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Kingdom of Saudi Arabia

King Saud University

College of ScienceDepartment of Geology

EVALUATION OF GROUNDWATER

RESOURCES IN WAJID AQUIFER IN WADI

DAWASIR AREA SOUTHERN SAUDI ARABIA

USING COMPUTER SIMULATION

Submitted in partial fulfillment of the requirements for the Masters Degree in the Department of

Geology at the College of Science- King Saud

University

By:

Hussain .J A. Al-Faifi

November 2005



I

CONTENTS

Acknowledgements…………………………………………………….a

Abstract…………………………………………………………………c

CHAPTER I

INTRODUCTION

1.1 – LOCATION……………………………………………… 1

1.2 - PURPOSE OF THE STUDY……………………………. 3

1.3 – CLIMATE………………………………………………... 4

1.4 – PREVIOUS WORK……………………………………... 7

CHAPTER II

GEOLOGICAL SETTING

2.1 – GEOLOGICAL SETTING………………………………. 13

2.2 – WAJID FORMATION STRATIGRAPHY……………... 16

2.2.1 - DIBSIYAH MEMBER………………………………….. 16

2.2.2 - SANAMAH MEMBER…………………………………. 19

2.2.3 - KHUSAYYAN MEMBER……………………………… 20

2.2.4 - JUWAYL MEMBER…………………………………… 21

2.3 – STRUCTURE……………………………………………... 24



III

4.4.2 - WALTON’S METHOD ………………………………... 48

4.4.3 - HANTUSH’S METHOD ……………………………….. 48

4.5 - GROUNDWATER DYNAMIC…………………………... 54

4.6 - GROUNDWATER QUALITY…………………………… 59

4.6.1 - TOTAL DISSOLVED SOLIDS (TDS)………………… 594.6.2 - CALCIUM (Ca

++)……………………………………….. 62

4.6.3 - MAGNESIUM (Mg++

)…………………………………... 65

4.6.4 - SODIUM (Na+)…………………………………………... 67

4.6.5 - POTASSIUM (K -)……………………………………….. 69

4.6.6 - CHLORIDE (Cl--)……………………………………….. 69

4.6.7 - SULFATE (SO4--)……………………………………….. 71

CHAPTER V

MODFLOW RESULTS

5.1 – MODEL AREA…………………………………………… 76

5.2 - BOUNDARY CONDITIONS…………………………….. 76

5.3 - MATHEMATICAL MODEL…………………………….. 78

5.3.1 – MODEL APPROACH………………………………….. 78

5.3.2 - MODEL CODE…………………………………………. 78

5.3.3 - MODEL GRID…………………………………………... 79

5.3.4 - MODEL SETUP………………………………………… 79



IV

5.3.5 – STEADY STATE CALIBRITION……………………..

5.3.5.1 - HYDRAULIC CONDUCTIVITY…………………….

5.3.6 - TRANSIENT CONDITIONS…………………………...

82

82

82

5.3.7 - RESULTS AND PREDICTIONS IN MODEL……….. 87

CHAPTER VI

AQUACHEM RESULTS

6.1 – STATISTICS……………………………………………… 94

6.1.1 - CORRELATION COEFFICIENT…………………….. 966.1.2 - LINEAR RELATIONS…………………………………. 100

6.2- IDENTIFICATION OF GROUNDWATER

CHARACTER…………………………………………………... 104

6.2.1 - WATER TYPE IN THE STUDY AREA………………. 104

6.2.1.1 - PIPER TRILINEAR DIAGRAM……………………. 104

6.2.1.2 - DUROVE'S DIAGRAM……………………………... 105

6.3 - IDENTIFICATION OF CHEMICAL PROCESS

EFFECT OF GROUNDWATER QUALITY…………………. 108

6.3.1 - CHEMICAL WEATHERING OF SILICATE

MINERALS……………………………………………………... 108

6.3.2 - PRECIPITATION AND DISSOLUTION OF

MINERAL………………………………………………………. 112

6.3.3 - APPRAISAL OF GROUNDWATER UTILITY……… 112

6.4 - SUITABILITY OF GROUNDWATER FOR

DOMESTIC PURPOSES………………………………………. 112



V

6.4.1 - TOTAL HARDNESS (TH)……………………………... 112

6.5 – DRINK ABILITY OF GROUNDWATER……………… 118

6.6 - SUITABILITY OF GROUNDWATER FOR

AGRICULTURE ACTIVITY…………………………………. 119

6.6.1 - SODIUM ABSORPTION RATIO (SAR)……………... 122

6.6.2 - MAGNESIUM HAZARD (MH)……………………….. 127

CHAPTER VII

CONCLUSIONS AND RECOMMENDATIONS7.1 – CONCLUSIONS………………………………………….. 129

7.2 – RECOMMENDATIONS…………………………………. 131

REFERENCES………………………………………… 132

ARABIC SUMMARY…………………………………. i



VI

LIST OF FIGURES

Figure

No.

Titles Pages

No.

1 - 1 General location map of studied area in Wadi Dawasir. 2

1 - 2 Satellite Image of Wadi Dawasir Area. 5

1 - 3 Satellite image of clouds above Saudi Arabia. 8

2 - 1 Geological map of Wadi Dwasir area. 15

2 - 2 Summarizing the stratigraphic succession of the Wajid Sandstone in the

region. 17

2 - 3 Modified structural sketch of the southern Najd. 25

3 - 1 Collecting and checking samples. 30

3 - 2 Determination of water level by device. 31

4 - 1 Wajid Aquifer extent. 43

4 - 2 Wajid outcrop. 44

4 - 3 Pumping test curve using Theis Method. 51

4 - 4 Pumping test using Walton’s Method. 52

4 - 5 Pumping test using Hantush Method. 53

4 - 6 Water level in the Wajid Aquifer in Wadi Dawasir. 56

4 - 7 Present groundwater level in the study area. 58

4 - 8 Sites of sampling.

614 - 9 Concentration of TDS in the study area (mg/l). 64

4 - 10 Concentration of calcium ion in the stuy area (mg/l). 66

4 - 11 Concentration of Magnesium in the study area (mg/l). 68

4 - 12 Cocentration of Sodium in the study area (mg/l). 70

4 - 13 Concentration of potassium of the study area (mg/l). 72



VII

4 - 14 Concentration of chlore of the study area (mg/l). 73

4 - 15 Concentration of sulfate ion in the study area (mg/l). 75

5 - 1 Modified map show the extent of the modeled area and grid used for

modeling (x = y =100; total = 10000). 77

5 - 2 Elevation of top part of the Wajid Aquifer in meter above sea level. 80

5 - 3 Elevation of the bottom part of the Wajid Aquifer in meter above sea

level. 81

5 - 4 Values of hydraulic conductivity in the Wajid Aquifer. 83

5 - 5 Distribution of hydraulic conductivities in the calibration procedure in

the Wajid Aquifer. 84

5 - 6 Distribution of calibrated water level in Wajid Aquifer in Wadi Dawasir

Area. 85

5 - 7 Recharge in the modeled outcrop of the Wajid Aquifer found in the

calibration procedure. 86

5 - 8 Initial head distribution for transient simulation (calibrated inetial head).

88

5 - 9 Simulated head distribution in meter above mean sea level after 20years

of pumping from the Aquifer (m3/day). 90

5 - 10 Simulated drawdown distribution in meter after 40 years of pumping

from the aquifer (m3/day). 92

5 - 11 Simulated drawdown distribution in meter after 60 years of pumping

from the aquifer (m3/day). 93

6 - 1 Distribution of major ions concentration in Wajid Aquifer . 101

6 - 2 Distribution of TDS & EC of the wells in the study area. 101

6 - 3 Relation between Ca and HCO3. 102

6 - 4 Relation between Cl & Na. 102

6 - 5 Relationship between major Ions and TDS (meq/l). 103



VIII

6 - 6 Piper diagram of major ions in the study area. 106

6 - 7 Water type using Durove Diagram in the study area. 107

6 - 8 Water types in the study area according the Durove plot. 110

6 - 9 Saturation index of minerals. 114

6 - 10 Concentration of TH of the groundwater in the study area. 117

6 - 11 Concentration of sodium adsorption ratio (SAR) of groundwater in the

study area. 124

6 - 12 Classification of water on the basis of sodium absorption and electrical

conductivity on the study area. 126

6 - 13 Concentration of magnesium hazard of the groundwater in the study

area. 128



a

ACKNOWLEDGMENT

I wish to express his deepest gratitude to Dr. A.M.AL-BASSAM,

Associate Prof. Of Hydrogeology, Vice Dean of College of Science, King

Saud University, for his kind help, significant comments, critical review of

the thesis and continuous support throughout the term of this work..

The author is forever indebted to Dr. M.T.HUSSEIN, Geology

Department, College of Science, King Saud University, for his tremendous

efforts, continuous support, professional advises and invaluable guidance

throughout various steps of this work, especially the critical review of the

manuscript.

The efforts of the Dr. M.N.EL-SABROUTY, Geology Department,

College of Science, King Saud University, are deeply appreciated as he was

the man who pushed the registration of this thesis, was a kind man and a

good friend (may ALLAH bless him… …Amen).

To authorities of the Geology Department, College of Science, King

Saud University, especially the head of Department Dr. N.S.AL-ARIFI,

and Mr. H.S.AWAD, Mr. M.S.AL-YOUSSEF and all members of

Department, the author is very much grateful for hosting this work and

making necessary facilities ready.

Another word of gratitude is due to Mr. A.AL-HUMYEN, Mr. H.AL-

NAKHLY, Mr.H.F. AL-AJMI, Ministry of water and electricity, for them



b

invaluable help in the field work, continuous encouragement and fruitful

discussions.

So many words of thanks are due to all examination members especially

Prof. A.S.AL-TORBAK, College of engineering, Department of civil

engineering, and Dr. A.M.AL-DAKHIL, Geology Department, College of

Science, King Saud University, for successfully discussions, and important

remarks.

Last, but not least, I wish to express my deepest gratitude to my mother,

my brothers, my wife and my sons for their help, continuous

encouragement and support. Without their feelings, this work would have

never been completed.



d

Hantush methods. The average transmissivity of the three methods is 252.8

m

2

/day, the average hydraulic conductivity is 0.421 m/day and the average

storage coefficient is 0.0035. The regional value of the specific yield is about

21%. At present time Wajid Aquifer is under stress and the aquifer is in a non

equilibrium state. The discharge is much greater than the groundwater

recharge and the total change in storage is negative. Because of this, the Heads

declined from about 700 m to 550 above sea level (a.s.l). Groundwater flows

towards the northeast and Wadi Dawasir is the main discharge area of the

aquifer. Most of the groundwater stored in Wajid Aquifer is fossil water – non

renewable groundwater. Average recharge rate is about 15mm/year.

This area lies within the Orbit-hot desert range where temperature rises

with low rate of precipitation and high rate of evaporation. There is a high

exploitation of water from the Wajid Aquifer with a limited recharge in the

outcrop area.

In this study, Visual Modflow was selected within the model area. The

model grid consists of 100 columns and 100 rows. A finite difference grid

distance in each directions x and y equal 94.350 km., covering an area 8092

km2. The model contains only one layer which represents the Wajid Aquifer

confined and unconfined.



e

For the steady and transient simulation conductivity and storage

coefficient from confined to unconfined conditions where considered by using

distribution, the discharge assumed from 51 wells (Q = 1800 USG/min =

9816.5 m3/day), then the model was calibrated under steady state and transient

conditions. From the initial condition of water level, scenarios that made on

the model show that the drawdown will be 43 m below the ground surface

after 20 years of pumping from wills, 96 m after 40 years and 141 m after 60

years.

The present study also includes chemical analyses of 20 water samples

taking from twenty wells tapping the aquifer in the studied area. The

groundwater in this area is classified into three hydrochemical facies; type (2)

that’s HCO3-

dominant and eight Mg2+

dominant or cations indiscriminant,

with Mg2+

dominant or Ca2+

and Mg2+

important, indicates water often

associated with dolomites; where Ca2+

and Na+

are important partial ion

exchange may be indicated, type (5) no dominant cation or anion, indicates

water exhibiting simple dissolution or mixing, type (8) Cl-

dominant and no

dominant cation indicates that the groundwater may be related to reveres ion

exchange of Na+-Cl

-water.



f

Then determined the hydro-chemical processes that caused the

variation in the groundwater quality and also suitability of groundwater for

domestic purposes and agriculture in the study area.



CHAPTER I

INTRODUCTION



1

CHAPTER I

INTRODUCTION

1.1 - LOCATION:

The study area is entirely located within Wadi Dawasir. It is located

between latitudes 19o30

/00

//N, 21

o00

/00

//N and longitudes 44

o00

/00

//E,

46o30

/00

//E some 650 km south Riyadh (Fig 1-1). The largest towns in the

study area are Al-Sulayyel, Al-Nuwayma, Al-Khamasin and Ledam.

Wajid Aquifer is the most important aquifer in the southern part of

Saudi Arabia. It is supplying Wadi Dawasir and vicinity areas with a fresh

water for drinking and agriculture.

The mean objective of the groundwater modeling of this study is to

predict the groundwater direction, drawdown, respectively the development of

groundwater heads, caused by pumping from the wells for the next 60 years of

pumping, and to predict of the future drawdown position and the assessment

of the groundwater resources a mathematical groundwater flow model was

developed, then analyze samples taken from the pumping wells that for known

their properties and suitable for drinking and irrigation in agriculture or other

purposes.



2

Fig. (1-1): General location map of studied area in Wadi Dawasir.



3

1.2 - PURPOSE OF THE STUDY:

Wadi Dawasir is one of huge agricultural areas in the kingdom of

central province of Saudi Arabia (Fig. 1-2). Wajid Aquifer is the most

important aquifer in Wadi Dawasir. The main objective of this study is to

evaluate the groundwater resources in Wadi Dawasir quantitatively and

qualitatively. It is supplying Wadi Dawasir and vicinity areas with afresh

water for drinking and irrigation water for agriculture.

The present study is also intended to predict the future conditions of

these resources under present and future management plans. The following

points will help to achieve the above mentioned objectives:

1- Preparation of well location map using Garmen 12 Global Positioning

System (GPS).

2- Realization of complete well inventory in the study area. The inventory

includes, groundwater depths, levels, well diameter, well depth, in-situ

measurement of water temperature, pH, Electrical conductivity

(EC)…etc.

3- Collection of water samples for major ionic composition.

4- Laboratory analysis of water samples.

5- Construction of water level contour map to predict groundwater movement.



4

6- Determination of aquifer properties permeability (K), storage coefficient

(S) and aquifer extension. Aquifer tests and geophysical electrical

methods are to be applied.

7- All these field and measurement data will be used for the construction of

modflow and aquachem models to predict the future scenario.

The main objective of the groundwater modeling of this study is to

predict the groundwater direction, drawdown, respectively the development of

groundwater heads, caused by pumping from the wells for the next 60 years of

pumping, and to predict of the future drawdown position and the assessment

of the groundwater resources a mathematical groundwater flow model was

developed, then analyze samples taken from the pumping wells that for known

their properties and suitable for drinking and irrigation in agriculture or other

purposes

Wajid Aquifer is the most important aquifer in the southern part of Saudi

Arabia.

1.3 – CLIMATE:

The importance of Wadi Dawasir area, it is consider one of the biggest

agricultural areas in the Kingdom of Saudi Arabia (Fig. 1-3). The climate in

study area is depend on several parameters like:



5

Fig. (1-2): Satellite Image of Wadi Dawasir Area



6

A - Temperature:

Annual average temperature is about 29

o

C. Maximum average

temperature is 43oC. Minimum average temperature is 6

oC. Mean average

temperature during summer is about 35oC. June is the hottest during the year.

During winter mean average temperature is about 25oC.

B - Relative humidity:

Annual average relative humidity is about 24%. It is probably more

than 70% during winter. Decrease of relative humidity occurs during summer.

C - Winds:

The wind direction is mostly eastward. This could be a dangerous factor

if wind is strong enough to carry Rub Al-Khaly sand dune eastern of the area.

The mean average of wind velocity is 7 knots/h (=13km/h). The maximum

velocity could reach 25 knots/h still not threatening building and farms.

D - Solar radiation:

The Sky is clear most of the year. Sunrise duration average at Wadi

Dwasir is about 11 hours daily.

E - Rainfall:

Rainfall is essential in agricultural development planning. Rainfall

average is 37.6 mm/year. Maximum rainfall was registered in March, which

indicate Mediterranean storm affect on winter rainfall.



7

1.4 – PREVIOUS WORK :

Previous work in Saudi Arabia on Wajid Sandstone comprise many

articles. Detailed description of the fluvial environment of the southern part of

Wajid Sandstone was presented by:

Dabbagh (1981) studied the environmental interpretation and tectonic

significance of Wajid Sandstone southwestern part of Saudi Arabia. Fining

upward sequence with channel systems and unimodal paleo-current trends

suggest a fluvial environment in southern outcrops. Littoral trace fossils in

more lithologically and structurally homogenous units in the north suggest a

shallow marine environment. Paleocurrents analysis based on cross-bed

measurements, indicate a unimodal northwesterly and northerly paleocurrent

trend pointing toward the Arabian Shield in the south and a unimodal

northeasterly trend in the north. The Wajid Sandstone has been deposited in a

platform-type basin in an area now occupied just after the cratonization of the

Arabian Shield in Late Precambrian and Early Paleozoic.

Dabbagh and Rogers (1983) studied the depositional environments and

tectonic significance of the Wajid Sandstone of southern Saudi Arabia.



8

Fig. (1-3): Satellite image of clouds above Saudi Arabia



9

The southern part of the formation consists of fluvial sandstone and

very minor siltstone and silty shale. The fluvial origin is very well

demonstrated. The northern part of the outcrop area consists of internally

homogeneous, tabular cross-bedded horizontally bedded sandstone apparently

formed in a shallow marine environment. Abundant cross bedding in both

facies of the Wajid Sandstone indicates a northward transport direction,

towards what is now the center of the Arabian Shield. The conversion from

basin to uplifted source may indicate a prolonged process of shield maturation

after initial stabilization.

Moshrif (1989) made a study with the help of applied technique

including vertical variation in grain size parameters, grain size distribution

curves, multivariation grain size parameter plots and the linear discriminate

function tests, he suggested that the southern part of Wajid Sandstone was

dominantly deposited in a fluvial environment. In addition, the sampled

outcrops can be characterized as negatively skewed, moderately to poorly

sorted, relatively coarse and are thus more likely to be fluvial, rather than

beach or eolian.

Moshrif and El-Hitti (1989) described six lithofacies in the Wajid

Sandstone. These lithofacies are identified as: silty and argillaceous sandstone,

fine-grained sandstone, coarse grained sandstone; conglomerate and massive



10

sandstone. Mineralogic composition suggests that the Wajid Sandstone is

considered clean sands for it consists 95% of quartz grains 5% heavy

minerals, mica, potash feldspar, clay matrix, ferruginous cement. In addition,

spectroscopic analysis reveals the presence of Si, Mg and Ca elements as

major constituents in the Wajid Sandstone.

Stump and van der Eem (1994) studied the Wajid Formation belt in

southwestern Saudi Arabia. They proved that the Paleozoic sediments are

represented by the Wajid Formation. The Early Devonian to Middle

Carboniferous Khusayyan Member, Wajid Formation unconformably overlies

the Qusaiba Member and was deposited in shallow marine, lagoon, eolian and

fluvial-deltaic settings. Major periods of uplift and subsequent erosion

produced the members of the Wajid Formation.

Pertaining Hydrogeology, Italconsult (1969) made a report about

water agriculture development in Wadi Dawasir. Their study includes the

geological setting, groundwater movement, recharge, groundwater

temperature, groundwater salinity and aquifer characteristics. They prepared

maps for water level and flow lines. The occurrence of about 100 meter

thickness of alluvial materials along Wadi Dawasir overlies the Khuff and

Sudair Formations, and comprises the alluvial aquifer. The main apparent

recharge to this system appears to be upward leakage from the Wajid and



11

Khuff Formations along the faulted and fractured zone. Much of the water in

the alluvial system is subsequently lost via evapotranspiration. The

construction of an piezometric map of the Wajid Aquifer from the well

exploration programs reveals several interesting and perplexing

hydrogeological features. The occurrence of the depression, cone appears to

be associated with the major wrench fault and indicates upward leakage along

this pressure relief zone. The water levels in the alluvial deposits corroborate

the upward leakage and there ft good correlation of the chemical quality of

water indicating, a source from the Wajid Sandstone. The northeastern

elongation of the depression cone indicates this configuration is controlled by

several geological features:

The western limit of the Wajid Sandstone on the north side of the fault.

The possible occurrence of tensional faults in the Wajid Sandstone. It has a

high transmissivity (up to 2 x 10-2

m2/sec) and a storage coefficient of 3 x 10

-3.

However, it was not evident that the above mentioned geological features

were reflected in the data.

Thickness of the Wajid sandstone is increasing as compared to a

thickness of 380 meters north of the fault.Wajid Formation extends westward

for a distance of more than 70 km, thus forming a vast reservoir.



CHAPTER II

GEOLOGICAL SETTING



13

CHAPTER II

GEOLOGICAL SETTING

2.1 – GEOLOGICAL SETTING:

The study area is found within the Wadi Tathlith quadrangle, which is

bounded by latitudes 19o30

/00

//N, 21

o00

/00

//N and longitudes 44

o00

/00

//E,

46o30

/00

//E (Fig. 2-1). It covers a surface area 8902 km

2of the southern Najd

province of Saudi Arabia. About two thirds of the quadrangle are underlain by

basement rocks of the Arabian Shield, much of it comprises an almost flat

pediment surface. The remaining third of the Wadi Tathlith quadrangle is in

the southwest is underlain by almost horizontally bedded Phanerozoic

sedimentary rocks. An agglomeration of villages including Al Khamasin, Al

Quwayz and Nuaimah lies at the edge of Irq al Wadi and is loosely known as

Wadi Dwasir. These villages, centered on an area of extensive agriculture

using ground water from the aquifers, contain about more than 50,000

inhabitants and lies on a major road between Riyadh, some 650 km away to

the north-northeast, and Tathlith to the southwest.

The oldest rocks of the southeastern Arabian Shield are interpreted to

have been formed in an 800-700-Ma-oldensimatic island arc (Schmidt et al.

1979; Greenwood et al. 1980, 1982). These rocks comprise a highly

deformed and metamorphosed succession of dominantly andesitic



14

metavolcanic rocks and interbedded volcaniclastic metasedimentary rocks (the

Halaban Group). The Halaban Group is intruded by nearly coeval sequence of

gabbro,diorite, tonalite, and culminant orogeny and resulted in the deposition

of a thick clastic and subordinate volcanic and carbonate succession upon the

older deformed rocks. This succession is interpreted by Hadley and Schmidt

(1980) to be a molasse-carbonate sequence and is correlated with the

Murdama group (Hadley, 1976; Kellogg, 1982a,b; Schmidt, 1981a; Brock,

1983) that crops out extensively in the central and northern parts of the shield

(Jackson et al. 1963) and that includes the Bani Ghayy group of the Wadi

Tathlith quadrangle. Voluminous and mostly undeformed postorogenic

intrusive rocks that either predated or intruded the Murdama group consist

predominantly of monzogranite, but include minor gabbro and alkali

granite. Metamorphic aureoles with grades up to biotite hornfels are

associated with these intrusive rocks. The smaller stocks tend to be circular or

elliptical in plan view. The southernmost of three major Najd fault zones,

striking northwestward across the Arabian shield and of latest Proterozoic or

Early Cambrian age, bisects the Wadi Tathlith quadrangle. Left-lateral

faulting along the Najd fault, and associated diapiric rise of gneiss antiforms

and small granitic intrusions along the zone marks the last



15

Fig. (2-1): Geological map of Wadi Dwasir area



16

major structural or plutonic event before the region was planed to a nearly flat

erosional surface. Platform sedimentation began during the Cambrian and

continued into the Ordovician with deposition of the Wajid Sandstone.

Subsidence during the Permian gave rise to the deposition of platform

carbonate sediments (Khuff Formation) under relatively calm conditions.

The Phanerozoic rocks lie unconformably on the Proterozoic of the

Arabian Shield. The contact, nowhere clearly exposed in the Wadi Tathlith

quadrangle, is commonly concealed by debris from the poorly consolidated

basal conglomerate of the Wajid Sandstone. Rough topography of the

Proterozoic rocks is preserved locally, as for example at Jabal Musayqirah

where Proterozoic marble is surrounded by the lower beds of the Wajid

Sandstone.

2.2 – WAJID FORMATION STRATIGRAPHY:

Wajid Formation is divided into four members from bottom to top (Fig.

2-2):

2.2.1 - DIBSIYAH MEMBER:

The Dibsiyah Member is 145 meters thick at its reference section on the

west flank of Jabal Dibsiyah latitute 200

12/40

//N and longitude 44

012

/00

//E.



17

Fig. (2-2): Summarizing the stratigraphic succession of the Wajid Sandstone in the

region.



18

The lower of the member, very poorly exposed on a pediment that is partly

covered by fluvial gravel and other detritus, begins with a poorly sorted basal

conglomerate of uncertain thickness composed largely of fragments of milky

quartz as much as 8 cm across. The remainder of the succession is composed of

very poorly sorted sandstone that, except for some layers with a siliceous and

ferruginous matrix, is fairly friable.

Conglomerate or microconglomeratic beds, with a clast size of generally

smaller than 2 cm, are present particularly in the lower third of the member. The

member is well stratified with beds ranging in thickness from a bout 10 cm to 15

cm; in places they display cross-bedding or inclined sets of diverse orientation.

The member as whole, except for the basal beds, shown abundant evidence of

bioturbation, the most common being tigillites (Scolithus pro syn.), which are

vertical tubular structures that probably present worm trails and range in diameter

from 5 to 20 mm and in length from 15 to 50 cm. The distribution of the tigillites

appears to depend on the grain size and stratonomic features of the rock; they are

most abundant in the massive sandstone beds and in fine-grained sandy layers,

are spares in beds with cross stratification or inclined sets, and are absent from

the coarsest grained layers. Trace fossils of unilobate, contorted, vermiform, and

irregular shapes occur on some bedding surfaces. Petrographic examination

shows the rocks to be poorly sorted and composed almost entirely of quartz. The



19

original clayey-ferruginous matrix is commonly replaced by a siliceous, clayey,

and calcite matrix.

The Dibsiyah Member is overlain by the Sanamah Member, or by Khusayyan

Member in place where the Sanamah Member is missing. The contact with the

Sanamah Member is distinct and the contact surface appears to by very irregular,

showing that intense erosion preceded deposition of the Sanamah Member. The

residual thickness of the Dibsiyah Member thus varies considerably from one

place to another.

2.2.2 - SANAMAH MEMBER:

The Sanamah Member, whose reference section is on an outlier of Jabal

Sanamah (lat 200

12/

25//

N., long 44014

/55

//E.) is 55 meter thick and rests on

tigillite-bearing sandstone of the Dibsiyah Member. The lower 20m consist of a

basal conglomerate, containing rounded quartz fragments as much as 5 cm in

size, overlain by massive coarse-grained conglomeratic sandstone that has eroded

to bold outcrops. Several rough joints are visible in detail and are associated with

intraformational channel surfaces marked by conglomeratic intervals. Several

sandstone beds, higher in the member and about 0.5 m thick, are overlain by

layers of irregularly bedded, pink to yellowish sandstone that, in places, contains

marble-size poikilitic calcite crystals. These beds are in turn overlain by

alternating beds of medium to fine-grained sandstone and red or white,



20

micaceous, fine grained sandstone. The rocks are all poorly sorted and composed

of quartz and feldspar (predominantly microcline with rare plagioclase). The

matrix is in places ferruginous and in places is composed of poikilitic calcite.

The Sanamah Member is laterally discontinuous sedimentary body and

commonly wedges out between the Dibsiyah and Khusayyan Members. It thus

varies considerably in thickness, attaining a maximum of 140 m in some places.

The sedimentologic characteristics of the Sanamah Member also vary; for

instance, at Jibal al Qahr the member appears to be distinctly bedded and meter-

scale slump structures are developed in some layers.

2.2.3 - KHUSAYYAN MEMBER:

The Khusayyan Member, with a thickness of about 200 meters, is the thickset

of the four member of the Wajid Sandstone. It is nowhere exposed in its entirety

and the reference section is made up of partial sections on the western flank of an

outlier of Jibal al Qahr latitude 200

02/25

//, 20

015

/00

//N, longitude 44

012

/05

//,

44040

/00

//E.

The Khusayyan Member is remarkably homogeneous, generally beginning

with a thin conglomeratic layer. It consist of white, medium to coarse-grained

sandstone that weathers to pale brown, with regular beds ranging in thickness

from 20 cm to 30 m and normally displaying cross-stratification inclined at 100

to

300

to the bedding. The cross-bedded layers strike predominantly northwest to



21

north-northwest and the bases commonly contain microconglomeratic streaks. In

places the sandstone contains of red and white, micaceous, fine-grained

sandstone. Cross-bedding toward the top of the member at Jabal Khusayyan

appears as imbricate festoons, the cores of which are composed of red platy

pelite.

In thin section, the sandstone shows mostly poorly sorted detrital quartz grains

together with rare muscovite. The matrix is clayey and commonly replaced by

micrite, calcitic microsparite, or poiklitic calcite. The layers at the top of the

sequence are abruptly overlain by yellowish-brown sandstone with irregular

stratification containing fragments of red reworked pelite. This change in

sedimentation marks the passage to the Juwayl Member, although deposition of

the latter was preceded by an erosion interval which a relief of some tens of

meters was cut into the Khusayyan Member, similar to that in the Dibsiyah

Member.

2.2.4 - JUWAYL MEMBER:

Several partial reference sections were required to establish a type section for

the Juwayl Member. This is on a north flank of the southern part of Jibal Juwayl

latitude 20o09

/30

//N, longitude 44

o28

/00

//E.

The Juwayl Member at Jabal Fard al Ban rest on anerosion surface is inclined

at about 40o

and contains scattered small quartz pebbles. The basal part of the



22

member consist of pink and white, fine-grained sandstone, thoroughly

disorganized, and without visible stratification, passing upward into yellowish,

medium-grained sandstone containing fragments of equally disorganized fine-

grained sandstone.

The section of Jibal al Juwayl consists of fine to coarse-grained sandstone,

micro-conglomeratic and conglomeratic toward the base with fragments of

quartz, and of very fine grained sandstone and pinkish, whitish, or yellowish

pelite. The conglomerate generally occur at the base of small sedimentary bodies

that occupy channels in fine-grained deposits. Bedding is nonexistent or poorly

defined in the lower part of the section, but higher up the sandstone displays

massive horizontal beds, beds with inclined sets, cross-stratification, and wavy

stratification.

The section at Bani Ruhayyah and the surrounding area succeeds the Jibal al

Juwayl section and consists of coarse to medium-grained sandstone in beds either

with inclined sets or with millimeter-thick laminae. Here a ferruginous crust, only

a centimeter thick and containing small rounded quartz pebbles, marks an abrupt

passage, without any angular discordance, to pale-gray dolomite of the Khuff

Formation. The basal of the Juwayl Member consist of rounded grains, 500 to

600 micron in diameter, dispersed in a silty matrix with angular fragments; a

texture reminiscent of deposits with a glacial component. The sandstone of Jibal



23

Juwayl is generally moderately well to poorly sorted and consist of grains of

quartz and rare feldspar; the sorting improves nearer to the contact with the Khuff

Formation. The matrix everywhere is varied and complex, being clayey,

ferruginous, siliceous, and calcitic, and having undergone several episodes of

alteration.

The Juwayl Member crops out of two distinct belts within the Wadi Tathlith

quadrangle; one trend north between the meridians 44o48/ 00// E. and disappears

beneath Quaternary deposits near Wadi Dwasir, and the other, between 3 and 8

km wide trends north-northwestward for some 35 km from the southern edge of

the quadrangle to latitude 20o16

/00

//N. the nature of the contact with the

underlying rocks and the sedimentologic characteristics of the member in the

latter belt suggest a paleochannel in which the earliest sediments display

pervasive slump structure, at least on the borders, and later sediments have fairly

clearly defined bedding and eventually regular stratification. Slump structure,

probably at the base of the Juwayl Member, are very well developed in the Jabal

Khurb al Ahmar area latitude 30o00

/45

//N, longitude 44

o35

/20

//E.

In the other sides out of the study area there are some stratified as following

sequences: Wajid formation, Khuff formation, Sudair formation, Minjur

formation, Dhruma formation, Tuwaiq, mountain formation, Hanifa formation,



24

Jubaila formation, Hith-Arab formation, Buwaib formation, Biyadh formation,

Alluvium deposits.

2.3 – STRUCTURE:

Wadi Dawasir Area forms part of the interior homocline structural

province. The recent investigations have played determinant role in clarifying the

structural conditions of the area, which have a marked influence on the

geohydrological conditions.

The structural outline of the Southern Tuwayq Segment of the interior

homocline (Fig. 2-3). This may subdivided into the following units:

-Northern Trough

-Southern Najd Uplift

-Wadi Dwasir Step-Fault System

-Al Arid Structural Trough

The structural unit having the greatest influence on the tectonic

development of the Wadi Dawasir Area is the Southern Najd uplift. This unit is

the southeasterly extension of a 150 to 200 km wide belt of the Shield,

characterized by very considerable tectonic disturbance. This belt is bordered to

the NE and SW in the shield area by wrench faults, along which the central

blocks has moved in a SE direction.



25

Fig. (2-3): Modified structural sketch of the southern Najd (Italconsult, 1969).



27

The Wadi Dawasir Area lies on the southern border of the Southern Najd

Uplift, which cuts diagonally across it. Hence the Area has been subject to

intense structural disturbance of considerable dimension. These disturbance

profoundly modified the original structure of the lower Paleozoic, which

consisted of a gentle homocline, and divided it into a number of blocks flanked

by fault striking mainly NW-SE, thus producing the typical step and horst-graben

structures. The faults are apparently of the normal gravity type.

The structure of the Lower Paleozoic is largely masked by the Pre-Khuff

unconformity when produced erosion rendered the surface of the Lower

Paleozoic virtually flat.

Reactivation of certain faults, probably in the Upper Triassic, again

brought out the structural trend of the Lower Paleozoic.

It is possible to identify two main step-fault systems and numerous

secondary faults en-echelon in the Wadi Dawasir Area. The main fault systems

lead to the formation of three major stepped blocks rising to the northeast, while

the secondary faults produce step and horst-graben structures.

The main southern fault system, having a NW-SE trend is clearly

recognizable on the basis of both surface and subsurface data. On the surface it is

marked by the large fault system running on the Crystalline Shield parallel to the



28

lower reaches of Wadi Bishah to the SE. In the subsurface the gravity anomaly

map indicate its presence.

The southern fault brings about a considerable diminution in the width of

the Wajid Formation outcrop, while that the north causes the total disappearance

of this formation both in outcrop and in subsurface, making an increase in

truncation as the major blocks rise northeastwards.

The throw along the main fault is considerable. It is thought that the

northern one causes vertical displacement of around 400 to 500 meters. There is

not sufficient information available to determine the throw of the southern fault,

but in any case it must be of the order of several hundred meters.

The most important of the secondary structural elements is the Kumdah

Graben. This has been outline on the basis of subsurface and surface information.

It can be followed from Nuemah up to Khashm Kumdah.

It is thought that the actual number of faults is far greater than that

identified of date. The presence of faults (mostly tension faults) has a great

influence on groundwater conditions.

Dips drop from about 19 m/km at the Pre-Wajid unconformity to 12

m/km at the top of the Khuff Formation. The strike of the strata swings from ESE

to ENE in a southerly direction.



CHAPTER III

APPLIED PROCEDURE

AND

METHODOLOGY



29

CHAPTER III

APPLIED PROCEDURE AND METHODOLOGY

3.1 – METHODOLOGY:

The geological and topographical maps in this study were used. Well

sites and their elevation were determined using a Global Position System

devise (GPS) type Garmen 12. Water level, temperature, pH, and electrical

conductivity where measured in site (Figs. 3-1 and 3-2) .

A pumping tests were performed for both wells, new and old, drilled by

the Ministry of Water and Electrecity in the study area. Step-drawdawn tests

were carried out in three stages 300 gallon/minutes, 400 gallon/minutes and

550 gallon/minutes and wells drilled by Italconsult (1969).

During the hydrological investigation groundwater samples were taken and

bottled for chemical analysis in the laboratory from both supply and

observation wells. The hydrogeologic investigation included complete

characterization of the following:

1- Subsurface extent and thickness of aquifers and confining units

(hydrogeologic framework).

2- Hydrologic Boundaries (also referred to as boundary conditions) which

control the rate and direction of movement of groundwater.



30

Fig. (3-1): Collecting and checking samples.



31

Fig. (3-2): Determination of water level by device.



32

3- Hydraulic Properties of the aquifer and confining units.

4- Description of the horizontal and vertical distribution of hydraulic head

throughout the modeled area for both beginning conditions (initial

conditions) and later conditions that may vary with time (transient

conditions).

5- Predict future of the aquifer with pumping from the wells and drawing

drawdown maps after periodic time.

6- After sample analyses, estimate the errors in analyses and making

distribution maps of ions concentration, statistical methods then suitability

of water for drinking and irrigation.

3.2 – GROUNDWATER MODELING THEORY:

3.2.1 - INTRODUCTION AND PURPOSE:

The use of groundwater models is prevalent in the field of

environmental science. Models have been applied to investigate a wide variety

of hydrogeologic conditions. More recently, groundwater models are being

applied to predict the fate and transport of contaminants for risk evaluation. In

general, models are conceptual descriptions or approximations that describe

physical systems using mathematical equations; they are not exact

descriptions of physical systems or processes. By mathematically representing



33

a simplified version of a hydrogeological system, reasonable alternative

scenarios can be predicted, tested, and compared. The applicability or

usefulness of a model depends on how closely the mathematical equations

approximate the physical system being modeled.

Groundwater models, however, even as approximations, are a useful

investigation tool that groundwater hydrologists may use for a number of

applications (Freeze and Cherry, 1979). Among these are:

* Wellhead protection area delineation.

* Evaluation of regional groundwater resources.

* Prediction of the effect of future groundwater withdrawals on groundwater

levels.

* Tracking the migration of groundwater contamination.

* Evaluation of design of hydraulic containment and pump-and-treat systems.

* Design of groundwater monitoring networks.

* Prediction of the possible fate and migration of contaminants for risk

evaluation.

This study deals mainly with flow modeling. Groundwater flow model

is intended to calculate the bulk, or average, rate and direction of movement of

groundwater through aquifers and confining units in the subsurface. These

calculations are referred to as simulations.



34

This requires a thorough understanding of the hydrogeologic characteristics of

the site. The hydrogeologic investigation should include a complete

characterization of the following:

1- Subsurface extent and thickness of aquifers and confining units

(hydrogeologic framework).

2- Hydrologic Boundaries (also referred to as boundary conditions) which

control the rate and direction of movement of groundwater.

3- Hydraulic Properties of the aquifers and confining units.

4- A description of the horizontal and vertical distribution of hydraulic head

throughout the modeled area for both beginning conditions (initial

conditions) and later conditions that may vary with time (transient

conditions).

5- Distribution and magnitude of groundwater recharge, pumping or injection

of groundwater, leakage to or from surface water bodies, etc. (sources or

sinks, also referred to as stresses). These stresses may be constant

(unvarying with time) or may change with time (transient).

The output from the model simulations are the hydraulic heads and

groundwater flow rates which are in equilibrium with the hydrogeologic

conditions (hydrogeologic framework, hydrologic boundaries, initial and

transient conditions, hydraulic properties, and sources or sinks) defined for the



35

modeled area. Through the processes of model calibration and verification, the

values of the different hydrogeologic conditions are varied to reduce any

disparity between the model simulations and field data, and improve the

accuracy of the model. The model can also be used to simulate possible future

changes to hydraulic head or groundwater flow rates as a result in future

changes in stresses on the aquifer system.

3.2.2 - TYPE OF FLOW MODELS:

There are two types of models, analytical and numerical. An analytical

model is a very simplified equation that can be solved exactly. A numerical

model approximates the partial differential equations describing groundwater

flow and solute transport. Numerical models, though still simplifications of

the actual hydrogeology, are typically much more complex than analytical

models. Each model may also simulate one or more of the processes that

govern groundwater flow or contaminant migration rather than all of the flow

and transport processes.

3.2.3 - MODEL CALIBRATION:

Model calibration consists of changing values of model input

parameters in an attempt to match field conditions within some acceptable

criteria. The calibration process typically involves a steady-state and transient

simulation. With steady-state simulations, there are no observed changes in



36

hydraulic head or contaminant concentration with time for the field conditions

being modeled. Transient simulations involve the change in hydraulic head

with time (e.g. aquifer test or and aquifer stressed by a well field). Models

may be calibrated without simulating steady-state flow conditions, but not

without some difficulty.

3.2.4 - MODEL VERIFICATION:

A calibrated model uses selected values of hydrogeologic parameters,

sources and sinks and boundary conditions to match historical field

conditions. The choice of the parameter values and boundary conditions is not

unique, another combination of parameter values and boundary conditions

may give very similar model results. History matching uses the calibrated

model to reproduce historic field conditions. The most common history-

matching scenario consists of reproducing a change in the hydraulic head of

the aquifer. The best scenarios for verification are ones that use the calibrated

model to simulate the aquifer under stressed conditions. The process of model

verification may result in further calibration refinement of the model. After the

model has successfully reproduced measured changes in field conditions, it is

ready for predictive simulations.



37

3.3 - COMPUTER METHODS:

After filtering of the hydrogeological data used in this study several

computer software were used for processing, graphical presentation and

analyzing of the study data. Following is brief description of each of the used

computer software:

3.3.1 - VISUAL MODFLOW PROGRAM:

Visual Modflow is a complete and modeling environment for practical

applications in three-dimensional groundwater flow and contaminant transport

simulations. This fully-integrated package combines MODFLOW,

MODPATH, Zone-Budget, MT3Dxx/RT3D, and Win-Pest with the most

intuitive and powerful graphical interface available. The logical menu

structure and easy-to-use graphical tools allow you to:

• Easily dimension the model domain and select units.

• Conveniently assign model properties and boundary conditions.

• Run the model simulations (MODFLOW, MODPATH, Zone-Budget,

MT3D/RT3D, and Win-Pest are seamless integrated).

• Calibrate the model using manual or automated techniques.

• Visualize the results using 2D or 3D graphics.



38

The model input parameters and results can be visualized in 2D (cross-

section and plan view) or 3D at any time during the development of the model

or the displaying of the results. For complete three-dimensional groundwater

flow and contaminant transport modeling.

3.3.2 – AQUACHEM PROGRAM:

AqauChem (Calmbach and Waterloo hydrogeologic) is designed

specifically for numerical and graphical processing of hydrochemical data.

The program has many functions ranging from simple unit transformation,

charge balance calculation, hydrochemical facies definition to more complex

mixing and geothermometry calculations. The graphical functions present the

data in the most commonly used hydrochemical diagrams (i.e. Piper, Durov,

Schoeller) and maps. The most powerful feature of AquaChem is the graphical

interface to the geochemical modeling program PHREEQC.

3.3.3 – PHREEQC PROGRAM:

PHREEQC (pH redox-equilibrium-equation) is a powerful C language,

geochemical modeling program (Parkhurst et al., 1980; Parkhurst, 1995;

Parkhurst and Appelo, 1999) based on an ion association aqueous modeling.

It has capabilities for speciation and saturation index calculations; reaction

path and advective transport calculations, and inverse modeling. Input data



39

include major and trace ions, alkalinity, Eh, pH, temperature, partial pressure

of gases, and aquifer geology. The output of PHREEQC is very extensive.

3.3.4 - SURFER PROGRAM:

Surfer (Golden Software Inc., 1997) is a contouring and three-

dimensional surface plotting program. The basic function of the program is

interpolating irregularly spaced XYZ data onto a regularly spaced grid, then

using this grided data to construct contour maps and surfaces. The program

uses two categories of griding methods, exact interpolators and smoothing

interpolators. Exact interpolator honors (uses) exactly the value of the data

point when the data point coincides with interpolated grid node. Kriging is the

exact interpolating method used for girding the study data. Smoothing

interpolators are used when there is no strict confidence in the data

measurements.

Surfer also has the capability of producing a file containing cross

section data, which can be imported to any plotting program.

3.3.5 - DUROV PLOT PROGRAM:

DurovPlot (Al-Bassam et al., 1997) is a QuickBASIC program that

calaculates and plots the expanded version of Durov diagram (Durov, 1948;

Burdon and Mazlum, 1958; Lloyd and Heathcote, 1985). This diagram



40

removes some of the shortcomings of Hill and Piper diagrams, also it allows

not only the classification of groundwater into types, but also definition of the

possible hydrochemical processes responsible for producing these types of

water.

3.3.6 - INFINITE EXTENT PROGRAM:

Infinite Extent (Starpoint Software) is a computer program designed for

analysis of pumping test data and estimating aquifer hydraulic properties. The

program utilizes the traditional graphical data analysis using type curve

matching (Theis, 1935; Hantush, 1956 and 1960; Walton, 1962; Neuman,

1975) and automatic parameter estimation, also it include special subroutines

to estimate the behavior of aquifer under the stress of pumping. The basic

input data of Infinite Extent is discharge, time or distance, and drawdown.



CHAPTER IV

HYDROGEOLOGY

&

HYDROCHEMISTRY



41

CHAPTER IV

HYDROGEOLOGY AND HYDROCHEMISTRY 4.1 – INTRODUCTION:

In this chapter, the input data required by the computer model is

printed from the developed data bank. This bank of data represents the

input interface of the used numerical model (Herbert and Anderson, 1982).

The data is ready for request, development and renewal. Request of data is

answered in the form of tables of maps.

4.2 - WAJID AQUIFER DESCRIPTION:

Wajid aquifer is considered as one of the most important

hydrostratigraphical units in the kingdom of Saudi Arabia (Fig. 4-1 and 4-

2). It is fairly well delimited in the Wadi Dawasir area. It is only to the East

that there remain any doubts as to its extent. The depth of the aquifer

which, from the zone where the formation disappears from outcrop to a

pointless than 75 km eastwards, reaches 1000 m has made it impossible to

detect the aquifer East of longitude 45o35/ 00// E. The unconfined part of

the aquifer in and near the outcrop zone of the Wajid formation is very

extensive. It can be followed from the southern bank of Wadi Dawasir to

the Yemen border in the South. The unconfined part of the aquifer seems to

be absent to the North of Wadi Dawasir. The confined part of the aquifer is

more extensive. The border between the unconfined and confined



43

Fig. (4-1): Wajid Aquifer extent.



44

Fig. (4-2): Wajid outcrop.



45

4.4 - AQUIFER PARAMETERS:

Any aquifer is characterized by two main properties. The first is its

ability to transmit water under natural field conditions. The second

property is its storage capability. These two parameters are named the

transmissivity and storage coefficient.

A pumping test was conducted, for this purpose in the Wajid Aquifer

of the study area at Al-Sharafa wells (Table 4-1). The pumping test data

was analyzed using Infinite Extent Program. It comprises three methods

Thesis, Walton and Hantush, assume the following:

• The aquifer has a seemingly infinite a real extent.

• The aquifer is homogeneous, isotropic and of uniform thickness over the

area influenced by the pumping test.

• Prior to pumping, the piezometric surface and /or phreatic surface are

(nearly) horizontal over the area influenced by the pumping test.

• The aquifer is pumped at a constant discharge rate.

• The pumped well penetrates the entire aquifer and thus receives water

from the entire thickness of the aquifer by horizontal flow.

It is be clear that the first assumption in particular is seldom satisfied in

nature. However, slight deviations are not prohibitive to the application of

the methods. When greater deviations from the above assumptions occur,

we come into the field of special flow problems. To understand the

assumptions of each individual method, Thesis assumes the following:



46

Client: MW

Title: MSc Project

Site Name: Sharafa

Location:WadiDawasir

Project Number: 1

Well DischargeRate: 1090.24 M3/day

Pumping WellRadius 0.35 meters

Aquifer Thickness: 600 meters

r=0.35meters

A = 0 meters

B = 600 meters

Time Drawdown

days meters

0.000 0

0.001 0.85

0.001 3.05

0.002 3.2

0.003 3.25

0.003 3.35

0.004 3.39

0.005 3.42

0.006 3.42

0.006 3.42

0.007 3.42

0.008 3.42

0.010 3.42

0.011 3.42

0.013 3.42

0.014 3.42

0.017 3.43

0.021 3.44

0.024 3.5

0.028 3.5

0.031 3.50.035 3.5

0.042 3.5

0.049 3.5

0.056 3.51

0.063 3.51

0.069 3.51

0.076 3.51

0.097 3.51

0.118 3.51

0.139 3.51

Table (4-1): Step drawdown of pumping test of Al-Sharafa Well in the study area.



47

4.4.1 - THEIS’S METHOD:

Besides the assumptions mentioned above, the following limiting

conditions should be satisfied:

• The aquifer is confined.

• The flow to the well is in unsteady state, i.e. the drawdown differences

with time are not negligible nor are the hydraulic gradient constant with

time.

• The water removed from storage is discharged instantaneously with

decline of head.

• The diameter of the pumped well is very small, i.e. the storage in the

well can be neglected.

∫ ∞−

π=

π=

u

y uW kD

Q y

dyekD

Q s )(44

Where:

u =kDt

S r

4

2

and, consequently 2

4

r

kDtuS =

s = The drawdown is m measured in a piezometer at a distance r in m

form the pumped well.

Q = The constant well discharge in m3/day.

S = The dimensionless coefficient of storage.

kD = The transmissivity of the aquifer in m

2

/day.



48

t = The time in days since pumping started.

4.4.2 - WALTON’S METHOD:

Besides the assumptions, the following limiting conditions should be

satisfied:

• The aquifer is semi-confined.

• The flow to the well is in an unsteady state, i.e. the drawdown

differences with time are not negligible nor are the hydraulic gradient

constant with time.

• The water removed from storage is discharged instantaneously with

decline of head.

• The well diameter is very small, so that the storage in the well can be

neglected.

Walton (1962) developed a method of solution along the same line of

reasoning as was followed for the Theis method, but instead of one type

curve, there is a type curve for each value for r/L. This means that using

the tables of values for the function W(u, r/L) as published by Hantush

(1956), a family of type curves has to be drawn.

4.4.3 - HANTUSH’S METHOD:

The following assumptions and conditions should be satisfied:

• Those listed for the Walton method and in addition the conditions.

• q > 2r/L



49

• t > 4t p

The drawdown the formula, which has the form:

)/,(4

Lr uW kD

Q sπ

=

can, according to Hantush (1964), alternatively be written as

)]()/(2[4

qW Lr K kD

Q s o −

π=

Where:

22

2 1

4 SL

kDt

u L

r q ==

If L

r q

2> can be approximated by:

)(

4

qW

kD

Q s sm

π

=−

Where, according to:

sm = maximum or steady-state drawdown

)/(

2

Lr K

kD

Qo

π

=

If sm can be extrapolated from a plot of s versus log t , the drawdown

at the infection point p can be calculated from

s p = 0.5 sm



50

and t p, the time corresponding with s p, can be read from the time-drawdown

curve. If a sufficient number of data fall within the period t > 4t p the

following procedure can be used.

The average of transmissivity is 252.8 m2/day. The average hydraulic

conductivity is 0.421 m/day and the average storage coefficient is 0.002.

The permeability of an aquifer is described by its transmissivity and

hydraulic conductivity. Transmissivity estimated from pumping tests in the

aquifer are in the range from 5.7x 10-4 to 2.1x 10-2 m/sec (Italconsult,

1969). The average transmissivity, calculated as the geometric mean, from

all pumping tests is T = 49.248 m2/day. The values of hydraulic

conductivity show a range from 5.5x10-7 m/s found in the unconfined part

to 3.0x10-8 m/s in the eastern confined part of the aquifer. The storativity of

an aquifer is defined by its storage coefficient, specific storage and specific

yield. The storage coefficient has been obtained from pumping test data in

the range of 0.004 to 0.0408 with average of 0.0224. Specific storage

ranges from 2x 10-1

(unconfined) to 2x 10-4

(confined). The specific yield

has been found to be 0.045 to 0.21 from pumping tests. The regional value

is about 21%.



51

Fig. (4-3): Pumping test curve using Theis Method.



52

Fig. (4-4): Pumping test using Walton’s Method.



53

Fig. (4-5): Pumping test using Hantush Method.



54

4.5 - GROUNDWATER DYNAMIC:

The static water level of Wajid aquifer in the area varies from beyond 40

m below ground level to more than 90 m above ground level, depending on

the topographic elevation. Table (4-2) and figure (4-6) show generalized

head distribution of the Wajid aquifer, the groundwater heads are dipping

gently from the outcrop area in the southwest towards the northeast. At

present time table (4-3) fig (4-7) Wajid aquifer is under huge withdrawal

quantities from the agricultural companies that mean the aquifer is in a non

equilibrium state, so the groundwater outflow discharge is greater than the

groundwater recharge, and that the total change in storage is negative. The

heads decrease from about 700 m to 550 above sea level (a.s.l). The

groundwater flow is directed to the northeast which is the main discharge

area for the aquifer especially in Wadi Dawasir area which is the maximum

withdrawal.

The groundwater inflow consists of direct groundwater recharge

from precipitation and of recharge caused by infiltration of run-off to

stream beds or of run-off pounded on the outcrop of the aquifer. For the

study area the average groundwater recharge in the outcrop area is

estimated to about 15 mm/year.

It must be mentioned, that most of the groundwater stored in Wajid

aquifer is fossil – non renewable – groundwater. The age of the

groundwater is dated up to several thousand years. Most of this



55

Well. Name Longitude Latitude WELL. deph ElevationDepth to

Water Water Level

SU 45.57 20.46 1318.5 601.35 9.14 610.49

T4 45.13 20.33 552.4 636.91 5.63 642.54

T5 45.15 20.48 559.65 634.27 5.22 639.49

T6 45.19 20.63 569 623.07 6.22 629.29

T7 45.13 20.33 551.5 634.94 5.72 640.66

T8 45.14 20.33 799.5 635.71 5.7 641.41

T11 45.4 19.95 1109 665 3.76 668.76

T12 45.13 19.87 603.5 711.98 12.3 724.28

T20 45.05 20.28 749 662 2.5 664.5

T21 45.06 20.24 793 675 1.79 676.79

T22 45.07 20.48 624 639 4.1 643.1

P1 45.14 20.34 798 635.16 5.65 640.81

Table (4-2): Ancient (Initial) well information in the Wajid Aquifer in Wadi

Dwasir Area.



56

4900000 4920000 4940000 4960000 4980000 5000000 5020000

2220000

2240000

2260000

2280000

2300000

2320000

2340000

Fig. (4-6): Water level in the Wajid Aquifer in Wadi Dawasir 1969.



57

WellName Long Latit

WellDepth

D toWater Elevation W.L

WD1 45.02 20.39 500 80 648.25 568.25

WD2 45.02 20.19 300 80 680.5 600.5

WD3 45.099 20.47 450 80 636.75 556.75

WD4 44.86 20.18 300 80 685 605

WD5 44.91 20.34 250 80 664 584

WD6 44.98 20.156 500 90 685.5 595.5

WD7 44.93 20.406 350 90 655.5 565.5

WD8 44.97 20.08 350 80 693.5 613.5

WD9 44.86 20.256 300 80 676.5 596.5

WD10 45.216 20.459 600 90 627.25 537.25

WD11 45 20.09 350 100 691.6 591.6

WD12 44.98 20.12 350 90 689.25 599.25

WD13 45.016 20.174 350 90 682.5 592.5

WD14 45 20.11 350 90 689.5 599.5

WD15 44.914 20.394 250 70 658 588

WD16 44.94 19.95 300 80 705 625

WD17 44.98 20.32 300 80 661 581

WD18 44.915 20.41 200 80 659.5 579.5

WD19 44.91 20.45 200 100 653.35 553.35

WD20 44.87 20.12 300 80 691 611

WD21 44.907 20.38 250 70 660 590

WD22 44.89 20.11 300 90 691.75 601.75

WD23 45.196 20.43 550 90 630 540

WD24 45.189 20.44 550 90 630.5 540.5

WD25 45.287 20.439 600 90 623 533

WD26 44.95 20.417 250 70 653 583

WD27 44.91 20.136 300 80 689 609WD28 44.97 20.24 300 80 675 595

WD29 44.95 20.39 250 60 625.5 565.5

WD30 44.97 20.144 300 100 687 587

WD31 44.9 20.173 300 80 685 605

WD32 44.97 20.168 350 100 684.5 584.5

WD33 44.91 20.14 300 80 688.5 608.5

WD34 44.97 20.106 350 100 691 591

WD35 45.2 20.44 600 90 629.5 539.5

WD36 44.98 20.22 300 80 677.75 597.75

WD37 44.97 20.34 250 80 659 579

WD38 44.91 20.38 250 80 659.5 579.5WD39 44.907 20.162 300 80 686.5 606.5

WD40 44.97 20.23 350 85 676.5 591.5

WD41 44.99 20.3 250 80 663 583

WD42 44.92 20.34 250 80 663.5 583.5

WD43 45.21 20.495 550 90 627 537

WD44 45.264 20.49 600 90 622.5 532.5

WD45 45.31 20.47 600 90 625.25 535.25

WD46 45.11 20.55 450 70 632 562

WD47 44.91 20.327 300 80 665.5 585.5

Table (4-3): Wells information of Wajid Aquifer in Wadi Dawasir 2002



58

4900000 4920000 4940000 4960000 4980000 5000000 5020000

2220000

2240000

2260000

2280000

2300000

2320000

2340000

Fig.(4-7): Present groundwater level in the study area 2002.



Table (4-4): Results of groundwater analysis in the study area (mg/l).

Well Ca Mg Na K Cations HCO3 Cl SO4 NO3 Anions Er

SU 2.56 1.56 3.59 0.46 8.18 2.56 2.64 2.74 0 7.95 0T4 4.09 2.22 4.13 1.3 11.75 2.54 4.94 4.17 0 11.64 0

T5 4.14 1.89 4 1.38 11.42 2.54 4.65 4.17 0 11.36 0

T6 3.24 1.48 2.83 1.38 8.93 2.54 3.1 3.13 0 8.77 0

T8 4.34 2.38 3.69 0.46 10.87 2.56 3.77 4.6 0 10.94 0

T11 4.77 1.54 2.3 0.52 9.12 2.71 3.47 3.11 0 9.3 0

T12 4.24 2.28 4.68 0.32 11.52 2.76 4.79 4.1 0 11.66 0

T20 5.39 2.72 6.12 0.43 14.67 1.74 7.32 5.37 0 14.43 0

T21 4.74 2.32 4.8 0.4 12.26 4.25 5.55 4.33 0 14.13 1

T22 4.82 2.39 4.88 0.46 12.55 2.32 5.47 4.76 0 12.55K1 9.98 3.21 4.83 1.48 19.5 2.89 12.97 8.33 0.35 24.54 5

D1 3.54 5.67 9.61 0.26 19.09 2.84 7.93 4.83 0 15.59

D2 2.59 4.28 7.87 0.36 15.1 3.26 6.01 3.75 0 13.02 2

D3 1.95 4.03 4.18 0.5 10.66 3.1 4 3.46 0 10.56 0

D4 1.8 4.77 2.65 0.28 9.5 3.3 7.64 3.29 0.37 14.6

D5 1.1 2.14 1.44 0.35 5.02 3.43 0.96 2.29 0 6.68 1

D6 3.24 6 7.52 0.54 17.31 2.66 4.63 3.81 0 11.09 6

D7 1.8 3.95 4.44 0.53 10.71 3.1 3.27 4.02 0 10.39 0

D8 0.95 2.38 1.7 0.33 5.36 3.84 1.04 2.27 0 7.15 1M1 3.74 2.47 1.48 0.41 8.1 1.97 7.05 2.56 0.35 11.93 3



61

44.8 44.9 45 45.1 45.2 45.3 45.4 45.5 45.6

19.8

19.9

20

20.1

20.2

20.3

20.4

20.5

20.6

SU

T4

T5

T6

T8

T11

T12

T20

T21

T22

K1

D1

D2 D3

D4

D5

D6

D7

D8M1

0 10 20 Km

Fig. (4-8): Sites of sampling.



62

For irrigation water and most other natural waters, 1 millimho

customarily is taken as equal to 640 mg/1 (Salinity Laboratory, 1954).

Groundwater is classified according to its TDS content as (Hem, 1970)

(Table 4-5):

Davis and DeWiest (1966) classified water with a TDS content of

1000 to 10000 ppm as brackish, of 10000 to 100000 ppm as salty, and of

more than 100 000 ppm as brine. By way of comparison, the TDS content of

seawater is about 34000 mg/1 and that of a saturated NaCI solution more

than 300000 mg/1. The recommended maximum limit for the TDS content

of drinking water is 500 mg/1, but water of double or even triple this

concentration is used if no other water is available.

In this study there are a three parts have a high cocentration of

TDS, one along the west and the other near to north east and the third one in

the south, the lowest values in far north east (Fig. 4-9).

4.6.2 - CALCIUM (Ca++

):

Calcium is one of the principal cations in groundwater. Sources of

calcium are igneous rock minerals like silicates, pyroxenes, amphiboles,

feldspars, and silicate minerals produced in metamorphism. Since the

solubility of these minerals is low, water from igneous or metamorphic rock



63

Type of water Measured disolved solids

(mg/l)

Fresh < 1000

Moderately saline 3 000-10 000

Very saline 10 000-35 000

Briny > 3 5 000

Table (4-5) : Classification of water according to the TDS (Hem, 1970).



64

44.8 44.9 45 45.1 45.2 45.3 45.4 45.5 45.6

19.8

19.9

20

20.1

20.2

20.3

20.4

20.5

20.6

500

550

600

650

700

750

800

850

900

950

1000

1050

1100

1150

1200

1250

0 10 20 Km

Fig. (4-9): Concentration of TDS in the study area (mg/l).



66

Km

44.8 44.9 45 45.1 45.2 45.3 45.4 45.5 45.6

19.8

19.9

20

20.1

20.2

20.3

20.4

20.5

20.6

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

0 10 20

Fig. (4-10 ): Concentration of calcium ion in the stuy area (mg/l).



67

rock, magnesium occurs as magnesite and other carbonates, sometimes

mixed with calcium carbonate. Dolomite contains calcium and magnesium

in equal amounts. Most groundwater contain relatively small amounts of

Mg, except where they have been in contact with dolomite (amounts of Ca

and Mg about the same), or with Mg-rich evaporites that could cause Mg to

become the dominant cation in the groundwater.

In the study area magnissium cocentration varies from less than 18

mg/l to more than 70 mg/l, the maximum cocentration is found in the north

west and in the south part of the study area. The minimum values distributed

in the east and a lettel in the north in two points. In the middel of the study

area, magnessium has a moderatly concentrations (Fig. 4-11).

4.6.4 - SODIUM (Na+):

Sodium is primarily derived from feldspars in igneous rock and its

weathering products (clay minerals) in other material. Shale and clay layers

often yield water with a relatively high sodium content. Other sources of

sodium are leachate and deep percolation water from the upper soil layers

(including atmospheric precipitation that has been subject to concentration

effects), and contamination of groundwater by salty connate water or water

of marine origin. Brines and other salty waters which usually occur at great

depths contain large amounts of sodium.



69

Sodium concentration varies in the study area from 30 mg/l to

more than 200 mg/l (Fig. 4-12). The maximum sodium concentration is

appear in the south and in the north parts of the study area and the minimum

values is found near along the east part and in two areas near the west part of

the study area. In the middel of the area sodium concentration has a

moderatly values.

4.6.5 - POTASSIUM (K -):

Potassium is less common than sodjum in igneous rock, but more abundant

in sedimentary rock as potassium feldspars. These minerals, however, are

very insoluble so that potassium levels in groundwater normally are much

lower than sodium concentrations. Potassium concentration ranges in the

study area from 10 mg/l to more than 55 mg/l, the minimum cocentration

values is found from the middel of the study area to along the south part and

the high cocentrations (more than 55 mg/l) occures mainly in the north and

north west (Fig. 4-13).

4.6.6 - CHLORIDE (Cl

--

):

Primary sources of chloride in groundwater are evaporites, salty

connate water, and marine water. Igneous rock materials contribute little

chloride. Ground- waters containing significant amounts of chloride also



70

44.8 44.9 45 45.1 45.2 45.3 45.4 45.5 45.6

19.8

19.9

20

20.1

20.2

20.3

20.4

20.5

20.6

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

210

0 10 20 Km

Fig. (4-12): Cocentration of Sodium in the study area (mg/l).



71

tend to have high amounts of sodium, indicating the possibility of contact

with water of marine origin.

Leaching of chlorides that have accumulated in upper soil layers

may be a significant chloride source in dry climates. The recommended

maximum concentration for chloride in drinking water is 250 mg/1,

primarily for reasons of taste.

Over the investigated area the chloride cocentration varies from 20

mg/l in the north west to more than 440 mg/l in the north east so it is take an

increasing from east to west (Fig. 4-14).

4.6.7 - SULFATE (SO4--):

Sulfate is formed by oxidation of pyrite and other sulfides widely

distributed in igneous and sedimentary rocks. The most important sulfate

deposits are found in evaporite sediments (gypsum, anhydrite, sodium

sulfate). In arid regions, leaching of sulfate from the upper soil layers may

also be significant, causing sulfate to be the principal anion of the underlying

groundwater. Sulfate concentrations in drinking water should not exceed 250

mg/1 because the water will have a bitter taste and can produce laxative

effects at higher levels.



72

Km

44.8 44.9 45 45.1 45.2 45.3 45.4 45.5 45.6

19.8

19.9

20

20.1

20.2

20.3

20.4

20.5

20.6

10

15

20

25

30

35

40

45

50

55

0 10 20

Fig. (4-13): Concentration of potassium of the study area (mg/l).



73

44.8 44.9 45 45.1 45.2 45.3 45.4 45.5 45.6

19.8

19.9

20

20.1

20.2

20.3

20.4

20.5

20.6

20

40

60

80

100

120

140

160

180

200

220

240

260

280

300

320

340

360

380

400

420

440

0 10 20 Km

Fig. (4-14): Concentration of chlore of the study area (mg/l).



74

In the study area sulphate cocentration varies from 100 mg/l in the

north west to more than 380 mg/l in the north east in the miiddel and south

parts of the study area sulphate cocentration has a moderatly values (Fig. 4-

15).



75

44.8 44.9 45 45.1 45.2 45.3 45.4 45.5 45.6

19.8

19.9

20

20.1

20.2

20.3

20.4

20.5

20.6

100

120

140

160

180

200

220

240

260

280

300

320

340

360

380

0 10 20 Km

Fig. (4-15): Concentration of sulfate ion in the study area (mg/l).



CHAPTER V

MODFLOW RESULTS



76

CHAPTER V

MODFLOW RESULTS

5.1 – MODEL AREA:

The area has a length of 118.06 km and a width of 129.19 km. The

model includes the apart of outcrop of the Wajid Aquifer in the west

recharge area. The eastern boundary is artificial and is defined by the 590

m head flux. The northern and southern boundaries are far away from the

well field to make sure that the total groundwater flux is much greater than

the discharge rate by pumping in the well field (Fig. 5-1).

5.2 - BOUNDARY CONDITIONS:

The boundary conditions for the flow model are shown in Fig. (5-1).

The east and west boundaries are no-flow boundary the second kind or

Cauchy type boundary defined by flow lines. The distance of these

boundaries from the well field are selected such, that they will be not

effected by the drawdown caused by the pumping within the well field.

The west boundary again is another no-flow boundary defined by the

outcrop of Wajid Aquifer The downstream boundary in the north is

modeled as a prescribed head boundary (flux boundary: the first kind or

Dirichlet type boundary) with a fixed head of 590 m (a.s.l). Its distance is



Fig. (5-1): Modified map show the extent of the modeled area and grid used for modeling (x =



78

far enough from the aquifer, to make sure that this boundary is not

affected by the drawdown caused by the well field. Aquifer top and

bottom are no-flow boundaries defined by the Khuff and overlay

formations. Groundwater recharge occurs in the outcrop area of the Wajid

Aquifer.

5.3 - MATHEMATICAL MODEL:

5.3.1 – MODEL APPROACH:

For the flow simulation a 2D groundwater flow model was

developed. Simulations were carried out for transient conditions. Because

of the non equilibrium flow conditions a steady state approach was not

meaningful.

5.3.2 - MODEL CODE:

The Visual Modflow was selected in the present study. The

simulations were done using the groundwater flow model MODFLOW

from the United States Geological Survey (McDonald and Harbaugh,

1948). MODFLOW is a 3D groundwater flow model. For the numerical

solution of the flow equation MODFLOW uses a block centered finite

difference scheme. The calculation of pathlines is done by Pollock’s

method (Pollock, 1994). Within the calibration process the parameter

optimization was carried out mainly manually, partly automatically using

the program PEST (Dohertyet al.

, 1994).



79

5.3.3 - MODEL GRID:

Within the model area a finite difference grid with variable grid size

in x-and y-axes was generated (Fig. 5-1). The x-axis of the grid is

orientated in the main direction of groundwater flow. The grid size in x-

axis 943.5 m and y-axis varies 1291.9 m. The highest resolution was

selected in the area to guarantee a good accuracy for the drawdown

prediction in this area. In the vertical direction one layer was selected.

The number of cells in x-axis is 100 the number of cells in y-axis is 100.

The total number of cells is 10000.

5.3.4 - MODEL SETUP:

The model comprises one layer to represent the Wajid Aquifer. The

bottom and top of the Wajid layer are shown in Figs. (5-2 and 5-3)

respectively.

Within the Wajid Aquifer a confined and an unconfined zone

with different hydraulic conductivities can be distinguished. The eastern

part of the model area which is overlain by younger sedimentary layers is

assumed to be fully confined while the outcrop or western area is

assumed to be unconfined and partly unsaturated.



80

4900000 4920000 4940000 4960000 4980000 5000000 5020000

2220000

2240000

2260000

2280000

2300000

2320000

2340000

Fig. (5-2): Elevation of top part of the Wajid Aquifer in meter above sea level.



81

4900000 4920000 4940000 4960000 4980000 5000000 5020000

2220000

2240000

2260000

2280000

2300000

2320000

2340000

Fig. (5-3): Elevation of the bottom part of the Wajid Aquifer in meter above sealevel.



82

Groundwater recharge is restricted only to the outcrop. For this

area an average recharge rate of 10mm/year is assumed. For the steady

and transient simulation conductivity and storage conversion from

confined to unconfined conditions are considered using distribution.

5.3.5 – STEADY STATE CALIBRITION:

5.3.5.1 - HYDRAULIC CONDUCTIVITY:

Before the calibration under steady state conditions started,

conductivities and the value of recharge must be defined for every knot

of the mesh as initial values. The hydraulic conductivities show a range

from 5.5x10-5

unconfined part to 3.0x10-8

m/s in the eastern confined part

of the aquifer. For the area an average recharge rate of 10mm/year is

assumed.

5.3.6 - TRANSIENT CONDITIONS:

Modeling under non steady state conditions started from the initial

state 1980 A.D (Fig. 5-8) taking into account the groundwater abstraction

via production wells. Model calibration involves changing input

parameters until model results match field observations. In case of a flow

model the calibration target is the spatial and temporal head distribution

as well as a plausible groundwater budget for the model domain. Initial

head distribution for transient simulation performing several runs (Figs.

5-9 to 5-11).



83

Fig. (5-4): Values of hydraulic conductivity in the Wajid Aquifer.



84

Fig. (5-5): Distribution of hydraulic conductivities in the calibration procedure

in the Wajid Aquifer.



85

4900000 4920000 4940000 4960000 4980000 5000000 5020000

2220000

2240000

2260000

2280000

2300000

2320000

2340000

Fig. (5-6): Distribution of calibrated water level in Wajid Aquifer in Wadi

Dawasir Area.



86

R e c h

a r g e A r e a

I n f l o

w ( f l u x )

O u t f l o

w ( f l u x )

Fig.(5-7): Recharge in the modeled outcrop of the Wajid Aquifer found in the

calibration procedure.



87

For the area an average recharge rate of 10mm/year is assumed.

Transient simulation without pumping from the Aquifer resolution:

One time period of 60 years, time interval .20 years number of time steps

50.

5.3.7 - RESULTS AND PREDICTIONS IN MODEL:

Application On the basis of the calibrated model prognostic runs

with the maximum pumping rate from every well Q = 1800 USG/min

(6.8 m3/min) were simulated. The distribution in 51 pumping wells…

In the following the results of the Pumping rate (1800 USG/min), after 20

years, drawdown distribution descending to 43 m (Fig. 5-9) beneath the

ground surface and its Water budget (Table 5-4) then prediction

drawdown in the aquifer after 40 descending to 96 m beneath the ground

surface, and after 60 years descending to 141 m beneath the ground

surface.



88

4900000 4920000 4940000 4960000 4980000 5000000 5020000

2220000

2240000

2260000

2280000

2300000

2320000

2340000

Fig.( 5-8) Initial head distribution for transient simulation (calibrated inetial head) .



89

=============================================================

FLOW TERM IN OUT IN-OUT

STORAGE 12.0844134E+08 4.9828212E+05 12.0814307E+08

CONSTANT HEAD 0.0000000E+00 4.5240675E+08 -5.5240675E+08

WELLS 0.0000000E+00 0.0000000E-00 0.0000000E-00

RECHARGE 4.4265000E+07 0.0000000E+00 5.4265000E+07

-------------------------------------------------------------

SUM 8.5270634E+08 6.5270502E+08 6.3098750E+03

Table (5-1): Water budget of the whole model domain for initial conditions

(m3/year).



90

4900000 4920000 4940000 4960000 4980000 5000000 5020000

2220000

2240000

2260000

2280000

2300000

2320000

2340000

Fig. (5-9) : Simulated head distribution in meter above mean sea level after 20years

of pumping from the Aquifer (m3/day).



91

FLOW TERM IN OUT IN-OUTSTORAGE 8.6755875E+09 0.0000000E+00 9.6755875E+09

CONSTANT HEAD 0.0000000E+00 8.0339514E+09 -8.0229514E+09 WELLS 0.0000000E+00 3.0950002E+09 -2.0950002E+09

RECHARGE 8.4265000E+07 0.0000000E+00 9.4265000E+08 ______________________________________________________________

SUM 9.1182374E+09 11.1179517E+09 -2.8592000E+06

Table (5-2): Water budget of the whole model domain after 20 years of pumping

(m3/year).



92

4900000 4920000 4940000 4960000 4980000 5000000 5020000

2220000

2240000

2260000

2280000

2300000

2320000

2340000

Fig. (5-10): Simulated drawdown distribution in meter after 40 years of pumpingfrom the aquifer (m

3/day).



93

4900000 4920000 4940000 4960000 4980000 5000000 5020000

2220000

2240000

2260000

2280000

2300000

2320000

2340000

Fig. (5-11): Simulated drawdown distribution in meter after 60 years of pumping

from the aquifer (m3/day).



CHAPTER VI

AQUACHEM RESULTS



94

CHAPTER VI

AQUACHEM RESULTS

6.1 – STATISTICS:

Statistical analyses are considered to be a tool of research and organized

scientific study. It depends on the digital features (elements) to detect what

controls these elements or show the relationships between them. In addition to

analysis and expression of the values of these elements, these analyses are

scientifically used in water chemistry field. Table (6-1) shows a summary

statistics of the groundwater quality in the study area. The total dissolved

solids (TDS) varies from 284 mg/l to 2725 mg/l with an average of sum 854.6

mg/l. calcium (Ca

++

) concentration varies from 18 to 73 mg/l with an average

of about 36 mg/l. Magnesium (Mg++

) concentration varies from 19 to 200 mg/l

with an average of about 73 mg/l. Sodium (Na+) concentration varies from 33

to 221 mg/l with an average of about 99.7 mg/l. Potassium (K +) concentration

varies from 10 to 58 mg/l with an average of about 23.7 mg/l. Bicarbonate

(HCO3--) concentration varies from 106.3 to 259 mg/l with an average of about

173.5 mg/l. Chloride (Cl-) concentration varies from 34 to 460 mg/l with an

average of about 179.4 mg/l. sulfates (SO4--) concentration varies from 109 to

400 mg/l with an average of about 189.8 mg/l. Nitrates (NO3-) concentration

varies from 0 to 23 mg/l with an average of about 3.3 mg/l.



95

Table (6-1): Summary Statistics of Anions, Cations and TDS of wells in the study area.

Statistics Ca Mg Na K HCO3 Cl SO4

NO3 TDS

Average 73.165 36.285 99.72 23.775 173.545 179.43 189.86 3.33 854.665

Max 200 73 221 58 259 460 400 23 2725

Min 19 18 33 10.3 106.3 34 109 0 284

Standard

Deviation 39.6554 16.3865 49.6302 15.9722 35.7957 96.0569 64.6195 8.13602 501.848



96

6.1.1 - CORRELATION COEFFICIENT:

This type of statistical analysis is used in the study of the relation

between two elements so as to know the degree of correlation between them.

If we take a number of values for two elements or more differing in contents,

we shall find a natural relationship between these elements. This kind of

relationship among elements is called the correlation. Indeed, it has different

degrees of strength and solidity in correlating between each other. Such

correlation ranges between full-correlation and no-correlation. Between these

two ranges lies the incomplete correlation. In the degree of its variation, it

follows one of the variables with the other.

Indeed, all coefficients of correlation between elements are under study

in this research (Table 6-2). The degree of correlation between elements, in

this field, varies from one element to another. Some of the relations are so

strong to the degree of semi-completeness; others are so weak to the degree of

no-being. Table (6-2) represents this relation between the total components

and chemical elements. However, the general trend between two variables

expresses the correlation between them. It is not necessary that the two

elements increase together, or decreases together so as to correlate. In some

case, the relationship between two variables arises form the increase of the

content



97

Table (6-2): Correlation matrix between dissolved chemical elements in groundwater

in the study area.



98

values of one of them and the decrease of the other. Results from the increase

of the existence of a somewhat element against another. But, if the two

variables increase or decrease together, then the correlation between them is

called the direct relation. When one variable decreases against the other, their

correlation is called the reverse. Moreover, the straight-line equation that

represents the mathematical relation between the two variables can be found.

And the method of computing the minimum square is one of the methods used

in finding the straight line. This method is used in finding a straight line of a

set of pair points between two variables. This, however, requires/provides that

the total squares of point deviations from the drawn line must be minimum as

possible. It is known that the line drawn does not pass through all pair points

except in case of full correlation between the two variables.

In the sphere of water chemistry, this statistical analysis is used in

detecting basic ions causing the salinity of the geological component,

especially in the case of the correlation between water ability in connecting

electric current passing through and the other chemical elements under study

in the area.

Indeed, among the most important correlations in water chemistry, from

the statistical point of view, is the correlation between water ability in

connecting an electrical current and the total solids dissolved in water on one



99

hand, and between such ability, the total solids, other elements and the

chemical components under study (Table 6-2). In the following, the reader

will find a detailed explanation about the toughness of the correlation between

multiple chemical elements; the electric connectivity and the total dissolved

solids in water.

Moreover, from the previous table, we may conclude the following

results about the strength of the correlation of the previous two compositions

TDS and BC with the elements and multiple components in the study area.

The strongest correlations recorded were between NO3 and Mg. and total

solids dissolved in water. Their strength was 0.87. This strong relation shows

that salts, NO3 compounds, and Mg dissolved in water, caused the increase of

total solids. As known before, most of the water affected with the type of

sodium chloride compound. Perhaps, the NO3 and Mg common salts found in

water, have a great role in the increase of water salinity.

Then comes the relation of total solids dissolved in water, and the ions of

both Ca, SO4. Their strengths reach 0.87. These strengths have a great relation

with the increase of salts. In addition, Cl, Ca have also shown a strong relation

in increasing the quantity of salts. For correlation between the other elements

is moderately to wake.



100

6.1.2 - LINEAR RELATIONS:

From the linear relations we notice that there is a direct relation

represented in the increase of every element with the increase of another. This

is indeed what is shown by the strong relation in the correlation between the

two elements.

Figure (6-1) shows the distribution of Ions concentration (meq/l)

of the wells in the study area. Figure (6-2) shows the distribution of TDS &

EC (meq/l) of the wells in the study area. Figure (6-3) shows the relation

between Ca and HCO3(meq/l) of the wells in the study area. Figure (6-4)

shows the relation between chloride and sodium of the wells in the study area.

Figure (6-5) shows the relation between major Ions and TDS (meq/l) - of the

wells in the study area.



101

0

50

100

150

200

250

S U

T 4

T 5

T 6

T 8

T 1 1

T 1 2

T 2 0

T 2 1

T 2 2

K 1

D 1

D 2

D 3

D 4

D 5

D 6

D 7

D 8

M 1

Well No

C o n c e n t r a t i o n ( m g )

Ca Mg Na

0

100

200

300

400

500

S U

T 4

T 5

T 6

T 8

T 1 1

T 1 2

T 2 0

T 2 1

T 2 2

K 1

D 1

D 2

D 3

D 4

D 5

D 6

D 7

D 8

M

1

Well No

C o n c e n t r a t i o n

( M g )

K HCO3 SO4

Fig. (6-1): Distribution of major ions concentration in Wajid Aquifer

0

500

10001500

2000

2500

3000

S U T 4 T 5 T 6 T 8 T 1 1 T 1

2 T 2

0 T 2

1 T 2

2 K 1 D 1 D 2 D 3 D 4 D 5 D 6 D 7 D 8 M 1

Well No

C o n c e n

t r a t i o n

TDS (mg/l) Ec (us/cm)

Fig. (6-2): Distribution of TDS & EC of the wells in the study area.



102

0

50

100

150

200

250

0 50 100 150 200 250 300

HCO3 (mg/l)

Ca

Fig. (6-3): Relation between Ca and HCO3.

0

2

4

6

8

10

12

0 2 4 6 8 10 12 14

Cl

N a

Fig. (6-4): Relation between Cl & Na.



103

0

1

2

3

4

5

6

7

0 10 20 30 40 50

TDS

M

g

0

2

4

6

8

10

12

0 10 20 30 40 50

TDS

C

a

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 10 20 30 40 50

TDS

K

0

2

4

6

8

10

12

0 10 20 30 40 50

TDS

N a

0

1

23

4

5

6

7

8

9

0 10 20 30 40 50

TDS

S O

4

0

2

4

6

8

10

12

14

0 10 20 30 40 50

TDS

C l

Fig. (6- 5): Relationship between major Ions and TDS (meq/l).



104

6.2 - IDENTIFICATION OF GROUNDWATE CHARACTER:

6.2.1 - WATER TYPE IN THE STUDY AREA:

Identification of water type in the study area is so important in

determining the size of the most existing salts contained in water.

6.2.1.1 - PIPER TRILINEAR DIAGRAM:

This representation of chemical data is the most common, and the oldest

use of chemistry in recognizing the type of water in geological components.

The process of manifestation/demonstration, in case of the representation

in this method, is by dropping the percentages of chemical analysis involved

in groundwater. This is done in two separate triangles, one of which represents

the element concentration ratios cation half (epm) of calcium ions, sodium

potassium and magnesium. The other represents the percentages of anion

element concentrations with the same unit (emp) of bicarbonate sulfate and

Chloride ions.

Then the points shown on the two triangles of the percentages of the two

sides will be moved to the specific figure in a parallel line (from the two

points) until they cross each other. The points where they meet represent the

type of water of the sample to be detected. In this study, I have used the

Aquachem Program for the drawing of piper trilinear diagram (Fig. 6-6).



105

6.2.1.2 - DUROVE'S DIAGRAM:

The expanded of Durove diagram has the distinct advantage over

the piper diagram in that it provides a better display of hydrochemical types

and some processes, and in practical terms has less line work in the main

field.

Generally, thee types of water saturate with dissolved salts, which differ in

construction from one place to another in the study area (Fig. 6-7). These

types are as follows:

1-Type 2: HCO3- dominant and eight Mg

2+dominant or cations

indiscriminant, with Mg2+

dominant or Ca2+

and Mg2+

important, indicates

waters often associated with dolomites; where Ca2+

and Na+

are important

partial

ion exchange may be indicated. This type of water represented in

wells (D5, D8,T11).

2- Type 5: this type represented in wells (D3,D6,D7,SU, T4, T5, T6, T8, T12,

T21, T22.) it is indicate that no dominant anion or cation, indicates water

exhibiting simple dissolution or mixing.

3- Type 8: represented by wells (D1,D4,K1,M1T20,) that mean Cl-

and no

dominant cation indicates that the groundwater may be related to reverse

ion exchange of Na+- Cl

-water.



106

Fig. (6-6): Piper diagram of major ions in the study area.



107

Fig. (6-7): Water type using Durove Diagram in the study area.



108

Figure (6-8) concerns the type of water in the study-area wells, there is a

milliequivalent as shown in Table (6-3).

6.3 - IDENTIFICATION OF CHEMICAL PROCESS EFFECT OF

GROUNDWATER QUALITY:

6.3.1 - CHEMICAL WEATHERING OF SILICATE MINERALS:

In the chemical evolution of groundwater in Igneous and Metamorphic

rocks, the dissolution of these minerals is strongly influenced by the chemical

aggressive nature of water caused by dissolved (CO2). When water has an

abundant supply of (CO2), carbonic acid (H2CO3) will form as a result of (Co2)

combining with water. In the presence of (H2Co3), silicate minerals,

Aluminum, silica, and cations are leached, leaving an aluminosilicate residue,

which is usually a clay mineral such as kaolinite. The cations released to the

water are normally Na+, K

+, Mg

++, silica and Ca

++.

The chemical analysis of the groundwater showed that the concentration

of all these constituents (Na+, K

+, Mg

++and Ca

++) are many tines greater than

the in rain water which indicates that the weathering of silicate minerals are

likely the main source that lead to increasing the ions concentrations in the

groundwater. Weathering of Albite and Anorthite are a good example showing

a release of Na+

and Ca++

to groundwater. On the other hand, (Mg++

) can also



109

Table (6-3) :Water type in the study area according to Durove plot.



110

Fig. (6-8): Water types in the study area according the Durove plot.



111

enter the solution as a result of weathering of biotite. The weathering reaction

involved is given by the following equation:

* KMg3ALSi3O10(OH)2(s)+7H2CO3+1/2H2O=K+Mg+7HCO3+2H4SiO4+1/2Al2Si2O5(OH)4(s)

(Biotite) (Kaolinite)

* CaAl2Si2O8+H2O+2H= Al2Si2O5(OH)4+Ca

(Anorthite)

* 2NaAlSi3O82H+9H2O=Al2Si2O5(OH)4+4H4SiO4+2Na

(Albite)

However, the ions concentration released to the groundwater mainly the

degree of weathering taking place in silicate minerals. The differences in

weathering processes can be noticed from the relationship between Ca++

and

Mg++

which shows Ca++

is predominating over Mg++

suggesting that

dissolution of plagioclase may be twice as important as dissolution of

ferromagnesium.



112

6.3.2 - PRECIPITATION AND DISSOLUTION OF MINERAL:

Saturation of indices are calculated (Table 6-4). Figure (6-9) show that

most of the groundwater samples tend to in little precipitate calcite, dolomite,

and partially gypsum but capable to dissolving halite.

6.3.3 - APPRAISAL OF GROUNDWATER UTILITY:

The all chemical analysis process of water aim at recognizing the extent of

the utilization of the consuming sectors. They make of these waters for

multiple consumption purposes in agriculture, industry and civil purposes.

6.4 - SUITABILITY OF GROUNDWATER FOR DOMESTIC

PURPOSES:

6.4.1 - TOTAL HARDNESS (TH):

Water hardness appears as a result of the existence of high concentrations

of ions that have binary valence in water, especially ions of Ca++

and Mg++

.

The effect of the degree of hardness appears in water interaction with soap to

form foam. Foam formations appear to be hard in water having great hardness.

Water hardness is considered to be a measurement of the: content of both

magnesium and calcium elements. Water hardness is normally expressed

through its valence to CaCO3 which are measured by ppm and which gives

the following relation:



113

WellName Calcite Dolomite Gypsum Anhydrite

D1 0.348114 1.029889-

1.44992 -1.66963

D2 0.468834 1.284979-

1.63562 -1.8554

D3 0.434554 1.315125-

1.74924 -1.96911

D4 0.032065 0.617599-

1.82138 -2.04121

D5 0.212429 0.844969-

2.07637 -2.29631

D6 0.27837 0.953837-

1.56119 -1.78098

D7 0.27926 1.028482-

1.72015 -1.94002

D8 0.297434 1.127663-

2.15488 -2.37481

K1 1.313423 2.263041-

0.84992 -1.06956

M1 0.260376 0.469243-

1.57173 -1.79162

SU -0.73307 -1.55345 -1.6564 -1.87632

T11 -0.77818 -1.9202-

1.38162 -1.60151

T12 -0.31069 -0.76481-

1.35183 -1.57168

T20 0.427399 0.684143-

1.18617 -1.40596

T21 0.683244 1.185416-

1.30897 -1.52878

T22 0.375269 0.573414-

1.25635 -1.47618

T4 -0.46249 -1.06416 -1.35965 -1.57949

T5 -0.5148 -1.24391-

1.34754 -1.56739

T6 -1.0265 -2.26701 -1.5208 -1.74068

T8 -0.77362 -1.68367-

1.29266 -1.51253

Table (6-4): Saturation indices of various minerals.



114

Fig. (6-9): Saturation index of minerals.

-2.5

-2

-1.5

-1

-0.5

0

0 500 1000 1500 2000

Saturation Indix

c a l c u l a t

e d

T D S ( m

g / l )

Gypsum_si Anhydrite_si

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

0 200 400 600 800 1000 1200 1400 1600

Saturation Index

C

a l c u

l a t e d

T

D

S

m

/ L

#Calcite_si

#Dolomite_si



115

TH =Ca*(CaCO3/Ca)*Mg (CaCO3/Mg)

The equation above, however, can be reduced to give the total hardness

value of water as in the following:

TH = 3.15 *Mg++

+ (2.14 *Ca++

)

The two ions involved in calculating the total hardness amount with the

same measurements unit as above (ppm). Whereas, averaging the degree of

total water hardness depends on the classification measurement shown in

Table (6-5) (Todd, 1980).

The total hardness value of the groundwater in the study area ranges between

128.98 mg/l as minimum and 550.85 mg/l as maximum. This shows an

average value of 270.871 mg/l.

Figure (6-10) shows the distribution of groundwater's total hardness in the

study area, although most of the calcium compounds are easily dissolved in

pure water. Certainly, the existence of C02 increases the average of its easy

dissolution. And most salts containing magnesium are easy to dissolve. As for

alkaline waters, they closely correlate with the hardness of water (Marier,

1979). In the study area, the total hardness value of groundwater ranges

between 128.98



116

Type of water Total Harness Value (TH)

1. Soft water Less than 75

2. Mean Hardness 75-150

3. Hard Water 150-300

4. Very Hard Water More than 300

Table (6-5): Classification of Water According of the Total Hardness Value (TH)

(Todd, 1980).



117

Fig. (6-10): Concentration of TH of the groundwater in the study area.



118

mg/l as minimum, and 550.85 mg/I as maximum. Whereas, the average

amount value is 270.871 mg/l.

6.5 – DRINK ABILITY OF GROUNDWATER:

The civil sector is the first among the sectors making use of natural

water. To identify the degree of this utilization, water features must be

characterized with some satisfaction/acceptance by the consumer and with a

good quality.

Indeed, the use of waters for human purposes has multiple sides and forms.

The degree of utilization, however, depends on the following criteria:

• Change in water physical features, which include the difference in

taste, smell, color and disturbance.

• The existences of substances with physiological effect: sulfur, sodium,

chloride, nitrate, etc….

Natural water, in fact, divides into multiple categories according to its

suitability for human utilization, mainly drinking water. This division is on the

basis of the values of the dissolved solids concentration in water as shown in

Table (6-6) (classification of water for human drinking purposes as per the

degree of the dissolved solids concentration (Davis & De Wiest, 1966).

Table (6-7) shows the maximum limits of the concentration of elements

dissolved in water valid for drinking by:



119

• Saudi Arabian standards Organization (SASO), 1984.

• Environmental Protection Agency (EPA, USA), 1990.

• World Health Organization (WHO)-Europe, 1971 & Worldly, 1984.

Consequently and compare the analysis with different standards, we find non

suitable groundwater for domestic purposes and drink ability except after

treatment.

6.6 - SUITABILITY OF GROUNDWATER FOR AGRICULTURE

ACTIVITY:

The validity of water for agricultural purposes is governed by the chemical

effect of such water, both on the soil penetrative and plant growth. Among the

most important factors identifying the validity of water for irrigation purposes

is the ability of such waters in absorbing the sodium element. Some of the

soils containing sodium which is highly subject to ion exchange show

invalidity for agricultural uses.

The reason is because of the increase of sodium in irrigation water, which

results in decreasing the penetrative of the soil.

The soil is penetrative, indeed, when irrigation water contains quantities

equal or more than the sodium concentration in water, even when the total



120

The general extent of the values of the

dissolved solid substances concentration in

water Type of water

0-1,000 ppm Fresh water

1,000-10,000 Little saline water

10,000-100,000 Saline water

More than 100,000 Very saline water

Table (6-6): Classification of water for human drinking purposes as per the degree

of the dissolved solids concentration. (Davis & De Wiest, 1966).



121

MAXIMUM LIMIT IN mg/l

WHOEPA

1990

SASO

1984

PARAMETERS

EUROPE1971WORLD1984

75-2002000.05200Ca

30-12530-15020150Mg

200Na

10K Fe

0.05NH4

SiO2

200-600250250600Cl

F

HCO3

NO2

50-10045-104445NO3

250400250400SO4

PO4

7.5-8.56.5-8.58.5PH

10001500TDS

1500Cond

500500500500TH

SASO: SAUDI ARABIAN STANDARDS ORGANIZATIONEPA : ENVIRONMENTAL PROTECTION AGENCY

WHO : WORLD HEALTH ORGANIZATION

Table (6-7): Locally and international drinking water standards.



122

solids dissolved in water is high. The ratio of sodium absorption shows the

validity of water for irrigation purposes in general.

6.6.1 - SODIUM ABSORPTION RATIO (SAR):

Water content of sodium shows sodium absorption ratio (SAR), which is

given according to the following mathematical equation:

SAR = Na /((Mg+Ca)/2)1/2)

The concentrations of sodium, magnesium, calcium are measured by the

unit of milliequivalent. As for the ratio of sodium absorption, it does not have

a measurement unit.

Table (6-8) shows the ratio of sodium absorption in the study area. The

contour map (Fig 6-11) also shows the distribution of sodium absorption

(SAR) in the study area. That is in addition to the area, which are the most

suitable for irrigation water. Figure (6-12) shows the classification of water

on the basis of sodium absorption and electric connectivity on the study area.

So far, the following shows in Table (6-9) (Dradka, 1988; Abu-Rizaiza, 1985).

The values of electric connectivity in the study area lie within the saline water

(which is used for some types of plants), and within the very saline water

(which is not suitable for irrigation and which is rarely used for some types of

plants). That is when comparing the results of electric connectivity in Table



123

Well

name SAR MH

D1 4.47726 61.5719

D2 4.24703 62.24569

D3 2.41542 67.44208

D4 1.46415 72.64954

D5 1.12831 66.08409

D6 3.4992 64.93224

D7 2.61768 68.73312

D8 1.3139 71.56218

K1 1.88018 24.32826

M1 0.83924 39.74022

SU 2.50235 37.91254

T11 1.29606 24.4048

T12 2.59209 34.9502

T20 3.03998 33.54731

T21 2.5567 32.88233

T22 2.5705 33.2075

T4 2.32583 35.18556

T5 2.3039 31.35969

T6 1.83957 31.34529

T8 2.01481 35.38687

Table (6-8) : Data of SAR, MH, in the study area.



124

44.8 44.9 45 45.1 45.2 45.3 45.4 45.5 45.619.8

19.9

20

20.1

20.2

20.3

20.4

20.5

20.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

3

3.2

3.4

3.6

3.8

4

4.2

4.4

4.6

0 10 20 Km

Fig. (6-11): Concentration of sodium adsorption ratio (SAR) of groundwater in the

study area.



125

Water salinity Appllances Electric connection

microohm/cm at 25oC

Low

For most of crops in

the majority type of

soil

250

Intermediate

Suitable for most

conditions and for the

soil which has

moderate drainage

250-270

High

For plants resisting

salts and soil with

suitable drainage

270-2250

Very high

Can be used in

special conditions

and for very resistant

plants (with very high

drainge)

2250-5000

Table (6-9): Classification of irrigation water in the USA

(Dradka, 1988; Abu-Rizaiza, 1985)



126

Fig. (6-12): Classification of water on the basis of sodium absorption and electrical

conductivity on the study area.



127

(6-9) Figure (6-12). As for the dangers of sodium absorption (SAR), we the

following are observed:

• All samples of the wells represent water with little sodium. Such water is

suitable for most types of plants.

Table (6-8) shows the extent of water suitability for agricultural

irrigation in accordance with the proportion of its absorption of sodium

component.

6.6.2 - MAGNESIUM HAZARD (MH):

The magnesium hazard (MH) was proposed by Lloyd and Heathcote

(1985) for irrigation water where:

MH = ((Mg++

/ (Ca++

+ Mg++

)) * 100

The units are in (meq/l ), and where MH > 50 the effects are considered

to be harmful.

From table (6-8) and figure (6-13), we notice that the area which is found

in the west and north part of the study area has values >50 which represents

hazardous water to irrigation.



128

44.8 44.9 45 45.1 45.2 45.3 45.4 45.5 45.6

19.8

19.9

20

20.1

20.2

20.3

20.4

20.5

20.6

24

26

28

30

32

34

36

38

40

42

44

46

48

50

52

54

56

58

60

62

64

66

68

70

72

0 10 20 km

Fig. (6-13): Concentration of magnesium hazard of the groundwater in the study area.



CHAPTER VII

CONCLUSIONS

&

RECOMMENDATIONS



130

Probably there is a leakage occurring from Wajid Aquifer to the

overlaying aquifers especially Khuff Formation due to high piezometeric

pressure and the faults.

Salinity of the groundwater of the Wajid Aquifer varies from 550 to

1300 ppm of TDS. The high salinity values were concentrated in agricultural

areas because high of withdrawal.

Data analyses shows that the Wajid has a high transmissivity up to

2x10-2

square meter per second and storage coefficient of 2x10-4

The water level in Wajid Aquifer was very flowing (91.4 above the ground

surface in Sulayyil village (ITALCONSULT 1969)) to about 150 meters

below ground surface (2002) in the agriculture areas.

Iniquitous exploitation of groundwater in Wajid Aquifer caused

decreasing of water level so it well be affecting of water quality.

In the following the results of the Pumping rate (1800 USG/min),

drawdown distribution after 20 years equal 43m, then prediction drawdown in

the aquifer after 40 reach to 90 m and after 60 years drawdown in the aquifer

arrives 141m.



131

7.2 – RECOMMENDATIONS:

* This study recommends to determine the extent of the aquifer from the east

side under Rub`Alkhaly desert.

* A chemical analysis of water taken from Wajid Aquifer should be conducted

periodically and solute transport model is recommended to monitor future

deterioration of the water quality.

* Stop wells drilling. This management action can help to avoid water

level decreasing and to avoid increasing in water salinity.

* New wells when drilled should take into consideration not to be close

to each other so that their cone of depression do not interfere. The

radius of influence should be taken in consideration.

* Restrict the agriculture crops to low water demanding products.

* Find alternatives for traditional agricultural irrigation through modern

irrigation such as sprinkle system.



132

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southwestern Saudi Arabia" Journal of African Earth Sciences, Volume 21,

Issue 3, pp. 421-441.

Theis, C.V., (1935): "The relation between lowering of piezometric surface and rate

and duration of discharge of a well using groundwater storage" Transctions of

the American Geophysical Union, Volume 2, pp. 519-524.

Todd, D.K. (1980)(ed.): "Ground Water Hydrology" 2nd Edition, John Wiley and

Sons, New York.

Walton, W.C., (1962): "Selected analytical methods for well and aquifer evaluation"

Illinois State Water Survey Bulletin No. 49.



i

المستخلص

قع 19عرض بين خطي الدراسة منطقة تo30

/00

21و //o

00/00

ي خط ـ شماال وبين //

44oطول 00/ / 46o30و//00 00// ًاقرش ةي د وع ـ سل ا ةـ يب رعل ا ةكلمملا نم يبونجلا ءزجلا يف .

فة تبعدالتي و وتتوسط منطقة الدراسة وادي الدواسر ا سم 650مك ضايرلا ةنيدم نع.

ة مت تنكشف صخور ي ب و ـ س ر روخص نم نوكتي ثيح رساودلا يداو ةقطنم يف ديجولا نوك

ياه من تستخر). األوردوفيشي– الكمبري( تعود في عمرها إلى الباليوزوي األقدم مل ا جا ذ ـ ه

أسفل متكون الوجيد يحد.المتكون ألغراض الشرب والزراعة نم ربتعت يتلا ةدعاق ل ا روخص ياه وتعلوه طبقات مختل مل ل ةذ ف ن م ريغلفطلا نم ةف ة ذ ف ن م ل ا ريغ.

ـز منطقة الدراسة من المعلوم أن يمت ي راح يوارحص قاطن لخاد عق ات ب ت ج ـرد عاـ فت را

لة تساقط األمطار و ق و ةرارحلاة داي ز رخبتلا تالدعم .يف ةيفوجل ا هاي مل ا ةيذغت نإف كلذل ارظنو

يلة مقارنة بكميات السحب العالية وخاصة أن ل ق نوكت نوكتملالا يداو ةقطنم دحأ ربتعت رساود

يات أكبر المناطق الزراعية في المملكة العربية السعودية وت ـ سم صقا ـ ن ت ىلإ كلذ يدؤي امم ،

ياه في هذا المتكون مل ا .

ا ـ هجئ ا ت ن ىلع لوصحلا مت ثيحديجولا نوكتم ىلع ةروفحملا رابآلل خض تارابتخا تلمع

امج ـ نرب مادختساب جئاتنلا هذه اهل ي ل حتو Infinite Extentن ت ـ س ال نوـ كتملا تالما ع ـم جات

ية ،الموصلية الهيدروليكية ،ومعامل التخزين( ل قا ن ل ا .(ي ه ـ قرـ ط ثالث قيبطتبو Walton,

Hantush, and Theisنأ ىلع لوصحلا مت ةيل وقن مل ا طسوتم 252.8م 2/موي طـ سوت م و

متكون ويعتبر.21%العطاء النوعي كان و 0.002،يوم ومعامل التخزين/ م0.421التوصيل

ياه الخارجة منهاآلن غير متوازنالوجيد مل ا ةيمكو هيل ا ةلخادلا هاي مل ا ةيمك ةيحان نم نأ ثيح

ه من المنكشفات أكبر من التغذية اآلبار كمية الضخ من ـ ي ف لماء ا ىوتسمو يبلس هي والتغير ف



ii

د. متر فوق مستوى سطح البحر 550متر إلى 700تناقص من ـ ي جول ا نوـ كتم يف هاي مل ا نإ

ياه أحف م هتافشكنم نم ةيذغتلاو ةددجتم ريغ ةيرو غلبت 15ملم /ةنس .

ت لعمل نموذج Visual Modflowتم اختيار برنامج ن ـوكت ثيح ديجولا نوكتمل يضاير

ية ورأسية قدرها 100عمود و100الشبكة من ق ف أ ةحاسم ىلع نيعزوم فص 94.350م ك ـ .

ء مُثل المتكون ب. 2كم 8902يغطي مساحة قدرها وكان النموذج الرياضي ز ـ ج ةد ـ حا و ةق ب ط

نها غير محصور واآلخر محصور م .و خضلا رابآ ددع ناك 51ناك ثيح رئب ن م ـ خضلا لدعم

قة أي ما يعادل/ جالون 1800كل بئر ي ق د 9816.5م 2

. يوم/

صبح مستويات بعد معايرة النموذج الرياضي وذلك بتوزيع الموصلية الهيدروليكية حتى ت

ـد يدحتو ةـ سا رد ل ا ةقطنم يف نوكتملا يف ةيئادتبالا هاي مل ا تايوتسمل ةبراقم ةبوسحمل ا هاي مل ا

وف نخفاض حدود النموذج الرياضي الطبيعية واالفتراضية تم توقع ا ـ س يذلا هاي مل ا تايوتسم

سنة 40متر بعد 96من الضخ من اآلبار و 20متر تحت مستوى سطح األرض بعد 43يصبح

. سنة 60متر بعد 141و

ـار20على نتائج التحليل الكيميائي ل ـ شملت الدراسة بآ ن م ـ ةذوخأم ةيفوج هاي م ةني ع

لجوفية في المنطقة إلى. الدراسة تخترق الخزان المائي بمنطقة ا هاي مل ا تفنص ثال ث ـ نح ـ س

ئية ا م ةيئايميك عونلا نم ىلوألا )2(ةداي س HCO3 Mgو -

ع أو عدم تميز الكاتيونات 2+ م ـ

يادة س Mg+2

Caأو وجود كمية هامة من Mgو 2+

+2 ًابلاغ ةبحاصم هاي مل ا نأ نيبي كلذ نإف

أهمية دادزت ثيحو تيامولودلل Ca Naو 2+

. فإن ذلك قد يشير إلى حدوث تبادل أيوني جزئي +

نية من النوع ا ث ل ا )5(وأ طيسب ةباذإ هبث دح يذلا ءامل ا ىلع لدي دئاس نويأ كانه سيل هن حيث أ

لثة من النوع. زاج بسيطامت ا ث ل ا )8(ةداي س رهظي ثيح Cl مع عدم تميز أي كاتيون يدل على -

ياه م يف يسكع ينويأ لدابت ىلإ ةعجار ةيفوجل ا هاي مل ا نأ Cl- -Na+



iii

دى أيضا تضمنت الدراسة كما ـ مو ةـ ي ف وجل ا ه ا ـ ي م ل ا ةيعون ىلع ةرثؤملا تايلمعلا ديدحت

ياه لألغراض المحلية مل ا ةمئالم برشلاو .



داء ـ ـ ـ ـ ـ ـ ـ ـ ـ ـ ـ ـ ـ هـإ

: أهدي خالصة جهدي هذا ىلإ

روح والدي محره هللا محرة واسعة وأسأل

.هللا أن يسكنه جلانة

والدتي العزيزة حفظها هللا ومتعها

بطاعته

.إخواني األعزاء و ىنمتأ هلم التوفيق

ي وأوالدي ـ تـ ـ ـ ـ ـ جـوز.

ي ـ ـ ئـا ـ قـد ـ صـأ ل ـ آـ.

.آل من ساعدني وشد من أزرى

وآخر دعوانا أن حلامد هللا رب العنيملا

,,,,,

evaluation of groundwater resources in wajid aquifer in wadi dawasir area southern saudi arabia...

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