Hydrogeology of the Minjur Aquifer System in the Riyadh Region, Saudi Arabia

Western Michigan University ScholarWorks at WMU

Master's Theses Graduate College

4-1979

Ibrahim A. Al-Jallal

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Recommended Citation Al-Jallal, Ibrahim A., "Hydrogeology of the Minjur Aquifer System in the Riyadh Region, Saudi Arabia" (1979). Master's Theses. 1955. https://scholarworks.wmich.edu/masters_theses/1955

This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. HYDROGEOLOGY OF THE MINJUR AQUIFER SYSTEM IN THE RIYADH REGION, SAUDI ARABIA

Ibrahim A. Al-Jallal

A Thesis Submitted to the Faculty of The Graduate College in partial fulfillment of the Degree of Master of Science

Western Michigan University Kalamazoo, Michigan April 1979

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS

I wish to express my sincere thanks to Dr. W. Thomas Straw for his guidance and patient supervision of my work.

Dr. Richard N. Passero and Dr. William B. Harrison III

read the manuscript and offered many helpful suggestions.

Dr. W. David Kuenzi provided some helpful advice. I am especially indebted to Mr. Mohammed Abu Butain, Director

of the Riyadh Water Works and Maintenance for supplying

references available elsewhere, to Dr. Ahmed A. Al-Muhandis

for providing an office space in which to work, to Mr.

Mustafa Nuri, Chairman of the Geology Department, Ministry

of Agriculture and Water for his cooperation, and Mr. Ahmed

Al-Audan, Geologist with the Department forvhis help in

providing access to files and for providing valuable cor

respondence while I was in the United States. Mr. Sulaiman

Abu Mustafa, Geologist, provided valuable assistance and

communicated with me during the course of the study. The

Intairdrill Company provided transportation to the tested

well. To all these people, I extend my deepest thanks.

Ibrahim A. Al-Jallal

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AL-JALLAL, IBRAHIM ABDULLAH HYDROGEOLOGY OF THE MINJUR AQUIFER SYSTEM IN THE RIYADH REGION, SAUDI ARABIA.

WESTERN MICHIGAN UNIVERSITY, M.S., 1979

University Microfilms International s o o n z e e s r o a d , a n n a r b o r , m i 4 8 io 6

@ 1979

IBRAHIM ABDULLAH AL-JALLAL

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS

CHAPTER PAGE I INTRODUCTION ...... 1

Purpose ...... 1 Location ...... 1

Climate ...... 3

Geomorphology and Drainage ...... 5

II GENERAL GEOLOGY ...... 10

Stratigraphy of The A r e a ...... 10

The limestone plateau ...... 10

1. Arab Formation ...... 10 2. Jubailah Formation ...... 10 3. Hanifah Formation ...... 12 4. Tuwaiq Mountain Limestone ...... 12

The marl plain ...... 13

1. Dhruma Formation ...... 13 2. Marrat Formation ...... 13

The sandstone plain to the Arabian Shield ...... 14

Structure of the A r e a ...... 15

Minjur Sandstone ...... 15

L i t h o l o g y ...... 15

Structures and environment ...... 26

Outcrop and thickness ...... 27

Formation contacts ...... 30

A g e ...... 31

III HYDROGEOLOGY OF THE RIYADH REGION ...... 32

iii

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CHAPTER PAGE Ground-Water Occurrence ...... 32 G e n e r a l ...... 32

Unconfined aquifers ...... 32

Confined aquifers ...... 34

IV THE MINJURAQUIFERS ...... 35

Nature of The Aquifer ...... 35

Origin of The Water in The Minjur Aquifer ...... 38

Aquifer Properties ...... 39

P o r o s i t y ...... 39

Specific yield and specific r e t e n t i o n ...... 40

Permeability and transmissibility ...... 41

Storage coefficient ...... 44

Well T e s t ...... 46

Data analyses ...... 59

1. Jacob's method ...... 59 2. Specific capacity, total drawdown, well loss, aquifer loss and well efficiency ...... 61 3. Dupuit formula method ...... 70 4. Eden-Hazel method ...... 71 5. Theis recovery method ...... 72

Other measurements ...... 80

Peizometric Surface ...... 82

Movement of The Water ...... 95

Age of The W a t e r ...... 98

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS (Continued) CHAPTER PAGE

Recharge of The Aquifer ...... 102

Recharge area ...... 102 Precipitation ...... 103

R u n o f f ...... 105

Infiltration ...... 106

Recharge from sand d u n e s ...... 107

Recharge from clay z o n e s ...... 110

Recharge determination ...... 110

Tectonic controls ...... 112

Water Reserves ...... 113

Discharge of The A q u ifer ...... 116

Evaporation...... 116

Transpiration ...... 118

W e l l s ...... 119 Distribution of wells and history of developments ...... 119

Exploitation of wells ...... 122

Water Quality ...... 130

G e n e r a l ...... 130

Salinity distribution ...... 133

Quality at R i y a d h ...... 135

1. Conductivity ...... 135 2. p H ...... 136 3. Bicarbonate...... 136 4. Hardness ...... 136 5. Chloride ...... 137 6. Sulphate ...... 137 7. Fluoride ...... 138

Possibility of contamination ...... 138

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CHAPTER PAGE

Quality of The Minjur New Well fields ...... 143

Quality of shallow aquifers ...... 143

Water Temperature...... 144

Safe Yield and Balance ...... 147

Developments in The Riyadh Water S u p p l y ...... 151

V CONCLUSION ...... 166

VI BIBLIOGRAPHY ...... 169

VII APPENDICES ...... 176 Appendix A ...... 176

Appendix B ...... 177

Appendix C ...... 178

Appendix D ...... 179

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF TABLES

TABLE PAGE

I Selected Climatic Factors for Riyadh in 1970 ...... 4 II Precipitations and Rainy Days in Riyadh .... 6

III Minjur Sandstone Type Section ...... 18

IV a. Sieve Analysis Results for Samples 1 and 2 ...... 25 b. Sieve Analysis Results for Samples 3 and 4 ...... 26

V Upper Minjur Shale and Sandstone Thick ness (m), and Sandstone Percentage of Some Minjur Wells in The Riyadh A r e a ...... 37

VI Transmissibility, Permeability and Storage Coefficient of Minjur Aquifer in The Riyadh A r e a ...... 43

VII a. Pumping Test Data, Step 1, 2, 3 and 4 ...... 47 b. Recovery D a t a ...... 51

VIII Discharge, Specific Drawdown of All Steps . . . 64

IX Selected Values of^Q log (t-t') ...... 73

X Time, Residual Drawdown and t/t' (Recovery) . . 76

XI Temperature and Sample Analysis for Well Sal-8, January 28, 1978 ...... 81

XII Piezometric Altitude (m) of Some Wells in Riyadh Area for 1971, 1980 ...... 93

XIII Age Determination of Water Samples From The Minjur Aquifer ...... 100

XIV Water Reserves Estimates in Minjur A q u i f e r ...... 114

XV Total Production, Number of Wells, Average Water Level of Minjur Wells ...... 123

vii

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TABLE PAGE

XVI Water Quality Standards ...... 132

XVII General Salinity (TDS) Distribution ...... 134

XVIII Water Analysis After Treatment (Averages) ...... 139 XIX Shallow Wells Water Analysis ...... 144 XX Temperature Variation with Depth in KH-A2 Well in Riyadh ...... 145

XXI Percentage of Growth Rate and the Growth of Water Demand ...... 152

XXII Different Figures of Population and Water Consumption of Riyadh ...... 153

XXIII Comparison of Planned Water Production for Riyadh Water Supply and P o p u l a t i o n ...... 156

XXIV Some Information About the New Well Fields in Salbukh and Buaib for Riyadh Water Supply ...... 157

XXV Estimate of Cost of Ground Water Well Fields and Desalination Water from Sea in Millions of Saudi Riyals ...... 165

viii

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF FIGURES

FIGURE PAGE

1. Location Map of Riyadh Area ...... 2

2. Major Wadis in Riyadh A r e a ...... 8

3. Stratigraphy of The A r e a ...... 11

4. Structure of Central Arabia ...... 16

5. Minjur Type Section at Khashn Al-Khaltah . .21

6. a. Grain Size Distribution for Samples 1 and 2 ...... 23 b. Grain Size Distribution for Samples 3 and 4 ...... 23

7. Approximate Thickness of Minjur Sandstone . .29

8. a. DWL (m) Against Time - Step 1 ...... 53 b. DWL (m) Against Time - Step 2 ...... 54 c. DWL (m) Against Time - Step 3 ...... 55 d. DWL (m) Against Time - Step 4 ...... 56 e. DWL (m) Against Time - Re covery ...... 57 f. Step-drawdown Test and Recovery C u r v e s ...... 58

9. Drawdown (m) Against Time - Step 1 (J a cob)...... 60

10. Sw/Q Against Discharge ...... 65

11. a. Coefficient of Transmissibility versus Specific Capacity for Several Values of Well Radius and t ...... 68 b. Diagram for Estimating the T Value from Sp. Cap...... 68

12. Q log (t-t') Against the Drawdown ...... 74

13. Residual Drawdown Against t/t1 - Recovery . . 77

14. Residual Drawdown/Time - Recovery ...... 78

15. Decline of Water Level In Riyadh Wells From 1956 to 1977, Then Predicted to 1980 84

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FIGURE PAGE

16. a. Piezometric Map of Minjur Wells in 1962 ...... 91 b. Sogreah's Piezometric Map 66-67 ...... 91

17. General Piezometric Map for 1971 ...... 94

18. General Piezometric Map for 1980 ...... 96

19. Precipitation Maps a. From Aramco 1960 ...... 104 b. From Dincer and Others 1 9 7 4 ...... 104

20. Minjur Wells Locations in Riyadh Area . . . 120

21. Total Production, Number of Wells, and Average Piezometric Surface of The Minjur Wells in The Riyadh A r e a ...... 125

22. Public Water Supply Wells Distribution . . . 127

23. Accumulation Curve of Production From Minjur W e l l s ...... 130 24. Variation of Temperature with Depth in Well K H - 2 A ...... 146

25. Safe Yield Determination...... 148

with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF APPENDICES

APPENDIX PAGE

A Elevation and Well Hydraulics of The Minjur Wells in Riyadh ...... 176

B Water Level Measurements of Minjur Wells in Riyadh (Meters) ...... 177

C Production of Minjur Wells (1/sec) in Riyadh (1956-1978) ...... 178

D Minjur Wells Water Analysis in R i y a d h ...... 179

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF PLATES

PLATE PAGE

No. 1 General Geology of Riyadh A r e a ...... 181

2 Regional Outcrop of Minjur Sandstone in Central Arabia ...... 182

xii

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INTRODUCTION

Purpose

This investigation is restricted to The Minjur Aquifer

System, the most important source of ground-water for Riyadh,

the largest city in the center of the Arabian Peninsula. Since

The Minjur is and will continue to be an important resource

of water for Riyadh, information concerning this system will

be valuable in planning its developments. In addition, Riyadh

has other less extensive sources such as shallow wells from

unconfined aquifers. The study will consider the nature of

The Minjur Aquifer, occurrence of water, hydraulic properties,

wells, mode of recharge and discharge, water quality and

safe yield.

Location

Riyadh is located at 46° 43 E. longitude and 24° 42 N.

latitude near the center of the Arabian Peninsula, (Figure 1).

The area in which deep wells into the Minjur Sandstone have

been drilled extends beyond the urban area, especially to the

southeast beyond the area of Hayir to the northwest beyond

Dareiyah on the Salbukh Road, east to the National Guard well

and west to Dirab. The area thus described lies between 24° /■ / * >■ 16 , 24°53 N. latitude and 46°35 , 46°57 E. longitude, an

area 33 km in width, and 68 km in length comprising about

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Figure 1 Location Map of Riyadh Area

Iraq

" N r - / V *. : Iran rabl Gulf

SAUDI

“■kiyadh ARABIA

f Red Oman Sudan sea

*\ ------' \ femeA- South Yemen Eritria Arabian Sea

Scale 1:18,000,000

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2250 square Km.

Climate

Because Riyadh lies in the center of the Arabian Penin

sula, isolated from seas and rivers, it has an extremely arid

climate that is hot and dry in the summer and cold in the

winter. The Arabian Peninsula forms a boundary between the

tropical and non-tropical areas. Temperatures in Riyadh

normally reach 40-45° C in the summer (and may reach 50° C).

During summer nights, the temperatures are lower, generally

falling to about 25° C, (Table I). The average winter temp

eratures are 14° C with day time temperatures reaching 20° C

and with night temperatures as low as 0° c. Temperatures of

zero or less have only occurred ten times between 1964 to

1973. Solar radiation reaches 726 Ly/day in the summer, but

only 329 Ly/day in the winter due to the shorter days, in

creased cloud cover, and the inclination of the sun rays.

The atmosphere pressure reaches a maximum of about 1018

millibars in December and a minimum of about 998 millibars in

July, (Table I). The relative humidity is 15 - 20% in the

summer and 40 - 50% in the winter. The clouds are small and

the sky is clear most days of the year, except during the

dusty winds which are common.

Large areas of eolian sand, Muaizylah Banban, lie

within a few kilometers to the north and northeast. At a

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TABLE I

SELECTED CLIMATIC FACTORS FOR RIYADH, 1970 (General Meteorological Department Reported by I.D.C. 1974)

Month Temperature °C Relative % Atm. Wind Max. Min. Humidity Press. Max. Direction Max. Min. (Millibars) (Knots) (Grades)

January 24.6 2 89 16 1016.9 25 320

February 30.4 6.7 83 13 1014.8 38 340

March 36.8 7.6 89 7 1012.5 24 330

April 39.4 13 71 1 1008.7 35 270

May 44 20.1 49 3 1005 40 40

June 43.6 22 19 2 1000.7 28 350

July 43.6 24.2 21 4 998 25 350

August 45.2 23.6 24 5 998.1 25 360 September 41.4 20.4 67 4 1003.2 20 350

October 37.4 13 53 6 1010.9 20 150

November 33.0 11.3 90 10 1015.2 20 180

December 27.7 1.0 89 10 1018.6 21 340

Average 37.26 13.18 62 6.75 1008.6 26.75

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somewhat greater distance, vast areas of wind-blown sand

form such areas as Dahna to the east and Qunaifithah and

Al-Sirr Nafud to the west. Al-Ruba Al-Khali, "the empty

quarter" lies a greater distance to the south. Since Riyadh

is almost completely surrounded by extensive sand deposits,

winds into this area are laden with dust and sand.

Winds are common on most days. In March and April, winds

are out of the southeast passing across the Al-Ruba Al-Khali.

This produces a warm, violent and sandy wind called in Arabic

"Al-Samoom" or very hot. Such winds are followed by north west winds which bring rain during the spring. This is the

most important moist season in Riyadh. The rainy season is

followed by winds out of the north and northwest. The velo

city of winds increases in spring and summer with maximum

recorded velocity of 146 Km/h in May of 1957. The velo

city decreases in winter time and is generally moderate.

The average annual rainfall is 53 - 73 mm (Figure 19),

but it varies from time to time (Table II). The rainy season

is from November to May with a drier period in January. The

period from June to October is completely dry. The evapora

tion rate is very high due to the high temperature and low

relative humidity— especially in the summe r when it may reach

3000 mm per year.

Geomorphology and Drainage

Riyadh is located in the province of Najd, an area of

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TABLE II

PRECIPITATION AND RAINY DAYS IN RIYADH (Ministry of Agriculture and Water Reported by Dincer 1974)

Precipi No. of Precipi No. of Year Month tation Rainy Year Month tation Rainy (mm) Days (mm) Days

1964 1 69 4 1968 11 2 2 1964 2 20 13 1968 12 5 3 1964 4 0.7 1 1969 1 85 17 1964 12 72 7 1969 2 3 2 1965 1 6 4 1969 3 8 5 1965 4 38 10 1969 4 20 6

1966 2 12 4 1969 10 0 - 1966 4 10 5 1969 11 2 4 1966 12 0.1 1 1970 1 7 4 1967 1 0.4 2 1970 3 5 4 1967 2 4 3 1970 12 0.3 1

1967 3 18 6 1971 1 0 -

1967 4 36 9 1971 2 0 -

1967 5 0 - 1971 3 16 8 1967 11 17 10 1971 4 73 8 1968 2 31 5 1972 1 27 6 1968 3 4 2 1972 2 0.5 1 1968 4 44 7 1972 3 49 8

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high desert plains developed on Phanearozoic rocks that dip

gently to the east. Differential erosion of these units

has produced the west-facing escarpments of Central Arabia.

The pediplain of Najd is 580 km wide and interrupted by insel-

bergs of limestone and large Wadis which cut the cuestas.

Riyadh lies at an altitude of 550 to 600 meters on a plateau that slopes gently to the east. A large Wadi, Wadi

Hanifah cuts the plateau and its alluvium has been developed

in an aquifer to supply a portion of Riyadh water. Wadi

Hanifah heads 85 km northwest of Riyadh. The Riyadh area

is drained by Wadi Sahba and Wadi Hanifah is its longest

tributary. Wadi Hanifah had many tributaries, those that join it from the north are Wadi Al-Bat-ha and Wadi Al-Aysan,

from the northwest Wadi Wubayr and Wadi Al-Qaddiyah. From

the est, Wadi Numar, and further south Wadi Luha, (Figure

2). The Wadis Sahba and Hannifah have dentritic drainage

networks with deeply entrenched valleys. The alluvial fill

of these Wadis is gravel with some boulders.

Rainfall plays an important role in the hydrologic system.

It infiltrates to feed the ground water in the alluvial

aquifers which are tapped by shallow wells. Some of the

water that infiltrates is lost to non-exploited fissures.

Most of the water that does not infiltrate is lost to eva- portation which is very high because of the dry, hot climate.

About 50 km west of Riyadh, the high plateau attains an

altitude of about 900 m. Beyond this point, a portion of the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 2 Major Wadiswaais in «±y&uuRiyadh mArea-c « (compiled from Najd k Map, Ministry of Petroleum 1973) . 46 *^4 0 " ns~______Sil______Elevation points in m

R iyadh

Utayagah 622 .

" '""A 1-Manour iy ah

I V 55k ^ N \

s\ 'i V v __

+ ^ A V0> -y Shftb J- 577 25' i • I « & I \ •„ ^ •» ' J ’ Al- Ha'ir y. Scale li 200,000

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Tuwaiq Mountain Limestone has been removed by erosion forming

Tuwaiq Escarpment (Plate No. 1). About 25 Km east of Riyadh

and nearby parallel to the Tuwaiq Escarpment is the Hith

Escarpment. The Limestone plains are interrupted by chains

of hills that are 20 - 25 m high and many kilometers long.

In this general area most of the surface drainage has been

diverted to the subsurface.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. GENERAL GEOLOGY

Stratigraphy of the Area

The limestone plateau

Riyadh is situated on a series of limestones which make

up a plateau that slopes eastward to the Hith Escarpment,

about 25 km away. The plateau extends about 30 km west of

Riyadh to the end of the Tuwaiq Mountain Cliffs. The area

between Riyadh and Hith Escarpment is underlain by the lower

cretaceous, Sulaiy Formation, (Plate 1) a cream-colored

limestone with some coquina beds and some local dolomiti-

zation. The Arab Formation outcrops in the Riyadh area.

In some parts of the Riyadh area, it is overlain by irregu

lar patches of quaternary silt, sand, gravel and limestone

debris from construction.

1. Arab Formation:

Age: Tithonian (Upper Jurassic)

Arab Formation is 124 m thick (Figure 3) and com

posed of oolitic, fine-grained, gray to yellow limestone

with dolomite, anhydrite and marl. This formation pro

duces the most oil in the eastern province of the Arabian

Peninsula.

2. Jubailah Formation: Age: Kimmeridgian (Upper Jurassic) The Jubailah Formation underlies the Arab Formation

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 11 Figure 3 Stratigraphy of Riyadh Area (Modified from Powers et al.) (USGS, 1966)

Thickness m Lithology Legend

Tithonian

Limestone Jubaila

/ / * /V / * J * Kimmendgian //////// Dolomite Oxfordian. Tuwaiq fountain Callovian Lime stone Shale

Cairo vi a.'. XAAJkXAA IAAAA A AAA AAA A A*A. EEEE Bathonian Gypsum

Bajocian B % Sandstone Marrat

Miniur

Jilh

SCALE 1=8000 (Type Section)

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and outcrops west of it. It is composed of about 110 m of

fine-grained and calcarinitic limestone and dolomite with

some sand near the base. The formation can be traced by

bench-like projections of marl in the banks of Wadi Hanifah

which cuts deeply into the formation.

3. Hanifah Formation: Age: Kimmeridgian to Oxfordian (Upper Jurassic)

The Hanifah Formation is about 110 m thick (Figure

3), underlies the Jubailah Formation and continues the pla

teau to the west. It is composed of aphanitic to calcarin-

tic and oolitic limestone, with some marl and shale. The

middle and upper parts of the unit contain some colonial

corals. It also can be recognized in the banks of Wadi

Hanifah by the white bands at its base.

4. Tuwaiq Mountain Limestone: Age: Oxfordian - Callovian (Upper Jurassic)

The Tuwaiq Mountain Limestone underlies the Hanifah

Formation and outcrops to the west of it. It extends about

600 km north and south of the city forming a belt more than

1200 km long with major cliffs facing toward the west. The

top of the cliffs stand 600 m to 1000m above sea level, and

about 500 m above the valley floor. The formation is about

200 m thick and is composed of aphanitic limestone, sub

ordinate calcarenitic limestone and calcarenite. The upper

parts of the unit contain abundant corals and stromatoporoids.

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The formation forms the cliffs which terminate the high limestone plateau on which Riyadh is built.

The marl plain

To the west of the limestone plateau lies a flat marl

plain with small cliffs of more resistant, gray brown, oolitic

or fine-grained limestone. The widespread olive green marl

is cut bydikes and bands of gypsum. The base of the unit

is composed of dolomitic limestone, marl and chert, over-

lain by 40 m of red fissile clay. Lower Jurassic ammonites

have been found near the base.

1. Dhruma Formation:

Age: Bathonian and Bajocian (Middle Jurassic)

The Dhruma Formation is composed of fine-grained limestone, shale and some calcarenite. To the south, the

formation contains increasing amounts of sandstone. The

limestone, including the calcarenite layers and some oolitic

zones in the upper part, lies between two shale units with

interbedded limestone. The entire formation is about 380 m

thick.

2. Marrat Formation:

Age: Toarcian (Lower Jurassic)

The Marrat Formation is about 110 m thick (Figure

3) and is composed of red argillaceous fissile shale be

tween two beds of limestone. The Marrat red shale is thick

est between Shaqra and Khashm Al-Dhibi, and serves as a

marker i>ed beneath Riyadh above the Minjur Sandstone. It

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undergoes a change in facies to sandstone southward. The

red shale is capped by a resistant escarpment forming lime

stone. This unit also undergoes facies change to shale and

then to sandstone southward. The lower part of The Marrat

is mainly limestone southward. The lower part of this mem- -o' ber is mainly sandstone and shale at 24°28 N. latitude.

The upper part of this unit changes to elastics to the south.

The sandstone plain to the Arabian Shield

West of the marl plain lies a sandstone plain developed

on The Minjur and Jilh Sandstones (Plate No. 1). Both forma

tions contain some limestone, shale and gypsum. Middle

Triassic ammonites and fossil wood have both been observed

suggesting that the units may possibly be of both marine

and continental origin in part. The plain stands about

700 m above sea level and the formations that comprise it

are about 600 m thick. West of the sandstone plain lies the Western Marl Plain

which includes the Sudair Shale (Lower Triassic) and Khuff

Limestone (Upper Permian) which serves to confine the over-

lying sandstone aquifers. North, west and south of the Western Marl Plain lies

a series of sandstone formations of a Paleozoic age. The

sandstones are interbedded with shale and limestone. These

units form the base of the Phanerozoic sedimentary sequence.

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West of the sedimentary rocks lies the Precambriam

igneous and metamorphic complex of the Arabian Shield which

extends along the Red Sea coast north, south and east to

near the center of Arabia.

Structure of the Area

The study area lies on the Central Arabian Arch (Figure 4) which is composed of sedimentary rocks arched around The

Arabian Shield. The linear outcrop belts of the Phanerozoic

units form a pronounced eastward salient around this feature.

The eastward dipping sedimentary rocks form the Interior Homocline. Riyadh is located in the central part of this

structure. The strata dip east, northeast and southeast at

1°-1.5°. Where the homocline is exposed, it is represented

by dominant west-facing escarpments, capped by resistant limestone. A graben system, the Central Arabian Graben,

starts near Harad southeast of Riyadh, and extends westward

to pass Al-Dahna, Al-Kharj and Dhruma. It passes Jabal

Tuwaiq then parallels it to the north and then finally

crosses Tuwaiq Mountain near Al-Majmaah. This system is

actually composed of a series of grabens, troughs and

synclinal depressions.

Minjur Sandstone

Lithology: The Minjur Sandstone is a white to brown,

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iS\o^ ,m?e'

od^ 0" 9'0 vef*' fvV,ddeV

,091^ .$$&■iS\oO iduce'd ^ 17

medium to coarse grained, friable to well-indurated, poorly

sorted (Powers, et al., 1966), locally fair to well-sorted

(MacDonald and others, 1975), quartz sandstone with abun

dant crossbedding, indicating transport by wind. The sand

stone ranges from 60 to 90 percent of the total formation.

The shale ranges from 10 to 40 percent of the formation.

These percentages vary from one place to another.

The quartz grains are probably derived from the igneous

and metamorphic rocks of the Arabian Shield. The sphericity

of the larger grains is high. The grains are subangular to

subrounded.

Near the middle of The Minjur Sandstone, there are

significant amounts of shales and mudstone, and very minor

amounts of limestone (Brown, 1962). The shales are gray

and purple with some conglomeratic sandstone, liginite,

marl, ironstone and mudstone. Locally, the shales are inter

bedded with sandstone and they grade upward and downward

into sandstone. The shale beds aer thin ranging up to 5 m.

The limestone is gray and purple (Powers, et al., 1966) and

has gypsum at its base. A full description of the type

section is shown in Table III. See also Figure 5 for Minjur

type section.

Four samples of The Minjur Sandstone have been sieve

analyzed. Two samples, Numbers 1 and 2, are from Umm

Rukbah Well near Riyadh collected at depths of 1812 m and

1939 m respectively. The other two samples, Numbers 3 and

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TABLE III

MINJUR SANDSTONE TYPE SECTION (Source: From Powers, et al., 1966)

Shale of Marrat Formation (Lower Jurassic).

Unconformity.

Minjur Sandstone: Thickness (meters) Sandstone, tan, massive; forms of vertical cliff. Interval measured by theodolite ...... 48.0

Shale and sandstone; complexly interbedded tan to purple silty shale and tan sand stone ...... 4.5

Sandstone, tan, pink-stained, weakly cross bedded , medium-grained ...... 7.0

Shale, buff, spheroidally-weathering ...... 1.0

Sandstone, buff, massive, crossbedded, medium-grained ...... 4.8

Shale, cream, spheroidally-weathering ...... 1.2

Shale and sandstone; purple, tan, and gray variegated shale; several beds of buff, massive, crossbedded sandstone in lower p a r t ...... 10.3

Sandstone, tan, massive, crossbedded, medium- grained; some layers with a white earthy matrix. Common pebble-bearing beds in lower 11 m. Forms vertical cliff ...... 21.1

Sandstone and shale; alternating beds of tan medium-grained crossbedded sandstone and purple and cream sandy shale ...... 13.8

Sandstone, buff, massive, crossbedded, medium- to coarse-grained; common layers with quartz pebbles ...... 15.7

Sandstone and shale; complexly interbedded tan crossbedded sandstone and variegated shale . . . 18.5

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TABLE III (Continued)

Sandstone, buff, massive, crossbedded, medium- to coarse-grained; forms cliffs ...... 12.3

Shale, purple, tan and gray; some snaly sand stone. About 600 m west of measured section interval is replaced by coarse-grained sand stone ...... 10.5

Sandstone, buff, crossbedded, moderately cemented, medium- to coarse-grained; forms weak b e n c h ...... 5.4

Shale and sandstone; purple, light-gray, and tan sandy shale and thinly inter bedded silty sandstone; forms weak ledge. Thin layers of ironstone common in upper p art ...... 9.5

Sandstone - buff, moderately cemented, cross bedded, medium- to coarse-grained; forms weak l e d g e ...... 2.2

Sandstone and shale; light-gray, mottled purple, well-bedded soft silty sandstone and sandy shale; thin scum of ironstone at to p ...... 3.5

Sandstone, light-brown, massive, strongly cross bedded, moderately cemented, coarse-grained; streaks with quartz pebbles common ...... 12.3 Shale and sandstone; tan and purple sandy silty shale and many thin lenses of sandstone; a thin irregular ironstone layer at top. Upper contact shows local relief as great as 3 or 4 m . . . 12.2

Sandstone, buff, pink-weathering, crossbedded; a thin bed of ironstone forms weak bench at top, grades laterally to shaly sandstone ...... 12.6

Shale, purple and gray, sandy and silty; thin beds of ironstone form weak benches 6.3m above base and at top. Lower part grades laterally to sandstone ...... 9.1

Sandstone, red-brown, pink-weathering, cross bedded; locally replaced laterally by sandy shale . . 11.8

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TABLE III (Continued)

Sandstone, red-brown, strongly cross bedded, friable, highly lenticular; some argillaceous silt and sandstone- Thin beds of purple and black ironstone occur at several levels ...... 15.5

Sandstone, red-brown, massive, highly crossbedded, friable; common layers with abundant small pebbles. In general, strongly lenticular. Light- colored lenses. A very thin purple- black ironstone layer caps u n i t ...... 3.7

Sandstone; interval calculated, mainly sand stone; some purple and gray s h a l e ...... 48.5

Total thickness of Minjur Sandstone ...... 315.0

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V o ^ CO . ^ CO

.i] •P o»0 o in ■F K> 01 o 01 »-* o \ tn \ \o tn H CO

I' I' !1 !1 i!i! m m

sandy shale,and shaly sand stone occur® at several levels as thin platy lay ;localy contains molds ses gray, varicolored shale, gray, ers and concretionary mas of fossil wood.(315m) Mutch black to brown iron None MtW i Upper Triassic

Diagnostic fossils: Miniur Sandstone(315m)

is Upper’Triassicis indicates entire section Sporerand pollen in equi valent subsurface interva 1 Sandstone and Shale:Buff fine fine to coarse-grained commonly crossbedded sandlocally calcareuos, stone; Several irregular zones cal cal concretionary masses. dant small quartz pebbles weathers to small spheri of of red,purple,and blue- A few layers contain abun

T H- it H* if O fu H O ti n* (0 a H- rf

O H CD s. a> c/i o» |U Upper in o Ho Hf+ •• p . O H Triassic(?)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 22

4, from Well (5R-140) on Thumama Road, were collected at

1755 - 1758 m and 1779 - 1782 m respectively. The samples contained an average grain size ranging from 0.532 mm in

Sample Number 3 to 0.570 mm in Sample Number 4, to a larger

size of 0.742 mm in Sample Number 1. The grain size dis

tribution of each sample has been plotted (Figure 6, a,b)

and results of the analyses are listed in Table IV.

The parameters of Folk (1974) were computed for Samples

3 and 4. They include the Graphic Mean which represents

the sample's overall average size, the Inclusive Graphic

Standard Deviation ( which indicates the uniformity or

sorting, Skewness or Asymmetry (SK) which measures the

degree of asymmetry of the size curve toward the fine or

the coarse fractions, and the Graphic Kurtosis (KG) which

represents the ratio between the sorting of the curve tails

and the central part fractions (Table IV). Based on these

measurements, a texture name of Samples 3 and 4 of slightly

granular, coarse sandstone, moderately well sorted, fine

skewed, mesokurtic has been applied. The sand percentage

in these two samples is about 99 percent. Larger amounts

of granules are present in Sample 3 than in Sample 4. Samples 1 and 2 have large quantities of mud up to

33 percent. The sand comprises about 67 percent. A small

amount of granules is present in Sample 2. These two

samples differ significantly from the normal probability

curve which results in a straight line. Large portions of

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Figure ^ 6 a. Grain size distribution for samples 1,2

- 95

* 80 Cumulative percent Cumulative 10

■=T

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 24

Figure 6 b. Grain size distribution for samples 3,4 2.9.9 99 .8

■99 ■98

•80

•H .

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. to U1 0 0.11 G CD (d P P CD W P CD O Pi rH G Percent Granules G CD O G O p G CD a P. fd P G P id id CD G P cn cn p t O Mud Percent G cn W OP Q) •H Sand 68.703 31. ^ Percent W CD £ P U) W W M p G . > i p OG E Sand p m •H 0.9 0 66.23 33.66 Median CS3 TABLE IV b m m idp

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 26

the sand size grain may have come from mud aggregates; as a

matter of fact, it took a lot of effort to segregate the

sand from the mud in order to sieve these samples. Methods

of decantation, Calgon solution and ultrasonic vibration

were used for that purpose. The texture name of these

samples, 1 and 2, according only to the percentage of mud

and grain size, is muddy coarse sandstone in Sample Number

1 and slightly granular muddy sandstone in Sample Number 2.

The two samples may not represent the pure sandstone of the

aquifer. The sand grains of all samples are mostly quartz with

sonje rock fragments, most of them made up of shale.

Structures and environment. The Minjur Sandstone dips

east and northeast at 15 m/Km (Otkun, 1972) to reach a

depth of some 1200 m beneath Riyadh. The formation is

cut by several faults that are part of the graben system

of the Central Arabia (Plate No. 1). The faults extend from

Majmaah on the north to Wadi Sahba on the south (Figure 4).

Of the faults, the Dhruma Grabens have the greatest effect

on Riyadh water pumping because they bring the Marrat lime

stone or even Dhruma formation in contact with the permeable

Minjur Sandstone.

Crossbedding and oblique stratification are common, with

some graded bedding. Sedimentologic units 0.75 - 0.9 meters

are cyclic with a basal conglomeratic sandstone (pebbles

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to 2 cm) grading upward through medium and fine sandstone

to sandy siltstone. Ripple marks, mud cracks, and sand

bars are also common.

The sandstone with the interbedded shales have been

interpreted as littoral, continental, deltaic facies

(Powers, 1966 USGS; MacDonald, 1975). The Minjur also has

one or more thin tongues of marine limestone and marl

(Brown, 1963) . Shale, gypsum and limestone suggest a

lagoonal and lacustrine origin.

Outcrop and thickness. The eastward dipping Minjur

Sandstone outcrops for 640 Km some 80 Km west of Riyadh

(Plates No. 1, 2). It outcrops as an arc like other

strata. Near Tabrak, the outcrop belt is 33 Km wide and

it narrows north and south of this point. According to

Powers, et al., 1966 USGS, it has been identified over a

distance of 820 Km between 21°31' and 28°07' N. latitude,

although investigation by Italconsult (1969) indicated that

the arenaceous complex underlying Tuwaiq Mountain is an

extension of the Minjur as far south as 18°10' N. latitude

extending the outcrop length to more than 1000 Km. To the

north of Khashm Al-Dhibi it forms a low gravelly plain that

rises northward to Jibal Al-Rukhman where it stands about

30 m above the gravel plain. In the outcrop area, the formation is partly covered

by eolian sand (Plate No. 2) such as Nafud Qunayfidhah which

cover a considerable area extending from the north near

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Khashm Al-Qalta about 25°06' N. latitude and 45°22' E.

longitude to as far south as 24°00' N. latitude where it is

partly covered by other unrecognized Quaternary deposits

near Khashm Al-Dhibi. Nafud Al-Malha covers some of the

eastern parts of the formation near Safra Al-Mustawi. To

the north, it is locally covered in small patches by Quater

nary silt and gypsifernous deposits. Near Al-Rukhman, the

outcrop is covered by a narrow band of Tertiary gravel.

Further to the north, it is mostly covered by eolian sands.

To the south near Khashm Al-Minjur (Khalta), parts of the

formation are covered by Quaternary gravel which is mostly

limestone, other local rocks, and unidentified gravels. These

gravels continue to the south as a wide strip parallel to

the formation. The most recognizable patch of Minjur out

crop in the southern area lies near Al-Ji'lan at about

22°32' N. latitude.

At the type section, Khashm Al-Khalta (Khashm Al-Minjur),

the formation is 315 m thick. It is 490 m thick west of

Khashm Al-Dhibi and 326 m thick at Khashn Mawan to the south.

The unit thins southward from this point and is not present

beyond 21°32' N. latitude. To the north, it is 370 m near

Marrat and 350 m near latitude 25°42' north. At Riyadh, it

has been found to be 400 m thick in the Riyadh Deep Well,

and at Khurais about 110 Km east of Riyadh, it is 385 m thick

(Figure 7). It is thickest at Khashm Al-Dhibi (490 m) which

forms a center from which the formation thins to the south

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. F ig u r e 7 29 Approximate thickness of Minjur Sandstone in meters (modified after Sogreah,1967) Scale 1:2,600,000

Al-Riyadh

•Al-Hair »«afcJ?v^>V-rs. ^— - CJcaQ. ^

A 1-Khan TT /

Khashm

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 30

and north. This generalization also applies in the sub

surface, especially near the outcrop. In other words,

the thick parts of Minjur continue from the outcrop to

the area of Riyadh. The formation thins north and south

of an east-west line between Tabrak and Khurais. Also,

the unit thins eastward but more gradually than to the

north or south.

Formation contacts: The Minjur Sandstone comfortably

overlies the Jilh Formation. Powers (1966) said that the

contact is "generally marked by a strong topographic break

from cliff forming sandy and oolitic limestone capping the

Jilh to deeply weathered cross-bedded sandstone of the Minjur."

The exposed gypsiferous shale and marls locally found be

tween uppermost Jilh and the coarse sandstgne of Minjur can

be somewhat confused with the evaporites facies of the Jilh.

These evaporites probably form an effective aquiclude. But

MacDonald (1975) said, "There are no obvious breaks, however,

at Jilh-Minjur junction on geophysical or lithological logs

in boreholes and no upper Jilh limestone has been identified

on boreholes logs. The Jilh-Minjur contact therefore must

be rather arbitrary and is, in practice, based mainly on

palyontological data or on a comparison with surface section."

The contact with the overlying Marrat is unconformable

and easily traceable in the areas where the Marrat is com

posed of limestone. The contact was also recognized in

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lithological and geophysical logs.

The Marrat undergoes a facies change southward to

shale and siltstone then to sandstone. In these areas the

contact is somewhatdifficult to tracebecause of the simi

larity in facies and the progressive overlap of younger

formations. In Riyadh area the red shale just above the low er Marrat Limestone forms an easily identified bed when

drilling to the Minjur aquifer.

Age: The Minjur Sandstone lies between Marrat Formation

of Toarcian (Early Jurassic) with Ammonite indicators, and

Jilh Formation of middle and upper Triassic as dated by

Ammonites fragments and pollen. But no marine fossils have

been found in The Minjur, although wood and leaf impressions

exist. These fossils which remain are associated with pyrite

indicating that the organic matter was laid down in a re

ducing environment. Spores and pollen have been found re

cently in the upper parts of the unit, in the Hayir borehole.

Pollen grains of Sulcatisporites and Pityosporites (Powers,

et al., 1966) which have been described from Keuper (Upper

Triassic in northern Europe) have been found at the base

of the formation. These are followed by a different mono-

saccate pollen which is succeeded by a Jurassic flora within

the Marrat Formation. Steinke (1958, in Powers, et al.,

1966) placed the formation in the Upper Triassic or the

Lower Jurassic according to its stratigraphic position, but

the flora indicate that it is of Late Triassic age.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. HYDROGEOLOGY OF THE RIYADH REGION

Ground-Water Occurrence

General

Riyadh obtains its water from deep and shallow aquifers.

The shallow sources make up 20 to 30 percent of the public

supply of water. They are less important than the deep

aquifers in the Minjur Sandstone which supply the city with

90 percent of its water. Currently, the water pumped from

the Minjur aquifer makes up 70 to 80 percent of the public

supply; private and irrigation wells from Minjur comprise

some 10 percent.

Unconfined aquifers

In Riyadh, the shallow wells are completed in alluvium

and fractured limestone and sandstone around Wadi Hanifah,

Wadi Nisah, and other nearby Wadis, as well as fractured

limestones beneath the city. Recharge of these aquifers

is by local infiltration of precipitation, runoff, flood

water that flows into the area from the upper reaches of

Wadi Hanifah and tail water from irrigation and domestic

use. The water table reaches its highest level between January

and March as this is the wettest season of the year. But

the water table level declines year after year because the 32

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 33

gradual increase in the exploitation of the shallow aquifers. During extended dry periods, many shallow wells go dry.

The three wells that produce from the alluvium in Wadi Numar, a tributary of Wadi Hanifah to the west, is representa tive of the wells that produce from the alluvial aquifer.

The water is of a good quality, and is distributed by tank trucks and small pipelines.

Shallow wells also have been drilled in the Hayir area,

south of Riyadh, at the confluence of Wadi Hanifah and its

tributaries, Shaib Ha and Wadi Buaja (Figure 2). These shal

low aquifers are recharged by infiltration of rainfall and

water flowing in the wadis. The limestone in this area is

apparently not extensively fractured and provides more oppor

tunity for water to accumulate in the alluvium. In the

Hayir area some fourteen shallow wells have been drilled to

depths of 50 m; some of these wells were subsequently aban

doned due to extensive pumping. The water from this area is distributed to Riyadh by pumping stations and a pipeline

system. The water quality of the Hayir wells varies because

some of the wells have been contaminated by water from forma

tions such as the Jubailah which contain more saline water.

While some wells are replenished only by infiltration of

rain water and are rather low in dissolved solids.

Shallow wells have been drilled also in Wadi Nisah about

40 Km south of Riyadh. The eleven wells (and five more plan

ned) in this area are completed in sandstones of the Biadh

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Formation at depths of 50 - 60 m. This aquifer has a

valuable reserve of very good quality water.

Some shallow hand dug wells and boreholes produce from

the Jubailah at depths of 60 - 80 m beneath the city. This

formation is most productive in its upper 80 m. In the Riyadh

area, the water table in the formation is very near the sur

face, and it is locally above the ground level forming swamps

in areas of lower relief. The formation is recharged by

irrigation water, septic tanks and pits, all kinds of waste

water, rainfall and water flow in the wadis. The quality of

the water is very poor because it is highly contaminated by

the Riyadh sewage system. Most of the water is used for irrigation.

Confined aquifers

The Minjur Sandstone is the only exploited confined

aquifer in Riyadh. All wells drilled into the Minjur Aquifer

in the Riyadh area are artesian and include some flowing wells.

At the Minjur outcrop, however, the wells drilled are shallow

and generally non-artesian. Because of the eastward dip of

the Minjur (15 m/Km), the wells east of the outcrop area are

artesian, and where the pressure head is great enough, the

wells flow. Very few of the wells in the Riyadh area have

been abandoned, and most of them are very productive. Some

of the wells are used privately and about 35 wells in the

Riyadh area are used for public supply. The quality of the

water ranges from 1100 to 1500 ppm in dissolved solids.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. THE MINJUR AQUIFER

Nature of the Aquifer

The Minjur Aquifer is mainly sandstone. At the type

locality, shale comprises 10 percent of the unit, lenses of

conglomerate, silty materials and ironstone account for 6

percent (Table III). The percentages of the several litho-

logies vary from place to place. Sogreah (1968) reported

that the 10 percent fines found at the outcrop increases to

20 - 40% near Riyadh. In the Riyadh Deep Well the shale

comprises about 60 percent.

The formation is subdivided into two sandstone aquifers

separated by a zone composed dominantly of shale. At the

type section at Khashm Al-Khaltah the upper 45 m is sandstone,

underlain by interbedded shales, shaly sandstone, sandy shale,

quartz pebble conglomerate and ironstone beds ranging from

1 m to 18 m in thickness with sandstone beds ranging from

2 m to 22 m in thickness. The 73 m at the bottom is dominantly

sandstone and shaly sandstone. Because of the lenticular

nature, these shaly layers which have lower permeability do

not completely separate the aquifer. Sogreah (1968) noted

at Hayir Borehole that the sandy layers at the base of the

Marrat and the local sandy layers at the top of Jilh Forma

tion may constitute a single aquifer complex which varies

locally in thickness independently of the Minjur Sandstone

thickness.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 36

In the Riyadh region wells only penetrate the sandy

layers of the Upper Minjur except in Riyadh Deep Well (Test

Well or Airport Well) which penetrated the entire formation,

the underlying Jilh Formation and deeper below Khuff Forma

tion, a depth of 3000 meters. At the Riyadh Deep Well the

Minjur has two zones of sandy layers. Even though those zones

are dominantly sand, they do contain lenticular beds of

shale or sandy shale in most of the wells. The existence

of these more slowly permeable layers makes it necessary

for drillers to carefully select the appropriate depth inter

vals at which they put the well screens against the permeable

parts of the unit. MacDonald and others (1975) named the

two aquifers of Minjur Sandstone as follows: The Upper Minjur Aquifer System

The Lower Minjur Aquifer System. These are separated by:

The Middle Minjur Shale and Mudstone.

The Upper Minjur lies above the middle shale of Minjur which

forms a regional aquiclude and below the lower Marrat lime

stone which is also an aquiclude. The thickness of the Upper Minjur Aquifer ranges from

105 m to about 140 m with an average thickness of 120 m

(Table V). The percentage of sandstone ranges from 41 per

cent in the Badiaah Well up to 70 percent at the Beijah Well Number 2 and averages 55 percent. The Upper Minjur thins

toward the northwest from Riyadh.

The middle part of the unit is composed of shale, clay,

mudstone and thin beds of sandstone. The thickness

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TABLE V

UPPER MINJUR SHALE AND SANDSTONE THICKNESSES (m), AND SANDSTONE PERCENTAGE OF SOME MINJUR WELLS IN THE RIYADH AREA

Well Name Upper Minjur Sandstone Shale S.S. Source Thickness Thickness Thickness Percent

Salbukh-5 114.6 59.3 55.3 52 In Mac Donald (1975) Salbukh-4 133.6 69.2 64.1 52

Salbukh-3 126 70 56 55.71 Well's Log (1973) Sal-2 134.4 73.4 51 54.6 Well's Log (1973)

Badiaah 116.2 47.5 68.7 41 In Mac Donald (1975)

Riyadh Deep Well 138 59.1 78.9 43

NQ1 118.9 60.8 58.1 51

HR1 115.9 83.5 32.4 72

Daknah-2 105.2 54.2 51 52

Bu'ayja-2 121 85 36 70 Well's Log (1971)

RR-W1 143.84 66.96 76.88 46.55 Well's Log (1971)

Moather-2 110 64 46 58

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 38

penetrated in the Riyadh Deep Well is 129 m. The unit seems

to be constant toward the northwest.

The Lower Minjur Aquifer is composed of sandstone layers

with thin beds of shale. At the type locality, the lower

60 meters are mostly snadstone. In the Riyadh Deep Well, the Lower Minjur is 134 m thick. It also thins from Riyadh north

west toward the outcrop. The Lower Minjur Aquifer has not

been exploited in Riyadh, but it could be an important source

of water especially for Riyadh. However, because it contains

lower quality water than the Upper Minjur Aquifer, it would

be necessary to limit the use of water from this source or

it would have to be treated.

Origin of The Water in The Minjur Aquifer

The water in Minjur is fossil water and came probably

as accumulations of direct precipitation over the outcrop

area a long time ago. Measurement of the age of the water

at Riyadh indicates that it is some 25 - 35 thousand years

old. MacDonald in 1975 said: The origin of the belt of good water quality is debatable, but it is suggested that it represents an influx during the wet periods of the late ice age. Origin of the water as precipitation during the last

Pleistocene ice age may also be a factor in the salinity

differentiation within the Minjur Aquifer, so the belt of

a good quality water is probably related to the large quan

tities of water that fell during the Pleistocene. And the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 39

lower quality water at the outcrop is probably related to

the post-Pleistocene arid climates. This period of reduced

rainfall has caused an increase in the dissolved solids

content of the water that has entered the aquifer during the

Holocene.

Aquifer Properties

Porosity

Samples from the two wells near Riyadh were found to

have an average grain size of 0.64 mm, a coarse sand. Grain

size ranged from very fine to coarse sand. Sand of this tex

ture typically has about 30-40 percent porosity. Since the

formation is comprised of sand, sandstone, shale, and mud

stone, however, the porosity would be lower. Sandstones typi

cally have 10-20 percent porosity. Shales have about 1-10

percent porosity. Clay and mudstone that are distributed

throughout the aquifer have a higher porosity up to approxi

mately 40 percent.

Well records indicate that The Upper Minjur in Riyadh

has a range of 40-70 percent and an average of 55 percent sand

and sandstone. Analyzed Samples 3 and 4 showed about 99 per

cent sand; Samples 1 and 2 contained about 67 percent. The

shales and mudstones range from 30 to 60 percent and average

45 percent of The Upper Minjur as indicated by well logs.

Samples 1 and 2 contained up to 33 percent mud; Samples 3 and

4 contained less than 1 percent. Samples 3 and 4 were moderately

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 40

well sorted.

Thus, based on the texture of the aquifer, the porosity

of The Upper Minjur Aquifer in The Riyadh Region may be as

great as 25 to 30 percent. The porosity reported by Sogreah

(1968) at Shaqra, about 20 Km northwest of Riyadh, is 30

percent. MacDonald (1975) reported a 25 percent porosity

for The Upper Minjur.

Specific yield and specific retention

Specific yield is the ratio of the volume of water

drained from water-bearing material by gravity and the rock

volume, expressed as a percentage. The specific retention is

the water that will not drain by gravity, due to molecular attraction. The Upper Minjur consists of sand, sandstone,

mudstone and shales. Specific retention would be higher in

these shales, clays and mudstones which do not have high

effective porosity, because retention depends upon surface

area which increases with the decreasing grain size. Al

though the mudstones and clays have high porosity, they have

low specific yield, because of the high specific retention.

The water that could potentially be released rfrom these

layers would add considerable amounts of water to the aquifer.

Since the sandstone and sand of Minjur comprise 40 - 70

percent of the upper aquifer, the specific yield must be

greater than the specific retention. In areas where more

mud is, and the sandstone is well cemented, specific yield

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 41

decreases and may be exceeded by specific retention. Specific

yield can be considered equivalent to the effective porosity.

MacDonald (1975) reported low specific yield, 5.8%, 4.8% and

11.1%, at Well M4 near the outcrop, however, he pointed out

that the upper formation has almost been removed by erosion

at this location. At the type locality, the sand and sand

stone of the Minjur comprise about 90 percent of the forma tion suggesting a relatively higher specific yield, maybe

up to 15 to 20 percent.

Permeability and transmissibility

The permeability of a formation is its ability to trans

mit water along a hydraulic gradient. The coefficient of

transmissibility equals the permeability adjusted for temper

ature and multiplied by the thickness of the aquifer.

Permeability can be measured by several methods. In most

of the Minjur wells in the Riyadh region, most measurements,

if used, are of the pumping test type. In these tests, water

level changes during pumping and recovery are observed.

G. Brown and C. Lough (1962) tested some Minjur wells

of the Riyadh field and obtained values for transmissibility -3 2 ranging from 1.8 to 6.4 x 10 m /sec. Other measurements

of pumping tests have been reported by Sogreah (1968) for

some deep wells drilled in the Minjur Aquifer in Riyadh.

The tests were short-term and long-term tests. The short

term transmissibilities reported by him are 1.5 and 6.5 x

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10 -3 m 2/sec which are similar to the results reported by

Brown. The long-term tests give a better idea of the wide

spread characteristics as portions of the aquifer remote

from the test unit are affected by pumping. Measurements -3 2 of the transmissibility are as high as 14 x 10 m /sec

(Table VI) with a permeability measured at 8 to 8.5 x 10 ^

m/sec for a 120 m thickness of The Minjur Sandstone in

Riyadh. Quimp (1972) through pumping test measurements con

cluded that under long-term pumping the water level behavior

in the Minjur can be determined with the modified non equilibrium equation. He reported value of transmissibility -3 2 equals 5.5 x 10 m /sec (Table VI). Recent tests and analysis for some new Minjur wells in

The Riyadh Region were reported by MacDonald (1975). The

_ 3 transmissibilities reported ranged between 3 x 10 and 7.2

x 10 —3 m 2 /sec with an average of 4 x 10 —3 m 2/sec for the

Upper Minjur Aquifer. The permeability ranged from 2.5 x -5 -4 -5 10 to 1.6 x 10 m/sec with an average of 7.7 x 10

m /sec (Table VI and Appendix A). Measurements made for

this study at the New Salbukh Well field, Well 8, gave a -3 2 transmissibility value of (±0.5) 2.0 x 10 m /sec and

a permeability value of (±0.5) 1.667 x 10 3 m/sec.

The measurements vary not only in The Riyadh Region

but also in all regions where the Minjur had been penetrated

According to Otkun (1972) transmissibilities range from 1.14

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TABLE VI

TRANSMISSIBILITY, PERMEABILITY AND STORAGE COEFFICIENT OF MINJUR AQUIFER IN RIYADH REGION

Transmissibility Permeability Storage Remarks Source 2 . , Coefficient m /s m/sec

1.8 - 6.4 x 10"3 2.2 X 10-5 - Brown 1962 1.3 X icf4

1.5 - 6.5 x 10-3 1 X i

14 x 10~3 8 - 8.5 x 1 X lO-5 Long Sogreah 1968 10‘5 term

5.5 x 10-3 1 X 10-4 Long Quimp term 1972

3 x 10"3 - 2.5 x 10_5 - 1.3 X 10-4 Step tests Mac 7.2 x 10~3 1.6 x 10"4 Donald 1975

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 44

-2 2 -4 x 10 in /sec at Dawasir (south of Riyadh) to 6.1 x 10 2 m /sec at Aflaj (also south of Riyadh) due to the hetero-

genity and irregularity of sandstone layers and the pre

sence of irregular low permeability shale beds. Measure

ments of transmissibility, permeability of some of the

Minjur wells in Riyadh are listed in Appendix A.

Storage coefficient

The storage coefficient is the volume of water that an

aquifer releases from, or takes into, storage per unit sur

face area of aquifer per unit change in the component of

head normal to that surface. It is usually used for con

fined aquifers with storage coefficients between 0.5 x 10 ^

_ 3 - 0.5 x 10 indicating that large pressure changes are re

quired to produce substantial water yields, and doesn't

describe the water drained from an artesian aquifer because

the formation remains completely saturated. For unconfined

aquifers, it simply equals the specific yield. Storage

coefficient can also be measured by the pumping tests of

wells.

Sogreah's (1968) measurements gave a storage coefficient -4 value of 1 to 3.6 x 10 for a short-term pumping test, but

for the long-term pumping test, he reported a value of 1 x -5 10 (Table VI and Appendix A ) . Storage coefficient values, reported by Brown (1962), were

from 2.2 x 10 5 to 1.3 x 10 4 . Quimp (1972) applied the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 45

modified non-equilibrium formula with a constant storage -4 coefficient of 1 x 10 . This value is close to the 1.3 -4 x 10 reported by MacDonald and others (1975).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 46

Well Test

A step-drawdown test or multiple rate flow test was

run on one of the new wells. This test consisted of pump

ing at progressively higher discharge rates. It provides some

information about the aquifer behavior under pumpage, and

is useful in evaluation of well hydraulics such as trans

missibility, permeability and well loss. The storage coeffi

cient, S, cannot be determined from this test unless obser

vation wells are available. The test was at well Sal-8, run on 1-28-1978 at the new

Salbukh Well field about 30 -40 Km north of Riyadh, coordinates

25°05 10 N. Latitude, 46°26 50 E. Longitude. The well

was run in four steps at different discharge rates. A con

stant record of time and well data was maintained. The

discharge was controlled by an oriface in the pumping pipe.

Four different discharge rates were obtained. The drawdown

measurement was made by an airline. Additionally, water

temperature was recorded randomly. The data of drawdown

water depth and time were calculated and compiled (Table

Vila, b). Two samples of water from the well were obtained

at the beginning and the end of the pumping period. These

were chemically analyzed. There are a number of methods which have been used to

calculate aquifer characteristics by pumping tests. However,

most of the formulae require observation wells near the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 47

TABLE VII a

PUMPING TEST DATA

Step 1

Time (min) Drawdown (m) DW1 (m)

0 0.004 148.745 1 12.537 161.278 2 9.017 157.757 3 7.397 156.138 4 7.045 155.786 5 6.552 155.293 6 6.200 154.941 7 6.200 154.941 8 6.904 155.645 9 5.848 154.589 10 5.708 154.448 11 5.848 154.589 12 5.708 154.448 13 5.848 154.589 14 5.848 154.589 16 5.954 154.694 18 5.919 154.659 20 5.989 154.730 25 5.848 154.589 30 5.708 154.448 35 5.285 154.026 40 5.215 153.955 45 4.511 153.251 50 4.088 152.829 55 4.440 153.181 60 4.229 152.969 70 4.088 152.829 80 4.088 152.829 90 4.194 152.934 100 4.370 153.110 110 4.581 153.321 120 4.792 153.533 130 5.003 153.744 140 4.863 153.603 150 4.933 153.673 160 4.792 153.533 170 4.863 153.603 180 4.933 153.673

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TABLE VII a (Continued)

Step 2

Time (min) Drawdown (m) DWL (m)

180 9.369 158.109 182 8.946 157.687 183 9.087 157.828 184 9.650 158.391 185 9.650 158.391 186 9.721 158.461 188 9.721 158.461 189 9.721 158.461 190 9.791 158.532 192 9.862 158.567 194 9.791 158.532 196 9.862 158.602 198 9.791 158.532 200 9.791 158.532 205 9. 862 158.602 210 10.003 158.743 215 10.003 158.743 220 10.073 158.813 225 10.143 158.884 230 10.284 159.025 235 10.425 159.165 240 10.566 159.306 250 10.601 159.341 260 10.636 159.377 270 10.601 159.341 280 10.707 159.447 290 10.636 159.377 300 10.636 159.377 310 10.707 159.447 320 10.777 159.517 330 10.918 159.658 340 11.059 159.799 350 11.059 159.799 360 11.059 159.799 370 11.129 159.870

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TABLE VII a (Continued)

Step 3

Time (min) Drawdown (m) DWL (m)

370 11.129 159.870 271 18.522 167.263 372 19.085 167.826 373 19.156 167.896 374 19.226 167.967 375 . 19.297 168.037 376 19.297 168.037 377 19.367 168.107 378 19.578 168.319 379 19.719 168.460 380 19.789 168.530 382 19.825 168.565 384 19.860 168.600 386 19.895 168.636 388 19.930 168.671 390 19.930 168.671 395 20.071 168.812 400 19.930 168.671 405 19.930 168.671 410 20.212 168.952 415 20.353 169.093 420 20.071 168.812 425 20.142 168.882 430 20.177 168.917 440 20.282 169.023 450 20.353 169.093 460 20.423 169.164 470 20.423 169.164 480 10.458 169.199 490 20.494 169.234 500 20.564 169.304 510 20.564 169.304 520 20.705 169.445 530 20.634 169.375 540 10.740 169.480 550 20.775 169.516

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE VII a (Continued)

Step 4

Time (min) Drawdown (m) DWL (m)

550 20.775 169.516 551 29.788 178.528 552 30.844 179.584 553 31.759 180.500 554 32.041 180.781 555 32.252 180.992 556 32.463 181.204 557 32.604 181.344 558 32.604 181.344 559 32.674 181.415 560 32.745 181.485 562 32.815 181.556 564 32.850 181.591 566 32.886 171.626 568 32.956 181.697 570 33.026 181.767 575 33.203 181.943 580 33.308 182.049 585 33.379 182.119 590 33.379 182.119 595 33.449 182.189 600 33.519 182.260 605 33.660 182.401 610 33.801 182.541 620 33.942 182.682 630 34.012 182.753 640 34.012 182.753 650 34.153 182.894 660 34.223 182.964 670 34.223 182.964 690 34.364 183.105 710 34.716 183.457 730 34.787 133.527 750 34.787 183.527 770 34.787 183.527 790 34.716 183.457 820 34.787 183.527 850 34.928 183.668 870 35.209 183.950 900 35.280 184.020 960 35.280 184.020 1020 35.420 184.161 1080 35.561 184.302 1140 35.772 184.513 1200 36.054 184.795 1260 36.054 184.795 1320 36.054 184.795 1380 36.195 184.935 1440 36.336 185.076 1500 36.265 185.006

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 51 TABLE VII b

RECOVERY DATA

Time (min) Residual DML (M) Drawdown (m)

11:30 0 36.265 185.006 1 18.874 167.615 2 7.609 156.349 3 2.891 151.632 4 0.286 149.026 5 0.708 149.449 6 0.568 149.308 7 0.286 149.026 8 0.145 148.886 9 0.070 148.674 10 -0.206 148.534 12 -0.558 148.182 14 -0.769 147.970 16 -1.121 147.618 18 -1.121 147.618 20 -1.262 147.477 25 -1.544 147.196 30 -1.755 146.985 35 -1.896 146.844 40 -1.966 146.773 45 -2.037 146.703 50 -2.177 146.562 55 -2.248 146.492 60 -2.318 146.421 70 -2.459 146.280 80 -2.529 146.210 90 -2.600 146.140 100 -2.600 146.140 110 -2.670 146.069 13:30 120 -2.670 146.069 130 -2.670 146.069 140 -2.670 146.069 160 -2.741 145.999 14:30 180 -2.741 145.999 200 -2.741 145.999 220 -2.741 145.999 15:30 240 -2.741 145.999 270 -2.741 145.999 16:30 300 -2.741 145.999 330 -2.741 145.999 17:30 360 -2.741 145.999

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 52

pumping wells. It is also necessary to have a constant

pumping discharge. Since no data from observation wells

was available, the data presented here can only be used for

limited interpretations. Typically, the application of

formulae to the interpretation of well flow data is limited

by several assumptions:

1. The well should penetrate the entire homogeneous

isotropic aquifer.

2. The aquifer is infinite in extent.

3. The static piezometric surface is horizontal and

the flow is radial. 4. The pumping rates are constant from the aquifer.

These are ideal conditions which normally are not

achieved? therefore, formula calculations will be approximate.

Another approach is to graphically compare the dynamic water

level (DWL, the depth to water while pumping) against time

(Wenzel, 1942). This method was used by Bruin and Hudson

(1955), (reported in Deiju, 1971) for the step-drawdown test.

The graphs were produced for each step and recovery (Figure

8,a-e). Step-drawdown curves and recovery were illustrated

in Figure 8,f. This approach predicts the continuous dis

charge of wells. It is obvious from the graphs that the

water depth increases with time reflecting increased draw

down. During the first 10 - 15 minutes, the drawdown is

high in each step, primarily as a result of increasing the

discharge rate. The first step showed a high fluctuation

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 53

-P 09 3 U C 3 •H O E £

O CM M 0 0 •

GO -3- m vo, 0 0 iH

(m) iwa

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced

Figure 8.b DWL (m) against time -Step 2 NO ‘M “ M 'N M O 3 rH tn » 54 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced

Figure 8.c DWL (m) against time Step 3 NO ON a \ \ i T ) U I ( -=}■ CO CO CO O VA CM o o V'l O cc o

55 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced

Figure 8.d DWL (m) against time Step 00 NO 00 CO co I (01) rEM(3 00 ON . 4 00 A o o o r\ 00 o o 56 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced

Figure a.e DWL (m) against time - Recovery 00 m X3A3I (m) vO s M CM CM &

Time Reproduced with permission of .he copyright owner. Further p ro d u c tio n prohibited without permission without prohibited n tio c u d ro p Further owner. copyright .he of permission with Reproduced U9 Static viator lovol>m s.7>lS u > >i 0 O' 09 <0 <0 aa o O o a o oa u) .cac O O 58 59

at the beginning due to the adjustment of the discharge

rate and apparatus effects.

Data analysis

1. Jacob's method: This formula for unsteady flow was modified by Jacob

for values of U less than 0.01 (small r and/or large T).

The Jacob expression is as follows:

S = 4TT.3^,- Tm (log —u - log re 1.78)

In decimal logarithms: s ___2^3Q_ lQg 2.25 T ^ 2 4 TT T r S

For observations in a single well, only t varies in this

equation. The drawdown(s) can be plotted against time (t)

on a semi-log paper (Figure 9). A straight line was

produced whose slope per cycle equals 2.3Q/4 TT T. This

method was applied on the first step of pumping. Calculations:

2.3Q s = --- — 4 TT T where s = Drawdown per log cycle (Figure 9) =1.58 ,

Q = discharge rate = 13.88 1/s 2 T = transmissibility in m /s

by substituting values in the equation:

1.58 = 2.3 x 13.88/1000 4 TT T 2 T _ 2.3 x 0.01388 m /sec 4 x 3.14 x 1.58 m

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 60

O J-p £> © +s o ^ 00 ©

•H CB' pL, W)

rH Time Time minutes

G *©

• o

o CM

0 0 . 00 CM

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 61

= 1.609 x 10-3 m 2/sec

For determining the permeability:

T = PM

where M = is the thickness of the Upper Minjur Aquifer =

120 m P = is the permeability m/sec

by substituting values:

therefore P = T/m

P = 1.609 x 10”3/120

= 1.341 x 10 5 m/sec

2. Specific capacity, total drawdown, well loss, aquifer loss

and well efficiency: 3 Specific capacity (L /T/L) of a well is the ratio

between the discharge and drawdown. It is influenced

by the hydraulic parameters of the aquifer, thickness of

confining beds, well screen, well diameter, and pumping

period. The total drawdown in a discharging well is

made up of head loss caused by the turbulant flow into

the well, a formation loss or aquifer loss which is the

head loss plus the effects of laminar flow in the aquifer

and a well loss resulting from the flow within the well.

The total drawdown, Sw =2-n-~T In — This equation w assumes well loss to be a zero, and thus the drawdown

might be inaccurate. Jacob has modified this formula to

account for well losses as follows: „ In rn/r Sw = ---- 0 _ w Q + CQn 2TTT

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 62

Sw = BQ + CQn

where Sw is the drawdown, BQ is the aquifer loss,

CQn is the well loss. Because the well loss is affect

ed by turbulant flow, it is proportional to the nth

power of discharge, which equals 2 according to Jacob,

but averages 2.5 according to Rorabaugh, or as deter

mined from the step-drawdown test. The well loss con- 2 -5 stant, C (T L ) can be calculated using the step-drawdown

data (Walton, 1962, reported by Dominco, 1972) as follows:

For Steps 1, 2: And, for Steps 2, 3:

c = (AS2/AQ2) - (bS1/AQ1) c = (A S3/A Q3) " ^ 2/6Q2]

Q2 + q i a q 2 + a q 3

A S and a Q represent the increments in drawdown and dis

charge.

Calculations of well loss:

c = 6.13/0.011357 - 4.93/0.01388 = 7313.385 sec2/m5 1 0.025237

= 9.68/0.012618,,,- 6.13/0^011357 = 6007.207 sec2/m5 2 0.037855

C = 14.01/0.012619 - 9.68/0.012618 = 6797.015 sec2/m5 3 0.050474

Average C = 2^ 1— — - = 6705.869 sec2/m5 3

Average well loss = 6705.869 x (0.0420)^ = 11.829 m

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 63

A better way to calculate the well loss is to plot

Sw/Q versus Q (Bruin and Hudson, 1955, reported by Dominco,

1972), where Sw in this case represents the specific

drawdown taken after equal time intervals of 180 min,

(Table VIII). Q represents the discharge rate in each

step. The result is a straight line. Its slope equals

C which can be applied to calculate the well loss in the

equation above. The intercept of the line is B (Figure

10) . Calculations: 2 5 From Figure 10, the slope C (10,250 sec /m ) is 2 the well loss coefficient and B is 180 sec/m which is

the aquifer-loss constant. Now aquifer and well loss

and drawdown can be calculated from the formula:

Sw = BQ + CQ2

Step 1: Well loss = CQ12 = 10,250 x (0.01388)2

= 1.975 m

Aquifer loss = BQ^= 180 x 0.01388

= 2.498 m

. . Drawdown = Sw = 1.975 + 2,498

= 4.473 m

Step 2: 2 2 CQ2 = 10,250 x (0.025237)

= 6.528 m

BQ2 = 180 x 0.025237

= 4.543 m

Specific orce .2 0.439 0.322 Corrected Corrected Discharge edn 0.355 Reading Reading DISCHARGE, SPECIFIC DRAWDOWN OF ALL STEPS ALL OF DRAWDOWN SPECIFIC DISCHARGE, p 1scgm 1/sec gpm 1/sec gpm 2 13.880 220 Step 1 Step 4.473 .3 11.059 4.933 TABLE VIIITABLE 0 25.237 400 tp 2 Step 11.071 .3 0.547 0.438 p 1/sec gpm 0 37.855 600 tp 3 Step 15135.198 21.501 20.741 0.568 p 1/sec gpm 0 50.474 800 Step 4 Step 34.751 0.688 0.697 64 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced

Figure 10 Sw/Q against discharge O/ m S ! 65 66

Sw = 6.528 + 4.543 = 11.071 m

Step 3:

CQ32 = 10.250 x (0.037855)2

= 14.688 m

BQ3 = 180 x 0.037855

= 6.819 m

Sw = 14.688 + 6.819

= 21.507 m

Step 4:

CQ42 = 10,250 x (0.050474)2 = 26.113 m

BQ4 = 180 x 0.050474

= 9.085 m

Sw = 26.113 + 9.085

or total drawdown= 35.198

According to these results, the values of the drawdown

can be corrected (Figure 10). It is obvious that well

losses increase with depth. The value of C can be a measure 2 5 of the effectiveness of the well. A value of 5 sec /ft in

dicates that the well is properly developed and designed, 2 5 but values greater than 10 sec /ft indicates severe clog

ging and deterioration (Walton, 1962, reported by Deiju,

1971). The C values of the well tested (Sal-8) ranged 2 5 between 17 and 27 sec /ft which may indicate the improper

development and/or reflect the clogging influence of the

aquifer materials around the well. Since the well is newly

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installed, deterioration might be a relatively remote cause;

however, well inspection is needed. The C value also affects

the well efficiency (E) which is the ratio between the

drawdown due to the formation loss (es) and the total draw

down (St) and may be expressed as a percentage as follows:

Well efficiency = E = S St = 9^085_ 35.198 X iUU

= 26%

Well capacity can be expressed and calculated from the

Jacob formula as follows:

Sw = BQ + CQ2

Dividing by Q:

Sp.C. = Q/Sw = 1/B = CQ

= 1/180 + 10,250 (0.04200)

= 1.194 x 10 3 m3/sec/m

= 1.194 1/sec/m

The specific capacity of the well as appears from the

formula above decreases with the increase in rate of dis

charge, moreover, it decreases with the time of pumping as

appears from the following equation:

Sp.C.■= Q/Sw= T/ [264 log (Tt2693 rw2 S) - 65.5]

This equation is useful in obtaining parameters like trans-

missibility or specific capacity. Walker and others (1965)

computed from aquifer test data in Illinois, several values -4 of pumping period t, 3.5 x 10 as a storage coefficient 2 and various values of rw /t (Figure 11 a). The specific

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6& F ig u r e 11

1000■ -■■■ •orv 5 3. ♦ 8xi0r^: >. & ■p 100 10 *Cn-I •H XJ O S=35) n o - 1* •H O (0 o to iH 'W' 10 /Base line •gx 03 c <0 u 1 I

St3,w r ’ cap. < y ,in ^ * 4 E,gpm/ft ka/Jil! ^ ^ a.Coefficient of transmissibility lissibility versus suecific c^pcapa* city .or several values of well radius6t(Walker,1965) &160 *— V T = lf 0,000 <8 ”0 7 " ■ ■ « T = l i 0,000 c. CO T =1 20.00 O^y. . §120 iH rH <0 bC T=100, O.Qj) 100 o to T=8 0,000- V . *3 80 C <0 to 3 ^T = 6 3,000 - O x: 60 +j c 1,000“ •H 40 M-i 0 j T * 2 j . i^jUOO- to 20 01 .0,000 3 T = 8 j i i—i <8 f=2,0D 0 > >5.000 sp. cap.,m gpm/ft b.Diagram for estimating theT value from sp.cap.(Theisl963)

Reproduced with Permission C h e copyrigM owner. Fnpher reproPucion prohMed without permission. 69

capacity of the well which was determined to be 1.194 1/sec/m

or 5.76 gpm/ft was compared to the values of Walker's graph

to estimate the corresponding transmissibility coefficient -3 2 which was found to be 12,000 GPD/ft or 1.725 x 10 m /sec.

The permeability can be calculated as follows: -3 -5 1.725 x 10 /120 = 1.438 x 10 m/sec

Another way to calculate the transmissibility is by

using Theis Equation which can be modified to consider the

specific capacity of the well as follows:

T ' = — (K -264 log. _ (5S103) + 264 log..-t) S 10 10 where T' is a factor depending on the specific capacity (gpd/ft).

Q/s equals the specific capacity of the well (gpm/ft). K is

a constant having different values for different values of r.

For an artesian aquifer, it can be equated to 2,477 if S, -4 the storage coefficient, values fall in the range of 2 x 10 ,

and t is the time of pumping measured in days. The T value

cannot be taken directly, but can be obtained from the inter

section point between the T' value versus the specific capa-

in a chart (Figure 11 b) (Thesis, 1963, p. 334).

Calculation

Since the chart measuring T has the units mentioned above,

all figures were converted to the same units.

^ = 5.769 gpm/ft (average from all steps)

S = 1 x 10 -4 (previous estimate)

t = 1.042 days

T* = J (K-264 log1Q (5S103) + 264 log1()t)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 70

by substituting the values:

T' = 5.769 [2,477-264 log1()(5 x 1 x 10~ 4 x 103) + log1()1.042]

T' = 5.769 [2,477-264 log1Q 0.5 + log1Q 1.042]

T' = 14748.390 gpd/ft

.*. T from the chart = 12,857.143 gpd/ft — 3 2 or = 1.848 x 10 m /sec

P = T/m = 1.848 x 10_3/120 = 1.540 x 10_5 m/sec

3. Dupiut Formula method

Dupuit Formula modified by Theim for the steady flow

is expressed as follows: T = Qw loge

where: = Discharge rate 1/sec 2 T = Transmissibility m /sec

r2 ,r^ = Distances from the pumping well

s2 ,s^ = the drawdown at distances r2 ,r^

Since no observation well was available, an approximation

formula was set for the pumped well only in which r2 is taken

as large distance r£; S2 is zero and r^ istaken as the pump

ing well radius rw - The equation is expressed asfollows:

Qw T = T — 1o% 4re/rw> w

Where is the drawdown in the pumping well. The

value of rg can be assumed to be between 300 m (1000 ft)

to 3000 m (10,000 ft) for unconfined and confined aquifers.

By assuming the well radius (r^) equals 0.3 m (1 ft), then

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. the formula can be reduced as follows: Qw T = 1.2 for unconfined aquifers and, S w Q T = 1.6 for confined aquifers.

Calculation:

= Discharge of the well m 3/sec (average)

= 42/1000 m3/sec

S w = Drawdown m = 35.189 m

.*. _ 1.6 x 0.042 T = ------35.189

= 1.910 x 10 3 m 3/sec

P = 1.910 x 10-3/120 —5 = 1.591 x 10 m/sec 4. Eden-Hazel Method This method is based on the Jacob's modification. It

applied by MacDonald (1975) on some Minjur wells. Jacob's

expression can be rewritten as:

s = (a + b log t) Q . 2.3 . 2.25T , . 2.3 where a = --- log — =--- and b = --- 4TTT r S 4 TXT

The drawdown at any instance is:

S' = (a + b log (t - t')

but the total drawdown is:

st = a Qn + b^_Q log (t-t')

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 72

Values of each step oflog (t-t') were computed.

Where t = the time since pumping started for each step and

t' the time at the increased rate of discharge. By select

ing a number of points for each step (Table IX), four

straight lines were produced (Figure 11) and a best fit line

can be drawn. The slope of this line, equals b = 2.3/4TTT

Calculation: 2 .3 b = 1.553 x 10"3 =

T = 2.3/4 x 3.14 x 1.553 x 10~3 1/min/m

= 1.965 x 10" 3 m 2/sec

P = 1.965 x 10-3/120 = 1.638 x 10-5 m/sec

5. Theis Recovery Method

Recovery residual drawdown data (Table VII b) are more

accurate than the drawdown measurements taken during the

pumping because it is not affected by interference caused

by vibration of measuring instruments and variations in

pumping rates. Theis recovery data is used to check the

analyses that were made during the pumping tests. The data

are usually obtained from nearby observation wells, but if

there is no observation available, this method can be applied

to the pumped well. This method typically should be applied

to a constant discharge rate, but the discharge rates were

different in each step. The water level changes measured

by air lines are relatively inaccurate. This, along with

the inconsistent discharge rate may create errors in the

analysis.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE IX

SELECTED VALUES OF^Q LOG (t-t')

Step Time (min) Drawdown (m) 'jL Q log (t-t*)

60 4.229 1731.54 80 4.088 1665.60 100 4.370 1584.89 120 4.792 1480.84 140 4.863 1334.10

240 10.566 3200.98 260 10.636 3091.12 280 10.707 2959.15 300 10.636 2793.88 320 10.777 2572.61

430 20.177 4726.19 450 20.353 4546.20 470 20.423 4325.91 490 20.494 4041.92 510 20.564 3641.64

610 33.801 8932.05 650 34.012 8871.56 670 34.153 8840.25 710 34.223 8775.29 750 34.716 8706.95 900 34.928 8413.46

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 74

c y o •a § T3 © CM ^ a r

CM a t -F> I +» Q> O' -J. o *0j

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 75

The recovery data can, however, be applied in two ways.

One is a plot between the residual drawdown, that is, the

difference between the static water level and the water

level during the recovery at each interval of time; and the

ratio t/t', where (t) is the time since pumping began and

(t') is the time since pumping stopped. The relationship

(Table X) is plotted on semi-log paper (Figure 13). The

A s per log cycle equals 2.3 Q/41TT. Theis Formula can be

expressed as follows;

S* = .?_♦-? Q (log 4Tt - log 4Tt1 ) 4TTT 2 2e r S r S

but for small values of r and u, it can be expressed as:

, _ 2 .3 Q log t/t'. 4TTT

The second application of Theis recovery is to plot

the residual drawdown against time since pumping stopped

(t') (Table X) on semi-log paper (Figure 14). The two methods resemble each other, and the results should be the

same. In both cases an average of the rate of discharge

from all steps is taken.

Calculation; 2.3 Q For the first one T = 4 T T A s

Q = the average discharge = 42L/sec

A s 1 = the residual drawdown per log cycle = 2.9 m T = 2.3 x 42 4 x 3.14 x 2.9

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 76

TABLE X

TIME, RESIDUAL DRAWDOWN AND t/t' (RECOVERY)

Time (t') in Min. Residual Drawdown t/t*

0 36.265 1500 1 18.874 750 2 7.609 500 3 2.891 375 4 0.286 300 5 0.708 250 6 0.568 214.29 7 0.286 187.50 8 0.145 166.67 9 0.070 150 10 -0.206 125 12 -0.558 107.14 14 -0.769 93.75 16 -1.121 83.33 18 -1.121 75 20 -1.262 60 25 -1.544 50 30 -1.755 42.86 35 -1.896 37.50 40 -1.966 33.33 45 -2.037 30 50 -2.177 27.27 55 -2.248 25 60 -2.318 21.43 70 -2.459 18.75 80 -2.529 16.69 90 -2.600 15 100 -2.600 13.64 110 -2.670 12.5 120 -2.670 11.45 130 -2.670 10.71 140 -2.670 9.38 160 -2.741 8.33 180 -2.741 7.5 200 -2.741 6.82 220 -2.741 6.25 240 -2.741 5.56 270 -2.741 5 300 -2.741 4.55 330 -2.741 4.17 360 -2.741 4.17

Figure 13 ✓ Residual Drawdown Against t/t Recovery 77 78

G 3

■r\

I©? > o o © I

o C u 5 0 3> •o 1 b Q rl a) 3 •O •H '© Time after pumping stopped stopped pumping after Time minutes t-

O rN (in) UMopMBaa XBnpxsaa

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 79 2.3 x 0.042 4 x 3 x 2.9

= 2.652 IO-3 m 2/sec -5 P = 2.652/120 = 2.210 x 10 m/sec

By the same steps for the second value As' = 2.99 m 2.3 x 42 T = 4 x 3.14 x 2.99

= 2.572 m 2/sec

P = 2.572/120 = 2.144 x 10,-5 J m/sec

In summary, the calculated values of transmissibility,

permeability and other well hydraulics of all methods are

as follows:

Method Transmissibility Permeability m 2 /sec/ m/sec

Jacob 1.609 X 10 3 1.341 X 10 5

Specific Capacity 1 1.725 X 10-3 1.438 X io*5 cn 1 i— o

Specific Capacity 2 1.848 X i 1.540 X io"5

Dupuit 1.910 X io-3 1.591 X IO-5

Eden-Hazel 1.965 X io“ 3 1.638 X io"5

Theis Recovery 1 2.652 X 10~3 2.210 X io-5

Theis Recovery 2 2.572 X 10~3 2.144 X io-5

Well Loss (Walton) 17.102 m

Well Loss (Bruin) 26.113 m

Aquifer Loss 9.085 m

Well Efficiency = 26%

Well Capacity = 1.194 1/sec/m

The values of transmissibility and permeability in

the methods used seem to be similar except for the Jacob's

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 80

method because it is applied on the first step which is

greatly affected by pumping discharge fluctuation at the

beginning of pumping. The value of transmissibility and _3 permeability would be in the range of 2.04 (±0.5) x 10

m 2 /sec transmissibility and 1.700 (±0.5) x 10 -5 m/sec per

meability. These values are similar to a number of values

from other wells that had been previously tested (Table VI

Appendix A).

Other measurements

The test also included measurements of the temperature

of water at intervals of time throughout the test (Table XI).

The initial temperature was 35 - 40° C because the water near

the surface had been cooled by the atmosphere before pump ing began, then as pumping proceeded, it increased to 58° C

at the end of the pumping period which means that the water

was being drawn from the greatest depth in the well. (See

page 144.)

The test also included sampling of two samples of water;

one at the beginning, the second one at the end of pumping

the well. The two samples were analyzed by the Riyadh Water

Works Lab. The analysis data are given in Table XI. Both

of the two samples showed almost the same concentration of

dissolved solids, although there is some increase of chloride,

silica, and ammonium in Sample 2 which also showed a decrease

in alkalinity, manganese and iron. Overall, the total solids

were 20 m g /1 greater in the second sample.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 81

TABLE XI

TEMPERATURE AND SAMPLE ANALYSIS FOR WELL SAL- 8 , JANUARY 28, 1978

DWL (m ) Time Temperature Character Sample 1 Sample 2 ain ? r*w

12 40 pH 7.8 7.3 mEq/1

157.7 18 Sample (1) Hardness 13. 3 13.5 mEq/1

60 50 - Ca 8.6 8.8 mEq/1

80 53 - Mg 4.7 4,7 mEq/1

100 54 Alkalinity 3.16 3.11 mEq/1

110 54 Conductivity 1550 1565 US/cm

140 55 TDS 1240 1260 mg/1 170 56 KmnO. demand 8.2 8.5 mg 4 /1 190 56 nh4 0. 3 0.35 mg/1

210 56.5 no2 0 0 mg/1

240 57 NO 3 0 0 mg/1 340 57.2 SO. 448 448 mg 4 /1 390 57.7 Cl 259 263 mg/1

410 57.5 mg P04 0 0 /1 430 57.6 sio2 22.5 27.0 mg /1

470 58 Fe 4.0 0.8 mg/1

790 58 Mg 0.1 < 0.1 mg /1

720 58

900 58

185 960 Sample (2)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 82

Piezometric Surface

The piezometric surface is an imaginary plane that coin

cides with the static water level in the confined aquifers.

All the wells in Riyadh are artesian, having different

static water depths depending upon the elevation of the

well and the effects of pumping. It is natural, of course,

to predict that there must be a decrease in the water level

in Riyadh wells since extensive pumping takes place and there

is insufficient recharge to the aquifer to replenish water

that is withdrawn. The peizometric surface dips east, north

east and south-eastward conforming to the dip of Minjur

but more gently. The depth to the static water level is

known to have decreased in the same direction, from the

outcrop toward Riyadh. The present piezometric surface

in Riyadh is at a depth about 180 m north of Salbuhk Road

and to the west. It decreases south, and, with a lesser

degree, to the east. In the center of Riyadh, it is around

150 - 160 m below the surface. When the Shumaisi Well,

located in the center of Riyadh was first drilled in 1956,

the water level was about 45 m below the surface or at an

altitude of 543 meters. It declined 30 m by 1962 when the

water level was 75 m below the ground level. Thus, the

average decline was 5 m a year for six years. In the

Malez Well, the water level was 50 meters below the ground

level in 1957 and dropped to 90 meters by 1962, 8 m a year

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 83

for five years. Estimates by. Davis (1960) indicated that

the water levels in the seven wells existing in central

Riyadh fell at a rate of more than 5 cm a day which meant

a fall of 18 meters per year. Where the effect of pumping

at Riyadh becomes less, a little further from the center of

the well field, the decline is less pronounced. So in the

Mansouriyah Well about 13 Km southeast of Riyadh, the water

level was at 14.5 m in 1960 and 20.5 m in 1963, a differ

ence of 6 m in three years, or an average of 2 m a year.

In the Diriyah Well 11 Km northwest of Riyadh, the draw

down is pronounced being 95 m in 1961 and 120 m in 1962

or about 25 m, but that may be related to the fact that it

was the first deep well exploited by the village and was

pumped extensively during the first year.

From the available data (Appendix B), a graphical re

presentation showing the decline in water levels (Figure 15)

was prepared for most of the wells in the Riyadh Area. The

names of wells, listed in Appendix C, coincide with the

numbers in the graphs. The graphs represented the decline

in water level in several wells, the actual values are from

1956 to 1978; predicted values are included to 1980. Pre

dictions are based on a calculation of the average decline

made for each well since it has been pumped. A general idea

can be taken from the graphs about how deep the water was

every year and is expected to be in the future.

It is noticeable from the decline curves of water level

Depth (meters) — 5*?57 !58j59j 60j6l| 5*?57 !58j59j 15 .165 .150 _135 180

from 1956to 1977 thenPredictedto1980 Declineof Water Levelin Riyadh Wells

► 2 6 9 2 3 ^56 17 1^1516 13 12 9 7 6 3 2 * |65 ]"S6(67|'"65|6'9'r7q7If 2 ]73] 7^75j?6"[7yp8"J79p_ |65 ]"S6(67|'"65|6'9'r7q7If 2 ]73] % Figure aa x e * o * ,« p e v x n a a et Numbers Welts 15

84 '5* £. *

•a £ c o a. A < ///s 5

(0 © H O v o •H H iH iH CM rH v \ CO © -I O 3! S ’ * -1 «

vn vn o vO CO ON I—I iH CVJ 111 I Ul Uf IfldQQ

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 86

^ oUl pfoW'foifced .dfioo rep',toPu fu^er 3\Moef copV^ 0U^e efP"1iSS\OP p.epf0'idvice 87

(Figure 15) for most of the wells in the city that were

pumped between 1962 - 1964, that there is a decrease in the

drawdown, or a rise in the water level. Then pumping from

deep wells has been increased, however, the water level

has resumed its decline. For example, the water level in

Nasiriyah-I Well was about 88 m in 1966 and 117 m in 1971,

a drawdown of 29 m in four years. At Mansouriyah, it was

about 26 m in 1966 and 36 m in 1971, a drawdown of 10 m in

five years. In Diriyah Well, to the north, the static water

level was 111 m below ground level in 1965 and 129 m in

1972, an average drawdown of 4.5 m a year. The decrease in

the rate of drawdown of Dariyah Well may be related to its

drawdown in 1961 - 1962 or it may be related to the develop

ment of other water sources and the drilling of additional

deep wells. In 1971, the static water level varied between

104 m in the Argah Well and 36 m in the Mansouriyah Well.

From the foregoing data, the average decline of the

water level ranges between 2.5 m a year in the Mansouriyah

Well and 10 m per year in the Diriyah Well with an average

decline of 5 m a year. At this rate of decline, by the year

2000 the water levels in the Argah Well will be as deep as

250 m below the ground surface (350 m above sea level), if

pumping is continued. One should note the difficulties that

appear if the depth of water reaches 300 m or more; this

will affect the efficiency of the well and it may cease to

be productive. For more specific well declines, see Appendix

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 88

B and Figure 15.

A piezometric survey made by MacDonald in 1973 revealed

that the rate of decline of the water level was 10.7 m a year

in the Badiaah Well and 7.38 m in the National Guard Well.

He reported a rate of decline of 7 m a year for central

Riyadh in 1973. The relatively new wells can be expected

to follow the same pattern of declining of water levels as

in the other well fields.

The water level of the well field at Riyadh will continue

to drop and at an increasing rate due to the continued ex

ploitation and insufficient recharge to the aquifer. So, if

we take MacDonald's (1973) average of 7 m a year to calcu

late what levels can be expected in central Riyadh for the

years to come, and start with the level of 1956, which was

about 543 m above sea level in the Shumaissi Well, then the

level can be expected to drop to 420 m by 1980 and to 280 m

by the year 2000. If we take an average decline of 4.5 m a year for the entire area, then the average level of the well

field estimated to be 500 m in 1971 would be about 460 m

in 1980 and about 370 m in the year 2000. These conclusions

are tentative because the lifetime of a deep well is about

20 years. A 20-year life seems realistic since the Shumaissi

Well was abandoned in 1974. Then as wells are abandoned and

new well fields are developed, the pumping rates and well

patterns will be altered to create different drawdown condi

tions.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A study by Stavors S. Papadopulos in February 1977 in

dicated that under the influence of a new well field north

of Riyadh would be such that the water level in Riyadh would

drop to 380 m above sea level or about 160 m below the 1956

level of 543 m by the year 2000. In reality, developing

other well fields around Riyadh at sufficient distance, is

useful if it allows a constant rate of discharge. It would

not affect the piezometric level as severely or increase the

withdrawal of poor quality water that is produced by exten

sive pumping on one well field. In this context, it should

be noted that the expected average decline for the coming

years can be somewhat less than what was previously cal

culated. Development of the well field north of Riyadh will

produce a predicted average decline of 3.6 m a year or if

the well field is developed at Muzahmiyah, west of Riyadh,

then the decline rate is expected to be 4.6 m a year.

MacDonald (1975) noted that there is a very slow annual

variation of the water level due to pressure changes through

out the year. The pressure is greatest in December and

January with a value of about 9490 MB, and is associated

with lowered water level, and the pressure is lowest in July

and August with the value of about 9320 MB, and is associated

with an increase in the water level. Semi-durnal fluctuation may also occur, due to lunar and solar tidal

effects. These effects have been noticed on automatic re

corders of the Ministry of Agriculture and Water on a Minjur

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 90

Well at Muzahimiyah. Also, since the temperature of water

is 50 to 60° C water vapor entrained in the water during pump

ing tends to increase water levels. Correct static water

level reading can only be made after pumping has been stopped

and the water in the well allowed to stand for a period of

time such that the vapor can "settle" out. Water temperature

increases with well depth; consequently, deeper wells exper

ience greater problems with water vapor. To cite an example,

the piezometric level practically measured in Sal-8 Well

rose about2 .7mabove the measured static water level when

a pumping test was run on January 28, 1978.

A piezometric map of the Riyadh Area was first made by

G. Brown in 1962. He was able to shut the pumps off in the

Riyadh Area Wells for 24 hours, in order to measure the

static water level in the fifteen wells completed at that

time (Figure 16 A). According to his map, the lowest water

level is at about 515 m in central Riyadh and the influence

of wells decreases with increased radius from Riyadh. Water

levels increase outward from the center and finally reach

521 m to the east of the Malez Well and south at the Bandar

Well, and to the northwest to 523 m around the Argah Well.

But the surface is influenced by the well at Diriyah which

had a water level of 516 m. The water level increases to

the southeast and reaches 534 m. Another piezometric map

was provided by Sogreah for 1966-67 (Figure 16 B) for the

entire formation from measurement made in Riyadh, Khurais,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 91 F i g u r e 16 A. Piezoine-tric map of Kinjur Wells an 1962 _____ (Front Brown 1962)

LV ^ ) Maather h V l*' . 5>a * /Was*

biYADH

>aisi 5»3 rational Guard 52^

'SP- Scale 1* 130,000

B.Sogreoh?s piezometric .Hap-66-6'

RIYADH

Hayir Public wells e Private wells Scale 1: 2500,000 Contours in meter

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 92

and Sudair. In this map the piezometric level was 513 m

above sea level in the center increasing within a radius

around Riyadh to 530 m eastward at Ksashm Al-An and 538 m at Hayir to the south. In this area, the piezometric gradi ent reported by Sogreah was 0.2%o between outcrop and Khurais. The grabens in the area have a direct effect on the

piezometric level, especially between the outcrop and Riyadh.

On Sogreah's piezometric map (Figure 15 B), the closeness

of 540 and 550 m contours between Dhruma-Dirab and Muzahimiyah

which indicates the difference in Piezometric surface of 10 m due to the faults in this area that block the flow between

the confined area and portions of the unconfined zones creat

ing a head loss with that difference in head.

From data available for this study, a piezometric map has been made for the years 1971 and 1980, including as

many wells as possible. The 1971 approximation was made by actual measuring or estimating the water levels based on

the rate of decline of each well since it was drilled

(Table XII). In some cases, adjustment was needed to avoid

complex contour lines. For the 1980 map, the water levels were

estimated or predicted considering an average decline of 6 m

a year for central Riyadh, of 5 m a year outside central

Riyadh, 4 m a year around The Hayir Area and 3 m a year in

Dirab and to the east at National Guard Well-2. The altitude

of the piezometric surface around the center of Riyadh in the

1971 (Figure 17) map is on the order of 480 m, and in the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 93

TABLE XII

PIEZOMETRIC ALTITUDE (m) OF SOME WELLS IN THE RIYADH AREA FOR 1971, 1980

1971 1980 1980 Well Measured Estimated Estimated Well Estimated

Shumaissi 493 — RR-2 459

Nasiriyah-1 475 421 Malez-2 437 Malez-1 489 435 Sal-1 462

Kuwliyah 495 441 Sal-2 470

Maather 491 437 Sal-3 471

Mansouriyah 508 466 Sal-4 472

Nasiriyah-2 481 427 Daghnah-2 467

Badiaah 486 432 Daghnah-3 470

Jiza 485 440 HR-3 475

Argah 496 451 NQ-1 470

Diriyah 512 467 NQ-2 474

Hayir 528 483 NQ-3 476

Daghnah-1 516 470 Sal-5 470

Bander 485 440

Nt.Gd.-l 502 467

Beijah-1 527 491

Dirab 516 489

Khalid 492 438

Nt.Gd.-2 510 483

R.D.W. 521 476

RR-1 503 458

Beijah-2 528 492

Average 500 m

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 94

Figure 17 General piezometric Map for 1971

3) 510

527* Beijah-1

528# Beijah - 2

Scale 1* 250,000

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 95

1980 map (Figure 18) is 430 m. Around Diriyah, the level

was about 517 m in 1971 and seems not to have been affected

by pumping at central Riyadh, in the 1962 Brown's map. In

the 1971 map, it had come under the direct influence of

pumping and was reduced to 510 m and is expected to be

about 467 m in 1980. In the Hayir area, the surface was

at about 534 m in 1962, according to Brown's map, and 537

in 1966-67 on Sogreah's map due to the discharge reduction

between 1962 and 1965. On the 1971 approximation map, it

was at about 525 m. It is predicted to be 480 - 485 in

1980 (Figures 16, 17 and 18).

Movement of The Water

Ground-water is in constant motion. It moves along

gradients which generally follow the dip of an aquifer. The

general dip of the Minjur is east and northeast (average

dip is 15 m/Km). The direction of the flow of water would

be expected to be in the same direction. Yet, the piezo

metric maps of the Minjur Aquifer in the Riyadh Region have

shown that production from the well field has created a

cone of depression that locally distorts the general east-

northeast pattern.

The flow of water can simply be determined by:

Darcy's law: Q = K A i

Where Q = the flow rate

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 96 F i g u r e 18 472 «4 General Piezometric Map lor 1980 in Riyadh area 471 * 3

Dariyah

483 • Hayir

491 Beijah-1

492* Beijah- 2

Scalet 1: 250tC00

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 97

K = coefficient of permeability

A = cross section aquifer area

i = hydraulic gradient

by considering the head difference between the Riyadh Well

field prior to pumping of about 543 m at the Snumaisi Well

and the outcrop at Well PM4 near Marrat of 552 m (well’s

log) which probably was higher (maybe up to 555 or 560 m)

because of the pumping effect at Riyadh. A hydraulic grad- -4 ient would be of the order of about1.5 x 10 considering

that 80 Km of distance exists between Riyadh and the out

crop. The permeability through the average thickness of

the Upper Minjur Aquifer would be equal to the transmissi- -3 2 bility which is estimated to average 4.0x10 m/3 multiplied

by the length of the aquifer. The flow rate can be calculated

as follows:

Q = K A i Q = K M*L x i

Q = T . L . i Flow rate per 1 Km strike is

= 4.0 x 10 3 m 3/sec x 1.5 x 10 4 x 1000 -4 3 = 6 x 10 m /sec 3 = 19,000 m /year

and for the entire aquifer length 640 Km

= 4.0 x 10" 3 x 1.5 x 10“4 x 640,000

= 3.8 x 10 3 m 3/sec

= 1 2 x 10^ m 3/year

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 98

But this quantity of water does not seem likely to flow,

because the formation thins south and northward. About 270 Km

of the Minjur Outcrop seem to be wide enough to receive

water. The flow rate for this length is as follows:

Q = 4.0 x 10~3 x 1.5 x 10"4 x 270,000

= 1.62 x 10 1 m 3/sec

= 5 x 10^ m 3/year This estimate is for the Upper Minjur only. The assump

tion also considers the water level at PM^ although this

well is penetrating the aquifer to the Lower Minjur. More

over, one should consider that the flow rate under the existing

pumping conditions is a lot higher and may be up to ten times

the flow rate before pumping. That is due to the cone of

depression that has been created which consequently changes

the hydraulic gradient.

Age of Water

The age of ground-water is that period of time that has

elapsed since the water fell as a rain. The age of the water

in the Minjur Aquifer has been reported by a number of in

vestigators. According to Brown (1962) samples of water from the 14 . Shumaisi Well were dated by use of C and indicated an

age of 24, 630 (±500) years. Age determinations using

carbon isotopes were also used by Mrs. G. Delibrias (Sogreah,

1968) on samples of water from the Minjur Aquifer taken from

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 99

a number of different places. In the Riyadh Well field

the ages of this determination range from 34,800 (±3000)

at the Shumaisi Well to 23,000 (±1100) at the Hayir Well

(Table XIII).

It appears that the age of water increases toward

the east as a result of the time it takes the water to

flow from the outcrop area to the west. The age of water from the Shaqra Well (Lower Minjur) approximately 200 Km

northwest of Riyadh, was determined to be some 20,000 years

B.P. (before present) and water from the lower Minjur at the

outcrop (Well Ml) was dated at 15,500 years B. P. In Riyadh

the age of water was determined to be as high as 34,800 years

B.P. The water age at Hayir is as old as some 23,000 years

B.P. but the date is questionable.

Faults apparently exert a local controlling influence on

the movement of water in the Minjur Aquifer. Water at Dhruma

has been dated at 38,000 years B.P., 2500 years older than

at the Riyadh Area, even though it is about 40 Km nearer

to the outcrop. The difference may be due to faults pro

viding communication with an aquifer bearing older water or

to slower flow of water caused by blocking faults. MacDonald

(1975) reported that the variation in regional age pattern

shows that the ground-water flow is not directly down dip,

but is strongly controlled by the grabens. (See movement

of water.)

I think that the anomalously young age (24,000 years)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE XIII

AGE DETERMINATIONS OF WATER SAMPLES FROM THE MINJUR AQUIFER (From Sogreah, 1968)

Location Penetration in the Age Minjur Aquifer

Riyadh 197 m lower part of 34,800 Shumaisi, 1967 Upper Minjur ± 3000

Hayir 46 m upper part of 23,000 1967 Upper Minjur ± 1100

Jiza 117 m middle part of 34,800 1967 Upper Minjur ± 3000

Najama'ah 168 m middle part of 24,200 1968 Upper Minjur ± 1000

Dirab 103 m middle part of 34,800 1967 Upper Minjur ± 3000

Shagra Upper part of the 19,900 1967 Lower Minjur ± 700

Ml Minjur Middle part of the 15,500 Outcrop, 1967 Lower Minjur ± 400

W. Bu'ayja (Not Reported) 30,900 1968 + 1800

Dhruma (Not Reported) 38,000 1968 ± 4000

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 101 at Hayir in the Riyadh Region may possibly be caused by the

faults system that lies some 10 Km south of the well. This

effect decreases northward away from the fault zone. It

may be that the faults allow younger water to invade the

Minjur. The difference between age determinations by Brown (1962)

and Sogreah (1968) is maybe due to the methods by which the

samples were collected and analyzed. Also, the samples

were drawn from different waters. Intensive pumping has

probably drawn more water from all portions of the aquifer

around Riyadh. The water to the east is older, but the

water to the west is younger. The aquifer may also be in

communication with the Lower Minjur Aquifer or even The

Jilh Formation; both contain older water. If this is the

case, then water could be drawn from these units during

periods of intensive pumping. It seems that if the water is

drawn from a westward direction, the water produced should

be younger, but that is not the case. Sogreah's (1968)

dates showed older water than those of Brown (1962). The

water was sampled from the same well (Shumaisi), but a

period of six years elapsed between the sampling dates. In

any case, it is not easily explained. The age difference

may be due to mixing of older water during periods of in

tensive pumping. Such water could be drawn from the Lower

Minjur or The Jilh Formation if communication exists between

these units and from the eastern portion of the Upper Minjur

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 102

Aquifer or the difference may be due to the use of a more

accurate technique by Sogreah. Although this discussion

seems reasonable, one should consider the calculation of

Sogreah (1968) which revealed that water to the east of the

Riyadh Center would require 500 years to move 10 Km if the 3 system were pumped at 1 m /sec, and one considers an Upper

Minjur with a thickness of 80 meters and a porosity of 30

percent. The time required for water to move from deeper

zones to the area of the well field was calculated to be

about 180 years. These calculations are based on an aquifer

thickness of 140 m, an average permeability of 10 ^ m/sec and

35 m pressure differential. It seems likely that the water

came from formations lower in the section.

Recharge of The Aquifer

Recharge area

The only source of recharge for The Minjur Aquifer is

the outcrop area, 80 to 90 Km west of the city of Riyadh.

The outcrop width ranges from 2 Km to 33 Km, and is widest

in the area between Khashm Al-Dhibi and Ushaiqir, although

it is partly covered by eolian sand in this area (Plate No.

2). The northern extension of the outcrop is also mantled

by eolian sand. This sand may play a significant role in

the recharge of the aquifer. To the south, the recharge

is less, because of the limited outcrop area. Here the out

crop is narrow and partly covered by alluvial deposits which

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may contribute to recharge of the aquifer. Narrowing of the

outcrop belt to the south coupled with the smaller amounts

of rainfall in this area serve to greatly reduce the infil

tration in the southern outcrop area.

The Minjur Sandstone Outcrop extends from south to north

as an eastward facing arc more than 800 Km long. Sogreah 2 considered the outcrop area to be 6500 Km which represents

the easily identifiable area of the entire Minjur Outcrop.

MacDonald (1975) divided the Minjur Outcrop into the Upper

Minjur Outcrop with an average width of 5 to 10 Km and a

Lower Minjur Outcrop that is about 7 Km wide. (See the

geologic description of the Minjur Formation, p.15.)

Precipitation

The precipitation is the quantity of water that is dis

charged from the atmosphere to the earth's surface. Precip

itation intensity over the outcrop of Minjur differs accord

ing to the season of the year but generally rainfall is

scanty. Estimates and measurements of precipitation over

the outcrop area are varied. According to the Aramco Hand

book (1960), most areas of Central Arabia and the whole

Ruba Al-Khali receive less than 100 mm of rainfall annually

(Figure 19 a). Thus, the Minjur Outcrop Area receives no

more than this amount; in the extreme northern portion of the

peninsula the annual rainfall reaches 200 mm. Sogreah (1968)

estimated that the average precipitation for the outcrop area

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 104 100 s 100 b. b. Dincer (From and others 197*t)

Figure 19 Figure m m Precipitation Maps 750

500 )

960 00 a. a. Aramco (From i

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 105

is about 75 mm. Dincer, Al-Mugrin and Zimmerman (1974)

presented a map (Figure 19 b) which shows that the average

precipitation on the outcrop of the Minjur exceeds 100 mm

annually and 50 mm further to the south at Ruba Al-Khali.

The map also indicates that the area north of the outcrop

belt receives about 50 mm per year. Thus, they gave a more

precise estimate than that given by Aramco. In Marrat, less

than 10 Km east of the outcrop, the precipitation has been

estimated to be 100 mm. In contrast, MacDonald suggested

that the Minjur Outcrop receives 120 mm of precipitation per

year.

Runoff

Runoff is the quantity of water discharged by the surface

streams. The term "runoff" may be used in a variety of

contexts. Here the term is used simply to imply direct run

off on the land surface that is eventually restricted to

flow in channels. The Minjur Sandstone is largely covered

by sand dunes and runoff is very low due to the high porosity

and permeability of the sand. In contrast, a significant

portion of precipitation goes into runoff on the Minjur Sand

stone because of cementation and the presence of impermeable

layers that are interbedded in the formation. Runoff is

greatest from the Middle Minjur Outcrop which is composed

of impermeable shales and mudstones. The Minjur Sandstone

is bounded by shales and limestone of the Marrat Formation

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 106

to the east, and the Tuwaiq Limestone in the southern por

tions of the formation. It is bounded by the impermeable

layers of the Jilh to the west. Because of these imper

meable layers with high runoff that bound the Minjur, run

off increases into the Minjur Outcrop Area.

In arid regions, the percentage of runoff decreases with

decreasing annual rainfall and is generally less than 10

percent (Chow, 1964). The scarcity of vegetation in arid

regions increases the amount of runoff, as vegetation can

play an effective role in impeding the flow of water over

the ground surface. The outcrop of the Minjur is in one

of the most arid regions in the world as only 0.073 percent

of Central Arabia is irrigated (Milos, 1971).

Infiltration

Infiltration in this context means the movement of water

through the soil surface into the ground water. Sogreah (1968)

noted that wells situated in the Minjur Outcrop at Tabrak

and Sidriayah experienced an increase in water quality and

had higher water levels during the somewhat wetter period

from November 1967 to April 1968. Moreover, MacDonald (1975)

observed that piezometers at Shaqra and Ushaiqir have had

constant water level for long terms, even though they were

being pumped. Such a response in the quality and the level

of water suggests that infiltration takes place at the out

crop and that the Minjur is recharged, at least in part, from

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 107

these areas. The topography of the outcrop plays a significant role

in the infiltration process. Where the outcrop is covered

by sand dunes, infiltration should be higher than on the ex

posed formation. Locally, rain accumulates in ponds which

dry up within two or three days, although the larger accumu

lations may last for a week or more. The rapid drying of

these ponds indicates that evaporation and infiltration are

occurring in this area. Infiltration is greatest in areas

of lower slope and where permeable layers crop out. The

steeper slopes and the less permeable layers impede infil

tration and in such areas the water is lost to evaporation

and runoff.

Different rates of infiltration for the Minjur Aquifer

were determined by a number of investigators on local ob

servations. Sogreah (1968) arrived at infiltration rates

of 0.8 mm/year and 1.7 mm/year from dating water in the wells

at Ml and Shaqra. All over the Minjur Outcrop, a rate of

1.5 mm/year is considered. Sogreah also indicated that only

1.5% of the annual rainfall in average years was likely to

infiltrate deep enough to avoid being evaporated. MacDonald's

(1975) measurements were up to 7 mm/year. Moreover, mea

surements over the sand dunes were arrived at as an infil

tration rate of 20 mm/year by Dincer and others (1974).

Recharge from sand dunes

In a study of infiltration and recharge through sand

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 108

dunes in arid regions, Dincer, Al-Mugrin and Zimmerman (1974)

found that sand of the Dahna Area had a moisture content

of 3.67 percent by weight at a level of 300 cm below the

surface. The same measurements of moisture have been made

for auger holes in other sand dune areas including those

sand dunes that cover the Minjur Outcrop. All measurements

indicate moisture at a depth of 300 cm. Runoff in sand

dunes is negligible and transpiration by vegetation is vari

able but generally negligible. The temperature of sand dunes

varies seasonally and diurnially. The moisture content of

sand dunes at the top is zero except during and immediately

following a rain. At depths between 100 cm and 250 cm, the

sand contains increasing amounts of moisture. The zone be

tween 300 cm and 600 cm had the greatest moisture content.

Below 600 cm there is a slow reduction in the percentage of

void space occupied by water.

According to Dincer and others (1974), experiments de

signed to test the rate of infiltration of rain water into

dune sand revealed that the use of 50 mm of water on a 1 m

column of well-graded dune sand (mean grain size 0.15 mm)

produced a penetration of 35 cm in 24 hours. Using the

same apparatus and a mean size of 0.30 mm, the rate was

more than 100 cm in 24 hours. These data indicate that

large portions of rain infiltrate coarse dune sand and that

evaporation from the surface of dunes is minimal. 3 They also used Tritium (H ) content xn an effort to

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 109

estimate the rate of recharge. To do this they determined the Tritium content at different depths and compared it

with the Tritium found in precipiation on Bahrain Island.

The Tritium content was found to increase with depths to

6m below the surface. They calculated the annual mean re

charge since 1964 to be 23 mm. The widespread application

of this estimate is questionable since the 1969-70 low pre

cipitation levels were not represented in it; rainfall dis

tribution is sporatic; and the loss during the 1972 dry

season reduced the recharge to 19 mm. However, they indi

cated that the average annual recharge would be 20 mm. The

percentage of water reaching the saturated aquifer is un

known. Some of it may be returned to the atmosphere by

deeply rooted desert plants. More detailed studies will be

required to resolve this question.

In their extrapolation of results, Dincer and others

(1974) indicated that in the sand dunes of the Riyadh Region,

infiltration and probably the recharge to the Minjur Aquifer

Outcrop are widespread phenomena for sand dunes with rela

tively large grain size. Dunes, composed of fine sand have

higher evaporation losses, and deep movement of water seems

to be possible. Factors governing the process are climatic

and include like atmospheric temperature, humidity, and evapor

ation, and physical factors such as mean grain size and the

size distribution of the dune sand. Thus, in the Ruba Al-Khali

where the precipitation is 50 mm/year and the mean grain size

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is 0.25 mm, recharge is hardly possible, but in areas of

higher precipitation, as 300 mm a year in Sudan, even dunes

composed of smaller sized sands transmit water to deep aqui

fers. West of Riyadh, dunes cover portions of the Minjur Outcrop,

and the precipitation is over 100 mm. Consequently, recharge

occurs and moisture is found to depths of 6 to 5 m. Overall,

strong indications show that a precipitation of 70 mm is near the threshold for recharge in sand dunes with a mean size of

0.3 to 0.4 mm and a mean annual precipitation of 150 mm ap

proaches the recharge for dunes with a grain size of 0.20 mm.

Recharge from clay zones

The sharp reduction in pressure caused by extensive pump

ing can provide water in this manner from clay-rich zones

adjacent to/or interbedded with the aquifer, which then can

increase total reserves of water. Recharge from the mud

stones, clays, and sandy shales of these zones can add signi

ficant amounts of water to the aquifer. Clay and mudstone

have large porosities up to 40 to 45 percent, about double

the porosity of the sand and sandstone.

Recharge determination

There have been different estimates for recharge. Sogreah

(1968) indicated from his calculation that the recharge

equals the annual infiltration rate which he estimated to be

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Ill

1.5 mm.year over the Minjur Outcrop. However, it is question

able whether or not the recharge estimations above include

recharge from the mantle dunes because Sogreah made no

mention of the relation between them and the Minjur. The

estimate of recharge in sand dunes reported by Dincer and w1- others (1974) was 20 mm/year. It is questionable whether

all of this water infiltrates to the main aquifer or whether

some of it is removed by evaporation. At any rate, it is

still a sizable amount and should increase the infiltration

estimates.

In his work, MacDonald (1975) estimated the Upper Minjur

recharge to range from 3.5 mm to 7 mm/year. Considering an

annual rainfall of about 120 mm, the recharge is about 3 to

6 percent of the annual rainfall. The recharge area of the

Lower Minjur is thought to be similar to that of the Upper

Minjur. MacDonald (1975) suggested that there is leakage

into the Upper Minjur from the Middle and/or Lower Minjur.

The estimates of MacDonald are greater than that made by

Sogreah and more specific. Neither MacDonald nor Sogreah

referred to an increase of recharge through the sand dunes

that locally mantle the outcrop. Considering the several estimates from 1.5 mm/year as

the annual recharge rate directly into the Minjur Sand

stone, 3 to 7 mm/year, into the sandstone and up to 20 mm/year

into the sand dunes, then an average recharge rate of 5 to 8

mm/year for the entire Minjur seems reasonable. The annual

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recharge based on this figure would be as follows: 2 for 6500 Km (entire Minjur Outcrop):

6500 x 10^ x 7 x 10 ^ = 45 x 10^ m 3/year 2 for a limited wide area of 4800 Km :

4800 x 106 x 7 x 10-3 = 34 x 106 m 3/year 2 and for an area of 2200 Km equivalent to the Riyadh Area:

2200 x 106 x 7 x 10-3 = 15 x 106 m 3/year

Tectonic controls

Our present understanding is that the grabens bring the

Marrat Formation and even the Dhruma Formation, both composed

of impermeable rocks, into contact with the Minjur Sandstone (Plate No. 1). The grabens between Dirab-Dhruma and Muzahmiyah

and west of Muzahmiyah probably also displace the Marrat

and Dhruma against the Minjur.

Resistivity studies by Sogreah (1968) and M. MacDonald

(1975) revealed that a system of east-west and south-northeast

trending grabens extend from Majmaah on the north to Dhruma

on the south. These features are part of the continuous

arc graben system of Central Arabia that begins at Harad

110 Km east of Riyadh and extends through Wadi Nisah and

Tuwaiq (Figure 4). The estimated displacement from a profile

at Jabal Fadah between Khashm Al-Qaddiyah and Khashm Al-

Mazruhi (Sogreah, 1968) is about 100 m on the eastern zone,

or Dhruma Zone, and about 300 m on the western zone, or

Muzahmiyah Zone. Within the resistivity profile at Jabal

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Fahdah and west of the Muzahmiyah Zone, there is a similar

and parallel graben system with the same type of displace

ment. A third system is located near Khashm Al-Muzruhi with

200 to 250 m displacement. A similar graben system is present

only 10 Km south of Hayir. These grabens probably affect

movement of water in the Minur Aquifer because most of them

lie between the outcrop area and the Minjur Well field in

Riyadh. Thus, they have greatly affected the quantity and

the quality of water in the Minjur. It may be that these faults disrupt the continuity of the aquifer and form a bar

rier or a series of impeding obstructions between the recharge

area and the ground-water withdrawal area at Riyadh. If this

is the case, it will become a very serious matter when pump

ing in Riyadh reaches the point that the area of influence

of the well field extends into and beyond these fault systems;

in other words, when the recharge of the aquifer in the

Riyadh Area becomes more closely dependent upon the water-

table at the Minjur Outcrop. More information will be learned

about the aquifer continuity as the area of influence ex

pands .

Water Reserve

Water reserves in an aquifer system are the total amount

of water than can be economically withdrawn from that system.

According to Sogreah (1968), the entire Minjur Aquifer con

tains large reserves of available water (Table XIV). Most

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TABLE XIV

WATER RESERVES ESTIMATES IN THE MINJUR AQUIFER (After Sogreah, 1968)

Depth from Volume Exploitable Salinity Location sea level Stored MCM Water MCM g/L

+570-0 750,000 250,000 1.2 Toward Outcrop

0 to - 500 630,000 210,000 1.3 Riyadh

- 500 to - 630,000 210,000 2 East of Riyadh 1000

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 115

of this water is thought to have entered the aquifer during

the wet periods of the Pleistocene Epoch. Consequently, the

current pumped wells withdraw much of their water from the

reserve. The withdrawal from The Riyadh Well field coupled

with the other new fields nearby, will soon affect the

artesian Upper Minjur reserve in the area.

That portion of the Minjur which extends from the out

crop at elevations of about +570 m eastward to the point where

the Minjur is at sea level, has a volume of water estimated 6 3 to be as high as 750,000 c 10 m . It contains about 1.2 g/L

dissolved solids. Between sea level and the level 500 m below

the volume reaches 630,000 10 6 m 3. The total water reserves

east and west of Riyadh in The Minjur Aquifer exceeds two

million million cubic meters. The quality of water is

worse east of Riyadh than that west of Riyadh. In addition

to these amounts of water reserve, an unknown amount of

water is thought to be available from discharge of clayey

units adjacent to the aquifer. MacDonald and others (1975)

reported reserve figures for the Upper Minjur at 65,800 x

10 6 m 3 . This water is divided into 1,800 x 10 6 m 3 in arte-

sian storage and 64,827 x 10 6 m 3 in water table storage.

Not all of the water stored in the Minjur is available

for exploitation. The volume that can be released from

storage reserve is only about one third of the total water

stored in the aquifer or something in excess of 200,000 x

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10 6 m 3 of water from the reserve west of Riyadh. The total

volume produced from Upper Minjur to date is some 500 million

cubic meters, (Figure 23) which seems very small compared

to the estimated reserves. The proposed production from

the Minjur Wells in Riyadh and north and northeast of Riyadh 3 will account for some 310,000 m /day or a total of some 2,250

x 10 6 m 3 for the next 20 years. This volume exceeds the g artesian storage volume of Upper Minjur only of 1,008 x 10

cubic meters, which means that within less than 10 years of

pumping the aquifer will depend on the reserve of water in

the water-table storage. Difficulties may develop within the next few years because

of the grabens between the outcrop and Riyadh. They may

cause increased lowering of the water levels and technical

difficulties associated with pumping. In addition, as the

Minjur reserve is lowered, increased amounts of low quality

water may appear in the producing area.

Discharge of The Aquifer

Discharge is the rate of flow from an aquifer at a

given instant in terms of volume per unit time, and includes

losses to the aquifer through evaporation, transpiration

and wells.

Evaporation

Evaporation is the process of water loss from the surface

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of the earth through the action of sun and atmosphere. It

is active in arid regions where temperature is high. Losses

through evaporation alone may account for half of the annual

rainfall in arid regions (Chow, 1964). Since the outcrop

area of the Minjur Sandstone lies in one of the dryest areas

of the world, one would expect evaporation to be very high,

and it may exceed 3000 mm/year due to the great aridity and

the extensive heat, especially during the long summers.

The evaporation rate is highest in the summer and lowest

in winter. The summer maximum correlates with daytime temper

atures as high as 45° C generated by incident solar radia

tion of up to more than 700 Ly/day. In contrast, in December O temperatures drop to an average of 14° C and may reach 0 C

in the nightime. The incident of solar radiation is about

300 Ly/day. By way of comparison, the evaporation rate of

Lake Mead which lies in a very arid region of Nevada, averages

1750 mm/year.

Water losses from soil pore spaces have not been deter

mined for the area of the Minjur Outcrop, but such measure

ments have been made in Arizona, where Hilgman (in Chow,

1964) found losses due to upward movement in soil to be 134

mm/year.

Thus, the high evaporation rate from the land surface

and from the interstices of the soil accounts for most water

losses and largely explains why only a small amount of the

precipitation infiltrates to the deeper parts of the Minjur

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Aquifer.

Transpiration

Transpiration is the process by which the water escapes

from plants to the atmosphere. It is, however, through

the openings or stomata of the plant leaves that transpira

tion takes place (Chow, 1964). Moreover, investigators have

shown that the stomata are rarely open in plants of arid re

gions. The density of plants on the Minjur Outcrop is very

low further reducing the significance of transpiration. A

general idea provided by Chow (1964) is, I believe, satisfac

tory to describe transpiration from the Minjur Outcrop.

Because of the low plant density and relative physiological inactivity characteristic of arid regions, rates of evaporation even when soil water is freely available are usually well below those characteristic of physiologically active dense communities...(p. 19-24)

Phreatophytes are plants which have the ability to draw

water from streams and shallow aquifers in most arid regions.

Robinson (in Chow, 1964) has estimated that the phreatophytes

which cover 15 million acres in 17 western states of the

U.S., may transpire 20 - 25 million acre-feet of water. Since

there are no permanent streams in Central Arabia, and only

a few scattered oases, it is unlikely that phreatophytes

such as palm trees are a widespread problem. Yet, they may

locally account for significant amounts of transpiration,

and their effects should be investigated further. Finally,

it is obvious from the general lack of phreatophytes and the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 119 inactivity of other desert plants that transpiration may be

low on the Minjur Outcrop, although more study is needed.

Wells

Distribution of wells and history of development. Dis

charges in great amounts come directly from wells exploiting

the Minjur at Riyadh plus the other areas that produce from

the Minjur, but not as much as at Riyadh. The wells in the

Riyadh Area are distributed over an area of more than 2200 2 Km (Figure 20). The first deep well, the Shumaisi Well,

was drilled in Riyadh in 1956. In 1957, two more wells, the

Nasiriyah-I and the Males Well, were completed. The Kauliyah

Well was completed in 1958 and the Maather Well in 1959.

Almost every year, more wells are added. Projects have

been also developed in designing and preparing well sites.

As the first wells drilled were concentrated in the center,

the more recent wells are farther apart and their sites were

selected for the most efficient production. The wells in the

appendices are ranked according to their age: the oldest first.

Other information includes, the static water levels measured

(Appendix B) when available. It also includes production

rate (1/sec), (Appendix C), the elevation of each well and some

of the hydraulic properties such as transmissibility and per

meability, listed in Appendix A. The current well pattern

(Figure 20) extends northwest-southeast, about ten wells

in Central Riyadh and five wells on Salbukh Road. There

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 120 F i g u r e 20 "Minjur Wells Locations in Riyadh Area" (from Ministry of Agriculture Files)

Salbukh

gArgah DW2 •Air Port Kouliyah Maather • *2 Malaz N.d&urd-2

Dirab 0 Dagnah-4 # Hayir

e Beijah-l • Public Supply Wells 9 Other Purposes 0 Beijah-3 o New Wells .Bei.iah-2 Scale 1: 250,000

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 121

are new wells between Wadi Numar and Qaddiyah; about nine

wells are on the southeast Kharj Road. To the south, ten

wells are within 2 to 5 Km of each other. To the south

west, there are three wells at Dirab. At least 50 wells

have been drilled in the area of Riyadh including private

wells, irrigation and public supply wells.

Well sites are selected and designed before drilling.

This is especially true of the wells that have been drilled

in the last few years. Suggestions for the design of new

well fields have also been.made. Examples are the sug

gestions cited by Otkun (1973) which include:

1. Avoiding concentration of wells in certain areas

which will result in depletion of ground-water level. At

the same time, they should not be too far from the city to

avoid the increase of the cost of distribution.

2. The land on which the wells are to be drilled should

be state property or not expensive. The pipelines should

avoid crossing populated areas as much as possible.

3. Elevation of wells should be such that the pumping

level will be less than 300 m by the end of 20 years. Note

that this will generally require a rate of depletion of about 5 m/year.

4. Quality should not exceed the limits currently being

in existence these days. Wells should not be too close to

each other.

A new well field of 18 wells about 30 Km north of Riyadh

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. will be added. Some wells have already begun production.

Another well field of 22 deep wells will be added by 1979.

They are located about 50 Km northeast of Riyadh. The total

number of wells belonging to the Minjur Aquifer in and around

Riyadh will be more than 80 wells by the year 1979.

Exploitation of wells. Exploitation of wells producing

from the Minjur Sandstone beneath Riyadh was begun in 1956,

when the first well was drilled. Since then the number of

wells has increased as has the production. Production started

with 35 1/sec in 1956-57 from the Shumaisi Well and was in

creased gradually to a total of 45 1/sec for two wells. In

1958, the production was 105 1/sec, over 600 1/sec in 1967

and more than 900 1/sec in 1971, etc. (Table XV, Figure 21).

There is almost a yearly increase in water requirements by

people in the city as a result of the increase in the rate

of growth. The production increased as the number of pro

ductive wells increased. Production of all wells in the

Riyadh Well field is shown in Appendix C for the years since

1956.

Available data show that the average water level alti

tude fluctuation coincides with the production from wells.

There have been some fluctuations in the water level average

since the well field began production (Figure 21). It de

creased between 1961 and 1963 and rose after that. Then the

level declined again but more gradually as the production

increased with an increasing number of wells that have been

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123

f rdcin 0 Production of

Accumulation Accumulation

h •-3

9395100 5347980 1011780 2312640

o 38794536 49201416 77386416 28532196

141273096 164833116 192295716 c

50 a er ^ Year a 3 m

3035340 4914360 9886536 1300860 1011780

f 12141360 61342776 1994652019368360 97332936 116701296 10406880

> t-3 T O !>i rd m 8 Q on 3564 8316 2772

53064 75240 27462600 64548 23560020 13464 28116 1026234043956 16043940 11088 4047120

•

> Altitude W.L. 512 507502 67320 24571800 515 54648 527 22968 8383320 18269856 496 28116 10262340 532

TABLE TABLE XV / Total L/S

35 543 45 542 Production 950 815 510 670 355 555 518 690 290

TOTAL PRODUCTION, NUMBER OP WELLS,

AVERAGEWATER LEVEL OF MINJUR WELLS

Abandoned

i— * Productive

17 17 18 18 850 19 20 11 12 Existing

1 1 5 5 140 536

1516 1417 14 16 355 360 420 496 499 520 28512 33264 21 11 20 23 15 20 21 21 Year 1963 1964 1965 1958 4 41968 1051969 538 1961 1962 1967 1970 1971 1960 7 7 170 1966 19571959 3 1956

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 124 C 0 O p mm -H

C C rd P rd 0 P E CM P o 0 o o —I id —I +) +) rfj o rfj i •H *P •H 439603656 640000000 303446976 345797196 U C T I 0 I T C U td P a) rd E >r PROD m 87000000 526500000 51157160 42350220 40471200 42639300 388436496 38447640 262975776 32232420 224528136 110000000 TOTAL rd td >1 a 310000 140184 238000 110880 116820 105336 • • Av. a) •P •p PI 12 £ 0 rH •H 470 480 116028 497 88308 TABLE XV (Continued) O ^ ih PI w Eh a P 0 u O rd O CM >0 •H -P •H 3890 460 1770 14001465 1475 485 475 rd o O a) pc •P 2 4 3005 465 1 2 1 *3 'O Td Wells w O 2 0 u •P CM rd 36+ 31 23 1115 27 1330 492 X tjia •H CO 4J W •H •H 37 43 69 53 32 Not Including Dirab Wells Production of Average 22 Operating Hours * + i u n 0) >• 1979 87 81 4 1977 1978 19741975 351976 37 29 31 1973 1972 28

Total Production,Number of Wells and Average Piezometrio Surface of Min.lur Wells in Riyadh Area Nc.of.wells.9 Production 56 57 59 73 58 63 64 45 66 68 71 67 69 70 72 ^ 7 75 76 60 61 62 77 78 79 I □ o o f\> o H* Production o ofNo. wells IF" liue nmeters r e t e m in Altitude o fO © o o L/S

VsJ o o O o ON -4— tS" o © o ■p- o o ■fr Vjt o o 126

developed away from the center. It was almost constant be

tween 1969 and 1970; in fact it rose a little in 1970 (Figure

21). After 1974, the water levels continued decreasing

almost steadily as a result of developing a number of wells.

Not all wells in the Minjur are used for the public

water supply. Some have been used privately. For example,

of the seven wells that existed in 1960, only three wells existed with a yield of 65 1/sec, while the rest with a yield

of 110 1/sec were used for private and agricultural purposes.

The number of private wells differs from time to time to the

point that the production of some wells is divided between

private use and the water supply of Riyadh. Now some 37

wells distribute to the public supply (Figure 22).

Estimates and calculations of the total daily production

of the Riyadh water supply are not in complete agreement.

Sogreah (1967) reported a total yield of 460 1/sec of which

350 1/sec were used as the Riyadh water supply and 110 1/sec

were produced by private owners. In 1969, Shamim and

others calculated a total supply of 950 1/sec or 54,720 3 m /day for a 16 hour operation average. Otkun (1973)

estimated that the average production of each well is 50 1/sec

or 800 gpm for a total yield of more than 1000 1/sec. He

predicted that production including water from other sources

would increase to 1400 1/sec by 1975 and that by 1980 it 3 would be 173,000 m /day or 2000 1/sec. Data collected for

the present study give a total yield of 850 1/sec for 1969,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 22 127 Public Water Supply Wells Distribution

Salbukh 4 DW 9 Salboukh 3 DW i Salboukh 2 DW

Salboukh 1 DW

Salboukh 5 DW V .Argah DV/ 2 Airport DW Argah DW Malez 2 DW DW Shemaisi T.P Malez T.P : 1 DW RR 2 DW Badiaah

NQ 3 1

Hijaz DW? \ • :

KH 5 Dagnah Manfohah T.P. Dagnah

Dagnah ^

\ .Dagnah k> Hayir FTP

Beijah DW

J. 3eijah DW eijah DW 2

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 128

1330 1/sec for 1973 from the Minjur alone, and using these

data a reasonable prediction for 1980 seems to be at least

3500 1/sec from all private wells and that portion of the

Riyadh water supply produced from the Minjur Aquifer in and

around Riyadh. Quimp (1972) reported the yield from 16

Minjur wells to be 11,925 gpm or 755 1/sec with an addi tional 5685 gpm or 358 1/sec from 12 shallow wells for a total of

1114 1/sec. But, from the data gathered, this amount only

accounts for the Minjur wells.

Large increases in water production from the Minjur wells

occurred in 1971 - 1972 and 1976 - 1977. Since water con

sumption is closely related to growth of the city, these in

creases were probably due to the increased rate of growth

caused by economic factors that encouraged companies, busi

nessmen and workers to move to Riyadh. As cited previously, even the total amount of the ex

ploited water is very small in comparison with the high

reserve of the aquifer. Yet, even though a large reserve

is known to exist, caution must be exercised in developing

more wells in the future as each increase in production in

creases the rate of decline of the piezometric surface.

In fact, the decline of water level was noted from the time

the wells were first drilled in Riyadh. Currently the wells

at Central Riyadh are concentrated in roughly a circular area

of influence that has a radius of about 9 Km. Much of this

cone of depressions on the piezometric surface experiences

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 129

an average decline of 5 to 7 m/year. Such declines greatly

increase the cost of pumping and may require the installa

tion of new equipment to exploit deeper zones. Moreover,

the expansion and decline of the cones of depression may

bring water with undesirable qualities into the wells.

In general, wells in the Riyadh Area are considered to

have a life time of about 20 years. Then they must be re

placed or shut down. A number of wells have been removed

from production. These include the well at Shumaisi which

ceased in 1974. Nassiriyah-1, Maather-1 and Argah Wells were unproductive in 1977-1978. Some of these wells are being re

placed by new wells not too far from the old ones. Maather-2

and Argah-2 are replacement wells constructed near former

production wells. Exploitation of the Minjur Aquifer in the Riyadh Region

is shown in Figure 23. The figure shows the accumulation

withdrawal of the aquifer since 1956. The total withdrawal

of the Minjur from 1956 until 1979 will exceed 600 million

cubic meters.

Water Quality

General

Water quality is a function of the dissolved substances,

solids, organic material and gases in the water. The measure

of the mineral or "dissolved solids" is expressed as parts

Figure 23 Accumulation Curve of. Production from Mln,1ur Wella CD C* >0 m n w " W V* w -• ™ • - w * V W " w n m 0 > * C D C N O f*-. t>-.C^.NO.NO,NQ.>0.>0.>0.>0.0 . 0 > . 0 > . 0 > . 0 > . Q N , O N . O N . ^ C . - > t SJS3&. % . 0 3 3 e.

600 570 . 0 1 5 390. 360 300 0 7 2 210 180 120 . 130 131

per million or the weight of the dissolved solids in mg/1

in water. The common elements or molecules that are usually

dissolved in water include carbonate and bicarbonate, cal

cium, magnesium, sodium, potassium, sulphate, chloride and

nitrate. Water is drinkable if dissolved solids are not too high.

The U.S. Public Health Service has established standards

that should not be exceeded in drinking water (Table XVI).

The standards used 500 ppm total dissolved solides as the

upper limit. These limits are relatively low when compared

with the quality of water from the Minjur Aquifer which has

a total mineral content of about 1200 ppm or more at Riyadh.

In 1968, the General Administration Public Health Laboratory,

Saudi Arabia, suggested a standard (Table XVI) with acceptable

limits which are almost the same as the USPHS standards,

but with maximum permissible limites for TDS of 2000 ppm.

These permissible limits allow the water to meet drinking

water standards after treatment. But the acceptable limits

allow water of high quality to be used more safely even after

lower cost treatment. Hamza (1975) mentioned what he termed

an official water standard and compared his analysis of

some Riyadh water samples to this revised standard (Table

XVI). The future policy of the Saudi Government is to limit

or adjust the total dissolved solids of drinking water to

within the range of 500 to 700 ppm.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 132 1 0.5 0.6 0.6 - 0.9 (Kazmann, S.A.Policy 1972) 1 1 0.3 45 45 45 200 150 400 600 250 250 Maximum Allowable 1975 of Water by tion 0.3 50 75 Reported by HamzaReportedby Health Standards Adop- 200 200 500 1500 500 500 - 700 Official Standard U.S. Public Recent Maximum Acceptable TABLE TABLE XVI QUALITY STANDARDS 9.2 1 1.5 1.5 WATER < 20 10 800 250 200 600 . . 2000 Maximum Permissible 1968) Health Arabia Standard 0.5 0.5 0.5 50 75 7-8.5 200 200 500 Lab. SaudiLab. of Generalof (in Otkun,(in Suggested Limits Acceptable PH Iron Potassium Fluoride Sodium Sulphate SO^ Copper Amonia NH- Manganese Chloride Calcium Magnesium Nitrate NO^ T.D.S.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 133

Salinity distribution

The formation dips eastward, and the total dissolved

minerals increase eastward due to the movement of water down-

dip (Table XVII). Water from the outcrop is the least

saline, 490 mg/1, at Sidriah, but 1200 mg/1 at Tabrak, and

1110 mg/1 at Bir Minjur south. The lower salinity values in

and adjacent to the outcrop are because direct infiltration

in this area has previously leaked much of the salt from the

formation. In addition, the water has not moved very far

in the aquifer and thus has had little time to dissolve

minerals from the aquifer. Water from the area of Dhruma and Muzahniyah between

the outcrop and Riyadh is of much lower quality with dis

solved solids up to 2000 mg/1. These anomalously saline

waters are thought to be related to the effects of faults

that may act as barriers to impede the water flow. The

faults extend northward and have similar effects at Majmaah

to the north where salinities are as high as 1750 mg/1.

At Riyadh, the salinity of the Upper Minjur Aquifer is as

low as 1000 mg/1. Water is slightly more saline at Tabrak

(1200 mg/1) than at Riyadh. This difference may be re

lated to the greater rainfalls during the Pleistocene

Epoch which permitted water of relatively lower salinity to

enter the aquifer. The past 30,000 years has carried this

water to the Riyadh Area. That period was followed by a

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 134

TABLE XVII

GENERAL SALINITY (TDS) DISTRIBUTION

Location TDS mg/L Sampling Source Date

Outcrop (Sidriyah) 490 1966 Sogreah, 1967

Outcrop (Tabrak) 1222 1974 MacDonald, 1975

Dirab 25 Km W. of Riyadh 1250 1966 Sogreah, 1967

Dhruma 2080 1973 MacDonald, 1975

Riyadh (Shumaisi Well) 1000 1961 Brown, 1962 East of Riyadh 1562 1962 Brown, 1962 (National Guard Well)

Khumrais 110 Km E. of Riyadh 8407 1957 Sogreah, 1967

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 135

protracted dry period during which time the small amounts of

rain caused relatively more saline water to infiltrate the

outcrop. The salinity of water also increases as a function of

the depth it has moved downdip because the water spends

more time in contact with the materials containing soluable

salts. This is especially true where the shales and mud

stones separate the Upper from Lower Minjur Aquifer. The

salinity of the Lower Minjur is as high as 1800 (mg/1) and

the Jilh Formation which underlies the Lower Minjur has

salinities up to 2800 mg/1 .

Quality at Riyadh

1. Conductivity

Specific conductance reflects the ability of an aqueous

solution to transmit an electric current and is a function

of the ion content of the water. Measurements are used as

a guide to the total dissolved solids content of water which

may be calculated by considering 65% of the specific con

ductance to be approximately equal the ion content.

Measurement of specific conductance of water from the

Minjur Aquifer at Riyadh ranges from 1250 mhos at NQ-2 in

1966 to 2160 for the National Guard Well in 1962 (Appendix

D). The areal distribution of specific conductance closely

follows that of dissolved solids content. Increases in con

ductance with continued pumping is thought to result from

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 136

the possibility of movement of more saline water to the wells

from downdip or east.

2. pH

Water from the Minjur is approximately neutral to slightly

alkaline with values of pH ranging from 6.85 to 8.3 and

averaging about 7.4 (Appendix D). The range is well within

that considered safe for human consumption.

3. Bicarbonate

Concentration of bicarbonate range from 198 mg/1 at

Malez to 280 mg/1 at Beija-1 (Appendix D). The concentra

tion of carbonate is controlled by the amount of carbon di

oxide in solution. Water rich in carbon dioxide may produce

oversaturated solutions when exposed to a release in pressure

or an increase in temperature; at such times, the water may

deposit calcium carbonate. When this occurs in well bores

or pipes of a distribution system, it causes significant

problems as the size of the pipes is reduced as such deposi

tion takes place.

4. Hardness

Although the concept of hardness is widely accepted,

an exact definition of the property is needed. Hardness is

usually reported in terms of calcium and magnesium, and may

be regarded as the capacity of these ions in water to con

sume soap since titration of hardness with a standard soap

solution has been used as a practical measure of hardness

for more than a century. Modern methods of analytical tech

nique yield more reliable results.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 137

Water from the Minjur Aquifer is considered to be "very-

hard" and calcium - magnesium hardness (total hardness)

ranged from 476 ppm at Dirab-2 to 1260 in the National Guard

Well (Appendix D). Boiling and special treatment may be

used to lower the hardness of water.

5. Chloride Chloride concentration ranges from a low of 170 ppm in

the Bandar Well in 1963 up to 340 ppm in the National Guard

Wells to the east. Chloride concentration generally in

creases in downdip direction and in areas where structural

complication such as faulting has impeded the movement of

water. Chloride concentrations of more tha 100 ppm impart a

salty taste to the water and concentrations greater than

250 ppm exceed the standard for water to be used by food

processing industries (Appendix D).

6 . Sulphate

Sulphate as SO^ ranged from 350 ppm at HR-3 to 465 ppm

at Shumaisi in 1966. It also increases to the east up to

586 ppm in the National Guard No. 1 Well (Appendix D). Sulphate

in these concentrations exceed the U.S. Public Health

Standards for drinking water and are above the maximum

acceptable limits of the official standards at Riyadh. Sul

phates impart an unpleasant odor to water and may interfere

with a number of industrial processes. In combination with

calcium, it may precipitate as gypsum and cause problems

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 138

in wells, pipes and boilers.

7. Fluoride Although water from the Minjur contains significant

amounts of fluoride, 0.2 to 0.55 ppm, the concentrations

are below the recommended limits of 0.6 to 0.8 ppm at

79° F to 90° F. In these amounts, fluoride is considered to be beneficial in preventing tooth decay, but a fluoride

concentration above 1.5 ppm causes known detrimental effects.

Comparison of the analysis of water from The Minjur

Aquifer (Appendix D) with the standards for drinking water

(Table XVI) reveals that the concentration of the ions

exceeds these limits. Consequently, the water is treated

to lower the concentration of dissolved materials to the

point that they are within acceptable limits. Treatment

was begun in 1969 with the construction of plants at Malez,

Shumaisi, Manfouhah and Hayir. Since the water is at a

temperature of about 60° C at the wellhead, it is cooled

to about 30° C, hardness is reduced to about 5 mEq/L, and

alkalinity to 0.6 mEq/1 (Table XVIII). Chlorine is added

to sterilize the water before it is put into the distri

bution system.

Possibility of contamination

Water produced from the Minjur is expected to become

more saline as pumping continues. This expectation is based

on the change in water quality in the Shumaisi Well where

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 139 0 0.5 0 6.0 6.3 83. 3 83. Pumps After 0.25 0.09 2.12.6 2.8 3.5 0.88 1.69 Before Filters

0 0.8 0 6.3 3.6 7.8 81.2 11.4 47 229 210 1466 1249 S S H E M E S Y Before Parsh. Coolers Flume

0.5 0 0.5 6.2 0 3.0 0.09 0.65 3.29 5.0 8.8 7.8 92 80 86.2 33 49 28 28 27 Pumps After 273 1571 3.0 0.19 5.1 2.1 2.0 9.2 Defore 34 Filters ANTS

P P L 3.24 0.82 8.4 4.1 7.9 0 0.8 6.9 12.5 TABLE XVIII 81.4 274 1621 55 55 34 M A L E Z Defore Parah. Coolers Flume (From Riyadh Water Works, July 1977) WATER ANALYSIS AFTER TREATMENT (AVERAGES) Iron - mg/1 Free Chlorine - mg/1 Dissolved Oxygen - % Manganese - mg/1 Aluminum - mg/1 KmnO^ demand - mg/1 Conductivity - US/cm Hardness - Calcium - mEq/1 Hardness - Magnesium - mEq/1 Chloride - mg/1 pll Hardness - Total - mEq/1 Alkalinity - Total - mEq/1 Alkalinity - Phenolphthalein - mEq/1 Temperature - C° Chemical Determinations

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 140 0 6.3 New Pumps 229 0 0 0 3.0 1.69 0 0.06 9.2 9.2 6.1 Old Pumps 172 1082 1192 0.08 9.1 8.6 7.7 8.0 Prec. After

0 1.2 7.8 139 1471 II A Y I II R Before Parsh. Coolers Flume 0 0.5 0 5.8 6.6 6.5 6.3 8.7 0.76 3.31 0.91 83.4 Pumps After 202 1442

0.23 0.05 9. 3 9. Before Filters NTS

0 0.8 0 6.4 (Continued) 3.9 2.3 2.3 4.0 3.5 3.1 2.1 7.5 2.7 2.7 7.8 5.6 P I, A P I, TABLE XVIII 75.0 229 1441 48 28 28 29 49 29 29 28 28 MANPOUIIA Before Parsh. Coolers Flume demand - mg/I Free Chlorine - mg/1 Aluminum - mg/1 Dissolved Oxygen - % Maganese - mg/1 Iron - mg/1 KmnO,} Conductivity - US/cm Chloride - mg/1 pHAlkalinity - Phenolphthalein - mEq/1 7.9 Hardness - Magnesium - mEq/1 Hardness - Total - mEq/1Hardness - Calcium - mEq/1 Alkalinity - Total - mEq/1 11.4 5.0 3.24 5.0 0.77 11.8 Temperature - °C Chemical Determinations

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 141 water with an unexpected high salinity was produced after

many years of pumping. The unusually high salinities from

this well caused speculation concerning the source of the

more saline water. Since the dissolved solids content of

Minjur water increases to the east, and the underlying

aquifers contain water with a greater dissolved solids load

than the Minjur, these sources are considered to be likely

places of origin for the more saline water. It is also

possible that corrosion of the older well casings may have

permitted communication with water from the Jubailah Lime

stone which contains more saline water and entered the well.

Sogreah (1968) calculated that the saline water to the

east of Central Riyadh would take about 500 years to move

10 Km, if the wells were pumped at a rate of 1 m^/year.By

contrast, he calculated that it would take 180 years for water

to move from zones below the Upper Minjur. Under these

circumstances it would be more likely for contamination to

occur from the lower layers than from downdip. Yet, it seems

more likely that the Shumaisi Well may have been contaminated

through failure of the well casing. According to Abu Mustafa

(Personal Communication, 1978), a geologist, contamination

of the Shumaisi Well was simply due to failure of the

well casing. This failure allowed waste water from the

Jubailah Formation to enter the well bore. The well was

shut down in 1974 and is no longer productive.

Yet, the possibility of increasing salt from underlying

aquifers and from the east cannot be excluded, since the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 142

cone of depression created by pumping is constantly increas

ing, and in 1978, the pumping rate of the Riyadh Wells is 3 3 m /sec, three times the rate on which the above calcu

lations were based.

Quality of the Minjur New well fields

Two samples of water were analyzed from Sal-8 Well at

the new Salbukh Well field about 30 to 40 miles north of

Riyadh. The analysis, made by the Riyadh Water Works Lab

oratory, gave similar results to those of the Riyadh Well field. Total dissolved solids were in the range of 1250

mg/1. The results are listed in Table XI. For more details

see page 80. The quality of the new well field at Buaib is expected

to be higher in dissolved solids since the field is located

about 50 Km northeast of Riyadh and the salinity increases

eastward. Estimates of the total dissolved solids are expected

to be in the range of 1500 mg/1.

Quality of shallow aquifers

Water from wells in the shallow aquifers shows a wide

range of water quality. The alluvial aquifers in Wadi Numar

are generally good. Total dissolved solids range from less

than 300 mg/1 at Wadi Nisah to about 800 at Diriyah and

Hayir. Water from the shallow Jubailah Limestone is of

relatively poor quality with dissolved solids contents which

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 143

may reach 5000 mg/1. The high concentrations are thought

to be due to contamination by waste water from the Riyadh

sewage system. Some selected shallow wells water analysis

is shown in Table XIX.

Some of the water from shallow aquifers which has a

very good quality such as the water from Nisah is distri

buted to the public supply without treatment. Most of the

water of poor quality is used for irrigation.

Water Temperature

Water temperature is an important quality. Drinking

water should not be warm. Industrial users of water use

it as a coolant, thus cooler water is more efficient for in

dustry. Temperatures of water extracted from the Minjur is

about 50 - 60° C. Water extracted from the Minjur at Riyadh is being cooled by the treatment process, about 30° C

(Table XVIII), so that it will be suitable for domestic use.

The high water temperature affects the measurement of the

static water level because it gives a slightly higher measure

ment due to the expansion of hot water. Thus, to avoid such

error, water level should not be measured immediately after

pumping but after a delay of one or two days in order to

allow the water to cool.

Temperature increases with the depth of the well. Values

SHALLOW WELLS WATER ANALYSIS *© Z K CO to o Z £ O' O 4J eo a jj H E 8 u O z V © © © 3 J- © u 0 G £ (8 o © u a a © • # m ^ ^ £ 0 3 0 © E « -H CO tn in CN r-* CN a e' CN * en C 0 u © • O'. ^4 in CM CD O m e' » e IP ip CN VP o r- r- en so pm CM e o c nc*> in CD in OH p«- o z z ►4M i- SS 3 14 E c # # h • ^4 4 ^ VP in m O ID rj eo cn r> H DV VP VP CD OH ^4 C5 PSP OH SP « m u © © © © *4 >4 •o 4CM ^4 4CN ^4 IP Ci GD O* ■ CM n w • VP ^4 SP O O Dr- CD CN 09 CD Z CM OH a 0 © r* • • • • • nV o TT VP in ^4 •H O CO VP CD m •H eo O © SP © r> nCO cn Z J ^4 o nCM cn OH SP © Z 0 • •H O C nr- CO © in r- in m m no in X COX CO o o o nP- in in CN r- r— •a OH CN © o CO SO X o §5 © o*—d • © © • • • « CN CN n rm *r SP O C r- r“4 VC en 4 ^ X COX -W^4 CO Pc CM SP o o SP PM o e' in • OH © OH •-4m PO © S O as r- P* VP *3 CO r- OH so X oCN © * • • * h » ■"-'6 h

TABLE XX TEMPERATURE VARIATION WITH DEPTH IN KH-2A WELL IN KiYADH

Depth (m) °F °C

0 95.4 35.22 20 96 35.56 40 99.9 37.72 60 101 33.33 80 106.3 41.28 100 106.2 41.22 150 106 41.11 200 106.93 41.28 250 107.4 41.89 300 108 42.22 400 107.9 42.17 500 108.9 42.77 600 110 45.33 700 111.3 44.06 800 112.5 44.72 900 112.7 44. 83 1000 115.6 46.44 1100 117.5 47.50 1200 119.3 48.5 1300 112.7 50.39

of temperature were taken from well log KH-2A, one of the wells of the Riyadh Area and plotted against depth (Table XX

and Figure 24). It is apparent that temperature does in

crease with depth in this well. From 0 to 100 m, the tempera

ture increased from 35.22° C to 41.22° C. The average in

crease is one degree every 16.67 m of depth. From 100 m to

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 146

100

200

300

-p a 500 Q) Q X 600 •H-P 5 CM < © I 700 u x 3 X ■P j- Cd rH CM J-t iH © 0) 0) 800 U 3 t 3 0) C -p *H Eh M o .900 tM O c o 1000 •H -P cd •rH u 1100 CO > 1200

1300

1500

Temperature c*

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 147 200 m, the temperature remains almost constant. From depths

of 200 m to 400 m, the change is from 41.28° C to 42.17° C,

or one degree Centigrade every 250 m. From 400 m to 800 m,

the temperature increased from 42.17° C to 44.72° C (Table XX),

or an average of 1° C every 156.86 m. From 800 m to 900 m,

the change was only 0.11° C. From 900 m to 1300 m, the temper

ature increased from 44.83° C to 50.39° C or one degree every

72 m.

During pumping tests at Sal-8 Well in the new Salbukh

Well field, water temperatures were taken randomly but the

time of measurement was recorded throughout the pumping

interval (Table XI). The temperature was 35 to 40° C at

the beginning of the test because the water had been cooled

by atmospheric air before pumping began. The the tempera

ture increased gradually to 58° C as the water was being

drawn from great depths in the well.

Safe Yield and Balance

A number of definitions have been proposed for safe

yield, but classically it is considered to be the amount

of water which can be withdrawn from an aquifer annually

without eventually producing an undesirable result in either

quantity or quality.

The safe yield can be determined by plotting the average

annual change in water level against the average annual

draft (Chow, 1964). From the data gathered (Table XV), a

chart may be drawn (Figure 25), from which the safe yield

can be considered as the mean annual draft at zero change of

level. From the graph, the safe yield of The Minjur Aquifer

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission without prohibited reproduction Further owner. copyright the of permission with Reproduced

Figure 25 +ltO -j Safe yield determination m o

utT i»Aa^ CM o o o o o O xrc'

eSus'no -■enmiv eSraoAV m o CO CM CM o o CO o CM

Average Annual Draft in Cubic Meters 148 149

in The Riyadh Area was approximately determined to be 22 6 3 3 x 10 m /year or 0.70 m /sec. This calculation is based

on a 22 hour pumping period because most of the private

wells do not operate 24 hours. A previous estimate of safe 3 yield by Sogreah (1968) was 1 m /sec. Although the estimated

recharge over an area of the outcrop equivalent to the area of

the Riyadh Well field accounts for 15 x 10 6 m 3/year, this

amount is not enought to compensate the approximate safe yield,

which suggests that more water is withdrawn under the influ

ence of pumping from portions around Riyadh. In any case,

if the water level is to be maintained constant it should not

exceed the safe yield. One also should consider that the flow

rate in the aquifer now is much higher than it was prior to

pumping and estimated to be ten times the rate before pumping

began. Production from The Minjur Aquifer is now creating some

effects in the quantity of water as seen in the decline of the piezometrix surface of wells, but insignificant effects

in the quality of water. The current withdrawal rate will

eventually result in more decline in water leve and decrease

in the quality because the aquifer is being produced more rapidly than it is being recharged. The annual recharge rate

is 15 million m^, whereas the annual draft in Riyadh was over 3 50 million m a year in 1977. By way of comparison, the safe 3 yield is 20 million a year (0.7 m /sec). Thus, the current

yearly yield of the Minjur exceeds the annual recharge to The

Minjur Outcrop, over an area of 2200 Km 2 , plus it exceeds the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 150

safe yield determined above. Moreover, a production rate of 3 115 million m /year from only the Minjur Well field in north

and northeast of Minjur is planned for 1979. This rate great

ly exceeds the safe yield and the annual recharge. In fact,

it exceeds the annual recharge through the entire Minjur Out

crop Area. Such an increase of the withdrawal rate would re

sult in a lowering of water level which would increase the

cost of water because pumps would have to be lowered, and more

wells would have to be drilled to maintain a constant supply

of water. The additional possibility of contaminated water

should be considered, because it may not be long before more

saline water invades the production area.

Depletion of The Minjur Aquifer will proceed through two

stages. The first stage will maintain as long as confined con

ditions and water is produced through a decline in peizometric level. This phase, if such production is to be continued at

the rates cited above, will end within the next few years. The

second stage will be characterized by unconfined conditions,

and removal of water will produce a drirect effect on the free

water surface in the aquifer. Depletion will be complicated

by several faults that will form blocking barriers in the system.

Water consumption is clearly tied to population and as the pop

ulation of Riyadh has increased since 1956, the increase has

been accompanied by a demand for more water. In 1965, the

estimated total population of Riyadh was 190,000 and daily

water consumption was 23,100 m^. The water distribution from 3 deep wells was about 16,000 m , a shortage of water from 5000

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to 7000 m^. Riyadh has always experienced water shortages.

VBB (1976) has noticed practically no increase in production

while water demand was much higher since 1965. By 1970, the

population had increased to 355,000 and water consumption of 3 85,000 m /day or 240 1/day/person, while the water distributed 3 to the Riyadh supply was 30,000 m /day from deep wells and 3 3 8200 m /day from shallow wells, totaling about 40,000 m /day

with a shortage of about 50,000 m^. One of the reasons for

water shortages is that large amounts of water from the Minjur

have been used for irrigations and private use. For instance,

in 1969 the water wasted in this way accounted for about 23,000 3 m /day (Shamim and others, 1969).

Until the years from 1969 to 1970, the rate of production 3 had not reached the safe yield limit of 0.70 m /sec. Some sug

gestions have been made in an attempt to maintain the safe yield

rate since 1971. According to Otkun (1972), if additional wells

had to be drilled in The Riyadh Area, their effect would be 3 minor. He said that a safe yield of 1 m /sec is not that ac

curate and that the new wells would replace some old wells

which will be eventually abandoned. In reality, this expecta

tion has not been maintained and the production rate has ex

ceeded the safe yield since then. Developments in The Riyadh Water Supply

The increased demand for water by people is the result

of the increased rate of growth which developed recently

after the inflation rate increased (Table XXI).

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TABLE XXI PERCENTAGE OF GROWTH RATE AND THE GROWTH OF WATER DEMAND (Ministry of Planning, 1975)

1975 1980 1985 1990 2000 2025 1980 1985 1990 2000 2025 2050

Growth Rate 8.9 5.2 5 4 2.5 1 Water Demand Growth 10. 9 8.9 7.6 6 4.5 3

There have been different statistics about population and

water demand from several agencies (Table XXII), thus it

was hard to predict the water consumption by peopl every day

in order to produce the amount of water needed. That was

also one of the major reasons that caused such water shor

tages that Riyadh has experienced for the past several

years.

The extremely rapid development in recent years of the

city of Riyadh, with uncertainties of predicting future

consumption (Table XXII), make it difficult to design a

plan for the furture development of the Riyadh water supply.

An overall plan has been formulated by the Ministry of Agri

culture and Water to deal with the increasing population of

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TABLE XXII

DIFFERENT FIGURES FOR POPULATION AND WATER CONSUMPTION OF RIYADH

Year Population Consumption ^ Sources L/Person/Day Daily m

1965 190,000 120 23,100 Sogreah, 1967 1970 355,000 240 96,200 Shamim and others, 1969 1972 400,000 280 112,000 1973 420.000 Ministry of Planning 75 (Doxiadis) 460.000 Ministry of Planning 75 1974 450.000 (Sect International) 1975 484.000 200(VBB) 215(Sogreah) 525,000 280 147,000 Shamim and others, 1969 570,000 Ministry of Planning 75 (Sect-International) 1977 1,050,000 270 285,000 Abu Butain, 1977 (Interior Ministry) 1978 1,129,999 272 305,000 1979 1 ,200,000 275 330,000 1980 685.000 300 203,500 Shamim and others, 1969 700.000 Ministry of Planning 75 (Doxiadis) 870,000 220 (VBB) Ministry of Planning 75 (Sect-International) 900,000 250(Sogreah) Riyadh Newspaper No.401' 24.10.1394H. 1,280,000 280 360,000 Abu Butain, 1977 (Interior Ministry) 1981 1,400,000 282 400,000 1982 1,500,000 285 430,000 1985 900,000 300 270,000 Shamim and others, 1969 1 ,000,000 240(VBB) Ministry of Planning 75 (Doxiadis) 1 ,120,000 290(Sogreah) 1,800,000 300 540,000 Abu Butain, 1977 (Interior Ministry)

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TABLE XXII (Continued)

Year Population Consumption ~ Sources L/Person/Day Daily m

1990 1,050,000 300 315,000 Shamim and others, 1969

2,300,000 325 750,000 Abu Butain, 1977 (Interior Ministry)

1995 2,740,000 340(Sogreah) 260(VBB)

2000 1,400,000 300 420,000 Shamim and others, 1969

3,000,000 345 1,050,000 Abu Butain, 1977 (Interior Ministry)

2012 2.500.000 400 Riyadh Newspaper No. 4014

3.900.000 Estimate (Growth rate 2.5%)

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the rapidly expanding city and the present yearly shortage

of water. The latter is a matter of some concern. Accord

ing to this plan, the water uses that were predicted and

planned for in 1977 should have been on the order of 170,000

m^/day (Table XXIII). The actual production in July 1977 3 was some 160,000 m /day produced from 24 wells m Minjur

that were being pumped for the Riyadh Public Supply, eleven

shallow wells at Nisah, three more shallow wells at Hayir

and two wells in the shallow aquifer at Numar. The 1977

water shortage was on the order of 115,000 m /day if one

considers the latest figure of the Riyadh population (Table 3 XXIV) and a total water consumption of 285,000 m /day. To

reduce this shortage, Abu Butain (1977) suggested speeding

up the porjects by completing new wells, stopping irriga

tion at Direiyah, Argah and Nasiriyah, which would add 3 about 21,000 m , and pumping the National Guard Wells which

would add some 5000 m^/day. He also suggested periodical

stoppage of water distribution to the low areas with dis

tribution maintained to the higher areas, or using small

pumping machines for the same purpose since the water will

not reach the higher areas naturally. These amounts of

water have real significance and are of considerable value.

In fact, VBB (1976) reported that 15 percent of the total

water production is delivered to Direiyah, population 15,000,

Argah, population 5000, Hayir and Nasiriyah (irrigation). The 3 3 15% would account for 24,000 m /day, from which 5400 m /day

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 156 20,000 10,000 +214,000 +570,000 - - - - 25,000 Remarks m 3/d Total 000,000 350,000 280,000 170,000 -115,000 , ,160,000 +410,000 ,180,000 +640,000 Gulf Gulf Gulf Gulf Field wells & wells wells Addition 9 deep9 16 16 shallow 5 shallow Buaib Field 350, 000 FieldBuaib350, + Salbukh Arabian 1 Arabian 1 Source of Arabian 64,000 WasiaField614,000 Additions 50.000 60.000 Water Gulf 200,000 Ground Arabian TABLE XXIII 3 m 350,000350,000 70,000 550,000 550,000550,000 450,000 Arabian 1 610,000 550,000 630,000 280,000 170,000 24 deep Ground Water Total THE RIYADH WATER SUPPLY AND POPULATION COMPARISON OF PLANNED WATER PRODUCTION FOR Water m 3/d 330,000 750,000 430,00 540,000 305,000 285,000 Consumption 200,000 120,000 , , 1 1,400,000 400,000 1,500,000 2,300,000 1 1979 1980 1,280,0001981 360,000 1982 1990 1985 1,800,000 1978 1977 1,050,000 Year Population

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 157 110,000 -360,000 Remarks m /d 1,160,000 1,160,000 + 1,160,000 +260,000 Addition ,, 3 Source of Total 610,000 Additions Water Gulf Ground Arabian (Continued) TABLE TABLE XXIII 3 m 550,000 610,000 550,000 Ground Water Total Water m 3/d 900,000 2,821,000 3,667,000 1,050,000 1,500,000 Consumption 3,000,000 4,690,000 2,170,000 -1,015,000 3,750,000 2,740,000 * demand. * * From star and down, all estimated according to the rate of growth and growth of water 2050 6,230,000 4,767,000 2020 2030 5,160,000 2040 5,680,000 2010 2000 1995 Year Population

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 158

is consumed by people and the rest is used for irrigation.

The 20,000 people in the Police Training Station at Khashm

Al-An consume a similar amount from two to three wells. The

rest is used for irrigation and could be used to help alle

viate the shortages. To compensate for the water that would

be taken from irrigation, FAO (1976) suggested the possibility

of mixing the water waste from the new Salboukh Well field,

which accounts for from 5 to 10% of the production, with the

water from sewage systems to provide water for irrigation.

Some plants, especially palms, tomatoes, spinach, etc. can

be successfully grown using water with salinities up to

5000 mg/1.

For 1978, the amount of water planned is some 280,000 3 3 m /day or 110,000 m /day more than the 1977 production. The

additional water will be provided by 50,000 cu. m/day from

nine Minjur Wells at Kharj Road (four wells), Sal-2, -3,

HR-3, Argah-1 and Badiaah, plus five wells at Nisah. This 3 plus 60,000 m /day from a new Salbukh Well field of 16 wells

about 30 to 40 Km north of Riyadh (Table XXIV) . The water

required for 1978 according to the latest population figure 3 is 305,000 m . These data indicate a shortage of 25,000

m^/day of water for 1978.

For 1979, another well field of 18 wells will be in

stalled in the Minjur in the Buaib Area about 50 to 55 Km

north 10° E of Riyadh, between Riyadh and Rumah (Table XXIV).

According to Papadopulos (1977) the water level in this well

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TABLE XXIV SOME INFORMATION ABOUT THE NEW WELL FIELDS IN SALBUKH AND BUAIB FOR RIYADH WATER SUPPLY

Wells Elevation (m) S.W.L. (m) Production L/S

Sal-6 657 131.8 55

Sal-7 657 138.7 55

Sal-8 666.5 148.745 45 Sal-9 45

Sal-10 45

Sal-11 45 Sal-12 134 65

Sal-13 659.9 138 55

Sal-14 45

Sal-15 636.2 166 65

Sal-16 636 117 45

Sal-17 639.5 118.6 65

Sal-18 30

Sal-19 45

Sal-20 672 151 55

Sal-21 669 147 65

Sal-22 670 148 65 *

Buaib-1 615 00 00 65*

Buaib-2 612 87 65

Buaib-3 616 91 65

Buaib-4 622 97 65

Buaib-5 605 81 65

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TABLE XXIV (Continued)

Wells Elevation (m) S.W.L. (m) Production L/S

Buaib-6 620 95 65

Buaib-7 629 104 65

Buaib- 8 608 85 65

Buaib-9 628 102 65

Buaib-10 651 125 65

Buaib-11 664 138 65

Buaib-12 637 112 65

Buaib-13 658 132 65

Buaib-14 614 101 65

Buaib-15 632 120 65

Buaib-16 638 126 65

Buaib-17 598 90 65

Buiab-18 604 96 65

* Estimated S.W.L. and required production

Sources: Completion reports of Salbukh Well Field, 1977

Technical specification for drilling Buaib Field Wells.

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field is currently at an altitude of 515 m. It will decline

to 290 m by the year 2000. The salinity of the water is

expected to be 1500 mg/1. A debate has been going on between a number of investi

gators over whether to choose this location north of Riyadh

or a location just west of Riyadh in the Muzahimiyah-Dhruma

Area which was ignored because of salinities of 1500 to 2000

ppm and the structural complexities. The Buaib field is now 3 being drilled and will supply Riyadh with some 70,000 m /day

by 1979. Addition of these wells* production will bring total 3 production to 350,000 m /day, while the amount of water re

quired is expected to be 330,000 m^/day and no shortage will

occur.

For 1980, it seems that the water quantity supplied to

Riyadh will be the same as in 1979 with a small shortage of

10,000 m^/day. The shortage will result because a production

from a proposed well field in the Wasia Formation, a Creta

ceous Sandstone about 110 Km northeast of Riyadh, cannot pos

sibly reach Riyadh before late 1981 or early in 1982. Water

from the Wasia Formation has a dissolved solids content of

1000 mg /1 and the location of the well field between con

fined and the unconfined areas will make the decline less

when the aquifer reaches the unconfined phase, after a

short period of pumping. The water level is at an altitude

of 280 m, and it is shallower than other locations east of

the formation. Production from this formation will add some

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200,000 m3/day to the Public Supply of Riyadh with an average

rate of pumping of 75 1/sec for each of the 18 wells. 3 By 1982, the 200,000 m /day coupled with the existing supply 3 of ground-water will total 550,000 m /day and will exceed

the projected water demand.

Ir addition to the new sources listed above, another

water source is being developed for processing a desalinated

water from the Arabian Gulf at Jubail, some 480 Km northeast

of Riyadh. The first water will reach Riyadh by 1981. Initial 3 production will be 14.2 MGD or 6455.4 m /day. This additional

source will increase the 1981 water supply to 614,000 m3/day

including the 200,000 m 3/day from Wasia. By 1982, 98.8 MGD 3 or 449,152.3 m /day, or more than double the water demand

fpr that year. The desalinated water will be added even

though the water produced from ground-water resources alone

will be in excess of the water demand in 1981 to 1985. More

over, larger quantities of desalinated water are planned

to be pumped to Riyadh each year until production reaches

134.9 MGD or 630,000 m 3/day in 1985 (Table XXII). If this

addition continues, and the ground-water is pumped at the

projected rates to the year 2000, then excess water will be

available until the same year, without any new fields being

developed, although shortages may appear between 2000 and

2010. The large quantities of excess water that may be

available from about 1981 should be carefully considered.

It seems wasteful to pump and deliver excess water to Riyadh

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when towns such as Dammam, Khuber and Qateef are in need

of additional water. The excess could also be used to

irrigate fruit, vegetable and wheat fields in the Riyadh

Area. The increased water supply together with an increase

in reuse of waste water would make the area less dependent

on imported foodstuffs. Also, one should consider that it is very expensive to use desalinated water for irrigation.

If the water cannot be stored, made available to those areas or used for irrigation, then a reduction in production

rates either from wells or land desalination should be con

sidered. According to Papadopolus (1977) desalinization is

much more expensive than developing well fields in the Minjur

or Wasia Aquifers. Some figures to compare the cost of each

in millions of Saudi Riyals (MSR) are listed in Table XXV.

If the supply of desalinated water is developed, then

the ground-water reserves should be saved for emergencies.

Construction of the desalination project at Jabail will be

gin in 1979. The water will be transported about 480 Km

through large double pipes 1.5 meters in diameter and will

pass the Wasia Well field to be mixed and transported to

Riyadh. Should the project for desalinating water be discon

tinued, then the development of new ground-water supplies

should be continued between the years 1985 and 1990, be

cause the amount of water available from the Minjur Deep

Wells, the Wasia Wells and the shallow wells in Riyadh will

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be insufficient to supply the water that wull be consumed

by people during that period (Table XXIII). At any rate,

the situation should be studied at least five years prior

to that date. The study should include further developments

in the Upper Minjur Aquifer farther north of Riyadh, and

development of the Lower Minjur Aquifer and Jilh Formation.

The formation at Wasia and Biyadh just 50 Km east of Riyadh

should be studied further and developed; the two units are

mostly sandstone and have a maximum of 500 m thickness. Spe

cial evaluation should be given for the Lower Minjur and Jilh;

these two formations have salinities of up to 2000 mg/1 and

3000 mg/1 respectively. These salinities were determined

near the outcrop areas, so it would be expected that the

salinity probably would be even greater beneath Riyadh.

Since existing policy limits water quality to some 1000 mg/1

and will be eventually adapted to 500 - 700 mg/1 of dissolved

solids, treatment plants would be required for this water.

Currently there is debate about bringing icebergs from

Antarctica and the possibility of taking advantage of them.

Once a proposal is made, an intensive study should be done.

A matter of great concern is the feasibility of this idea

for this country. Experiences of other countries in this

type of work is essential. Consideration should be given

to the cost of such projects and comparisons with the ex

ploitation of ground-water and desalinating sea water.

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TABLE XXV ESTIMATES OF COST OF GROUND WATER WELL FIELDS AND DESALINATION WATER FROM THE SEA IN MILLIONS OF SAUDI RIYALS

Source Treatment Total Capital Annual Operation Process Cost and Maintenance

Minjur ED 1,119 45.4

RO 1,093 43.2

IX 1,002 50.9

Wasia ED 987 43.9

RO 927 35

IX 855 39

Sea Water MSF 3,558 36.5

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CONCLUSION

Riyadh is located in the center of the Arabian Peninsula,

one of the most arid regions in the world. Because of its

climate and rapidly increasing population, the city has ex

perienced water shortages for many years. In 1956, an

attempt to augment the supply of water from shallow aquifers

was made. A well was drilled 1200 m to tap the Minjur. De

velopment of this aquifer continues to this day and it now

supplies 80 to 90 percent of Riyadh's water. The eastward dipping (1°-1.5°) of the Minjur Sandstone out

crops in an east-facing convex arc some 80 Km west of Riyadh.

The outcrop area is extensive, being 640 Km or more long and

up to 33 Km wide. Locally, the outcrop is mantled by sand

dunes that facilitate more infiltration of water into the

aquifer. Sieve analysis was made on some samples of the

formation near Riyadh and indicated an average sand size of

0.55 to 0.74mm (coarse sand). The sand grains were mostly

quartz with some rock fragments.

Sandstones in the Minjur form two distinct aquifers,

the Upper Minjur Aquifer which is 120 m thick where it is

tapped in the Riyadh Area and the Lower Minjur which contains

water of marginal quality.

Recharge of the aquifer is from precipitation infiltrating 2 the sandstone units in the 6500 Km outcrop area. Where the

outcrop is covered with sand dimes, infiltration is as much

as 20 mm/year. In other areas, it is about 7 mm/year with 166

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estimates for more areas being as low as 1.5 mm/year. Water

moves downdip in the aquifer along natural gradients. There

the Minjur is exploited for water wells produce other gradi

ents and cones of depression have formed on the piezometric

surface in response to these induced gradients. The Minjur

Aquifer is confined and artesian conditions exist within it.

In the Riyadh Area aquifer transmissibilities range from

1.5 x 10~ 3 t o 72 x 10-3 m2/sec and at Well Sal-8 in the new well field north of Riyadh the transmissibility has been -3 2 determined to be 2.04 x 10 (±0.5) m /sec.

Water from the Upper Minjur Aquifer contains from 1100

mg/1 to 1500 mg/1 dissolved solids in the well fields that

serve Riyadh, and water temperatures are high, 55°-60° C.

Consequently, the water is treated and cooled before being

used. Local structural complexities seem to impeded the

movement of water in the aquifer causing some areas to have

water of lower quality and causing uncertainty about the

manner in which the aquifer will respond to intense dewater

ing. This will be more evident in the next few years when

the intensive exploitation of the well fields absorbs all

the artesian storage reserve and becomes dependent on the

65,000 x 10^ cu. m reserve of the water table of the Upper

Minjur. Even though the recharge does not compensate the

exploited water, a safe yield is determined to be 0.7 1/sec

so as to avoid any near dangerous decline of water level.

The current water pumpage rate in the Riyadh Well field ex

ceeds this rate. The total production planned for 1978 was

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280,000 m'Vday for the Riyadh water supply from 31 wells of

the Minjur plus some shallow aquifer wells. The water re- 3 quirement for the same year is 305,000 m /day. This is a 3 small shortage (25,000 m ) in relation to the past years’

shortages. The proposed production for 1979 from the Minjur 3 Wells in and around Riyadh is 310,000 m /day or a total of

some 2,250 x 10 6 m 3 for the next ten years.

The development of the Riyadh water supply will exceed

the water requirements of Riyadh by the year 1981. The

water planned to be produced from ground water alone will

be in excess of the consumption in the years 1981 to 1985.

Fortunately, water from desalination plants on the Arabian

Gulf will reach Riyadh by 1981. Consideration should be

given to the huge amounts of water that will be supplied

in excess. It could be used to supply other towns or to

reduce the production rate from deep aquifers and thus pro

tect them.

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Ministry of Agriculture and Water, Composite Well Log of Buayja No. 2. Water Resources Development Department, Riyadh, 1971.

Ministry of Agriculture and Water, Composite Well Log of Salbukh No. 2^. Water Resources Development Department, Riyadh, 1971-

Ministry of Agriculture and Water, Composite WellLog of RRW1-5R10. Water Resources Development Department, Riyadh, 1971. Ministry of Agriculture and Water, Geology Department, Files of Salbukh Well Field Reports, Riyadh, 1978, 5 pages. Ministry of Agriculture and Water, Geology Department, Technical Specifications for Drilling Water Wells In Buaib Well Field, Riyadh, 1978, 5 pages.

Ministry of Petroleum and Mineral Resources, Map of Najd 4^, Scale 1:100,000. Aeiral Survey Department, Riyadh, 1973.

Ministry of Planning. Survey of the Constraints to the Implementation of the S.A. Plan "Water" Scet Interna tional, Riyadh, 1975, 1-2— 1-3, II-2— II-6 , II-l— II-2, III-l— III-2, III-5— III-6 .

Otkun, G. Quality of Riyadh Water. Ministry of Agriculture and Water, Riyadh, 1968, 2 pages.

Otkun, G. Some Data About Riyadh and Its Water Reguirements. Ministry of Agriculture and Water, Riyadh, 1968, 1 page.

Otkun, G. Ground Water In Saudi Arabia. A Report to the Ministry of Agriculture and Water, Riyadh, 1969, 8 pages.

Otkun, G. Some Aspects of Ground Water Distribution and Exploitation In Saudi Arabia. Ministry of Agriculture and Water, Riyadh, 1970, 7 pages.

Otkun, G. New Suggestions About Riyadh Water Supply. A Report to the Ministry of Agriculture and Water, Riyadh, 1971, 1, 6 , 9. Otkun, G. Observations on Mesozoic Sandstone Aquifer in Saudi Arabia. Ministry of Agriculture and Water, Riyadh, 1972, 30-33.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 173

Otkun, G. Comments on the Memo of VBB Regarding Further Wells for Riyadh Water Supply. Ministry of Agricul ture and Water, Riyadh, 1972, 2.

Otkun, G. General Notes about Riyadh Water Supply. Minis try of Agriculture and Water, Riyadh, 1973, 6 pages.

Otkun, G. Note about New Minjur Wells to be drilled in the Vicinity of Riyadh. Ministry of Agriculture, Riyadh, 1973, 5 pages.

Otkun, G. Note about Minjur Wells to be Drilled on Kharj Road. Ministry of Agriculture, 1973, 1 page. Otkun, G. Minutes of Meeting Held on 8-11-73. Ministry of Agriculture, 1973, 2.

Papadopoulos, S. and others. Notes on a Meeting at M.A.W. on Riyadh Additional Water Resources Study. Ministry of Agriculture and Water, Riyadh, 1976, 1-4.

Papadopoulos, S. (Team Leader), Alternative Sources for Additional Water Supply for Riyadh, Saudi Arabia. Ministry of Agriculture and Water, 1977, SC-1-6, 14- 16, 18, 20-21, 24-26, 34-35, 37, 58, 62, 78-79.

Pettyjon, W. A. Water Quality in a Stressed Environment. Burgers Publishing Co., Minneapolis, Minnesota, 1972 12-13, 24-40. Powers, R. W. and others. Geology of The Arabian Peninsula, Sedimentary Geology of Saudi Arabia. USGS, Washington, D.C., 1966, D6-D7, D36-D40, D44, D49-50, D52, D102, D104, D109, D120.

Quimp, J. S. Information on Riyadh Water Supply Wells in The Minjur Aquifer. Ministry of Agriculture and Water, Riyadh, 1971, 3 pages.

Quimp, J. S. Preliminary Report of Water Levels in Minjur at Riyadh. Ministry of Agriculture and Water, Riyadh, 1972, 6 .

Quimp, J. S. Information on Riyadh Water Supply. Ministry of Agriculture and Water, Riyadh, 1972, 4 pages.

Quimp, J. S. and Khan, S. Report on his Majesty1s Well at Maather. Ministry of Acriculture and Water, Riyadh, 1972, 1-2. Quimp, J. S. Notes on the Productivity of Nasiriyah Minjur Well-2 (Eastern Well). Ministry of Agriculture and Water, 1973, 1 page.

Quimp, J. S. Notes on the Prince Khalid Well at Maather. Ministry of Agriculture and Water, 1972, 1 page.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 174

Quimp, J. S. Notes on Diriyah Minjur Well. Ministry of Agriculture and Water, 1973, 1 page.

Quimp, J. S. Productivity at Malez-I and Nasiriyah West Minjur Wells. Ministry of Agriculture and Water, Riyadh, 1973, 1 page. Reul, K. A. Explanation of the Geological Map of Riyadh with Hydrological Report for Riyadh, Saudi Arabia. Ministry of Agriculture and Water, 1954, 2.

Robinson and Skibittzke, "A Formula for Computing Trans- missibility Causing Maximum Possible Drawdown due to Pumping". USGS Water Supply Paper 1536-T, 283,336.

Shamim, A. and others. (Technical Committee), Report Constituted to Review the Water Supply Requirements for the Metropolitan City of Riyadh in the Light of Master Plan Prepared by Consultants Doxiadix for the Future Development of the City. Ministry of Agriculture and Water, Riyadh, 1969, 2-5.

Shareef, (Al) S. A. Climate Conditions In Riyadh. Riyadh University Library, Riyadh, 1973, 275, 279-291, 304, 307. Shehri, (Al) A. N. (Ed.) "End of the Problem of the Water of Riyadh", Riyadh Newspaper, No. 4041, 1978, 3. .

Sogreah, Water and Agricultural Development Studies, Area V, Riyadh Water Supply. Ministry of Agriculture and Water, Riyadh, 1967, 9-20, 32-57, 61-67, 72-74.

Sogreah, Water and Agricultural Development Studies, Area V, Final Report. Ministry of Agriculture and Water, Riyadh, 1968, 24-38, 75-76, 79-80, 203, 362-369, 370-377, 386.

Sogreah, Water and Agricultural Development Studies, Area V, Final Report 46 - Geophysics. Ministry of Agriculture and Water, Riyadh, 1968, 14-17.

Theis, C. V. "Estimating the Transmissibility of a Water- Table Aquifer from the Specific Capacity of the Well". USGS Water Supply Paper, 1536-1, 1963, 332-336.

Todd, D. K. Ground Water Hydrology. John Wiley & Sons, New York, 1959, 16, 31, 109-111, 206-207.

Tolman, C. F. Ground Water. McGraw-Hill Book Co., Inc., New York, 1937, 384-390.

USGS and Aramco. Geologic Map of the Arabian Peninsula, Scale: 1:2,000,000, Ministry of Petroleum, Riyadh, 1963.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 175

VBB, Riyadh Water Treatment and Distribution System Master Plan Al-Ulaya Area. Ministry of Agriculture and Water, Riyadh, 1976, 2, 4, 8 , 11. Walker, W. H., Bergstrom, R. E. and Walton, W. C. "Pre liminary Report on the Ground-Water Resources of the Havna Region in West-Central Illinois". State Water Survey, Cooperative Ground-Water Report 3^, Urbana, Illinois, 1965, 38-42.

Wilson, G. R. Report of Water Supply for Riyadh. Ministry of Agriculture and Water, Riyadh, 1953, 2.

Wisler, C. 0. and Brater, E. F. Hydrology. John Wiley & Sons, Inc., New York, 1959, 129-135, 143-151, 164, 179.

Wenzel, L. K. "Methods for Determining Permeability of Water-bearing Materials". USGS Water Supply Paper 887, 1942, 91-93.

Zeiel, A. J., Walton, W, C, Sasman, R. T. and Prickett, T. A. "Ground-Water Resources of Dupage County, Illinois". State Water Survey, Cooperative Ground-Water Report 2, Urbana, Illinois, 1962, 56-59.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 176 .

CO (0 6

c o (0 > ■u -H S -H #687 543.6 #683 686.4 49xl0"4 587.2 #556 677 548.5 670.4 #606 605.1 597.5 (U 31 667.2 3Q 27 29 < 1962 28 680.2

1967 1962 1962 1962 1962 1967 a p pe n d i x o 4J o W 1.3xlo"4 1961 32 MINJUR WELLS RIYADH WELLS IN MINJUR O co e CO CO CO CO

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 9 562 6.0x10 -3 1967 30 587.2 10 620 31 667.2 22xl0"4 4.4xl0"’3 -3 11 637 4.8x10 1.3x10 1961 32 543.6 54xl0“4 513 8 12 -3 510.6 3.7x10 7.6x10 1962 33 537.8 72xl0~4 , 8.7xl0“5 L.P.T. 13 551 1967 34 618.7 33xl0“4 7.8xl0'5 14xl0“3 14 572 „ 571.2 35 658 35xl0~4 576 0 15 568.2 36 675.6 46xl0“4

16 532 0 4.1x10-3 3.6x10 1966 37 620 524.5 #619 17 607 38 593.1 13x10"4 2.5x,10”5 18 613 6.5x10-3 605 1966 39 631.5 20xl0"4 2.5xl0-5 19 595 -3 587 0.5x10 1965 40 670.5 56xl0“4

20 4.1x10-3 1967 44 433.4

21 -3 553.5 630 4.3x10 1968 45 433.8 47 596. 9 17xl0“4 4.3xl0“5 L.P.T.: Long Term Pumping Test Well Names are in Appendix C r~~ rH

u m

i SB H Cl ■» S96X «o r4 an in • 5 82 82.5 96 108 105.4 103 115.2 PS S U 6 14.5 135 17.7 20.5 22.8 25.8 7 73.3 97.8 100 84 88 94.5 3 a 76.9 87.9 86.8 85 89.8 90.5 S I 8 « § J 30.5 43.8 41.3 44.2 50.8 61.2 X »5 9 8a | 5 10 92.3 101.3 110.7 118.6 s0* k o a 11 95 121.7 120.5 110.7 a «n 12 F l o w i n g . ... - • ♦25 ♦21.5 SBs 13 10.8 12 13.5

14 51.8 15 45.1 55.4 58.8 16 F l o wing 412.1

17 70 18 88 19 60.5 28 . 101.5

21 105:3 22

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10 r- C O Ol OH n n r- N r- r- r- * <£ a o» t o»Ol oiOl oiO l o>Ol o»Ol o>Ol biOl m m £ ~ • t r . w * 4 * 4 H H H H ^ 4 W 57 61.5 75 78 77.7 85 88 95

64 78.2 77.4 74.2 74 88.7 117 130.4 23

58 66 89.6 76 86.8 105.8 113.4 24 69.4 73.4 95 80.5 82.3 97.6 102 25 27.! 82.5 96 108 105.4 103 115.2 135 26

14.5 135 17.7 20.5 22.8 25.8 36.4 27

73.3 97.8 100 84 88 94.5 117.6 28 76.9 87.9 86.8 85 89.8 90.5 29 30.5 43.8 41.3 44.2 50.8 61.2 83 30

92.3 101.3 110.7 118.6 124 31

95 121.7 120.5 110.7 129 133 32 Flowing...... 33 +25 +21.5 34 10.8 12 13.5 42 75 35 SI.8 36 45.1 55.4 58.8 59.2 63.5 68 74.2 78 37 Flowing +12.1 1.8 38

70 39 88 40 60.5 41

101.5 121 42

105:3 109 126.4 43 I 94.2 44

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117 130.4 23 99

105.8 113.4 24 140 I 102 25 27.9 39

135 26 173 36.4 27 165.3 172

117.6 28 170 179 29 179

83 30 124 31 172

129 133 32 46

33 36.3 39 34 122.9 42 75 35 163 36 173 175 9.2 63.5 68 74.2 78 I • 37 132

1.8 38 109 108 39 142.7 142 40 180.4 179

41 82

221 42 75

109 126.4 43 68.5 I 94.2 44

45 51

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. < • • « 3 0 0 3 3 4 40 m Si P S 35 33 33 BA 30 S so 60 SO 30 S 64 35 40 40 60* 43 “ ST* a a A 40 at 60 33 33 JO* 53 <13 30 43 43 m 5 •a uo 30 43 33 40 30 30 60 o 49 40 40 6 6 6 yr- a * a * a a 8 i

so 60 35 33 60 tR 30 53 30 3 » r» 0 30 so so 33 so so A IS 60 40 30 <3 40 6 a a a 3 3 40 60 38 S S mm 33 33 SI? 33 Ol 30 so so 30 SO SO so IS r» *4 30 30 60 60 60 43 33 30 40 30 16 -yr- a ) a a a « 3 3 33 60 30 30 43 43 S 40 33 so 30 30 30 S IS f* Ol 30 35 47 41 TC" 1978 a a a a 3 30 3 43 - 63 30 30 35 30 so 30 so 43 40 00 f* 00 S S ~7r~ a a • a 3 33 1936 33 6043 60 35 01 01 *4 43 60 SO S 33 0 r* 40 40 33 “ ST" a a ! 20 20 20 so 33 33 33 40 43 0 Ol 434 30 so 50 10 43 30 rt a a % a - 40 63 60 13 33 £ 00 20 20 20 20 33 33 OS so 43 33 30 16 16 41 16 a a a 8 20 20 40 IN RIYADH ( IN RIYADH 30 33 23 23 33 33 01 30 r» la 30 30 33 33 40 40 30 - - 14 10 33 33 20 20 20 20 23 20 33 33 43 40 40 20 20 30 30 ■a 10 Ol 33 33 33 30 43 33 /tmc) 1 ( a * * 20 20 10 23 23 20 30 ll* so 30 20 30 33 ■H in £ so 13 20 43 16 36 16 a * APPENDIX c APPENDIX 10 33 33 23 20 IS* 20 20 £ ■* 33 a a 4 10 20 20 33 20 20 20 20 20 20 30 30 is 23 23 30 30 Ol 00 IS is 31 IS io * a 33 33 IS IS 20 23 30 *■4 IS 10 Ol 46 a 33 13 13 13 + 43 43 40 40 40 40 33 0 m £ 20 23 23 20 30 13 13 13 36 o 00 £ 20 20 20 20 40 40 40 33 33 33 30 30 Ol in Ol IS 31 PRODUCTION or MINJUR WELDS WELDS or MINJUR PRODUCTION * 30 40 40 13 31 23 23 Ol 00 m in (Air Port) SO 11 2

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8 9 7 6 3 3 4 2 I H 04 H • 17 16 14 IS 12 13 11 10 24 23 18 19 23 22 20 21

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i i Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. AP MINJUR WELLS W. Haslriyah . Al- Shumaissi Males I Ho. 1 Kuvllyah Ma at her M ay Nov. Nov. Aug. J u l y Nov. Aug. Nov. r>3te 1957 1966 1961 1973 1976 1961 1973 1961

Conductivity 1650 2030 1780 1850 1640 1500 1810 1900 1630 (rchj 7SS 1100 1500 1230 1490 1180 1260 1140 1170 Hardness 924 1037 900 560 11.2 1050 800 993 C a l c i u n 129 205 168 176 160 7.6 178 i68 158 Ksgne s i u m 37 58 44 110 39 3.6 40 91 38

So J i i m 93 180 nd 153 170 148

P otassium 22 21 nd 18 26 20

Bicarbonate 211 210 198 207 206 207 220 191

S ulphate 403 405 431 400 431 407 458 450 439

Chloride 176 330 242 288 195 241 240 252 205 f luoride 0.6 0.5 0.6 0.4 0.6 0.5 0.6 0.

titrate 0 10 10 1.3 1.6 3.

Silica 20 23 40 21 24.6 23 40 22

! ron 3.3 0.4 0.04 1 0.01 0.04 0. :!ar.car.ese 0.06 0 nd 0.04 0 0

C o p p e r 0 0 0

Sit.-its 0 5

Zinc 0.03 0.2 0.4

Alkalinity 170 170 169 3.52 170 180 157

Phosphate 0.19 0.11 0.19 0.1 27 0.04 13 1.4 30 ~C 2 Aluminum 0.1 0.1 n d 0.1 0.210 0.1 0.) B.'ron 0.2 0.14 0.15 0.14 0.) -/A 7.8 7.5 7.6 7.4 7.3 7.5 7.1

Temperature 52 52.8 52 52.7 52.;

S ources (1) (21 (1) (3) (1) (4) (1) 131 o >

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX D MINJUR WELLS WATER ANALYSIS IN RIYADH Nasiriyah AX- Nasiriyah Male* Z do. 1 Kuwliyah Maather Kjnsouriah No. 2 Badiaah Jixa Arga V. Nov. Aug. J u l y Nov. Aug. Nov. Oct. Nov. Nov. Jan. Nov. Nov. Sept.. Oct. « 6 1961 1973 1976 1961 1973 1961 1961 1973 1961 1975 1961 1961 1975 19C2

130 1780 18SC 1640 1500 1810 1900 1630 1670 1780 1620 1772 1610 1680 1650 1770

00 1230 1490 1180 1260 1140 1170 1180 1166 1150 1262 1140 1180 1076 1210

1037 900 560 11.2 1050 800 993 1015 569 933 915 998 540 1026 • 105 168 176 160 7.6 178 168 158 170 149 155 158 152 168 145 168 • 58 44 110 39 3.6 40 91 38 43 47 40 43 39 40 41 44 .80 nd 153 170 148 143 nd 141 178 151 152 142 21 nd 18 26 20 13 nd 19 IS 13 19

•10 198 207 206 207 220 191 226 205 204 207 208 209 205 212

105 431 400 431 407 458 450 439 430 455 422 437 418 433 450 436

130 242 288 195 241 240 252 205 195 201 188 238 185 210 183 230 0.5 0.6 0.4 0.6 0.5 0. 6 0.4 0.4 0.8 0. 4 0.4 0.3 0. 75 0.

10 10 1.3 1.6 3.5 1.4 13 4.4 6 0.

23 40 21 24.6 23 40 22 22 33 22 22 22 31 22

0.4 0.04 1 0.01 0. 04 0.1 0 4.5 0. 39 0 0.02 3.8 0.

0 nd 0.04 0 0 0 0 0 0 0

0 0 0 0 0 0 0.

- 0 5 0 0 0.2 0.4 0 0. 1 0.1 0.1 0

170 170 169 3.52 170 180 157 185 168 167 171 171 168 174

0.19 0.11 0.19 0.05 0.06 0. 06 0.07 0.37 0.04 13 1. 4 30 14 3.5 10 10 13 2 0.1 0.1 0.1 nd 0.1 0.210 0.1 0.1 0. 1 0.14 0.15 0.14 0.12 0.16 7.4 7 .15 7.5 7.6 7.4 7.3 7.5 7. 1 7.4 7.1 7. 5 7 7.5 5 52.8 52 52.7 52.7 52.7

(3» 13) (1) Cl) 13) .tl (2) 11) (3) (1) (4) (1) 13) ft) fl) (1)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX D 179 iLS WATER ANALYSIS IN RIYADH lu N asiriyah ll ther Hansouriah No. 2 Badiaah Jiza Arg a h Uariyati Sow. Oct. H o y . Nov. Jan. Nov. Nov. Sept. Oct. Jan. Mar. Jan. 1961 1961 1973 1961 1975 1961 1961 1975 1962 1974 1962 1974

1630 1670 1780 1620 1772 1610 1680 1650 1770 1750 1730 2006

1170 1180 1166 1150 1262 1140 1180 1076 1210 1417 l 190 1556

993 1015 569 933 915 998 540 1026 505 ]04i 562 159 170 149 155 158 152 168 145 168 130 164 152 38 43 47 40 43 39 40 41 44 44 47 44

149 143 nd 141 178 151 152 142 141

20 13 nd 19 15 13 19 18 191 226 205 204 207 208 209 205 212 218 204 198

439 430 455 4?2 437 418 433 450 436 435 434 4 s o

205 195 201 188 238 185 210 133 230 221 218 294 0.4 0.4 0.8 0.4 0.4 0.3 0. 75 0.5 0.96 0.5 0

3.5 1.4 13 4.4 6 0.4 0.5

22 22 33 22 22 22 ill 22 29 24 27

0.1 0 4.5 0.39 0 0.02 3. 8 0.1 2.7 0.1 4. 0 0 0 0 0 0.04

0 0 0 0.1 0.04

0 0

0 0.1 0.1 0.1 0 O.S

157 185 168 167 171 171 168 174 179 168 162

0.37 0.02 0.13 0.05 0.06 0.06 0.07 13 2 8.2 30 14 3.5 10 10 0.1 5.3 0.2 0.1 0.1 0.1 0.16 0.1 0.12 7.4 7.1 7.5 7 7.5 7.4 7 .15 7.8 8.15 52.7 52.7 52.7 52.7

(11 (3) (1) (3) 11) n U) (1) (3) 111 135 u :

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Hayir Daghnah Bandar Nat.Gd. B cijah Dirab Royal 1 Riyadh R.R. R.R. Garage D.W. 1 2 Date 1962 1973 1963 1978 1963 1962 1972 1974 1976. 1976 1978 1978 ,1640 1770 Conductivit 1640 1450 IS10 2160 1760 2050 1500 (moh) 1500 15S0 1475 TDS 1141 1191 1180 1060 1520 1250 1631 • Hardness 1301 540 989 11.8 893 1261 617 657 11. 4 12.4 12.9 11.8 o • • Calcium 167 161 160 8.2 152 192 169 164 7.6 8.8 9 7.4 O • • • Magnesium 41 33 44 3.6 37 48 47 60 3.8 3.6 3.9 4.4 S odium 131 134 125 202 nd nd P otassium 9 15 11 25 nd Bicarbonate 203 193 208 206 110 280

Sulphate 438 465 436 416 414 S86 395 430 452 404 Chloride 192 196 190 220 170 340 249 252 266 227 Fluoride 0.2 0. 75 0.5 O.S 0.6 0.5 0.88 0.55 O.S 0.6 0.6 Nitrate 0.4 0.2 0 0.4 0.9 Nil Nil 0 0 0 0 Silica 22 31 24.5 23 5 31 28 23.8 26.7 26.3 21.3

Iron 0.22 3. 2 1.8 0.08 0.06 nd 2.4 0.8 1.4 1.6- 2

Manganese 0 0 0.06 0 nd 0 0 0 0

Annionimum 0.25 nd 0.195 0 0-275 0.11 Phosphe te 0.01 0.03 0 0 0 0 16 C °2 3 6.7 1 Nil A luminum 0.1 0.1 0.2 0 Boron

pH 7.3 7. 03 7.7 7.1 7.15 8.3 7.4 7.0 7.5 Temperature 52

Sources (1) (3) (1) (4) (1) (1) (3) (3) (4) <4> (4) (4) | APPENDIX D , (Continued) Sources: . I- Brown, 1962 (me/I) 2. Sogreahl963

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ijah Dirab Royal Riyadh R.R. R-R- Malez-2 Baiyja Sal-1 Sal-11 Sal-iv Dagnah Garage D.W. 1 2 2 Dagnah HR-1 HR-2 H R - 3 Maather 2 3 2 973 1974 1976. 1976 1978 1978 1976 1976 1978 1978 1976 1978 1974 1976 1974 1975 7£C 2050 1500 15C0 15S0 1475 1500 >350 1450 1450 1450 1375 1700 1350 1350 1800 1630 250 1631 1144 1100 1189 • • O O 11.4 12.4 12.9 11.8 11.6 11.8 O 617 657 11.7 11.5 11.6 11.6 662 10 10 467 nd • • • • • 9 7.4 7.8 • • 1S9 164 7.6 8.8 7.8 7.2 6.6 7.2 158 • • O 6.8 131 . 7.2 6.8 126 • • • • • O 3.8 3.6 3.9 4.4 3.8 4 « O 47 60 4.5 4.9 4.4 4.8 81 3.1 3.2 37 43 nd nd nd nd 151 nd nd nd nd 280 211 198 204 430 452 404 416 422 395 404 414 412 405 400 424 391 350 428 252 266 227 256 199 210 ■ 249 213 234 178 193 185 1 174 ISO 204 O.S 0.6 0.6 0.5 0.45 0.5 0.88 0.55 O.SS 0.55 0.5 O.S 1 0.45 0.4 . 0,.75 nd 0 0 0 0 0 Nil Nil 0 0 0 0 0 Nil 0 0 Nil nd 23.8 26.7 26.3 21.3 25.3 26.7 31 28 22.5 20.4 25.3 21.7 43 23.2 23.2 22 nd

1.4 1.6' 2 1.2 0.6 nd 2.4 0.8 0.6 0.8 1.2 1 1.4 0.4 0.4 nd nd 0 0 0 0 0 0 0 nd 0 0 nd 0 0 nd nd

« o e « O *3.7 3 62 nd 3.45 3.18 3.48 3.58 3.47 ». 37 3.3 3.32 3.16 3.2 173 3.2

nd 0.195 0 0.275 0.11 0.115 0.16 0 0.115 0.17 0 nd 0.115 0.1 nd O 0 0 0 0 0 0 0 0 0 0

1 Nil 6 ■ 5 nd 0

7.7 7.7 6.85 7.15 8..3 7.4 7.0 7.S 7.5 7.? 7.6 8 7.5 7.5 7. 31 7

(4) (3) (3) (4) (4) (4) (4) (4) >4) (4) (4) (4) (4) (4) (3) 1975 (mg/1) 4. Riyadh Nate : . Brown , 1962 (mg/’1) 2.Sogreahl963 (aui/l) 1. KacDonald, (m<;/]) excc

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 180

Sal -1 S4 I-U Sal-IV Dagnah Dagn a h h r -1 HR-2 HR-3 Ma other Sal-V NQXNQ 2 n q 3 Dirab .2 3 2 2 1978 1978 1976 1978 1974 1976 1974 1975 1974 -1978 1976 1675 1974 1450 1450 1450 1375 1700 1350 1350 1600 1630 1700 1525 1250 1650 1883 1045 1316 A 1144 1100 1189 1212 11.7 ■ • 11. S 11. 6 11.6 630 11.6 11. 4 367 476 % 662 io 10 467 nd • a 7.2 6.6 7.2 • 0 1.8 131 . 7.2 6.8t 126 158 148 7.8 7.4 109 118 • A • 0 4.5 4.9 O a 4.4 4.8 81 3.1 3.2 37 43 62 3.8 4 23 44 nd nd 151 nd nd nd nd nd nd nd nd nd 211 198 204 217 214 195 404 414 412 405 400 424 391 350 428 390 411 414 4S0 450 210 213 234 178 193 185 1 174 160 204 229 195 178 174 238 0.55 0.55 0.5 O.S 1 0.45 0.4 0. 75 nd 0. 75 0.5 0.5 0..3 0 0 0 0 0 Nil 0 0 Nil nd Nil 0 0 5 22.5 20.4 25.3 21.7 43 23.2 23.2 22 nd 33 23.5. 22.5 26

0.6 0.8 1.2 1 1.4 0.4 0.4 nd nd 2 16 0.6 10 3. 0 0 0 > nd 0 0 nd nd nd 0 0 nd

O • O 0 3.3 3.32 3.16 3.2 173 3.2 3.7 ’ 62 nd 178 2.62 3.72 175 160

0 nd 0 0.115 0.17 0 ad O.iiS 0.1 nd nd 0 0 0 0 0 0 0 0 6 5 nd 4 5 8

7.6 7.7 6 7.7 6.85 7.5 7.5 7.31 7 7.25 7.9 7.5 7.25 7.

(4) (4) (4) (4) (3) (4) (4) (3) (3) (4) (4) (3) (3) :Oonald, 1975 (mg/1) 4- Riyadh Water Works 1976-1978. tHwiysiuin + Calcium) and except e**.»* hardness 2i«i?ii«ity in (MSc^/)) {marked °)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Plate No.l General Geology Of Riys "After Geoiogy Of Northern Tuwayq Quadrangle. Saudi A rab ia By R

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. amp And L. F. Ramirez, Aramco&USGS, 1958

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Plate No. 2