of the aquifer behaviour, observation wells have to be drilled and equipped with atomic water level indicators especially around the development areas. iii. It has been also recommended that basins containing mudstone layers, lenses or silicified sandstone, need a lithological study. iv. As result of the hydrogeological and hydrochemical investigations, it is strongly recommended to abstract ground water from high potential of aquifer system and suitable fresh water. v. Drill more productivity well out of the saline zone. vi. Continue monitoring of quality of water supply in the wells under study and focus on the chemical study. vii. Rehabilitation of old wells which consumed a lot of hand (pumps – filters – pipes). viii. More scientific researches to identify the scientific problems resulting from bad water quality and quantity. ix. Better designing and development for the wells to obtain large amount of water. x. Accuracy in the analysis of samples taken from wells to obtain accurate results in the chemical studies of groundwater. xi. You most choose suitable dimension between wells so there is no overlap between the configurations and consumption in a small area and limited. xii. Add amount of the chlorite in the water distribution system especially in shallow wells close to the Nile. xiii. The lower aquifer is to be protected from contamination by any mean. xiv. Further studies are recommended to determine accurately the east boundary. xv. Irrigation is to be confined to pumping from upper aquifers. xvi. Sewage disposal is to be controlled or prohibited within the study area.

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APPENDICES Appendix (1):

WHO (2011) & SSMO (2009) Guidelines for drinking water.

Parameters WHO (2011) Units PH 6.5-9.2 - EC 1500 µS/cm TDS 1000 mg/l Ca2+ 200 mg/l Mg2+ 150 mg/l Na+ 200 mg/l K+ 20 mg/l Cl‾ 250 mg/l

SO4 250 mg/l

HCO3 350 mg/l

NO3 50 mg/l

Total Hardness as CaCO3 500 mg/l

Appendix (2): Well Data (I)

NO Name Easting Northing Chemical Properties ( Cation ) (Dec) (Dec) Calcium Magnesium Sodium Potassium mg/l mg/l mg/l mg/l

1 Zakiabb-S- 32.58497 15.7734 33.6 6.96 202 2.75 Sariacomplex

2 Hattab 2 32.60552 15.70896 110.4 147.36 2420 50.8

3 Hattab 3 32.67555 15.69608 33.6 96.96 773 16.9

4 Zakiab-KadaroNorth 32.56902 15.77163 41.6 7.68 48 6.8

5 East-Hattab (police- 32.6824 15.72794 81.6 116.6 2410 36.8 camp)

6 Dar-Assalam-N(2) 32.66203 15.63622 24 12.24 - 5.1

7 Sourc-For- 32.8182 15.54958 40 27.12 - 9.6 SheikhAmin

8 Assumra 32.66809 15.76695 68.8 87.36 328 19.8

9 Umm-Esheir-S 32.81439 15.60001 36.8 8.16 123 3.1

10 Selate-N 32.64277 15.80907 32 7.68 95 3.4

11 Faihay-baraka-blk- 32.64002 15.59646 12.8 6.48 29 3.2 3

12 El Ghar 32.67789 15.65462 31.2 20.4 136 4.9

13 Eid- 32.72635 15.61313 37.6 25.68 124 9.2 Babikir(Eltaweedablk- 5) 14 Zakiab- 32.57857 15.77604 30.4 9.12 71.5 5.3 IslamicComplex

15 Horabb 32.7322 15.58915 43.2 36.48 195 11.9

16 Tukonabb 32.7593 15.58406 46.4 43.68 197 12.9

17 Umm Algura 32.59429 15.76759 44.8 18.24 88 4.2

18 Geraif-east 32.60141 15.57777 12.8 5.75 27.5 3

19 Eid-Babikir 4 32.67307 15.61229 54.4 40.8 169 9.9

Note: the (-) value = data not calculated or not directed

Well Data (II)

NO Name Easting Northing Chemical Properties ( Anion ) (Dec) (Dec) Chloride Sulphate Nitrate mg/l mg/l mg/l

1 Zakiabb-S-Saria-complex 32.58497 15.7734 156 81 6.6

2 Hattab 2 32.60552 15.70896 2960 1440 2.97

3 Hattab 3 32.67555 15.69608 1000 350 2.31

4 Zakiab-Kadaro-North 32.56902 15.77163 72 90 1.98

5 East-Hattab (police-camp) 32.6824 15.72794 2750 1500 2.97

6 Dar-Assalam-N(2) 32.66203 15.63622 48 46 0.99

7 Sourc-For-Sheikh-Amin 32.8182 15.54958 180 72 0.66

8 Assumra 32.66809 15.76695 410 590 2.64

9 Umm-Esheir-S 32.81439 15.60001 72 72 1.65

10 Selate-N 32.64277 15.80907 56 45 2.97

11 Faihay-baraka-blk-3 32.64002 15.59646 6 0 1.98

12 El Ghar 32.67789 15.65462 84 88 1.32

13 Eid-Babikir(Eltaweeda-blk- 32.72635 15.61313 146 52 2.64 5)

14 Zakiab-Islamic-Complex 32.57857 15.77604 18 30 0.99

15 Horabb 32.7322 15.58915 148 144 4.29

16 Tukonabb 32.7593 15.58406 216 204 1.98

17 Umm Algura 32.59429 15.76759 52 66 2.31

18 Geraif-east 32.60141 15.57777 5 0 2.1

19 Eid-Babikir 4 32.67307 15.61229 180 165 0.99

Well Data (III)

NO Name Easting Northing Physical Properties (Dec) (Dec) TDS Total Total mg/l Alkalinity Hardness mg/l mg/l 1 Zakiabb-S-Saria complex 32.58497 15.7734 565 204 113

2 Hattab 2 32.60552 15.70896 5210 456 890 3 Hattab 3 32.67555 15.69608 1427 336 488 4 Zakiab-Kadaro-North 32.56902 15.77163 486 44 136 5 East-Hattab (policecamp) 32.6824 15.72794 4780 440 690

6 Dar-Assalam-N(2) 32.66203 15.63622 353 180 111 7 Sourc-For-Sheikh Amin 32.8182 15.54958 575 148 213 8 Assumra 32.66809 15.76695 1773 226 536 9 Umm-Esheir-S 32.81439 15.60001 388 180 126 10 Selate-N 32.64277 15.80907 302 160 112 11 Faihay-baraka-blk-3 32.64002 15.59646 164 96 59 12 El Ghar 32.67789 15.65462 444 208 163 13 EidBabikir(Eltaweedablk- 32.72635 15.61313 657 160 201 5) 14 Zakiab-IslamicComplex 32.57857 15.77604 275 180 114

15 Horabb 32.7322 15.58915 888 236 260 16 Tukonabb 32.7593 15.58406 853 180 298 17 Umm Algura 32.59429 15.76759 415 200 188 18 Geraif-east 32.60141 15.57777 141 92 56 19 Eid-Babikir 4 32.67307 15.61229 766 210 306

Appendix (3):

NO Well Name Easting Northing Yield Elevation S.W.L Depth to (m3/h) water 1 ALGHAR 32.7 15.66666 11.3 392.689 28.9 363.789 2 SALAMET 32.8 15.58333 8 396.993 66 330.993 ELSHETAT 3 IDD BABIKER 32.66666 15.61666 17 386.873 32 354.873 EAST 4 ELAOLYAB 32.66666 15.8 12.73 397.05 26.7 370.35 5 ELGIRAIF EAST 32.61666 15.58333 33 384.357 18 366.357 6 ELAOLYAB (2) 32.65 15.73333 16.36 390.71 26.6 364.11 7 EL SAMRA 32.66666 15.7 7 389.042 28 361.042 8 EL SIDAIR 32.76666 15.66666 17 385.615 32 353.615 9 UMM GIRA (2) 32.77833 15.73111 15 416.379 36.6 379.779 10 ELRIHANA 32.75 15.58333 20.45 395.113 37.3 357.813 VILLAGE (2) 11 EL AISAB 32.58333 15.78333 8 381.538 28 353.538 12 ELTOKONAB 32.78333 15.6 30 399.298 37 362.298

Appendix (4): VESes

Easting Northing VES 32.61391351 15.8209625 VES 1 32.63316454 15.81175549 VES 2 32.63383415 15.79166745 VES 3 32.62842154 15.82288761 VES 4 32.63232754 15.84007404 VES 5 32.64817477 15.84141324 VES 6 32.68394444 15.80875 VES 7 32.70772222 15.80730556 VES 8 32.74258333 15.80902778 VES 9 32.74019444 15.55016667 VES 10 32.75569444 15.56969444 VES 11 32.74513889 15.59633333 VES 12 32.78586111 15.59769444 VES 13 32.78883333 15.59030556 VES 14 32.79952778 15.57427778 VES 15

Appendix (5):

Appendix (6): (VES 7, 8 and 9) & (VES 13, 14 and 15) respectively.