Hydrochemical characteristics of groundwater in the Ummbadda member, Omdurman area, Khartoum State, Sudan.
By Abubakr Alsiddig Bashier Alfadil B.Sc. Geology
A Thesis Submitted to the Graduate College – AlNeelain University in partial fulfillment of the requirements for the degree of Master in Hydrogeology (Hydrochemistry).
Department of Hydrogeology Faculty of Petroleum and Minerals Al Neelain University
2017
I
ABSTRACT
The study area lies in Omdurman town which bounded by latitude (15° 33ʹ – 15° 37ʹ) and longitudes (32° 21ʹ – 32° 30ʹ), which constitutes part of northern Khartoum basin. The study has been conducted on Ummbadda member to investigate groundwater quality for domestic and irrigation uses and to study hydrochemical evolution (mechanism and process), in addition to calculate aquifer hydraulic parameter and determine groundwater recharge zones. Evaluation of lithological logs and groundwater characteristics revealed that, the main water bearing strata occur at a depth between 550 to 1000ft. Aquifers system in the study area are characterized by their confining nature, considerable thickness and confined by mudstone. Flow net analysis of the aquifer indicated that the general flow direction of groundwater is to the south west and the main recharge area is the Nile. Pumping test data analysis indicate that there is slight variation in storage coefficient within the aquifer but generally indicates confining condition and their variation may be due to geological and structural setting in the basin. Physio-chemical parameter such as (pH, TDS, and EC…etc.) in addition to the major ions conveniently used to assess groundwater quality indicate suitability for human exploitation based on the WHO guideline for potable water. Many factors were used to identify the suitability of groundwater for irrigation purposes such as (SAR, SP, RSC, MAR, KR, and PI) and the results generally indicate that the water is suitable for irregular purpose. In addition, majority of samples fall within the field of good to excellent water class. The water type in the area is calcium bicarbonate, which characterized by the alkalis exceed alkalis earth and mixed type. The processes controlling the groundwater quality have been found to be an ion exchange process deduced from negative chloro-alkaline indices which supported the result from Durov diagram except one samples, which has positive, value that indicates normal ion exchange. Depending on Gibbs plot, water rock interactions is main process in the study area in addition to reduction process control the concentration of sulphate in the study area.
I
الخالصـــــــــــــــــــــــة
تناولت الدراسة هيدروكيميائية منطقة امدرمان الواقعة بين دائرتي عرض (ʹ37 °15 – ʹ33 °15) و خطي طول (ʹ30 °32 – ʹ21 °32) والممثلة للجزء الشمالي من حوض الخرطوم الرسوبي.
أجريت الدراسة الحالية للمياه الجوفية في عضو امبده لمعرفة نوعية المياه وصالحيتها لالستخدامات المختلفة )المنزلية-الزراعية( وفقا للمعايير العالمية, كما ركزت الدراسة على معرفة التطور الهيدروكيميائي من خالل العمليات التي تحدث اثناء حركة المياه في الخزان الجوفي باإلضافة لحساب قيم المعامالت الهيدروليكية و تحديد نطاقات التغذية.
الدراسة التفصيلية للقطاعات الصخرية تؤكد وجود طبقة حاملة للمياه الجوفية تقع في أعماق تتراوح بين 550 الى حوالي 1000 قدم محصورة بين طبقتين من الطين والتي تمثل ظروف خزان جوفي محصور.
تحليل شبكات الجريان يشير الى ان التصريف العام في اتجاه الجنوب الغربي كما ان الخزان يتغذى تغذية مباشرة من النيل الذي يمثل مناطق جهد هيدروليكي عالي.
اعتمدت عملية تقييم نوعية المياه الجوفية في منطقة الدراسة ألغراض الشرب على مجموعة من المعامالت الفيزيوكيميائية مثل االس الهيدروجيني و مجموع االمالح الذائبة و غيرهما, باإلضافة لمجموعة االيونات الذائبة و مقارنتها بمعايير منظمة الصحة العالمية و التي اشارت الى ان المياه صالحة ألغراض الشرب, كما تم حساب عدد من المعامالت الخاصة بصالحية المياه ألغراض الري مثل نسبة امتصاص الصوديوم و غيرها و التي اشارت في مجموعها الى ان المياه صالحة ألغراض الزراعة.
استخدمت عدة طرق لتصنيف المياه والتي اشارت الى ان المياه يغلب عليها طابع بيكربونات الكالسيوم باإلضافة الى نوع خليط (mixed type).
العمليات المتحكمة في نوعية المياه تشير الى تأثير عملية التبادل االيوني حيث يمثل العملية الرئيسة في توزيع االيونات في منطقة الدراسة باإلضافة الى تأثير عملية تجوية السليكات وذوبات الكربونات. توزيع الكبريتات يتأثر بصورة مباشرة بعمليات االختزال التي تحدث في إتجاه الجريان.
II
DEDICATIONS
To MY FATHER
TO MY MOTHER
BROTHERS
SISTERS
AND
FRIENDS
III
ACKNOWLEDGEMENT
First and above all, I praise Almighty Allah, the almighty for providing me this opportunity and granting me the capability to proceed successfully. This thesis appears in its current form due to the assistance and guidance of several peoples. I would therefore like to offer my sincere thanks to all of them. I would like to express my deep thanks to my esteemed supervisor Dr. Hago Ali Hago for the trust, insightful discussion, offering valuable advice, for his support during the whole period of study, and especially for his patience and guidance during the writing process.
Dr. Osman M. Elhassan, I greatly appreciate your excellent assistance, your spiritual supports for excellent advices, detailed review, and me during the preparation of this thesis.
Special thanks to Mr. Omer Bashier for his assistance and supporting at the initial steps.
My gratitude to Mrs. Qurashi T. K. for her assistance during preparation of the thesis.
I cannot finish without express my deep appreciation and thanking to my father Mr. Bashier A. Mohammed for his moral and spiritual support during the preparation thesis.
IV
LIST OF CONTENTS
Abstract I
II الخالصـــــــــــــــــــــــة
Dedication III
Acknowledgement IV
List of contents V
List of figures X
List of plates XIII
List of tables XIII
List of abbreviations XV
1 1. INTRODUCTION 1.1General Overview 1
1.2 Study area 1
1.2.1 Location 1
1.3 Physiography 3
1.3.1 Topography 3
1.2.3 Drainage pattern 5
1.3.3 Climate 5
1.3.4 Vegetation 5
1.4 Population and their economic activity 6
1.5 Previous studies 8
V
1.6 Objectives 9
1.7 Methodology 10
11 2. GEOLOGY AND TECTONIC SETTING
2.1 Geology 11
2.1.1 Basement complex 11
2.1.2 Omdurman Formation 12
2.1.2.1 Umm Bada member (late Albian – early Turonian) 13
2.1.2.2 Merkhiyat Member (Turoian – Early Senomanian) 13
2.1.3 Volcanic Rocks 15
2.1.4 Superficial Deposits 16
2.2 Tectonic Setting 17
3. HYDROGEOLOGY 19
3.1 Overview of the freshwater resources of Sudan 19
3.2 Hydrogeology of the study area 22
3.3.3 Groundwater movement and Recharge 25
3.3.4 Hydraulic aquifers properties 28
3.3.4.1 Hydraulic conductivity 28
3.3.4.2 Transmissivity 29
3.3.4.3 Storage Coefficient 29
3.3.5 Pumping test analysis 29
3.3.5.1 Cooper and Jacob method 30
VI
3.3.6 Pumping test results 31
32 4-GROUNDWATER QUALITY
4.1 Introduction 32
4.2 Accuracy of chemical analysis 32
4.3 Quality of groundwater for Municipal use (Drinking purposes) 33
4.3.1 Hydrogen-ions activity (pH) 33
4.3.2 Total Dissolved Solid (TDS) 36
4.3.3 Electrical Conductivity (EC) 38
4.3.4 Hardness (HT) 40
4.3.5 Major dissolved ions in groundwater 43
4.3.5.1 Cations 43
4.3.5.2 Anions 51
4.4 Quality of groundwater for irrigation 58
4.4.1 Sodium Absorption Ratio (SAR) 58
4.4.1.1 Sodium (Hazard) vs Salinity hazard Classification 59
+ 4.4.2 Percent Sodium (% Na ) 61
4.4.3 Residual Sodium Carbonate (RSC) 61
4.4.4 Permeability index (PI) 62
4.4.5 Magnesium Adsorption Ratio (MAR) 63
4.4.6 Kelley Ratio (KR) 64
5. HYDROCHEMISTRY 66
VII
5.1 Classification of hydrochemical data 66
5.1.1 Stiff Diagrams 66
5.1.2 Durov Diagram 69
5.1.3 Trilinear Diagram (Piper Diagram) 70
5.1.4 Chadha classification 71
5.1.5 Saturation indices 73 5.2 Graphical solutions of relationship between different chemical 77 parameters 5.3 Hydrochemical processes and mechanism controlling groundwater 80 quality 5.3.1 Silicate weathering process 82
5.3..2 Ion exchange process 83
5.3.2.1 Chloro-alkaline indices 83
5.3.3 Sulphate reduction/oxidation process 87
89 6. SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS 6.1 Summary and conclusion 89
6.1.1 Aquifer geometry and its hydraulic characteristics 89
6.1.2 Water quality for domestic use 89
6.1.3 Water quality for irrigation 90
6.1.4 Water classification 90
6.1.4.1 Stiff diagram 90
6.1.4.2 Piper diagram 91
6/1.5 Saturation indices 91
6.1.6 Hydrochemical processes 91
VIII
6.2 Recommendations 92
References 93
Appendices 101
IX
LIST OF FIGURES
1.1 Location of studied wells. 2 1.2 Digital Elevation Model of the study area and their surrounding. 4 1.3 Population in the study area 7 2.1 Geological map of the study area and its surrounding 16 2.2 Topographic map showing the location of the mesozoic rift 18 3.1 Groundwater basins in Sudan 21 3.2 Section directions in the study area 23 3.3 Cross-sections in the study area 24 3.4 Strip logs for wells in the study area 25 3.5 Flow net map of the the study area 27 4.1 pH concentration in the study area. 35 4.2 Spatial distribution of pH in the study area. 35 4.3 TDS compared with the WHO in the study area. 37 4.4 Spatial distribution of TDS in the study area 37 4.5 Distribution of EC compared with WHO (2011) in the study area. 39 4.6 Spatial distribution EC in the study area 39 4.7 Distribution of Total hardness compared with the study area 42 4.8 Spatial distribution of TH in the study area 42 + 4.9 Distribution of Na in the study area 44 + 4.10 Spatial distribution of Na in the study area. 44 + 4.11 Distribution of K in the the study area 45 + 4.12 Spatial distribution of K in the study area. 46 2+ 4.13 Distribution of Ca in the study area 47 2+ 4.14 Spatial distribution of Ca in the study area 48 2+ 4.15 Distribution of Mg in the study area 49
X
2+ 4.16 Spatial distribution of Mg in the study area. 50 - 4.17 Distribution of Cl in the study area 51 - 4.18 Spatial distribution of Cl in the study area 52 - 4.19 Distribution of HCO3 in the study area 53 - 4.20 Spatial distribution of HCO3 in the study area 54 2- 4.21 Distribution of SO4 in the study area 55 2- 4.22 Spatial distribution of SO4 in the study area 56 - 4.23 Distribution of NO3 in the study area 57 - 4.24 Spatial distribution of NO3 in the study area 57 4.25 USSL classification for groundwater study area 60 4-26 Permeability index diagram 63 5.1 Stiff map of the groundwater samples in the study area 68 5.2 Durov plots for the groundwater samples. 69 5.3 Piper diagram for classification groundwater samples 70 5.4 Chadha classification of groundwater samples. 72 5.5 Saturation indices for Anhydrite and Gypsum 74 5.6 Saturation indices for Aragonite, Calcite, and Dolomite 75 5.7 Saturation indices for Halite and Sylvite 76 - + 5.8 NO3 – K relationship of the groundwater samples in the study area 79 - 5.9 pH – HCO3 relationship of the groundwater samples in the study 79 area
5.10 Gibbs diagrams of the groundwater samples in the study area 81 5.11 EC- – Na+/Cl relationship of the groundwater samples in the study 82 area 5.12 Total Cation (TZ) – Ca/Mg relationship of the groundwater in the 83 studied area
XI
5.13 Variation in chloro-alkaline indices of groundwater samples 85 5.14 Ca+Mg – SO4+HCO3 relationship of groundwater in the study area 86 5-15 SO4+HCO3-Ca+Mg of water samples in the study area 86 2- - 5.16 SO4 – Cl relationship of the groundwater samples in the study area 87 2- 5.17 EC - SO4 relationship of the groundwater samples in the study 88 area
2- 2- 5.18 SO4 – SO4 /Cl relationship of the groundwater samples in the 88 study area
XII
LIST OF TABLES
1.1 Climate data for Omdurman 6 1.2 population increment in the study area 7 2.1 The stratigraphic column of the study area. 15 3.2 Hydraulic aquifer parameter of the aquifer 31 4.1 classification of water salinity according to (TDS) in (ppm) 36 4.2 General classification of groundwater based on EC. 38 4.3 Hardness Classification of Water. 40 4.4 Concentration of permanent hardness in the study area 42 4.5 Sodium hazard classes based on USSL classification 59 4.6 USSL classification of studied groundwater samples for irrigation purpose 60
4.7 Sodium percentage water class 61 4.8 Groundwater quality based on RSC (Residual Sodium 62 Carbonate) 4.9 Classification of studied groundwater samples for irrigation 63 purpose based on PI 4.10 Classification of studied groundwater samples for irrigation 64 purpose based on MAR 4.11 Classification of studied groundwater samples for irrigation 64 purpose based on KR 4.12 Calculated parameters for suitability of groundwater in 65 irrigation purposes
5.1 Stiff water type in the study area 67 5.2 Water type based on Chadha classification 72
XIII
5.3 Correlation matrix of chemical parameter in the aquifer 77 5.4 Chloro-alkaline indices in the study area 85
LIST OF PLATES
1.1 Topography and vegetation in the Markhiyat area. 3
XIV
LIST OF ABBREVIATIONS
µS/cm Microseimens/centimeter CH Carbonate hardness
EC Electrical Conductivity epm Equivalent per million
HT Total Hardness K Hydraulic conductivity
KR Kelley Ratio
MAR Magnesium Adsorption Ratio meq/l Milli-equivalent per liter mg/l Milli-gram per liter NCH Non-carbonate hardness NSSF Nubian Sandstone Formation
PI Permeability Index
RSC Residual Sodium Carbonate S/m Seimens/meter
SAR Sodium Absorption Ratio SCCG Sydney Coastal Counsils Group SI Saturation Index SP Sodium percent
ST Storage coefficient T Transmissivity TDS Total Dissolved Solid USSL United State Salinity Lab WHO World Health Organization
XV
CHAPTER ONE INTRODUCTION
1.1 General Overview
Groundwater is one of the most important sources of fresh water, that provide significance quantities. Sudan is characterized by its arid to semi-arid climatic conditions i.e. the precipitation rate is negligible, for this reasons, the groundwater is a main sources for domestic uses and agricultural activities, as well as the groundwater quality is nearly of equal importance to quantity. Therefore its necessary to make chemical, physical, and bacterial analyses for groundwater to determine its suitability for different purposes (drinking , irrigation, …, etc..). In last decades excessive exploitation of groundwater in many regions resulted in disturbing the balance between natural recharge and discharge, this phenomenon is very clear when the discharge exceeding certain limits and also lead to increase salinity and deteriorate its quality. So the study and exploration of the groundwater occurrence and their characteristics is very considerable.
1.2 Study area
1.2.1 Location
The study area lies in Khartoum state on the western part of the River Nile (Omdurman city). The area bounded by latitudes (15° 33ʹ – 15° 37ʹ) and longitudes (32° 21ʹ – 32° 30ʹ), which formed a part of northern Khartoum basin (Fig. 1.1).
1
Fig. 1.1: Location of studied wells
2
1.3 Physiography
1.3.1 Topography
The study area is low relief, which generally, has gently slope toward the River Nile that consider to be the most depressed ground in the area (Fig.1.2). High to moderate relief observed in hills around the area, such as J. Murkhyat in the N to NW area, J. Aulia at the southern periphery of basin, and Jebel Es- Silitat and Es-Sufur complexes in the NE boundary of Khartoum State. Due to NW normal faults all sedimentary hill preserved in area which made of
ferruginous and siliceous sandstones resistant to wind abrasion (Plate 1.1).
Plate 1.1: Topography and vegetation in the Markhiyat area
3
Fig. 1-2: Digital Elevation Model of the study area and its surrounding.
4
1.2.3 Drainage pattern
The River Nile represents the main distinctive landscape in the area and consider as the main perennial valley. In addition to many ephemeral Wadis that flow through the area and recharge the River Nile. The major water divide characterized the area is the Qoz Abu Dulu ridge that divide white Nile course from wadi El Mugadam to the west.
1.3.3 Climate
The study area located in semi-arid zone with three month rainy seasons (July, August, and September). The annual average rainfall range from (100- 200)mm/y. Occasionally the arrival of the seasonal southwesterlies and their rains in central Sudan can be delayed, or completely failed that may affect the annual fluctuations of the River Nile, the flood plains, and the nearby farm season. If that happens draught and famine follow. Based on annual mean temperatures, Khartoum is one of the hottest major cities in the world. Temperatures may exceed 40°C in summer from April to June and from 20-30 °C from July to October and decrease in winter season from November to March between 15° to 25°C (Table 1.1).
1.3.4 Vegetation
Climate conditions in the area control the plant species and type of vegetation cover, which is dense along watercourses, especially Riverbanks. The desert and semi-desert vegetation types dominated by Acacia species.
5
Table 1.1: Climate data for Omdurman (Source after: World Meteorological Organization)
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Average 30.8 33 36.8 40.1 41.9 41. 38.4 37.3 39.1 39. 35.2 31. 37.1 high °C 3 3 8
Average 15.6 17. 20.5 23.6 27.1 27. 25.9 25.3 26.0 25. 21.0 17. 22.7 low °C 0 ) 3 5 1
Average 0 0 0 0 .4 4.0 46.3 75.2 25.4 4.8 .7 0 156. precipita 8 tion mm Average 0 0 .1 .1 .9 1.2 4.8 4.8 3.2 1.2 0 0 16.3 precipita tion days Average 27 22 17 16 19 28 43 49 40 28 27 30 28.8 relative humidity (%) Mean 141 21 260 330 360 39 400 390 365 300 260 180 3,58 monthly 1 0 7 sunshine hours
1.4 Population and its economic activity
Huge tribal mass movement as exodus and refugees from arm conflict regions, Darfur for instance, cause distinctive demographic change in distribution map of Sudan in last few years (Fig. 1.3), for these reasons different tribes comes to Omdurman area in addition to other tribes looking for education, health, and improving their income. The native inhabitants now become as a relict close to border of the area and their income is very low. On the other hand the migrating people occupies the center of the town which characterized by their high income (Table 1.2).
6
Table 1.2: Population increment in the study area (Source after: https://en.wikipedia.org/wiki/Omdurman)
Year Population 1909 (Census)[8] 42,779 1941 116,196 1956 113,600 1973 299,399 1983 526,284 1993 1,271,403 2007 Estimate 2,127,802 2008 2,395,159 2010 2,577,780
Population 3,000,000
2,500,000
2,000,000
1,500,000
1,000,000
500,000
0 1909 1941 1956 1973 1983 1993 2007 2008 2010
Fig. 1.3: Population in the study area
7
1.5 Previous studies
Study area received different studies by different researchers. Most of contributions focused on the stratigraphy and palynogical investigation to form the geologic column, but little attention concerned to hydrological, and hydrogeological investigations, in the following paragraph glimpse on most important studies. Kheirallah (1966), used the expression of Nubian sandstone formation (NSSF) to denote the sedimentary beds of different colors around Khartoum. He divided the Nubian sandstone formation between Khartoum and Shandi into five main rock units. Whiteman (1971) used the expression of Nubian sandstone formation to describe the beds of conglomerates, grits, sandy mudstone, mudstone, that lie unconformable on the basement rocks. On the other side, Saeed (1976) studied the hydrogeology of Khartoum state using piezometric boreholes and assumed the major water-bearing formations are the Nubian sandstone formation, Gezira formation, and alluvial deposits. Vail (1988) introduced the expression of the Nubian super group but Barazi (1989) has further introduced the expression of Nubian sandstone Khartoum Type. However, Bireir (1993) from his side, divided the Omdurman formation into upper and lower units. Awad (1994) studied the stratigraphy and paleo- ecology of the late Jurassic to middle Tertiary sediments of Khartoum basin and subdivided the Omdurman formation into Markhiyat member which formed by outcrop sequence and Ummbadda member which represented by the subsurface. Eisawi (1999); studied Omdurman formation based on palynology and deduce some effort concerning detail age determination. Abd Elraheem (2000) investigate the decline of groundwater level in Khartoum area, in addition to characterization of groundwater quality, and
8 hydrochemical processes responsible for groundwater mineral content, he conclude that groundwater quality of Khartoum is strongly affected by the River Nile water chemistry as well as the Nile’s flood and draught seasons. Chemically, the groundwater type in Omdurman area is calcium magnesium bicarbonate rich and calcium magnesium sulphate rich water types. The water is hard and not suitable for industrial uses. Hussein (2009) showed two major water types in Omdurman area, calcium magnesium bicarbonate, and sodium bicarbonate, in addition he suggested that the hydrochemistry is affected by lithology and flow regime, as well as the ground water salinity is due to the presence of mudstone. Elkrail (2012) identify four chemical water types; Na-
Ca-CO3, Ca-Mg-HCO3, Na- Mg-Ca-HCO3-Cl, and Na-Cl-HCO3-SO4.
1.6 Objectives of the study
Study of water resources in Omdurman area is very important because of high population density, in addition to possibility of pollution, especially organic pollutants.
The main objectives of the present work
To investigate groundwater quality ( i.e. suitability for domestic agricultural uses ) To study hydrochemical evolution ( mechanisms and processes) To delineate aquifer hydraulic parameters (permeability, transmissivity, and storage coefficient) To determine the general groundwater flow and deduce recharge zones
9
1.7 Methodology
The current study has been carried out through many steps.
1.7.1 Office work
During this session, most of previous studies had been reviewed, in addition to preparation satellite images as a base map for the study area, as well as tabulation of collected data.
1.7.2 Field work
Field works were conducted for groundwater samples collection, also to identify the rocks unit exposures around the study area, and understanding the time relationship between them, and also pumping test to get deep knowledge about aquifer hydraulic parameters. Many chemical field tests such as pH, EC,.. etc. were carried out.
1.7.2 Laboratory work
This session comprise;
sixteen samples postdate 2016 were chemically analyzed. Processed color composite image used as base map to prepare hydrogeological and geological maps, and to exhibit the spatial distribution of different species over the study area with aiding of ARC GIS package and Surfer program. Processing of pumping tests data were done with aiding of aquitest software (ver. 2.5) to calculate the hydraulic parameter of the aquifer. Aquichem program were used to process the hydrochemical data.
10
CHAPTER TWO Geology and Tectonic settings
2.1 Geology Many authors, e .g. Andrew (1948), Kheiralla (1966), Whiteman (1970, 1971), Vail (1988), Bireir (1993), Awad (1994), Eisawi (1999) and others have extensively investigated the lithostratigraphy of the study area. The oldest rocks exposed in the region are mainly of Proterozoic age such as gneisses and schists, whereas 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, 1994). These are fluvio-lacustrine, siltstone and conglomerates. Extrusive and intercalation of Paleogene age basalts are also encountered in the Khartoum basin either cropping at the surface as the case in Jebel Touriya, or from wells, as penetrated by an exploration well in the Khartoum Basin. However, their aerial extent is not well known and all these units covered by superficial deposits. A generalized geological map of the study area and vicinity is shown in (Fig. 2.1). Based on these studies the following general stratigraphical succession (Table 2.1) has been identified
2.1.1 Basement Complex
The basin sediments lie unconformable on Pan-African (Neo-proterozoic) metamorphic and igneous rocks, which are exposed in Sabaloka area and south west Jebel Aulia ( Fig. 2.1 ). Kroner (1987) suggested that the gneisses
11 exposure were formed along and ancient continental margin onto which juvenile arc assemblages were accreted. The basement in the study area is composed of high-grade metamorphic grey gneiss of proterozoic age. The grey high-grade metamorphic gneisses were found to outcrop on the far southern part of the area. They usually form massive, boulder outcrops or eroded to flat, or sand–covered plains. These gneisses are poorly to moderately foliated, generally grey in color, medium– grained, and consist of quartz, orthoclase, muscovite and magnetite. These units metamorphosed under the condition of the upper amphibolites facies with relics of the granulite facies rocks.
2.1.2 Omdurman Formation
Kheiralla (1966) used the term Merkhiyat sandstone to describe the siliciclastic, medium– to coarse–grained sedimentary outcrops near Omdurman. (Whiteman, 1970) renamed it Omdurman formation. Bireir (1993) adopted the term Omdurman formation for the sedimentary rocks in the Khartoum state, and further subdivided this formation into:
Upper Omdurman formation (outcropping Sediments). Lower Omdurman formation (subsurface Sediments).
The Albian age Omdurman formation crops out across the study area (Awad, 1994; Schrank and Awad, 1990). Awad (1994) described two discrete lithological these are:
Merkhiyat member (represented by the outcrop sequences). Umm Badda member (from the subsurface).
12
2.1.2.1 Umm Badda Member 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, , and several other places. Lithologically, this member consists mainly of tabular cross-stratified, fine–grained sandstone of different colors (brownish, greyish or light greyish), and different cementing material mainly kaolinitic. Siltstones, clay stones and shale are subordinate, individual units show horizontal low–angle bedded sandstone alternating with finely laminated siltstone, claystone, and rarely massive claystone. They are hard to moderately consolidated, sometimes show mud cracks and load casts structures. Eisawi (1999) studied spores and pollen grains association in this member, which indicate fluvial to lacustrine depositional environment, in addition to adjust their age to late Albian- early Turonian.
2.1.2.2 Merkhiyat Member This member crop out at the surface and form a thick sedimentary sequence preserved in many localities in Khartoum state and vicinity. The type section of this member is located at Jebel Merkhiyat (Awad, 1994). Systematic description of selected outcrops around Khartoum state was carried out by Eisawi (1999) which can summarized as follow; These sediments comprise flat lying or gently dipping siliciclastic sedimentary rocks consisting mainly of conglomerates, pebbly sandstones, and medium- to coarse–grained sandstones, siltstone, and shale. The conglomerates are mostly grain- supported of oligomictic nature, pebbles size range between 2 and 5 cm
13 although some gravelly portions have been observed. The color of these conglomerates is mainly greyish and brownish. They are commonly massive and rarely exhibits planar cross stratification.
The pebbly sandstones are most common observed sedimentary rocks in the study area. Their color varies from brown to grey rarely dark grey. The most common observed sedimentary structures in these beds are trough and tabular cross bedding. These structures indicate northwestward and less common northward paleocurrent 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 2-5cm in size. They are cemented by ferruginous, kaolintic or siliceous material.
The medium to coarse–grained sandstone beds comes as second-order 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 Argillaceous . Trough cross-bedding is the most observed sedimentary structures in these beds from which a northward to northwestward paleocurrent 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 coarsing upward sequences. In common, both types end abruptly, rarely they end with shale or iron crust.
14
2 1.3 Volcanic Rocks
In the study area, basic igneous rocks were emplaced within the stratigraphic sequence of Khartoum basin during the Paleogene period. Two small outcrops of olivine basalt occur south and west of Omdurman. The former makes up the low 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 (Fig. 2.1). Similar rocks are reported from borehole in the area between Jebel Aulia and Khartoum (Khartoum Basin), and undoubtedly other buried intrusive masses of the same rock are present elsewhere in the region.
2.1.4 Superficial Deposits
All above mentioned units are cover with Neogene deposits that include Nile silt, wadi deposits, and wind-blown sands that are fine to medium grain in size.
Table 2.1: The stratigraphic column of the study area.
Geological Unit Age Reference Superficial deposits Neogene Vail (1988) volcanic Rocks Early Vail (1988) Paleogen
Omdurman Merkhiyat Turonian – Early Schrank formation Member Senomanian &Awad (1990), Awad (1994) UmmBada Late Albian - Early Eisawi (1999) Member Turonian Basement complex Precambrian Sun oil Company (1989, unpublished rep.)
15
Fig. 2.1: Geological map of Omdurman area (After Awad, 1994).
16
2.2 Tectonic Setting
The Khartoum Basin is one of several Mesozoic rift basins in Sudan associated with the Central African Rift System (CARS) (Fig. 2.2). The initial development of the Sudanese basins has been linked to extension throughout the Afro-Arabian region associated with the separation of east and west Gondowana and sea-floor spreading of the proto-Indian Ocean in the Jurassic (Reynolds, 1993). A second phase of rift development occurred in the Cretaceous during the opening of the South Atlantic (Browne et al., 1985; Fairhead and Green, 1989) and faulting along the Central African Shear Zone (Fig. 1) (Bosworth, 1989; Browne and Fairhead, 1983; Browne et al., 1985; Fairhead, 1986). The structure of the Sudan rift basins. Which align in a northwest to southeast direction, has been investigated previously using potential field data, seismic reflection data and well logs (e.g., Hussein, 1992; Mann, 1989; Schull, 1988). The basins are bounded by listric normal faults (Mann, 1989; Reynolds, 1993), and the amount of extension is variable among them. In the Muglad Rift, for example, about 45 km of crustal extension is documented (Browne and Fairhead, 1983; Jorgensen and Bosworth, 1989). While in the White Nile rift basin about 10 km of extension has occurred (Brown et al., 1980). Similarly, sediment thickness also varies between the basins, with up to 15 km of fill in the Muglad basin (Schull, 1988) and possibly as little as 10 km in the Blue Nile rift (Jorgensen and Bosworth, 1989).
The Khartoum Basin is part of the Blue Nile rift basin system, which lies in the north between the White Nile and the Blue Nile, and stretches to the southeast across the Blue Nile (Fig. 1) (Awad, 1994). The basin may be a ‘sag’ basin because its edges do not appear to be controlled by major bounding
17 faults, and it may be quite shallow, with a maximum sediment thickness of not more than a few kilometers (Mohammed, 1997).
S9
Fig. 2.2: Topographic map showing the locations of Mesozoic rift basins of central Sudan and the Central African Shear Zone (After El Tahir, 2013). 1 Muglad rift, 2 Melut Rift,3 Bara Basin, 4 Kosti, 5 Bagbag Basin, 6 Abyad Basin, 7 Humar Basin, 8 Khartoum Basin,9 Blue Nile Basin, 10 Atbara basin, 11 Gedarif Basin, 12 Abbay River Basin, B.N. Blue Nile, W.N. White Nile.
18
CHAPTER THREE
HYDROGEOLOGY
3.1 Overview of the freshwater resources of Sudan
In a country that is half desert or semi desert, the issue of freshwater availability is critical. At present, much of Sudanese population suffer from a shortage of both clean water for drinking, and reliable water for agriculture. These shortages are a result of natural conditions as well as underdevelopment.
Important sources of fresh surface water in Sudan include the following sites:
Blue Nile throughout Gezira, Sennar, and Khartoum state: River Nile north of Khartoum-though to Dongola : White Nile From Runk to Khartoum : Al Gash River at Kassala: Atbara River at Atbara: Major dams in central Sudan: Jebel Aulia across the white Nile River, Sennar and Roseires dams across Blue Nile River, and Khashm El Girba across Atbara River; and Haffirs in Darfur, northern Kordofan, and Kassala state.
Sudan boasts as a significant number of diverse and relatively pristine wetlands that support a wide range of plants and animals and provide extensive ecosystem services to local population. The principle wetlands are the Sudd- shich is a source of livelihood for hundereds of thousands of pastoralists and fisherman – Dinder and other blue Nile Mayas, and lade
19
Abiad. In addition, there are a large number of smaller and seasonal wetlands that host livestock in the dry season and are important for migrating birds.
Sudan also posses significant groundwater resources. Indeed, one of the worlds largest aquifers – the deep Nubian sandstone aquifer system – underlies the northwestern part of the country (Fig. 3.1), while the Umm Rawaba system extends over a large of central and south Sudan , and has a moderate to high recharge potential. In Western Darfur and south – western Sudan, groundwater resources are generally limited but locally significant, due to the basement complex structure and geology. At last, in the coastal zone, limited groundwater is occurred as brackish to saline.
20
Fig. 3.1: Groundwater basin in Sudan (after Hago, 2014)
21
3.2 Hydrogeology of the studied area
A hydrogeological unit (aquifer) is defined as a formation, part of formation of group of geological formations which have permeability and porosity contain and allow the movement of water with different velocities bounded from the bottom or top or both layers of deposits of deaf impermeable to water (Walton, 1970).
Geological formations (either rock or sediment layers) in which groundwater occurs can generally be classified as aquifers, aquitards or aquicludes (SCCG, 2006).
According to the hydrogeological division (Fig. 3.1) which shows the main aquifers and aquifer groups of Sudan. The studied area is not considered as independent hydrogeological basin, but it lies within big basin represented by Khartoum basin.
The study of lithological logs from water wells with aiding of Rockware (v.16) program for cross-section preparation, the aquifer layer has considerable thickness and extend, which composed of medium to coarse sandstone that occur in depth greater than 550m. this aquifer has confined nature that underlain and overlain by mudstone, also due to lateral change in facies numerous lens were observed.
Two cross-sections has been carried out that, delineate the subsurface structure through which fault is make a displacement, in addition to increasing of thickness of the aquifer northward.
22
Fig. 3.2: Section direction in the study area
23
.
Fig. 3.3: Cross-section in the study area
24
Fig. 3.4: Strip logs for wells in the study area
3.2.1 Groundwater movement and Recharge
Groundwater can moves laterally within the aquifers and vertically from layer to another through leakage process, all these movement mechanism related to the aquifer materials and their geometry. Within groundwater system the movement depend on the hydraulic gradient and hydraulic conductivity. The gradient can be described as the change in head per unit distance in a given direction, and can be calculated based on the following equation;
I = dh/dl (3.1)
Where: I: Hydraulic gradient dh: Head loss between two water points. dl: Horizontal distance between the same two water points
25
And also the flow rate through the aquifer depend on the aquifer material such as the movement through gravel and sand materials is relatively rapid, whereas it is exceedingly slow in clay and other fine-grained rocks.
The groundwater movement in the study area had been studied through the measurement of groundwater level in each well and draw equipotential lines and perpendicularly flow line to construct the flow net.
Detailed flow net analysis (Fig. 3.5) indicated that the River Nile is the main recharge region to the aquifer through which water flow initially toward west and other contribution from North to south and all groundwater discharged toward southwest area which considered as the lowest potential area.
26
(a)
(b)
Fig. 3.5: a. Flow net map of the aquifer, and b.3D. piezometric surface and movement direction
27
3.2.2 Hydraulic aquifers properties
Studying and knowledge of aquifer hydraulic properties are necessary to estimate groundwater flow velocities, flow volume, and travel times. Common techniques for estimating the hydraulic properties of aquifers are usually based on solutions to groundwater flow equations simulating the response of an aquifer to pumping stress (Victoria, 2006).
To find out the hydraulic properties of the aquifer, pumping test have proved to be the most suitable means of achieving this purpose. The important properties are as follows:
3.2.2.1Hydraulic conductivity (K)
Defined as the volume of water that will move through a porous medium in unit time under a unit hydraulic gradient through a unit area measured at righ angles to the direction of flow. Hydraulic conductivity can have any units of (Length/Time) represented by the following equation (Kruseman and de Ridder, 2000):
푸 K= (3.2) 푨푰 Where: K= Hydraulic conductivity (m/day) Q= Discharge (m3/day) A= Area of groundwater (m2) I= Hydraulic gradient (dimensionless unit)
The values of hydraulic conductivity for a particular unit varies from place to another, because of the way in which geological deposits are formed (Domenico and Schwartz, 1998). Hydraulic conductivity values commonly
28 range between 0.02 and 40 m/day for unconsolidated sediment aquifers, less than 0.5 m/day for sandstone, and below 0.0001 m/day for clays or shale (SCCG, 2006).
3.2.2.2 Transmissivity (T)
It is defined as the rate of flow of water under a unit hydraulic gradient through cross-section of unit width over the whole saturated thickness of the aquifer (Kruseman and de Ridder, 2006). It equals the product of multiplying the average hydraulic conductivity by the saturated thickness of the aquifer, expressed in (m2/day) (David, 2002):
T= K × b (3.3) Where: T: Transmissivity (m2/day) K: Hydraulic conductivity (m/day) B:Saturated thickness of aquifer (m).
3.2.2.3 Storage Coefficient (ST)
The storage coefficient (Ssc) of a confined aquifer is defined as the volume of water released from storage per unit surface area of a confined aquifer per unit declined in hydraulic head. The storage coefficient generally ranges between 0.00005 and 0.005 in confined aquifers, which is a dimentionless unit (Kruseman and de Ridder, 2000).
3.2.3 Pumping test analysis
in a pumping test, large volumes of water are pumped from a well for a period of time, and changes in head are monitored at the pumping well and / or nearby observation wells. Typical pumping tests involved pumping for
29 hours, days, or weeks. These tests measure the average horizontal hydraulic conductivity and storage parameters of the aquifer being pumped. The resulting parameters apply most to the near vicinity of the pumping well, and to a lesser degree to the region encompassed by the observation wells (Fitts, 2002). There are several published methods for analyzing pumping tests data, the following method have been used are :
3.2.3.1 Cooper and Jacob method
Cooper and Jacob (1946) suggested that for small values of (r) and large values of (t), the following method may be applied for the analysis of pumping test of a well. Accordingly, the value of transmissivity (T) can be obtained by noting (t/tº) for one log-cycle, then log t/tº =1, where; r: Distance from pumped well to observation well (m) t: Time of pumping (min) tº: Intercept point of the fitted line on the time axis.
Therefore, if ∆s is the drawdown difference per log-cycle of t, then the equation below can be set to determine (T) value as follows (Todd, 2007);
ퟐ.ퟑ 푸 T = (3.4) ퟒ흅∆풔
Where;
T: Transmissivity (m2/day) ∆s: Difference in the drawdown (m) per log-cycle of t. Q: Discharge (m3/day)
30
3.2.4 Pumping test results
The hydrogeological characteristics of the aquifers depend on the single well pumping test data which are available for 16 wells drilled in the study area that are obtained from General Commission for Groundwater.
Observation wells are not available in the studied area, thus the storage coefficient determined based on the assumption that, the distance to observation well is too small about (0.01m).
Cooper-Jacob method has been used in the treatment of these data and the results were listed in the (Table 3.1). The processed data and their locations were listed in the appendix (C).
Table 3.1: Hydraulic aquifer parameter in the study area
Well name T S K Ummbadda Sq. (4) 0.0139 0 4.56 Ummbadda Alrashideen 0.0194 215 0.000647 Dar Es-Salam - Palestine yard 0.0792 0.716 0.0022 Dar Es-Salam Sq. (16) 0.165 5.88 0.00458 Dar Es-Salam Sq. (17) 0.281 6.35 _ Dar Es-Salam Sq. (18) 0.702 60 0.0195 Dar Es-Salam Sq. (19) 0.0924 0.0455 0.00192 Dar Es-Salam Sq. (22) 1.73 0.00393 0.0482 Dar Es-Salam Sq. (26) 0.086 552 0.001 Dar Es-Salam Sq. (27) 0.0235 6.76 0.000785 Dar Es-Salam Sq. (28) 0.0613 8.35 0.007 Dar Es-Salam Sq. (30) 0.027 76.2 0.00075 Dar Es-Salam Sq. (42) 0.412 8.1 0.0137 Althora Sq. (18) 0.222 5.85E-10 0.0185 Et-Takamul 0.412 8.1 0.0137
31
CHAPTER FOUR GROUNDWATER QUALITY
4.1 Introduction Water quality analysis is one of the most important aspect in groundwater studies, which is nearly of equal importance to quantity. Therefore its necessary to make chemical, physical, and bacterial analyses of groundwater to determine its suitability for different purposes (drinking , irrigation, …, etc..). A standard groundwater chemical analysis will as a minimum comprise values for temperature, EC, pH, the four major cations (Na+, K+, Mg2+, Ca2+) and four - - 2- - major anions (Cl , HCO3 , SO4 , NO3 ) (Appelo and Postma, 2005 ). The chemical parameters (EC, pH, and temperature ) must be taken in the field immediately after sampling, because water chemistry can change rapidly once a sample is extracted from a well and exposed to light, warmth, cold, air, or other environmental factors (Sanders, 1998). Study of groundwater quality in the study area depend on the major ionic concentrations. Beside, these ionic concentration study also involves the salinity (total dissolved solids, TDS), electrical conductivity (EC), and pH. The water samples were collected from (16) wells in the study area. 4.2 Accuracy of chemical analysis In general, two types of errors are discerned in chemical analysis: Precision or statistical errors which reflect random fluctuations in the analytical procedure. Accuracy or systematic errors displaying systemtic deviations due to faulty procedures or interferences during analysis
32
The accuracy of the analysis for major ions can be estimated from the electrical balance (E.B.) since the sum of positive and negative charges in the water should be equal:
(푆푢푚 푐푎푡푖표푛푠+푆푢푚 푎푛푖표푛푠) Electrical Balance (E.B., %) = × 100 (4.1) (푆푢푚 푐푎푡푖표푛푠−푆푢푚 푎푛푖표푛푠)
Where cations and anions are expressed as meq/L and inserted with their charge sign. The sums are taken over the cations Na+, K+, Mg2+, and Ca2+, and - - 2- - anions Cl , HCO3 , SO4 , and NO3 and sometimes other elements contribute 3+ + significantly, for example ferrous iron (Fe ) or NH4 in reduced groundwater, or H+ and Al3+ in acid water ( Appelo and Postma, 2005).
4.3 Quality of groundwater for Municipal use (Drinking purposes) Water for drinking purposes should be potable, i.e. safe and good to drink. The water quality should satisfy the WHO requirements, in the following paragraph comments on the chemical characteristics of groundwater sampled from the aquifer with respect to WHO (2011) drinking water guideline.
4.3.1 Hydrogen-ions activity (pH) A reliable pH measurement is one of the most important field parameters to be measured, and must be made with care and patience. pH is an expression of the negative log H+ activity
pH = - log {H+} (4.2)
Natural water, pH value generally range between 6.5 and 8. A (pH) value of 7 indicates neutrality, that is the concentration of hydrogen (H+) and hydroxide (OH-) ions are equal. Water with pH less than 7 is said to be
33
“acidic”, whereas levels above 7 are termed “alkaline”, groundwater most commonly occurs under reducing conditions, where the limited oxygen present is consumed by chemical and biological activity, as a result, a decrease in pH values occur and tend to be less than 7 (SCCG, 2006). The dissolution and mobility of metals in natural water are greatly influenced by the (pH) (Thompson et al., 2007). In the present study, pH values ranged between 7 – 7.9 with the average value of 7.48, indicating an alkaline nature of groundwater (Fig. 4.1). Spatial distribution of pH in the study area can be summarized as follow; the high pH values occurred in central part of the aquifer in the study area, which form zone extends in the NW direction, that reflect high alkaline water. These values decrease gradually in the same direction of groundwater flow (SW direction) and becomes almost neutrally near basaltic intrusion in Toriya area, also slightly decease towards NE direction observed (Fig. 4.2).
34
pH 8 7.8 7.6 7.4 7.2 pH 7 6.8 6.6 6.4
Wells
Fig. 4.1: pH concentration in the study area
Fig. 4.2: Spatial distribution of pH in the study area
35
4.3.2 Total Dissolved Solid (TDS)
Total dissolved solids (TDS) is the total amount of solids remaining when a water sample evaporated to dryness (Drever, 1997). Dissolved solids include both organic and inorganic materials dissolved in a sample of water and are commonly used as a general indicator of water salinity or quality (Bates and Jackson, 1984) (Table 4.1). TDS represents a total summation of ionic concentrations of cations and anions, it is measured by the (ppm) or (mg/l) units (Boyd, 2000). Table 4.1: Classification of water salinity according to (TDS) in (ppm) Water class Altoviski (1962) Drever (1997) Todd (2007)
Fresh water 0 – 1000 < 1000 10 – 1000 Slightly water 1000 – 3000 1000 – 2000 - Slightly – 3000 - 10000 2000 -20000 1000 – 10000 brackish water Brackish water 10000 – 100000 - 10000 – 100000 Saline water - 35000 - Brine water > 100000 > 35000 > 100000
In the study area, the concentration value of TDS ranged between 155 – 750 mg/l with average value about 366.24 mg/l. TDS in the study area falls within the permissible limits of the WHO (2011) guideline of 1000 mg/l, and classified as fresh water. Depending on the above mentioned criteria the water in these aquifers are good for human exploitation (Fig. 4.3). Three distinctive regions have been mapped from the TDS contour distribution patterns. The high TDS region occur in the middle area which form close elliptical contours trending in the NW direction. Consequently the
36
TDS value decreases with highly gradient to NE (abruptly change), as well as another gradually decreases to the west and SW direction (Fig. 3.4)
TDS 800 700 600 500 400 300
TDS, (mg/l) TDS, 200 100 0
Wells
Fig. 4.3: TDS compared with the WHO in the studied area
Fig. 4.4: Spatial distribution of TDS in the study area
37
4.3.3 Electrical Conductivity (EC) Electrical conductivity is proportional to the quantity of dissolved ions present in solution and can provide a rough idea of the total dissolved solids (TDS) (Clark and Fritz, 1997). EC increase with the increases of the total dissolved solids (Detay, 1997). For most groundwater, the EC value, in 휇푆/퐶푚 corrected to 25°C, is about 50% greater than the TDS expressed as mg/L and can be estimated according to: TDS = A × EC (흁푺/푪풎) (4.3) A = 0.55 in bicarbonate water A = 0.75 in high sulphate water A = 0.9 in high chloride water
Table 4.2: General classification of groundwater based on EC (USSL. 1954) Class EC, µS/cm Water quality C1 100-250 Excellent C2 250-750 Good C3 750-2250 Doubtful C4 >2250 Unsuitable
The overall groundwater EC value is ranging between 282 – 1309.1 μS/Cm with average value 625.5 µS/cm and standard deviation 224.3 in the studied sample (Fig. 4.5). There is anomalous value of EC in Ummbadda Alrashideen well which gives odd statistical results. The large variation in EC is mainly attributed to geochemical processes prevailing in this region. All samples fall into the permissible limits for human exploitation based on WHO. Similar
38 spatial distribution pattern were observed also in EC isocone map (Fig, 4.6), because of its strong positive correlation factor.
EC 1400 1200
푚 1000 퐶
/ 800 푆
휇 600
400 EC , EC 200 0
Wells
Fig. 4.5: Distribution of EC compared with WHO (2011)
Fig. 4.6: Spatial distribution of EC in the study area
39
4.3.4 Hardness (HT) Is results from the presence of divalent metallic cations, of which calcium and magnesium are the most abundant in groundwater. This ions react with soap to form precipitates and with certain anions present in the water to form a scale. Because of their adverse action with soap, hard waters are unsatisfactory for household cleaning purposes, hence, water-softing processes for removal of hardness are needed. Low pH conditions develop and lead to the solution of insoluble carbonates in the limestone formations to convert them into soluble bicarbonates (Todd, 1980).
Hardness HT is customarily expressed as the equivalent of calcium carbonate. Thus,
HT = 2.5 Ca + 4.1 Mg (4.4)
Table (4-3) Hardness Classification of Water (after Sawyer and McCarty, 1967)
Hardness, mg/l as CaCO3 Water class aquifer(16 samples) 0 – 75 Soft One sample 75 – 150 Moderately hard 3 samples 150 – 300 Hard 12 samples Over 300 Very hard
There are two kind of (TH) (Hem, 1989) I. Temporary Hardness (Carbonate hardness) represent calcium and magnesium concentration, combined with bicarbonate of water. This TH removed by boiling the water.
Ca (HCO3)2 CaCO3 +H2O+CO2 (4.5)
40
II. Permanent hardness or non.– carbonate hardness occur when the
hardness value exceeds the alkalinity value. This type of hardness can be removed by adding sodium carbonate.
CaCl2 + Na2 CO3 CaCO3 + 2NaCl (4.6)
Table 4.4: Concentration of permanent hardness in the study area
Well name TH CH NCH South Alarda 83.42361 54.0275 29.3961 Ummbadda Sq. (4) 142.8521 165.3569 0 Ummbadda Alrashideen 237.817 188.2777 49.53933 Dar Es-Salam - Palestine yard 178.7372 163.7197 15.01751 Dar Es-Salam Sq. (16) 182.6862 147.3477 35.33847 Dar Es-Salam Sq. (17) 210.4367 170.2685 40.16822 Dar Es-Salam Sq. (18) 194.6838 171.9057 22.77807 Dar Es-Salam Sq. (19) 198.6328 165.3569 33.27585 Dar Es-Salam Sq. (22) 202.5818 180.0917 22.49007 Dar Es-Salam Sq. (26) 198.5897 168.6313 29.95844 Dar Es-Salam Sq. (27) 202.5818 166.9941 35.58765 Dar Es-Salam Sq. (28) 148.9047 155.5337 0 Dar Es-Salam Sq. (30) 158.7771 163.7197 0 Dar Es-Salam Sq. (42) 184.5531 168.6313 15.92184 Althora Sq. (18) 206.1409 188.2777 17.86324 Et-Takamul 108.406 148.9849 0
Based on hardness classification of water after (After Sawyer and McCarty, 1967), the studied water samples classified as hard water, in addition to a few samples classified as moderately hard and one sample is soft water (Table 4.3). Majority of samples contain permanent hardness (Non-carbonate hardness) which attributed to the presence of sulphate and chloride in addition to four samples free from non-carbonate hardness (Table 4.4). Total hardness distribution map is given in (Fig. 4.8), indicate high TH value occur in the middle area which contain non-carbonate hardness, and these
41 value sharply decrease to the east and gradually decrease to the SW with the dominance of carbonate hardness.
T.H
300 ) 3 250 200 150 100
mg/las CaCO 50
0 T.H,(
Wells
Fig, 4.7: distribution of Total hardness in the study area
Fig. 4.8: Spatial distribution TH in the study area
42
4.3.5 Major dissolved ions in groundwater The abundance of major ions largely depends upon the nature of rocks, climatic conditions and mobility. The ion distribution is also influenced by the infinite complex surface and subsurface physiochemical environments (Aghazadeh and Mogaddam, 2010). To asses these geochemical processes the collected samples are chemically analyzed for the major cations (Na+, K+, 2+ 2+ - 2- - - Ca , and Mg ) and major anions (Cl , SO4 , NO3 , and HCO3 ). The distribution of major cations and anions western Omdurman area are briefly summarized
4.3.5.1 Cations
Sodium (Na+) Sodium is the most important and abundant of the alkali metal in natural waters to which the salinity of the groundwater is directly related. Sources of sodium (Na+) are halite (NaCl), sea spray, hot springs, brines and some silicates or rare minerals such as Nahcolite (NaHCO3) (Ghoraba et, al., 2013). In groundwater source of sodium content is greatly dependent on the rock type of aquifer and cation exchange. The concentration of sodium in the studied sample ranged between 16.2 – 155.4 with mean 58.97 mg/l in the aquifer (Fig. 4.9). Based on WHO, all samples fall in the permissible limits except Ummbadda Alrashideen well exhibits anomalous concentration due to geochemical processes prevailing in the aquifer system such as reverse ion exchange and silicate weathering. Anomalous sodium concentration in Alrashideen well affected on the spatial distribution pattern of Na+ in the study area, which create distinctive close contour (Fig, 4-10). However, the distribution similar to those in TDS and EC
43 maps. This similarity clearly reflects the contribution of Na+ in the TDS and EC values.
Sodium 180 160 140 120
mg/l) mg/l) 100 ( 80 +, +, 60 Na 40 20 0
Wells
Fig. 4.9: Distribution of sodium in the study area
Fig. 4.10: Spatial distribution of Na+ in the study area
44
Potassium (K+) The main sources of potassium is the products formed by weathering of igneous minerals like (orthoclase, microcline, mica (biotite) and the feldspathoid (leucite) and sedimentary rocks. Potassium is commonly present in clays within the structure like illite or adsorbed on other clay minerals, evaporate rocks include sylvite and other potassium salts and organic remains (plant) (Hem, 1985). Fertilizers increases the potassium concentration in the water (Daly, 1994).
The concentration of Potassium (K+) (Fig. 4.11) ranged between 1 – 8.3 with average 4.68 mg/l aquiferous zone. All samples fall in the permissible limits.
Potassium 9 8 7 6 5
(mg/l ) 4 ,
+ 3
K 2 1 0
Wells
Fig. 4.11: Distribution of K+ in the study area
45
Spatial distribution map of potassium content in the study area reflects increases in the direction of flow (i.e. low content in recharge area and high content in discharge area) (Fig. 4.12)
Fig. 4.12: Spatial distribution of K+ in the study area
Calcium (Ca2+) Calcium is an essential constituent of carbonate sedimentary rocks, and it results from the erosion of igneous and metamorphic rocks. It is abundant almost in the all soils (White, 2005). Calcium is alkaline-earth metals and is an essential element for plant and animal. It is produced as a result of dissolution processes of sedimentary rocks (limestone, dolomite, and gypsum) and from weathering of igneous rocks like (pyroxene, amphibole, plagioclase
46 feldspar (Anorthite)). Calcium also occurs in other silicate minerals that are produced in metamorphism (Hem, 1989).
In the present study, the concentration of Calcium (Fig. 4.13) ranged 18.4 – 46.4 mg/l with average value 37.35 mg/l for the aquifer zone, which is acceptable for domestic uses.
The distribution pattern of calcium content in the study area (Fig. 4.14) is very different, which can be divided into four main zones that occur in an oval shape. The first zone occurs in the NE part of the area, which decrease gradually toward SW, and the second zone also having high content of calcium decrease to the NE. These two zones form in between the third zone, which having low value with respect to the above and decrease gradually to the S and SE, the last zone occur in the SW part of the area which have low content of calcium.
Calcium 50 45 40 35 30
(mg/l ) 25 , 20
+2 15 10 Ca 5 0
Wells
Fig. 4.13: Distribution of Ca2+ in the study area
47
Fig. 4.14: Spatial distribution of Ca2+ in the study area
Magnesium (Mg2+)
Magnesium is an alkali-earth metal with one oxidation state in water (Mg2+). Magnesium ions are smaller than sodium and calcium ions and it is one of the necessary elements of the plants and animals (Hem, 1989). Dolomite, limestone, and clay minerals are considered as essential sources for magnesium ion. Magnesium is found also in igneous rocks and minerals such as (Olivine, Pyroxene, and amphibole) and metamorphic rocks such as (Serpentine and talc) (Todd, 2007). The concentration of Magnesium (Fig. 4.15) ranged between 8.4 – 29.67 mg/l with average value 20.49 mg/l in aquifer, which is acceptable for drinking usage.
48
Magnesium 35 30 25
20 (mg/l ) , 15 +2 10
Mg 5 0
Wells
Fig. 4.15: Distribution of sodium in the study area
Magnesium distribution contour pattern reflects the general decrease in concentration occur toward SE direction (Fig. 4.16). In addition to close similarity in the distribution pattern of calcium and magnesium ions.
49
Fig. 4.16: Spatial distribution of Mg2+ in the study area
50
4.3.5-2 Anions Chloride (Cl-) The common sources of chlorides are halite (NaCl), sea spray, brines and hot springs. High concentrations of chloride can occur near sewage and other waste outlets. Chloride ion cause severe problem in the crops at concentration > 350 mg/l (Hopkins et al., 2007). Variation in chloride concentration were observed between 13 – 132 mg/l with average value of 48 mg/l in the aquifer (Fig. 4.17). All samples fall within the permissible limits for drinking according to WHO standard. The extremely concentration of chloride in Ummbadda Alrashideen well which effects on the range of data in the study area.
Chloride 140 120 100 80
(mg/l) 60 ,
- 40 Cl 20 0
Wells
Fig. 4.17: Distribution of Cl in the study area
51
Anomalous Chloride concentration in Alrashideen well affected on the spatial distribution pattern of Cl- in the study area, which create distinctive close contour (Fig. 4.18). However, the distribution similar to those in TDS. EC, and Na+ isocone maps. This similarity clearly reflects the contribution of Cl- in the TDS and EC values.
Fig. 4.18: Spatial distribution of Cl- in the study area
52
- Bicarbonate (HCO3 ) Most bicarbonate ions in groundwater are derived from carbon dioxide in the atmosphere, carbon dioxide in the soil, and dissolution of carbonate rocks. Bicarbonate is an ion that is common to all natural waters because all bicarbonate are water soluble. This concept can be explain be the following equations;
CO2 + H2O H2CO3 (4.7) + - H2CO3 H + HCO (4.8)
Bicarbonate ions varied between 66 – 230 mg/l with the average value 196 mg/l in the study area (Fig. 4.19).
Bicarbonate represent the prevalent anion and plays a main role in describe the water type in the study area.
Bicarbonate 250 200
150
, (mg/l , ) -
3 100
50 HCO 0
Wells
Fig. 4.19: Distribution of HCO3 in the study area
53
High bicarbonate concentration in the study area except Alarda well, and their spatial distribution is very different from the above mentioned ions. The high bicarbonate content zone trends in the NE direction which decrease sharply toward east and decreases gradually toward south and NW directions (Fig. 4.20).
- Fig. 4.20: Spatial distribution of HCO3 in the study area
2- Sulphate (SO4 )
Sulphates occur naturally in numerous minerals. Gypsum (CaSO4.2H2O) and
Anhydrite (CaSO4) are generally the common sources of sulphate. Sulphur is an essential element in plant nutrition and in form of sulphate it is readly available to plants. The sulphate content increases in water with increase of salinity content. Water containing more than 1000 mg/l sulphate are harmful for the plants (Sagnak, 2010).
54
Sulphate ions varies between 10 – 159 mg/l with average value 41.17 mg/l (Fig. 4.21). The high concentration of sulphate in Ummbadda Alrashideen well lead to change the range which can ascribe to localized geological body and different hydrochemical processes.
Sulphate 180 160 140 120 100
, (mg/l , ) 80
2 -
4 60 40 SO 20 0
Wells
2- Fig. 4.21: Distribution of SO4 in the study area
Anomalous sulphate concentration in Alrashideen well affected on the spatial 2- distribution pattern of SO4 in the study area, which create distinctive close contour (Fig. 4.22). However, the distribution similar to those in TDS. EC, Na+, and Cl- isocone maps. This similarity clearly reflects the contribution of
2- SO4 in the TDS and EC values.
55
2- Fig. 4.22: Spatial distribution of SO4 in the study area
- Nitrate (NO3 ) Nitrate is a major problem in some shallow aquifers and is increasingly becoming a threat to groundwater supplies. There are numerous sources of nitrate in groundwater system. Most of them are strongly influenced by human activities. Nitrogen fertilizers are widely used in agricultural practices, organic nitrogen is present in number of waste products, notably sewage effluents, animal excrement and manure and municipal wastes. The Nitrate in the groundwater varies between 1.2 – 7.04 mg/l with average value 3,08 mg/l (Fig. 4.23). - Distribution of NO3 in the study area is different from major ions. The NE area corresponding to high content of nitrate compare to the other areas, that considered the most polluted area and the concentration decrease with flow
56 direction up to the centre of the area at Alrashideen well, also there is increase in the SW part and the lower concentration area occur in the western part. The presence of nitrate in water due to human activity in the study area.
Nitrate 8 7 6
- 5 3 4 NO 3 2 1 0
Wells
Fig. 4.23: Distribution of NO3- in the study area
Fig. 4.24: Spatial distribution of NO3 in the study area
57
4.4 Quality of groundwater for irrigation The suitability of water for irrigation depends on the effects of the mineral constituents of water on both the plant and the soil (Raihan and Alam, 2008). Salts may harm plant growth physically by limiting the uptake of water through modification of osmotic processes, or chemically by metabolic reactions such as those caused by toxic constituents. Irrigation of food crops presents a possible risk to food consumers if the quality of irrigation water is inadequate. The salinity of water suitable for irrigation also depends on the composition of soil, permeability of soil, the topography of the land, the amount of water used and methods of applying it, the kinds of crops grown, the climate of the region and the nature of the groundwater and surface water drainage system. In this study, the discussion of water quality for irrigation is mainly based on the following factors (Table 4.10) these are;
I. Sodium Absorption Ratio (SAR); II. Sodium percentage (SP); III. Residual Sodium Carbonate (RSC); IV. Magnesium Absorption Ratio (MAR); V. Kelley Ratio (KR); VI. Permeability Index (PI).
4.4.1 Sodium Absorption Ratio (SAR) The relationship between Na+ and Ca2+ Mg2+ ions content affects to great extent the physical properties of soil. This relation can be expressed by sodium absorption ratios (SAR). The ratio estimates the degree to which sodium will be adsorbed by the soil. High value of SAR implies that sodium in the irrigation water may replace calcium and magnesium ions in the soil, potentially causing damage to the soil structure. It is defined by :
58
퐍퐚 SAR = (Richard, 1954) (4.9) √(퐂퐚+퐌퐠)/ퟐ
Where the ion concentrations are expressed in equivalent per million (epm). Using sodium hazard classification, all samples fall within S1 class which characterized by the excellent quality of water for irrigation (Table 4.5).
Table 4.5: Sodium hazard classes based on USSL classification Sodium Hazard SAR in Eqivanlents Remark on Aquifer Class per mole quality S1 < 10 Excellent .77 – 4.38 (all 16 samples) S2 10 – 18 Good S3 18 – 26 Doubtful S4 > 26 Unsuitable
4.4.1.1 Sodium (Hazard) vs Salinity hazard Classification
This classification proposed by US Salinity Laboratory (USSL) staff (1954). when the SAR and specific conductance of water are known the classification of water for irrigation can be determined by graphically plotting these values on the USSL diagram which divided into sixteen hazard class (Fig. 4.25). Based on the above mentioned diagram, the groundwater samples from study area are presented in the Table (4-6) and grouped into four main class as follow; About 87.5% of total samples from the aquifers are grouped within C2-S1 which represents good salinity and excellent Sodium hazard class. In addition to 6.25% of total samples are belong to the C3-S1 which represents doubtful salinity and excellent Sodium hazard class. About 6.25% of total samples are
59 grouped within C3-S2, which represents doubtful salinity and good Sodium hazard class.
Table 4.6: Classification of studied groundwater samples for irrigation purpose Class Remarks Lower Aquifer ( 16 Samples) C2-S1 Good Salinity + Excellent Sodium hazard 87.5% (14 Samples) C3-S1 Doubtful Salinity +Excellent Sodium hazard 6.25% (One Sample) C3-S2 Doubtful Salinity + Good Sodium hazard 6.25% (One Sample) C4-S3 Unsuitable Salinity + Doubtful Sodium hazard
Fig. 4.25: USSL classification for groundwater in the study area 60
4.4.2 Percent Sodium (% Na+) The sodium in irrigation waters is usually denoted as percent sodium and can be determined using the following formula (Wilcox, 1995)
% Na = (Na) × 100/(Ca + Mg + Na + K) (4.10) Where the quantities of Ca, Mg, Na, and K are expressed in milli equivalents per litre (epm).
Sodium percent classification exhibits two suitable water classes, the first one range between 29.4 – 39.2 and represents 62.5% from total samples that describe as good water class, as well as the second class range between 40.40 – 57.72 and represents 37.5% that can be describe as permissible class (Table. 4.7) Table 4.7: Sodium percentage water class Sodium (%) Water Class Aquifer < 20 Excellent 20 – 40 Good 29.4 – 39.2 (62.5%) 40 – 60 Permissible 40.40 – 57.72(37.5%) 60 – 80 Doubtful > 80 Unsuitable
4.4.3 Residual Sodium Carbonate (RSC) In waters having high concentration of bicarbonate, there is tendency for calcium and magnesium to precipitate as the water in the soil becomes more concentrated. As a result, the relative proportion of sodium in the water is
61 increased in the form of sodium carbonate. RSC is calculated using the following equation.
RSC = (HCO3 + CO3) – (Ca +Mg) (4.11) Where all ionic concentration are expressed in epm
All groundwater samples having residual sodium carbonate content less than 1.25, which can be described as good class for irrigation purposes (Table 4.8).
Table 4.8: Groundwater quality based on RSC (Residual Sodium Carbonate) RSC Remark Aquifer < 1.25 Good (-.9) - .8 (100%) 1.25 – 2.5 Doubtful > 2.5 Unsuitable
4.4.4 Permeability index (PI)
Doneen (1964) has evolved a modified criterion based on the solubility of salts and the reaction occurring in the soil solution from cation exchange for estimating the quality of agricultural waters. According to him, soil permeability, as affected by long-term use of irrigation water, is influenced by;
1. Total dissolved solid 2. Sodium contents 3. Bicarbonate contents.
The permeability index is given by the following formula;
Na+ HCO3 PI = √ ∗ 100 (4.12) Ca+Mg+Na
Majority of samples fall in class I and the rest fall in class II (Fig. 4-26), these results reflect suitable water for irrigation purpose (Table 4.9). 62
Table 4.9: Classification of irrigation water based on PI Class PI Remarks aquifer (16 samples) Class I ≥75% Suitable 81.25% (13samples) Class II 75%-25% Suitable 18.75% (3samples) Class III <25% unsuitable
Fig. 4-26: Permeability index diagram 4.4.5 Magnesium Adsorption Ratio (MAR)
MAR was calculated by the equation Raghunath (1987) as;
푴품 MAR= ∗ 100 (4.13) 푴품+푪풂
63
Where all the ionic concentrations are expressed in meq/l. MAR values were found from 31,87 to 55.28 in the aquifer.
Table (4.10) show the majority of water samples fall on the suitable class and about 25% of total samples exhibit magnesium hazard.
Table 4.10: classification of groundwater based of MAR MAR Remarks Aquifer <50% Suitable 75%(12 samples) >50% Unsuitable 25% (4 samples)
4.4.6 Kelley Ratio (KR)
Kelley’s Ratio was calculated using the equation kelley (1940) as;
KB = Na/(Ca+Mg) (4.14)
Where, all the ionic concentrations are expressed in meq/l. The kelly’s ratio values were ranged between 0.42 – 1.4 in the studied water samples. Most of samples have kelly ratio less than 1 which classified as suitable and about 12.5% were fall into unsuitable class (Table. 4.11)
Table 4.11: classification of groundwater based of Kelly ratio KR Remarks aquifer (16 samples)
<1 Suitable 87.5% (14 samples)
>1 Unsuitable 12.5% (2 samples)
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Table 4.12: Calculated parameters for suitability of groundwater in irrigation purposes
Well name SAR PI MAR KR Remarks South Alarda 0.771492 73.49585 44.96979 0.422335 Suitable Ummbadda Sq. (4) 2.305132 81.49573 55.28784 0.964323 Ummbadda 4.383193 75.54806 51.32036 1.421147 Alrashideen Dar Es-Salam - Suitable 1.685324 69.71094 46.39707 0.630298 Palestine yard Dar Es-Salam Sq. (16) 1.621955 66.8652 47.55577 0.600006 Suitable Dar Es-Salam Sq. (17) 1.895035 66.03258 49.7291 0.653171 Suitable Dar Es-Salam Sq. (18) 2.160064 70.4751 43.61089 0.774055 Suitable Dar Es-Salam Sq. (19) 1.536968 64.91014 44.73196 0.545267 Suitable Dar Es-Salam Sq. (22) 2.010883 68.84779 45.80932 0.70641 Suitable Dar Es-Salam Sq. (26) 1.388977 63.98611 46.73017 0.492818 Suitable Dar Es-Salam Sq. (27) 2.032275 67.97181 45.80932 0.713925 Suitable Dar Es-Salam Sq. (28) 1.604056 75.39477 49.0625 0.657257 Suitable Dar Es-Salam Sq. (30) 1.36698 72.11095 52.22971 0.542423 Dar Es-Salam Sq. (42) 1.367188 66.57425 53.49397 0.503196 Althora Sq. (18) 1.923768 68.30283 45.77668 0.669947 Suitable Et-Takamul 2.339497 90.40089 31.87433 1.123481
65
CHAPTER FIVE HYDROCHEMISTRY
5.1 Classification of hydrochemical data
Hydrochemical facies were worked out by developing Stiff, Piper, and Durov diagrams and others.
5.1.1 Stiff Diagrams
Geochemistry of groundwater is discussed by means of its major ions, Stiff (1951) diagram is a graphical representation of the different water ions. The average ionic composition analysis by Stiff diagram
Based on stiff diagrams (Table. 5.1) , all studied samples in the aquifer exhibit prevailing bicarbonate water-type but half of them contain considerable amount of chloride and one sample contain little amount of sulphate. Sodium is the most dominant cation in the water samples in addition to small quantities of calcium and magnesium (Fig. 5.1).
66
Table 5.1: Stiff water type in the study area Wells Water type South Alarda Ca Mg Na HCO3 Cl Ummbadda Sq. (4) Na Mg Ca HCO3 Ummbadda Alrashideen Na Mg Ca HCO3 Cl SO4 Dar El-Salam - Palestine yard Na Ca Mg HCO3 Cl Dar El-Salam Sq. (16) Na Ca Mg HCO3 Cl Dar El-Salam Sq. (17) Na Ca Mg HCO3 Cl Dar El-Salam Sq. (18) Na Ca Mg HCO3 Cl Dar El-Salam Sq. (19) Ca Na Mg HCO3 Cl Dar El-Salam Sq. (22) Na Ca Mg HCO3 Cl Dar El-Salam Sq. (26) Ca Na Mg HCO3 Cl Dar El-Salam Sq. (27) Na Ca Mg HCO3 Dar El-Salam Sq. (28) Na Ca Mg HCO3 Dar El-Salam Sq. (30) Na Mg Ca HCO3 Dar El-Salam Sq. (42) Mg Na Ca HCO3 Althora Sq. (18) Na Ca Mg HCO3 Et-Takamul Na Ca HCO3
67
Fig. 5.1: Stiff map of the groundwater samples
68
5.1.2 Durov Diagram
Durov (1948) introduced another diagram that provides more information on the hydrochemical facies by helping to identify the water types and it can display some possible geochemical processes that could help in understanding quality of groundwater and its evolution. The diagram is a composite plot consisting of two ternary diagrams where the cations of interest are plotted against the anions of interest: sides form a binary plot of total cation vs. total anion concentration: expanded version includes electrical conductivity (휇푆/푐푚) and pH data added to the sides of the binary plot to allow further comparisons.
Fig. 5.2: Durov plots for the groundwater samples.
The plot (Fig. 5.2) indicates that the ion exchange is the main geochemical process. The pH part of the plot reveals that the groundwater in the study area
69 is alkaline which is preferred for drinking and the electrical conductivity of water samples lies in the range of drinking water standard.
5.1.3 Trilinear Diagram (Piper Diagram)
Piper Diagrams (Piper, 1944), are a combination anion and cation triangles that lie on a common baseline diamond shape between them can be used to make a tentative conclusion as to the origin of the water represented by the analysis and to characterize different water types. Piper divided waters into four basic types according to their placement near the four corner of the diamond. Water that plots at the top of the diamond is high in Ca2+ Mg2+ and - 2- Cl SO4 , which results in an area of permanent hardness. The water that plots 2+ 2+ - near the left corner is rich in Ca Mg and HCO3 and is the region of water of temporary hardness. Water plotted at the lower corner pf the diamond is + + - 2- primarily composed of alkali carbonates (Na + K and HCO3 +CO3 ). Water lying nears the right-hand side of the diamond may be considered saline (Na+ + - 2- + K and Cl + SO4 ).
70
Fig. 5.3: Piper diagrams for classifying groundwater. Based on piper diagram (Fig. 5.3), the groundwater classified into the following facies; i. Calcium bicarbonate type, which furthermore that the alkalies were greater than alkaline earth (15 samples). ii. Mixed type (no cations – anions exceed 50%) (One sample).
5.1.4 Chadha classification Chadha diagram is constructed by plotting the difference between alkaline earth and alkali metals and the difference between weak acidic anions and strong acidic anions by milliequivalent percentage (eqm%) on the axis of X and Y. X-axis represents the difference between Alkaline earth and Alkaline metallic {(Ca2++Mg2+)-(Na++K+)}(epm%), while Y-axis represents the
- 2- - 2- difference between weak and strong acids{(HCO3 +CO3 )-(Cl + SO4 )} (epm%) (Chadha, 1999). Chadha classification can be used to interprets the
71 general properties of water for more accurate details which are not available in the Piper classification. Chadha divided the plotting into eight parts each part represents one type of water as follows;
1. Alkaline earths exceed alkali metals. 2. Alkali metals exceed alkaline earths. 3. Weak acids anions exceed strong acids anions. 4. Strong acids anions exceed weak acid anions. 5. Alkaline earths exceed alkali metals and weak acids anions exceed strong acids anions. This type has temporary hardness. 6. Alkaline earths exceed alkali metals and strong acids anions exceed weak acids anions. This type has permanent hardness and not residual sodium carbonate in irrigation use. 7. Alkali metals exceed alkaline earths and strong acids anions exceed weak acids anions. This type generally creates salinity problems in both irrigation and drinking uses. 8. Alkali metals exceed alkaline earths and weak acids exceed strong acids. This type deposit residual sodium carbonate in irrigation and cause foaming problems.
72
Fig. 5.4: Chadha classification of groundwater samples.
Studied samples classified into five-water type (Fig. 5.4), which summarized in the Table 5.2)
Table 5.2: Water type based on Chadha classification Class Samples 2+ 2+ + + - 2- - 2- (Ca +Mg ) > (Na +K ) and {(HCO3 +CO3 ) > (Cl + SO4 ) 75% (12 samples) (Ca2++Mg2+) > (Na++K+) 6.25% (one sample) - 2- - 2- (HCO3 +CO3 ) > (Cl + SO4 ) 6.25% (one sample) + + 2+ 2+ - 2- - 2- (Na +K ) > (Ca +Mg ) and (Cl + SO4 ) >{(HCO3 +CO3 ) 6.25% (one sample) + + 2+ 2+ - 2- - 2- (Na +K ) > (Ca +Mg ) and {(HCO3 +CO3 ) > (Cl + SO4 ) 6.25% (one sample)
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5.1.5 Saturation index (SI)
Saturation indexes are used to evaluate the degree of equilibrium between water and minerals. Changes in saturation state are useful to distinguish different stages of hydrochemical evolution and help identify which geochemical reactions are important in controlling water chemistry (Langmuir, 1997). The saturation index of a mineral is obtained from equation below
SI =log (IAP/KSp) (5.1) Where: IAP is the ion activity product of the dissociated chemical species in solution. Ksp is the equilibrium solubility product.
An index (SI), equal zero, indicate that the groundwater is saturated with respect to that particular mineral. An index (SI), less than zero, indicate that the groundwater is undersaturated with respect to that particular mineral. Such a value could reflect the character of water from a formation with insufficient amount of the mineral for solution or short resident time. An index (SI), greater than zero, specifies that the groundwater being supersaturated with respect to particular mineral phase and therefore incapable of dissolving more of the mineral. Such an index value reflects groundwater discharging from an aquifer containing ample amount of the mineral with sufficient resident time to reach equilibrium. Nonetheless, supersaturation can also be produced by other factor that include incongruent dissolution, common ion effect, and evaporation, rapid increase in temperature and CO2 exsolution (Appelo and Postma, 1996 ).
74
1
0
-1 Anhydrite -2 Gypsum
-3 Saturationindices
-4
Wells Fig. 5.5: Saturation indices for Anhydrite and Gypsum
1
0.5
0
-0.5
-1
Saturatuion indices Aragonite
-1.5 Calcite Dolomite -2
Wells
Fig. 5.6: Saturation indices for Aragonite, Calcite and and Dolomite
75
2 0 -2 -4 -6 -8 Saturationindices Halite -10 Sylvite
Wells
Fig. 5.7: Saturation Indices for Halite and Sylvite
All groundwater samples in the study area were undersaturated with respect to Anhydrite, Gypsum, Halite, and Sylvite (Fig. 5.5 and 5.7). In other hand three samples were oversaturated (Positive SI) with respect to Calcite, Aragonite and Dolomite while the rest exhibit slightly negative SI value (Fig. 5.6) (Appendix B)
76
5.2 Graphical solutions of relationship between different chemical parameters
Linear relation between chemical parameters were identified through graphically representation of data. The general equation of straight line is;
y= mx + c (5.2)
where, m is the gradient c is the y-axis intercept y is the dependent variable x is called the independent variable
Correlation matrix of different chemical parameter in the aquifer were calculated with aid of Microsoft Excel ver. 2013 (Table 5.3).
Table 4.3: correlation matrix of chemical parameter in the aquifer pH EC TDS Na K Ca Mg HCO3 Cl SO4 NO3 pH 1 EC -0.233 1 TDS -0.292 0.991 1 Na -0.155 0.911 0.895 1 K -0.419 0.567 0.589 0.599 1 Ca -0.304 0.712 0.680 0.555 0.495 1 Mg 0.068 0.682 0.648 0.607 0.320 0.766 1 HCO3 -0.342 0.579 0.571 0.567 0.695 0.750 0.745 1 Cl -0.096 0.869 0.839 0.846 0.246 0.614 0.627 0.347 1 SO4 -0.102 0.894 0.876 0.960 0.450 0.550 0.634 0.444 0.887 1 NO3 -0.320 -0.214 -0.240 -0.132 0.137 -0.175 -0.389 -0.085 -0.224 -0.249 1
`
77
The following paragraph summarized short comments on the significance relationship between hydrochemical parameters as follow;
1. Very strong positive linear relationship (r ≥ 9) i. EC vs TDS, Na+ + 2- ii. Na vs SO4 2. Strong positive linear relationship (9 > r ≥ 7 )
++ - 2- i. EC vs Ca , Cl , SO4 - 2- ii. TDS vs Na, Cl , SO4 + - -2 iii. Na vs Cl , SO 4 ++ ++ - iv. Ca vs Mg , HCO3 ++ - v. Mg vs HCO3 - 2- vi. Cl vs SO4 3. Moderate positive linear relationship (7 > r ≥ 5) ++ - i. EC vs Mg , HCO3 + ++ ++ - ii. TDS vs K , Ca , Mg , HCO 3 + + ++ ++ - iii. Na vs K , Ca , Mg , HCO3 + - iv. K vs HCO3 ++ - 2- v. Ca vs Cl , SO4 ++ - 2- vi. Mg vs Cl , SO4 4. Weak positive linear relationship (r < 5 ) + ++ ++ - 2- - i. K vs Ca , Mg , Cl , SO4 , NO3 - - 2- ii. HCO3 vs Cl , SO4 5. Weak negative linear relationship i. pH vs all chemical parameters - + ii. NO3 vs all chemical parameter except K
78
- + NO3 vs K 9 8 y = 0.1483x + 4.424 R² = 0.1754 7 6 5 4 3 2 1 0 0 2 4 6 8 10 12 14 16 18
- + Fig. 5.8: NO3 - K relationship of the groundwater samples in the studied area
- pH vs HCO3 250
200
- 150 3
HCO 100
50
0 6.8 7 7.2 7.4 7.6 7.8 8 pH
- Fig. 5.9: pH – HCO3 relationship of the groundwater samples in the studied area
79
5.3 Hydrochemical processes and mechanism controlling groundwater quality
Hydrogeochemical process occurring within groundwater zone by interaction with aquifer minerals result in the chemical nature of water. Geochemical processes are very important as they control the composition of the groundwater in the aquifer system. The geochemical processes are responsible for the seasonal and regional variation in groundwater quality as discussed earlier. The geochemical process changes the groundwater quality during its flow from the recharge area. The geochemical properties of various groundwater bodies are determined by the chemistry of water in the recharge area as well as the subsurface formation. The various geochemical processes that are responsible for the chemical character of the groundwater of this area are discussed below.
Gibbs (1970) proposed a diagram to understand the relationship of the chemical components of waters and classified the groundwater chemistry resulting due to three mechanisms as shown in (Fig. 5.10). This plot explains the relationship between water chemistry and aquifer lithology. Such a relationship, help to identify the factor controlling the groundwater chemistry. Fig. (5.10) suggests that the chemical weathering of rock-forming minerals is influencing the quality. As most of the points plot in the region of rock water interaction, this is likely to be the dominant process controlling the groundwater chemistry of this area.
80
Fig. 5.10: Gibbs diagram of the groundwater samples in the studied samples
81
5.3.1 Silicate weathering process
Silicate weathering process is an important process that is expected to control the groundwater chemistry especially where there is dominant exitance of crystalline rock. Rogers (1989) state that Na/Cl ratio greater than one indicate excess sodium which might have come from silicate weathering. If silicate weathering is a probable source of sodium the water sample would have HCO3 as the most abundant anion. This became of the reaction of feldspar with the carbonic acid in the presence of water, which release HCO3 (Elango, 2003). If halite dissolution is responsible for sodium the Na/Cl ratio should be approximately equal to one whereas a ratio greater than one is typically interpreted as Na release from a silicate weathering material (Mayback, 1987) (Fig. 5.11). High Ca/Mg ratio (>2) indicate of silicate minerals which contribute calcium and magnesium to groundwater (Katz, 1998). If the Ca/Mg=1 dissolution of dolomite should occur, whereas a high ratio is indicative of greater calcite contribution (Maya and Loucks, 1995) (Fig. 5.12).
Na/Cl 5 4.5 4 3.5 3 2.5 Na/Cl 2 1.5 1 0.5 0 0 200 400 600 800 1000 1200 1400 EC
Fig. 5.11: EC- – Na+/Cl relationship of the groundwater in the studied area
82
2.5
2
1.5
Ca/Mg 1
0.5
0 0 2 4 6 8 10 12 14 TZ
Fig. 5.12: Total Cation (TZ) – Ca/Mg relationship of the groundwater in the studied area
5.3.2 Ion exchange process Ion exchange occurs when one type of ion displaces another from a coordination site at a mineral surface. An ion exchange reaction where calcium displaces sodium would be, for example,
(5.3)
Where:
X represents the cation-exchanging solid. It is hard to analyze ion exchange reactions quantitatively, because the activities of sorbed phases are “all but unknown” (Morel and Hering, 1993). Different indices were used to describe ion exchange as follow;
5.3.2.1 Chloro-alkaline indices
Schoeller (1965) suggested two Chloro-alkaline indices CAI1 and CAI2 to indicate the exchange of ions between groundwater and its host environment.
83
The ion exchange and reverse ion exchange was confirmed using Chloro- alkaline indices.
CAI1= Cl-(Na+K)/Cl (5.4) CAI2= Cl-(Na+K)/SO4+HCO3+CO3+NO3 (5.5)
(All values are measured in meq/l)
When there is an ion exchange between Na+ or K+ in groundwater with Mg2+ or Ca2+ in the aquifer material (rock/weathered layer), both of the indices are positive, indicating reverse ion exchange of sodium in groundwater with calcium or magnesium in the weathered material. While in ion exchange both indices are negative when there is an exchange of Mg2+ or Ca2+ in the waters with Na+ and K+ in the rocks. The chloro-alkaline indices (CAI1 and CAI2) are used to evaluate the event of base-exchange process during rock water interaction.
In the study area (Fig. 5.13) the values of these indices are negative except one value corresponding to (South Alarda well), which have positive value. Depending on the above mentioned, these indices indicating that exchange reactions seem to be occur in the normal direction, so that the cation exchange process is one of the most important geochemical process that control the groundwater chemistry in the study area.
84
Chloro-alkaline indices 1
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 -1
-2 CAI2 CAI CAI1 -3
-4
-5 Well s
Fig. 5.13: Variation in Chloro-alkaline indices for the groundwater samples
Table 5.4: Chloro-alkaline indices in the study area
Well name CAI1 CAI2 Remarks South Alarda 0.191042 0.128052 Reverse Ion exchange process Ummbadda Sq. (4) -2.67597 -0.52533 ion exchange process Ummbadda Alrashideen -0.86725 -0.45515 ion exchange process Dar Es-Salam - Palestine yard -0.95453 -0.29215 ion exchange process Dar Es-Salam Sq. (16) -0.35577 -0.16046 ion exchange process Dar Es-Salam Sq. (17) -0.51446 -0.23039 ion exchange process Dar Es-Salam Sq. (18) -0.75485 -0.30273 ion exchange process Dar Es-Salam Sq. (19) -0.56043 -0.20105 ion exchange process Dar Es-Salam Sq. (22) -0.77263 -0.29381 ion exchange process Dar Es-Salam Sq. (26) -0.65077 -0.19923 ion exchange process Dar Es-Salam Sq. (27) -2.23725 -0.48204 ion exchange process Dar Es-Salam Sq. (28) -1.68217 -0.37244 ion exchange process Dar Es-Salam Sq. (30) -4.05278 -0.38673 ion exchange process Dar Es-Salam Sq. (42) -0.94732 -0.24711 ion exchange process Althora Sq. (18) -1.25198 -0.33778 ion exchange process Et-Takamul -2.60363 -0.54227 ion exchange process
The plot of Ca+Mg versus SO4+HCO3 will be close to 1:1 line if the dissolution of calcite and dolomite and gypsum are the dominant reactions in system. Ion exchange tend to shift the points to the right due to excess of SO4
85 and HCO3 (Cerling, 1989; Fisher and Mulican, 1997), if reverse ion exchange is the process, it will shift the points to the left due to a large excess of Ca+Mg over SO4+HCO3.
8
7
6
5
4 Ca+Mg 3
2
1
0 0 1 2 3 4 5 6 7 8 SO4+HCO3
Fig. 5.14: SO4 + HCO3 vs Ca + Mg
The plot of Ca + Mg vs SO4 + HCO3 (Fig. 4.14) show that most of groundwater samples are plotted on and below the 1:1 line which is due to the excess of bicarbonate (ion exchange process), except one sample which has high value of Ca + Mg that indicate reverse ion exchange.
86
5.3.3 Sulphate reduction process
Datta and Tyagi (1996) had observed that groundwater with high Cl- and low SO4-2 probably indicates reduction. Very low SO4-2/Cl- ratios (Appendix A) (low concentration of SO4-2) suggest that sulphate is being depleted, possibly by sulphate reduction (Lavitt, et al., 1997) (Fig. 4.15).
Sulphide minerals when oxidized give rise to soluble sulphates. Locally abnormal concentration of sulphate may characterized groundwater traversing through zone of oxidation of sulphide ore bodies.(Fig. 5.16 and 5.17)
FeS2 + 7O + H2O FeSO4 + H2SO4 (5.6)
SO4 vs Cl 140
120
100
80
- Cl 60
40
20
0 0 20 40 60 80 100 120 140 160 180 2- SO4
2- - Fig. 5.15: SO4 – Cl relationship of the groundwater in the studied area
87
2-- Fig. 5.16: EC - SO4 relationship of the groundwater in the studied area (Fields after Karanth, 1972)
-2 -2 - Fig. 5.17: SO4 – SO4 /Cl relationship of the groundwater in the studied area (Fields after Karanth, 1972)
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CHAPTER SIX CONCLUSION AND RECOMMENDATIONS
6.1 Summary and Conclusion
6.1.1 Aquifer geometry and its hydraulic characteristics
The siliciclastic aquifer system in the Umm Badda member has been studied characterized by their considerable thickness ranging between 550 and 1000ft, which composed from medium and coarse sandstone layers. These layer are confining in nature which bounded by mudstone layers.
Analysis of pumping test data indicate variation in storage coefficient, which can ascribe to geological and structural setting and the results support their confined nature.
Deep flow net analysis, indicated that the River Nile is the main recharge region to the aquifer through which the water moves initially toward west, in addition to other contribution from North to south and all groundwater discharged toward southwest area which represent the lowest potential area.
6.1.2 Water quality for domestic use sixteen samples from different borehole were used to assess groundwater quality based on their major ions concentration, in addition to the salinity, EC, and pH. These can be summarized as follows;
i. Alkaline nature of water with some exceptions such as Et-Takamul well with neutral pH value. ii. Salinity falls in the permissible limits, of WHO, and classified as fresh water.
89
iii. Electrical conductivity range between 282 – 1309.1 µS/cm , this extended range is due to high anomalous value of Ummbadda ELRashideen well which classified as C3 (doubtful ). iv. The water samples are classified as hard water except few samples are moderately hard and one sample is soft. v. Ummbadda ELrashideen well exhibits increase sodium, chloride , sulphate compare to the rest. vi. Decrease in bicarbonate in Alarda well and there is incease in nitrate content in Thaura sq18. Based on the above mentioned the water is suitable for human exploitation 6.1.3 Quality of groundwater for irrigation Integration of different factors were used to discuss the groundwater quality for irrigation these are; SAR, SP, MAR, KR, and PI. All samples are classified as suitable for irrigation based on SAR, SP, RSC, and PI (class I and II). There are slightly increase in magnesium hazard in four wells and two wells have increasing in Kelley ratio, but generally water is suitable for irrigation purpose. 6.1.4 water classification 6.1.4.1 Stiff diagram The water type has been classified based on stiff diagram into four main categories as follows; Sodium bicarbonate, Calcium bicarbonate, magnesium bicarbonate and sodium bicarbonate with considerable amount of sulphate. The last water type occur in Ummbadda Alrashideen well.
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6.1.4.2 Piper diagram Based on piper diagram, the groundwater classified into the following facies;
i. Calcium bicarbonate type. ii. Mixed type (no cations – anions exceed 50%)
6.1.5 Saturation indices All groundwater samples are undersaturation with respect to Anhydrite, Gypsum, Halite, Sylvite, Calcite, Aragonite, and Dolomite except three samples have positive SI value with respect to carbonate minerals 6.1.6 Hydrochemical processes Gibbs plot were used to identify hydrochemical mechanism that controlling hydrochemistry of water that indicate dominant of water rock interaction. Chloro-alkaline indices were used to describe ion exchange process indicate negative values, and consequently ion exchange, except Alarda well which indicate reverse ion exchange process. In addition to considerable amount of silicate weathering processes and carbonate dissolution.
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6.2 Recommendations Many recommendations may be taken into account 1. Establish a monitoring station program of groundwater level flunctuation, in order to protect groundwater reserve and to control the random drilling of wells, and to evaluate conditions for the different purposes. 2. Organic contaminants must drain far away from the aquifer system and need deep biological investigation to determine the degree of contamination.
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References
1. Abd Elraheem, A. M. (2000): Pollution in Khartoum Drinking Water, in Engineering Geology Bulletin, Springer Verlag, Germany. 2. Aghazadeh and Mogaddam, 2010: “Assessment of Groundwater Quality and its Suitability for Drinking and Agricultural Uses in the Oshnavieh Area, Northwest of Iran. Journal of Environmental Protection, 1:30-40. 3. Altovisiki, M. E., 1962: Hand book of hydrogeology. Geogoelitzet, Moscow, USSR (In Russian), 614p. 4. Andrew, G. 1948: Geology of Sudan. Inj. D, to thills (eds.) Agriculture in the Sudan. PP 84-128. Oxford University Press, UK. 5. Appelo, C. A. J. and Postma, D. 1996: “Geochemistry, groundwater and pollution,” Balkema,Rotterdam, pp. 536. 6. Appelo, C. A. J. and Postma, D., 2005: Geochemistry, groundwater and pollution, 2nd edition. Balkama, Rotterdam, 536p. 7. Awad, M. Z., 1994: Stratigraphic, Palynological and. paleoecological studies in the East- Central Sudan (Khartoum and Kosti Basin). Ber liner geo wiss - Abh. A 161, PP. 163, Berlin. 8. Barazi, N. 1989: The Sedimentary Rocks around Khartoum Area, 4th International Conference of Fluvial Sedimentary Programme and Abstracts, Barcelona. 9. Bates, R.L., and Jackson, J.A., 1984 : Dictionary of geological terms, New York, Doubleday, various pagination. 10. Bireir, F. E., 1993: Sedimentological investigation around the State of Khartoum Part of the Gezira, Central Sudan. M.Sc thesis. University of Khartoum, PP. 172.
93
11. Bosworth, W., 1989: Detachment geometries and kinematics in continental rifts. 28th Int. Geo. Congr. (Washington, D.C.) (abstract 45). 12. Boyd, C. E., 2000: Water quality an introduction, Kluwer Academic publisher, USA.330p. 13. Brown, C., Girdler, R.W., Rehner, R.G.B., 1980: A gravity traverse a cross north Africa. Journal of Geophysical Research 85, 6436–6442. 14. Browne, S. E., Fairhead, J.D., Mohamed, I.I., 1985: Gravity study of the White Nile Rift, Sudan and its regional tectonic setting. Tectonophysics 113, 123–137. 15. Browne, S.E., Fairhead, J.D., 1983: Gravity study of the Central African Rift: a model of continental disruption. Tectonophysics 94, 187–203 16. Cerling, TE, Pederson BL, Damm KLV 1989: Sodium-calcium ion exchange in the weathering of shales: Implications for global weathering budgets. Geology 17:552–554 17. Chadha, D.K., 1999: A proposed new diagram for geochemical classification and interpretation of chemical data. Hydrogeology, J7: pp431-4393. 18. Clark, I.D. and Fritz, P., 1997: Environmental isotopes in hydrogeology. CRC Press, Boca Raton, 328 pp. 19. Cooper, H.H and Jacob, C.E 1946: A generalized graphical method for evaluating formation constants and Summarizing well field history, Am Geophys Union trans,27:526-534. 20. Daly, D. ,1994 : Chemical Pollutant in Groundwater: a Review of the Situation in Ireland. Conf. "Chemicals a cause for Concern?", Cork, 3- 4/11/1994.
94
21. Datta, P.S. and Tyagi, S.K. 1996: Major ion chemistry of groundwater in Delhi area: Chemical weathering processes and groundwater flow regime. Geol. Soc. India. 47: 179-188. 22. David, D, 2002: Introduction to hydrogeology, University of Oklahoma, USA, 468p. 23. Detay, M., 1997: Water Wells- implementation, maintenance andrestoration, John Wiley and Sons, London, 379p. 24. Domenico, P. A, Schwartz, F. W., 1998: Physical and chemical hydrogeology, John Wiley and Sone, inc. New York. 506p.
25. Doneen, L. D. 1964: “Notes on Water Quality in Agriculture,” Water Science and Engineering Paper 4001, University of California, Davis. 26. Drever, J.I., 1997: The geochemistry of natural water, surface and ground water environments (3rd ed). Prentice hall, USA, 436P. 27. Durov, S. A. 1948: Natural waters and graphical representation of their composition. Dokl. Akad. Nauk. USSR 59,87-90. 28. Eisawi, A., 1999: Palynological, Paleoenvironmental, and facies interpretation of the Omdurman formation (Khartoum Basin). M.Sc. Thesis. University of Khartoum. 29. El Krail, A., Hamid, A., Obeid, B., 2012: Hydrochemistry of groundwater at Omdurman area Khartoum state, Sudan. International Journal for Civil and Structural Engineering 2. 30. El Tahir, N., Nyblade, A., Julia, J., Durrheim, R., 2013: Crustal structures of the Khartoum basin. Journal of Tectonophysics, 10p. 31. Elango L, Kannan, R. Senthil. Kumar, M., 2003) Major ion chemistry and identification of hydrogeochemical processes of groundwater in a part of Kancheepuram district, Tamil Nadu, India. J Environ Geosci 10(4):157–166.
95
32. Fairhead, J.D., 1986: Geophysical controls on sedimentation within the African rifts ystem. Geological Society, London, Special Publications, 25 19–27. 33. Fairhead, J.D., Green, C.M., 1989: Control on rifting in Africa and the regional tectonic model for the Niger rift basins. Journal of African Earth Sciences 8, 231–249. 34. Fisher RS, Mulican III WF 1997: Hydrochemical evolution of sodium-sulphate and sodium-chloride groundwater beneath the Northern Chihuahuan desert, Trans-Pecos, Texas, USA. Hydrogeol J 5(2):4–16. 35. Fitts, C. R. 2002: Groundwater science. Academic press, London, 467p. 36. Gibbs, R. J., 1970: Mechanisms controlling worlds water chemistry.Science 170:1088–1090. 37. Ghoraba, S. M., Khan, A. D., 2013: Hydrochemistry and groundwater quality assessment in Balochistan province, Pakistan, IJRRAS, vol 117. 38. Hago, A., 2014: Hydrochemical characteristics of groundwater mid stream area-Gash River Basin, Eastern Sudan, Ph.D. Thesis. Berlin,
159pp. 39. Hem, J.D., 1985: Study and interpretation of the chemical characteristics of natural water. 3rd. ed. U.S.G.S. Water supply paper. 2254. 263p. 40. Hem, J. D., 1989: Study and interpretation of the chemical characteristics of natural water U.S geological survey, water supply paper 2254, 246p. 41. Hopkins B.G., Horneck, D. A., Stevens, R.G., Ellsworth, J.W. and Sullivan, M. 2007:” Managing irrigation water quality for crops
96
production in the Pacific Northwest, Pacific Northwest extension pub., 597p. 42. Hussein, M.T., 1992: On the depositional framework of the Cretaceous Omdurman formation in Khartoum area, Sudan. Journal of African Earth Sciences 14, 559–566. 43. Hussein, S. 2009: The Hydrochemistry of the Groundwater of the Khartoum State, M.Sc. thesis, University of Al Neelain. 44. Jorgensen, G.J., Bosworth, B., 1989. Gravity modelling in the central Africa Rifts System, Sudan: rift geometries and tectonic significance. Journal of African Earth Sciences 8, 283–306. 45. Karanth, K. R., 1972: Interpretatioon of sulphate anomalies in hydrogeodrochemical prospecting for sulphide ore bodies, Indian geohydrology, III (i), pp 42 -55. 46. Katz BG, Coplen TB, Bullen TD, Davis JH 1998: Use of chemical and isotopic tracers to characterize the interaction between groundwater and surface water in mantled Karst. Groundwater 35(6):1014–1028 47. Kelley, W. P. 1940: Permissible composition and concentration of irrigation waters, Proc. ASCE, 66, 607. 48. Kheiralla, M. K., 1966: Study of the Nubian Sand Stone Formation of the Nile Valley between 14° N and 17° 42 N, with referenvce to the
ground - water geology .M. SC. Thesis U. of K.PP. 2096 49. Kroner,A., Stern, R,J, Dawoud A.S. Composition,W., Reischman,T, 1987: the pan African continental margin in northeast Africa:Evidence from geochronological study Granulites at Sabaloka, sudan Earth and Plantery Science lellers 85-104.
97
50. Kruseman, G .P. and de Ridder, N.A., 2000: Analysis and Evaluation of Pumping Test Data. International Institute for Land Reclamation andImporovement, Wageningen, the Netherlands, 372p. 51. Langmuir, D. 1997: “Aqueous environmental geochemistry,” Prentice Hall, Inc., pp. 601, D. 52. Lavitt, N., Acworth, R.I. and Jankowski, J., 1997: Vertical hydrochemical zonation in a coastal section of the Botany Sands aquifer, Sydney, Australia. Hydrogeology Journal, 5(2): 64-74. 53. Mann, D.C., 1989: Thick-skin and thin-skin detachment faults in continental Sudanese rift basins. Journal of African Earth Sciences 8, 307–322. 54. Maya AL, Loucks MD (1995) Solute and isotopic geochemistry and groundwater flow in the Central Wasatch Range, Utah. J Hydrol 172:31–59 55. Mayback M 1987: Global chemical weathering of surficial rocksestimated from river dissolved loads. Am J Sci 287:401–428 56. Mohammed, I.A., 1997: Geology and structures of the area west of the White Nile as deduced from gravity measurements. M.Sc. Thesis, Khartoum Univ. (unpublished). 57. Morel, F. M. M. and J. G. Hering. 1993: Principles and Applications of Aquatic Chemistry, Wiley and Sons, New York. 58. Piper, A. M 1944: A graphic procedure in the geochemical interpretation of water analysis, U.S.Geol.Surv. Groundwater, note12.
59. Raghunath, I. I. M. 1987: “Groundwater,” 2nd Edition, Wiley Eastern Ltd., New Delhi, pp. 344-369.
98
60. Raihan, F. And Alam,J. B. 2008:” Assessment of Groundwater Quality in Sunamganj of Bangladesh, IranianJournal of Environmental Health Science and Engineering, 5(3): 155-166. 61. Reynolds, P.O., 1993: Plate tectonic aspects of continental rift basin formation in Central and Western Sudan. In: Thorweihe, U., Schandelmeier, H. (Eds.), Geoscientific Research in Northeast Africa. Balkema, Rotterdam, pp. 207–212. 62. Richards, L. A. 1954: “Diagnosis and improvement of saline and alkali soils”. Agric. Hand Book 60, United States Department of Agriculture, Washington, D. C., Pp160. 63. Rogers R., J. 1989: Geochemical comparison of groundwater in areas of New England 64. Saeed, E. M, 1976: Hydrology of Khartoum Province and Northern Gezira Area, Geology and Mineral Resources Department, Bull. No. 29 Khartoum, p. p (138). 65. Sagnak, C. 2010:”Groundwater Pollution Originated from Geological Formation (Example of Konya-CumraKarapinar Plain with GIS Application). 66. Sanders, L. L., 1998: Manual of field Hydrogeology. Library of Congress Cataloging in Publication Data. 381p. 67. Sawyer C. N., and Mecarty P. L., 1967: Chemistry of Environmental Engineering. 3rd. ed., MCGraw-Hill book VSA. 68. SCCG, 2006: Groundwater Management Handbook, Sydney Coastal Councils Group and Groundwater Working Group. Sydney, September 2006, First Edition. P 167. www.sydneycoastalcouncils.com.au
99
69. Schoeller, 1965: Hydrodynamique lans lekarst (ecoulementedemmagusinement). Actes Colloques Doubronik, I, AIHS et UNESCO, pp 3–20 70. Schrank, E., Awad, M.Z., 1990: Palynological evidence for the age and depositional environment of the Cretaceous Omdurman Formation in the Khartoum area, Sudan, vol. 120.1. Berliner geowiss. Abh. A, Berlin, pp. 169–182. 71. Schull, T.J., 1988: Rift basins of interior Sudan. Petroleum exploration and discovery. American Association of Petroleum Geologists Bulletin 72, 1128–1142. 72. Stiff, H, A.J 1951: The interpretation of chemical Groundwater analysis Geol. Sur Puble. No 43.
73. Sun oil company 1989: geological report 74. Thompson, T., Fawell, J., Kunikane, S., Jackson, D., Appleyard, S., Callan, Ph., Bartram, J. and Kingston, Ph., 2007: Chemical safety of drinking water: assessing priorities for risk management, WHO, Geneva, 142 p. 75. Todd. D.K, 1980: Groundwater Hydrology 2nd edi. John Wiley andsons new York, 535p 76. Todd, D. K., 2007 : Groundwater hydrology third edition, John Wiley and Sous, Third Reprint. Inc. India. 535p. 77. USSL, 1954: Saline and Alkali Soils – Diagnosis and Improvement of U.S. Salinity Laboratory, Agriculture Hand Book No.60. 78. Vail, J. R, 1988: Outline of the geology and mineral deposits of the democratic Republic of the Sudan and adjacent area
100
79. Victoria EPA. , 2006: Hydrogeological Assessment (Groundwater Quality) Guidelines , Publication 668 , September 2006 ,Australia, pp 26 80. Walton, C.W., 1970: Groundwater Resource Evaluation Mc Graw Hill Co., 664. 81. White man, a .J, 1970: Nubian group origin and status AAPGB 11, USA. 82. White man, A. J, 1971: the geology of Sudan republic, pp290, Clarendon press oxford, UK. 83. White, W. M., 2005: Geochemistry, John-Hopkins University Press,www.geo.cornell.edu/geology/classes/geo455/booklogo.gif, 701 P. 84. WHO, 2011: “Gide Lines for Drinking Water Quality ”, WHO Labrary Cataloguing-in-Publication Data, fourth Edition, Vol.1, Geneve. 85. Wilcox, L. V. 1995: Classification and use of irrigation waters, US Department of Agriculture, Washington Dc, p-19
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APPENDICES
A = Chemical analysis for major dissolved ions and calculated parameter (in mg/l)
B = SO4/Cl ratio
C = Saturation indices
D = Pumping test graphs
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Appendix (A)
Well name Lat Long pH * EC ** TDS T.H HCO3 Cl SO4 NO3 Ca Mg Na K South Alarda 15.63335 32.471683 7.9 282 155 84 66 32 10 3.6 18.4 9.12 16.2 1 Ummbadda Sq. (4) 15.648868 32.452494 7.9 548 301.4 144 202 28 31 4.4 25.6 19.2 63.34 5.8 Ummbadda Alrashideen 15.62635 32.44735 7.4 1309.1 720 240 230 132 159 1.2 46.4 29.67 155.4 7.56 Dar Es-Salam - Palestine yard 15.624963 32.371867 7.5 668 368 180 200 43 32 1.4 38.4 20.16 51.8 4.6 Dar Es-Salam Sq. (16) 15.63984 32.36626 7.5 704 387 184 180 61 40 2.2 38.4 21.12 50.4 5.5 Dar Es-Salam Sq. (17) 15.639762 32.375106 7.5 817 449 212 208 68 39 4.1 42.4 25.44 63.2 6.1 Dar Es-Salam Sq. (18) 15.630792 32.37434 7.4 647.41 356.07 196 210 64 49 2.7 44 20.64 69.29 6.03 Dar Es-Salam Sq. (19) 15.631781 32.36608 7.4 708 389 200 202 52 36 2 44 21.6 49.8 4.8 Dar Es-Salam Sq. (22) 15.633671 32.383224 7.5 810 446 204 220 60 39 2.3 44 22.56 65.8 5.4 Dar Es-Salam Sq. (26) 15.62513 32.38328 7.2 615 370 200 206 45 35 2.8 42.4 22.56 45 5.4 Dar Es-Salam Sq. (27) 15.61701 32.3832 7.8 765 421 204 204 34 52 1.8 44 22.56 66.5 8.3 Dar Es-Salam Sq. (28) 15.608946 32.382931 7.3 555 333 150 190 28 19 3.8 30.4 17.76 45 6.3 Dar Es-Salam Sq. (30) 15.61441 32.37353 7.3 506 304 160 200 13 26 1.7 30.4 20.16 39.6 5.1 Dar Es-Salam Sq. (42) 15.63275 32.34858 7.9 404.43 222.43 186 206 36 25 - 34.4 24 42.7 4.7 Althora Sq. (18) 15.716822 32.495321 7.3 608 304 207.6 230 46 44.7 7.04 44.8 22.94 63.5 6.26 Et-Takamul 15.561838 32.394542 7 557 334 109 182 26 22 5.2 29.6 8.4 56 8.1
*pHunit
**µS/cm
103
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Appendix (B)
Well Name SO4/Cl Ratio South Alarda 0.230626 Ummbadda Sq. (4) 0.817075 Ummbadda Alrashideen 0.888959 Dar Es-Salam - Palestine yard 0.549212 Dar Es-Salam Sq. (16) 0.483937 Dar Es-Salam Sq. (17) 0.423267 Dar Es-Salam Sq. (18) 0.565034 Dar Es-Salam Sq. (19) 0.510926 Dar Es-Salam Sq. (22) 0.479702 Dar Es-Salam Sq. (26) 0.574003 Dar Es-Salam Sq. (27) 1.128711 Dar Es-Salam Sq. (28) 0.500788 Dar Es-Salam Sq. (30) 1.476007 Dar Es-Salam Sq. (42) 0.512502 Althora Sq. (18) 0.717147 Et-Takamul 0.624465
A
Appendix (C)
Saturation indices calculated from water samples
Well name Anhydrite Aragonite Calcite Dolomite Gypsum Halite Sylvite South Alarda -3.31 -0.56 -0.41 -0.79 -3.01 -7.82 -8.59 Ummbadda Sq. (4) -2.79 0 0.14 0.51 -2.49 -7.31 -7.91 Ummbadda Alrashideen -1.97 -0.3 -0.15 -0.16 -1.67 -6.27 -7.15 Dar Es-Salam - Palestine yard -2.62 -0.24 -0.1 -0.13 -2.32 -7.21 -7.83 Dar Es-Salam Sq. (16) -2.53 -0.29 -0.15 -0.21 -2.23 -7.07 -7.6 Dar Es-Salam Sq. (17) -2.52 -0.2 -0.06 -0.01 -2.22 -6.93 -7.51 Dar Es-Salam Sq. (18) -2.4 -0.29 -0.15 -0.27 -2.1 -6.92 -7.54 Dar Es-Salam Sq. (19) -2.52 -0.29 -0.15 -0.26 -2.22 -7.15 -7.73 Dar Es-Salam Sq. (22) -2.5 -0.16 -0.02 0.02 -2.2 -6.97 -7.62 Dar Es-Salam Sq. (26) -2.55 -0.52 -0.37 -0.67 -2.24 -7.26 -7.74 Dar Es-Salam Sq. (27) -2.38 0.11 0.26 0.57 -2.08 -7.21 -7.68 Dar Es-Salam Sq. (28) -2.91 -0.56 -0.42 -0.72 -2.61 -7.45 -7.87 Dar Es-Salam Sq. (30) -1.98 -0.62 -0.48 -0.8 -1.68 -7.86 -8.31 Dar Es-Salam Sq. (42) -2.77 0.13 0.28 0.75 -2.47 -7.37 -7.89 Althora Sq. (18) -2.44 -0.35 -0.21 -0.36 -2.14 -7.1 -7.67 Et-Takamul -2.83 -0.92 -0.78 -1.76 -2.53 -7.39 -7.79
B
Appendix (D)
C
D
E
F
G
30
H
I
J
11